potential for formation of disinfection by-products from
TRANSCRIPT
Report Reference: DWI 12852.02
March 2018
Potential for Formation of Disinfection By-
Products from Advanced Oxidation
Processes
RESTRICTION: This report has the following limited distribution:
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Potential for Formation of Disinfection By-
Products from Advanced Oxidation Processes
Authors:
Abraham Negarash
Senior Processes Engineer
Treatment Processes
Date: March 2018
Report Reference: DWI 12852.02
David Shepherd
Senior Process Engineer
Treatment Processes
Project Manager: James Froud
Project No.: 16700-0
Leon Rockett
Senior Toxicologist
National Centre for Environmental Toxicology
Client: DWI
Client Manager: Peter Marsden
Anwen Clementson
Toxicologist
National Centre for Environmental Toxicology
Richard Hooper
Materials Technologist
Resource Efficiency
Justin Silver
Senior Process Engineer
Treatment Processes
This report was funded by Defra. The views expressed in it are those of the authors, and not necessarily those of Defra or DWI.
Document History
Version
number
Purpose Issued by Quality Checks
Approved by
Date
V1.0 Draft report issued for comment. Justin Strutt James Froud 24/11/2017
V2.0 Final report issued to client. James Froud Abraham Negaresh 08/03/2018
© WRc plc 2018 The contents of this document are subject to copyright and all rights are reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted, in any form or by any means electronic, mechanical, photocopying, recording or otherwise, without the prior written consent of WRc plc.
This document has been produced by WRc plc.
Contents
Glossary ................................................................................................................................... 1
Summary .................................................................................................................................. 4
1. Objective 1: Definition of the range of advanced oxidation processes that are or may soon be in use in England and Wales ............................................. 10
1.1 Introduction ................................................................................................................ 10
1.2 Literature search ....................................................................................................... 10
1.3 Water company survey ............................................................................................. 22
1.4 Conclusions ............................................................................................................... 24
2. Objective 2: Review of chemical reactions and potential formation of Disinfection by-products ............................................................................................ 27
2.1 Introduction ................................................................................................................ 27
2.2 Radical Chain Reactions ........................................................................................... 27
2.3 Advanced Oxidation Processes ................................................................................ 28
2.4 Conclusion ................................................................................................................. 38
3. Objective 3: Systematic review of the formation of DBPs by AOPs ......................... 39
3.1 Introduction ................................................................................................................ 39
3.2 Search methodology ................................................................................................. 39
3.3 Outcome .................................................................................................................... 48
4. Objective 4: Prioritisation and Toxicity Review ......................................................... 49
4.1 Prioritisation of DBPs ................................................................................................ 49
4.2 Literature Search and Data Collation ........................................................................ 53
4.3 Toxicity Summary ...................................................................................................... 55
5. Objective 5: Risk Assessment ................................................................................... 89
5.1 Hazard Identification ................................................................................................. 89
5.2 Hazard Characterisation ........................................................................................... 89
5.3 Exposure Assessment .............................................................................................. 90
5.4 Risk Characterisation ................................................................................................ 91
5.5 Risk Communication ................................................................................................. 91
5.6 2-Hydroxy-5-nitrobenzoic acid .................................................................................. 91
5.7 2-Methoxy-4,6-dinitrophenol ..................................................................................... 92
5.8 2-Nitrohydroquinone .................................................................................................. 94
5.9 3,5-Dinitrosalicylic acid .............................................................................................. 95
5.10 4-Hydroxy-3-nitrobenzoic acid .................................................................................. 96
5.11 4-Nitrobenzene-sulfonic acid ..................................................................................... 98
5.12 4-Nitrocatechol .......................................................................................................... 99
5.13 4-Nitrophthalic acid.................................................................................................. 101
5.14 5-Nitrovanillin ........................................................................................................... 102
5.15 Summary and Conclusions ..................................................................................... 103
6. Objective 6: Review of analytical methods for detecting disinfection by-products from advanced oxidation processes ......................................................... 106
6.1 Introduction .............................................................................................................. 106
6.2 Literature Review .................................................................................................... 106
6.3 Method Reviews ...................................................................................................... 107
6.4 Nitrobenzene diol .................................................................................................... 110
6.5 Conclusions ............................................................................................................. 113
7. Objective 7: Sampling and analysis strategy for future research projects .............. 115
7.1 Introduction .............................................................................................................. 115
7.2 Removal of prioritised DBPs ................................................................................... 115
7.3 Outline of strategy ................................................................................................... 115
7.4 Analytical method development .............................................................................. 116
7.5 Identification of sites for sampling ........................................................................... 118
7.6 Communication ....................................................................................................... 119
7.7 Sampling strategy for AOP treatment works ........................................................... 120
7.8 Conclusions and Suggestions ................................................................................. 122
References ........................................................................................................................... 124
Appendices
Appendix A Water company survey .......................................................................... 137
Appendix B Water company responses .................................................................... 142
Appendix C Inclusion and exclusion criteria used in the literature review ................ 165
Appendix D Search strings and outcomes of searches, for formation of
DBPs ..................................................................................................... 169
Appendix E Summary of reviewed literature ............................................................. 185
Appendix F Literature Review ................................................................................... 236
Appendix G Ozone DBP Assessment ....................................................................... 239
List of Tables
Table 1.1 Flow rates and AOP doses – UV/H2O2/O3 .............................................. 23
Table 1.2 Summary of current and potential future usage of AOPs ....................... 24
Table 2.1 DBPs formed following peroxone treatment process (US EPA, 1999) ....................................................................................... 30
Table 2.2 DBPs from the ozonation of raw water .................................................... 32
Table 2.3 DBPs from the UV / Cl2 of raw water ....................................................... 35
Table 3.1 Search terms specifically related to AOP techniques ............................. 40
Table 3.2 Search terms for the formation and occurrence of DBPs........................ 41
Table 3.3 Inclusion and exclusion criteria used....................................................... 41
Table 3.4 List of DBPs found (UV / H2O2) .............................................................. 43
Table 3.5 List of DBPs found (O3 / H2O2) .............................................................. 44
Table 3.6 List of DBPs found (O3 / UV / H2O2) ...................................................... 45
Table 3.7 List of DBPs found (UV and Hypochlorous acid) .................................... 46
Table 3.8 List of DBPs (UV and persulfate) ............................................................ 47
Table 3.9 DBPs found (UV and titanium dioxide) .................................................... 47
Table 4.1 Thirteen DBPs excluded based on existing available toxicity data .......................................................................................................... 52
Table 4.2 Final list of DBPs for assessment in this project ..................................... 52
Table 4.3 Table 4.4 VEGA predictions for 2-hydroxy-5-nitrobenzoic acid .......................................................................................................... 57
Table 4.5 VEGA predictions for 2-methoxy-4,6-dinitrophenol ................................ 59
Table 4.6 OECD Toolbox predictions for 2-methoxy-4,6-dinitrophenol .................. 60
Table 4.7 VEGA predictions for 2-nitrohydroquinone .............................................. 63
Table 4.8 VEGA predictions for 3,5-dinitrosalicylic acid .......................................... 65
Table 4.9 OECD Toolbox predictions for 3,5-dinitrosalicylic acid ........................... 66
Table 4.10 VEGA predictions for 4-hydroxy-3-nitrobenzoic acid .............................. 69
Table 4.11 VEGA predictions for 4-nitrobenzene-sulfonic acid ................................. 71
Table 4.12 OECD Toolbox predictions for 4-nitrobenzene-sulfonic acid .................. 72
Table 4.13 VEGA modelling software toxicity predictions for 4-nitrocatechol ............................................................................................ 75
Table 4.14 OECD Toolbox predictions for 4-nitrocatechol ........................................ 76
Table 4.15 VEGA predictions for 4-nitrophthalic acid ............................................... 78
Table 4.16 OECD Toolbox predictions for 5-nitrovanillin .......................................... 80
Table 4.17 VEGA predictions for 5-nitrovanillin ......................................................... 82
Table 4.18 Summary of PoD for each DBP ............................................................... 83
Table 5.1 Uncertainty Factor considerations ........................................................... 89
Table 5.2 Summary of risk characterisation of DBPs based on their estimated daily intake ............................................................................ 105
Table 6.1 DBPs assessed ..................................................................................... 106
Table 7.1 DBPs for further assessment ................................................................ 116
Table C.1 Inclusion and exclusion criteria applied to the selection of relevant papers for the each AOP ......................................................... 166
Table C.2 List of words used for the exclusion of irrelevant papers for ozonation ............................................................................................... 168
Table D.1 Search string for formation of DBPs from UV / H2O2 using Scopus ................................................................................................... 169
Table D.2 Summary of numbers of papers identified, excluded and assessed (UV / H2O2) ............................................................................ 170
Table D.3 Search string for formation of DBPs from hydrogen peroxide and ozone treatment using Scopus ....................................................... 171
Table D.4 Search string for formation of DBPs from hydrogen peroxide and ozone treatment using Science Direct ........................................... 171
Table D.5 Summary of numbers of papers identified, excluded and assessed (O3 / H2O2) ............................................................................. 172
Table D.6 Search string for formation of DBPs from ozone and UV treatment using Scopus ......................................................................... 173
Table D.7 Summary of numbers of papers identified, excluded and assessed (O3 / UV) ................................................................................ 173
Table D.8 Search string for formation of DBPs from hydrogen peroxide and onzone and UV treatment using Scopus ........................................ 174
Table D.9 Summary of numbers of papers identified, excluded and assessed (UV / H2O2) ............................................................................ 175
Table D.10 Search string for formation of DBPs from UV and hypochlorous acid using Scopus ........................................................... 176
Table D.11 Summary of numbers of papers identified, excluded and assessed (UV / HOCl) ........................................................................... 177
Table D.12 Search string for formation of DBPs from UV and persulphate using Scopus ..................................................................... 178
Table D.13 Summary of numbers of papers identified, excluded and assessed (UV / S2O8) ............................................................................ 178
Table D.14 Search string for formation of DBPs from UV and titanium dioxide treatment using Scopus ............................................................ 179
Table D.15 Summary of numbers of papers identified, excluded and assessed (UV / TiO2) ............................................................................. 180
Table D.16 Search string for formation of DBPs from UV, titanium dioxide and hydrogen peroxide treatment using Scopus ...................... 181
Table D.17 Summary of numbers of papers identified, excluded and assessed (UV / TiO2 / H2O2) .................................................................. 181
Table D.18 Search string for formation of DBPs from ozone treatment using Scopus ......................................................................................... 182
Table D.19 Search string for formation of DBPs from ozone treatment using Science Direct .............................................................................. 183
Table D.20 Additional ‘In Any Field’ Exlusion Words ............................................... 183
Table E.1 DBP formation from UV / H2O2 process ................................................ 185
Table E.2 DBP formation from O3 / H2O2 ............................................................... 201
Table E.3 DBP formation from O3 / UV .................................................................. 207
Table E.4 DBP formation from O3 / UV / H2O2 ....................................................... 211
Table E.5 DBP formation from UV / Cl2 ................................................................. 214
Table E.6 DBPs formation from UV / S2O8 ............................................................ 219
Table E.7 DBP formation from UV / TiO2 ............................................................... 221
Table E.8 DBP formation from Ozonation ............................................................. 223
Table E.9 References ............................................................................................ 234
Table F.1 Generic search terms used within Scopus ............................................ 236
Table F.2 Generic search terms used within PubMed .......................................... 236
Table F.3 Results from literature searches in Scopus and PubMed search .................................................................................................... 237
Table G.1 High priority DBPs formed by ozone ..................................................... 239
Table G.2 VEGA predictions for 1-bromo-1,1-dichloropropanone ......................... 241
Table G.3 OECD Toolbox predictions for 1-bromo-1,1-dichloropropanone ................................................................................. 242
Table G.4 VEGA predictions for dichloroacetaldehyde .......................................... 245
Table G.5 OECD Toolbox predictions for dichloroacetaldehyde ........................... 246
Table G.6 Summary of risk characterisation ozone DBPs ..................................... 251
List of Figures
Figure 2.1 Reaction mechanism for UV / H2O2 treatment ......................................... 28
Figure 2.2 Potential reaction mechanism for UV / H2O2 treatment ........................... 29
Figure 2.3 Reaction mechanism for O3 / H2O2 treatment .......................................... 30
Figure 2.4 Reaction mechanism for O3 / UV treatment ............................................. 31
Figure 2.5 Reaction mechanism for O3 / UV / H2O2 treatment ................................. 33
Figure 2.6 Potential reaction mechanism for O3 / UV / H2O2treatment ..................... 33
Figure 2.7 Reaction mechanism for UV / Cl2 treatment ............................................ 34
Figure 2.8 Reaction mechanism for UV/[S2O8]2−
treatment ...................................... 35
Figure 2.9 Reaction mechanism for UV/TiO2 treatment ........................................... 36
Figure 4.1 Prioritisation of DBPs to identify those chemicals to be considered for toxicological assessment ................................................. 50
Figure 6.1 Structures of compounds ...................................................................... 107
Figure 6.2 Structures of compounds ...................................................................... 109
Figure 6.3 Structures of compounds ...................................................................... 110
Figure 6.4 Structures of compounds ...................................................................... 112
Figure 6.5 GC-MS trace for 4-nitrobenzene sulfonic acid ...................................... 113
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 1
Glossary
[S2O8]2-
Persulphate ion
2–MIB 2-Methylisoborneol
ADI Acceptable daily intake
AOP Advanced oxidation pathway
ATSDR Agency for Toxic Substances and Disease Registry
Br- Bromide ion
BrO3- Bromate ion
bw Bodyweight
CIP2 UKWIR Chemicals Investigation Programme 2
Cl- Chloride ion
Cl• Chlorine radical
Cl2 Chlorine
CO2 Carbon dioxide
CO3•- Carbonate radical anion
CO32-
Carbonate anion
DBP Disinfection by-product
DNA Deoxyribonucleic acid
DOC Dissolved organic carbon
DWI Drinking Water Inspectorate
ecb- Photo-excited electron
ECD Electron capture detector
ECHA European Chemicals Agency
EFSA European Food Safety Authority
Fe(OH)3 Ferric hydroxide
Fe2+
Ferrous ion
FeCO3 Ferrous carbonate
FePO4 Ferric phosphate
GAC Granular activated carbon
GC Gas chromatography
GC-MS Gas chromatography – mass spectroscopy
GDWQ Guidelines for Drinking-water Quality
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© WRc plc 2018 2
GHS Globally harmonised system
h+ Positive hole
H+ Hydrogen ion
H2O Water
H2O2 Hydrogen peroxide
HAA Haloacetic acid
HBGV Health-based guidance value
HCO3- Bicarbonate ion
HCO3• Bicarbonate radical
HO2- Hydroperoxide ion
HOCl Hypochlorous acid
HSDB Hazardous substances databank
hv UV irradiation
ITSD eq. Internal Standard equivalent
JECFA Joint Food and Agriculture/World Health Organization Expert
Committee on Food Additives
LC / HR-MS Liquid chromatography / high resolution mass spectroscopy
LD50 Median lethal dose
LDLo Lethal dose low
LO(A)EL Lowest observed (adverse) effect level
LOD Limits of detection
LP Low pressure UV (monochromatic)
M moles/litre (mol/l)
M+O3
- Metal-ozone compound
MLD Mega-litre per ray
MOE Margin of exposure
MP Medium pressure UV (polychromatic)
MtBE Methyl tert-butyl ether
N-DBP Nitrogenous disinfection by-product
NDMA N-Nitrosodimethylamine
NO(A)EL No observed (adverse) effect level
NOM Natural organic matter
O(1D) Excited singlet state
O•- Oxygen atom radical anion
DWI
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O• Oxygen radical
O2 Oxygen
O2•- Superoxide radical
O3 Ozone
OCl- Hypochlorite ion
OECD Organisation for Economic Co-operation and Development
OH• Hydroxyl radical
PAA Peracetic acid
PoD Point of departure
QSAR Quantitative structure-activity relationship
QToF Quadrupole time of flight
RfD Oral reference dose
RO Reverse osmosis
ROS Reactive oxygen species
SCF European Scientific Committee for Food
SO4•- Sulphate radical anion
SO4• Sulphate radical
TDI Tolerable daily intake
THM Trihalomethane
TiO2 Titanium dioxide
TOC Total organic carbon
TTC Threshold of Toxicological Concern
UF Uncertainty factor
US EPA United States Environment Protection Agency
UV Ultraviolet
UVT UV transmittance
VOC Volatile organic carbon
WHO World Health Organisation
DWI
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Summary
i Reasons
Due to the introduction of the EU Drinking Water Directive (98/83) (implemented in England
through regulation 26(2)(a) of the Water Supply (Water Quality) Regulations 2016) there is a
legal requirement to minimise disinfection by-product (DBP) formation. The regulatory focus
has primarily been on DBPs arising from chlorine (notably trihalomethanes, THMs) and ozone
(bromate). Concern about chlorinated by-products has contributed to the adoption of
alternative oxidants in water treatment, notably ozone, and the wider application of UV
disinfection. Advanced oxidation processes (AOPs) have also been introduced to degrade
micropollutants such as pesticides. Advanced oxidation processes generate highly reactive
hydroxyl radicals (OH•), which are potent, but non-selective, oxidants that react orders of
magnitude faster than molecular ozone. Advanced oxidation processes that have application
in drinking water treatment utilise combinations of ozone (O3), hydrogen peroxide (H2O2) and
ultraviolet (UV) light to generate the free radicals. Alternative approaches are available in
other industrial sectors, for example UV in combination with titanium dioxide (TiO2). In
practice, AOPs mineralise only a small proportion of organic material such that a wide range
of organic and potentially inorganic disinfection by-products are formed.
Previous studies have been carried out by the Drinking Water Inspectorate (DWI) regarding
the formation of DBPs produced following ozonation. There is, however, less knowledge of
the types of DBPs produced following AOPs. Therefore the aim of this project is to identify
potential DBPs that may be formed as a consequence of AOPs, identify potential hazard
posed by the DBPs and to carry out a risk assessment to estimate the risk they may pose to
public health.
ii Objectives
This project has been divided into seven objectives:
Objective 1. Define the range of advanced oxidation techniques that are or may soon
be in use in England and Wales.
Objective 2. Review of chemical reactions and potential formation of Disinfection by-
products (DBPs).
Objective 3. Conduct a systematic review of the published and grey literature issued
since 1990 on the formation of by-products from the advanced oxidation processes
identified under objective 1 and their potential removal by subsequent treatment
processes.
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Objective 4. Review existing knowledge of toxicity of the DBPs identified under
objective 3 above.
Objective 5. Conduct a high level risk assessment based on the outcome of objectives
3 and 4.
Objective 6. Review the availability of methods of analysis for the DBPs identified.
Objective 7. Devise a sampling and analysis strategy that could be employed as part of
a future research project to investigate any issues arising.
iii Conclusions
Objective 1
A scoping study identified 14 AOPs with actual or potential application for drinking water
treatment. Of these, one is currently used in England and Wales, and seven were judged as
being realistic options for use within 10 years. The review of DBPs in subsequent objectives
focussed on these eight AOPs.
AOP Overview Status
UV / H2O2 Worldwide applications for potable water and water
re-use. Currently used in the UK. In use in the UK
O3 / H2O2 Worldwide applications for potable water. Has been
trialled in UK at pilot scale.
Possible use in
the UK in the near
future
O3 / UV
Available commercially, has been used in US for
groundwater treatment and remediation. UK
experience as individual processes. Including O3 and
UV is potentially expensive.
Possible use in
the UK in the near
future
O3 / UV / H2O2
Available for industrial wastewater applications, with
potential use for potable water. May offer improved
treatment efficacy than a two-component AOP.
Including O3 and UV is potentially expensive.
Possible use in
the UK in the near
future
UV / Cl2
Potential users may have DBP concerns because of
Cl2. No trials identified in UK. However, available
commercially in US. May have operational cost
benefits relative to UV / H2O2.
Possible use in
the UK in the near
future
DWI
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AOP Overview Status
UV / S2O8
Available commercially for industrial wastewater
treatment. Tested at bench-scale for odour treatment
but no trials identified in UK, but has potential due to
high oxidation level.
Possible use in
the UK in the near
future
UV / TiO2
Commercially available outside of UK, used for
wastewater, groundwater remediation and water
treatment applications. Has only been investigated at
laboratory scale in UK. An AOP with no chemical
addition may be of particular interest as would
represent lower costs.
Possible use in
the UK in the near
future
UV / TiO2 /
H2O2
No commercial applications found. Data from pilot and
bench-scale research in wastewater. Process has
been researched for over 10 years. No trials identified
in UK. Conceptually straightforward extension of UV /
TiO2, to potentially enhance treatment efficiency.
Possible use in
the UK in the near
future
Objective 2
The radicals formed by AOPs are strong oxidising agents that will react with organic and
inorganic constituents of water to produce various DBPs. Oxidation by molecular ozone, or
photolysis by UV, can also contribute to the formation of DBPs. Types of DBPs identified in
treated water are therefore dependent on the nature of the water being treated and the AOP
applied. The formation of DBPs by each of the eight AOPs identified in Objective 1, were
reviewed in Objective 3.
Objective 3
Systematic literature reviews of each of the eight AOPs from Objective 1 identified a total of
78 DBPs.
Objective 4
A 5-step prioritisation process was applied to the 78 DBPs identified in Objective 3, to exclude
those which had already been assessed for potential risk by WHO or DWI, or for which
UKWIR/WRc Toxicity datasheets already exist; or are not likely to be formed under conditions
of relevance to UK treatment processes. By this approach, nine DBPs were prioritised for high
level risk assessment in Objective 5.
DWI
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© WRc plc 2018 7
DBP
2-Hydroxy-5-nitrobenzoic acid
2-Methoxy-4,6-dinitrophenol
2-Nitrohydroquinone
3,5-Dinitrosalicylic acid
4-Hydroxy-3-nitrobenzoic acid
4-Nitrobenzene-sulfonic acid
4-Nitrocatechol
4-Nitrophthalic acid
5-Nitrovanillin
Objective 5
A summary of the risk characterisation of the nine DBPs prioritised in Objective 4 is given
below.
DBP
TDI
(µg/kg
bw/day)
TTC
(µg/kg
bw/day)
Estimated Daily Intake
(TDI)
Estimated Daily Intake
(TTC)
Adult Child Adult Adult Child Infant
2-Hydroxy-5-nitrobenzoic
acid - 0.0025 - - - Below Above Above
2-Methoxy-4,6-
dinitrophenol 90.6 0.0025 Below Below Below Below Above Above
2-Nitrohydroquinone - 0.0025 - - - Below Below Below
3,5-Dinitrosalicylic acid 29.6 0.0025 Below Below Below Below Below Below
4-Hydroxy-3-nitrobenzoic
acid - 0.0025 - - - Below Above Above
4-Nitrobenzene-sulfonic
acid 871 1.5 Below Below Below Below Below Below
4-Nitrocatechol 1472 0.0025 Below Below Below Below Above Above
4-Nitrophthalic acid - 0.0025 - - - Below Below Below
5-Nitrovanillin 166 0.0025 Below Below Below Below Below Below
- No data; modelled NO(A)EL/LO(A)EL could not be derived
Below; estimated daily intake is below the proposed TDI/TTC value, adverse health effects are not anticipated
Above; estimated daily intake is above the proposed TDI/TTC value, adverse health effects cannot be excluded
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Objective 6
Analytical methods for the prioritised nine DBPs that were potentially formed in water
following AOP processes and for which a human health risk assessment was carried out have
been investigated. Some methods are well developed such as nitrobenzene diols and
dinitrophenols whereas other methods for compounds such as the hydroxynitrobenzoic acids,
4-nitrobenzene sulfonic acid, 4-nitrophthalic acid and 5-nitrovanillin will need further
development to ensure they are robust and reliable. Additionally problems with limits of
detection for these methods may not be low enough to detect the concentrations of these
compounds in drinking water. Advances in chromatography during the past twenty years has
allowed for better quantification of hydroxynitrobenzoic acids without the need to use less
accurate colorimetric spectrophotometry. However these methods are yet to be verified as
industry standards.
Objective 7
A range of potential DBPs may arise as a result of the use of AOP treatment. However, the
identified DBPs went through a prioritisation process as part of Objective 4. Nine DBPs were
identified requiring further consideration.
As part of Objective 1 it was identified that currently only two plants are using AOP within
England and Wales. The research undertaken has identified that both of these plants
currently employ the use of GAC.
Based on the data currently available, it may be a reasonable expectation that, following
formation of these potential DBPs via AOP treatment, their concentrations in drinking water
will subsequently be reduced by GAC adsorption, assuming effective operation of the GAC.
This conclusion is based on limited data and further monitoring may be required to validate it.
Prior to instigating a full sampling programme, a number of preliminary steps are required to
ensure that the sampling programme is fit-for-purpose. Further analytical method
development is required using ‘spiked’ water samples to optimise detection limits in UK
drinking water and ensure that results are repeatable. This includes optimisation of calibration
curves and further refinement of LODs.
There is also a lack of understanding as to the conditions that may favour the formation of
these DBPs. Prior to full-scale sampling, bench-scale analysis should conducted with different
water conditions to determine these conditions. This information can then be used to
determine sites where, should AOPs be employed, there is a reasonable expectation that
these DBPs will be formed. These sites should be the primary focus of the sampling survey.
Once the survey sites have been identified, a number of approaches can be taken. A one-
year, bimonthly sampling strategy is proposed, and has been broadly described in this report.
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However, due to a number of unresolved questions, this approach may need to be adjusted
once bench-scale results are known. The approach of sampling over the course of one year
allows for the determination of any seasonal variability of the surface water quality that may
influence the formation of these DBPs.
Within this sampling programme, sampling at each water treatment works will be conducted
over a range of times of the day (morning, afternoon, evening) to address this question. To
fully understand the effects of changes in water conditions that may potentially affect DBP
formation (such as high rainfall events), a sampling programme has also been recommended
to determine the influence of these events.
Sampling in this manner allows for the majority of samples being collected immediately after
AOP treatment. Assuming this represents the highest concentration of DBPs in water this
represents a ‘worst-case’ by which to estimate exposure to the consumer. Sampling after
GAC has also been proposed to confirm the effectiveness of this treatment in reducing DBP
concentrations.
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1. Objective 1: Definition of the range of advanced oxidation processes that are or may soon be in use in England and Wales
1.1 Introduction
Objective 1 aims to establish the range of AOPs that are available and their likelihood to be
used in England and Wales either currently or within 10 years of this report. Information was
collated through a desk based scoping study utilising literature available in the public domain
and through a survey of water utilities in England and Wales.
1.2 Literature search
1.2.1 Methodology
The desk-based scoping study examined publically available literature to identify AOPs that
are commercially available, at a pilot feasibility stage or are currently in development. This
search was not limited geographically; any AOPs identified as being commercially available or
in development globally were considered.
The scoping study consisted of a number of areas of interrogation.
The initial search strategy on commonly applied processes, such as UV / H2O2 and O3 /
H2O2, was based on information gained from previous projects carried out by WRc.
A brief high level search of peer reviewed journals was undertaken in Scopus and
Science Direct using the keywords “AOP”, “Advanced Oxida*” and “Oxida* Treatment”.
This search did not, however, identify the less commonly practiced AOPs, some of which are
not commercially available. As such, a further search of the following online resources was
conducted:
Research Gate
Suppliers of AOP technology (e.g. Xylem Water Solutions and Trojan Technologies) were
also contacted to enquire about AOP systems that are either currently commercialised or in
development. In addition, the Water Science & Technology department at Cranfield
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University, active in the field of AOP research, was contacted to discuss the future use of
AOPs in water treatment.
1.2.2 Identified AOPs
The following AOPs were identified from the scoping study:
Ultraviolet / hydrogen peroxide (UV / H2O2)
Ozone / hydrogen peroxide (O3 / H2O2)
Ozone / ultraviolet (O3 / UV)
Ozone / ultraviolet / hydrogen peroxide (O3 / UV / H2O2)
Ultraviolet / hypochlorous acid (UV / Cl2)
Ultraviolet / persulphate (UV / S2O8)
Ultraviolet / titanium dioxide (UV / TiO2)
Ultraviolet / titanium dioxide /hydrogen peroxide (UV / TiO2 / H2O2)
Ultraviolet / titanium dioxide / ozone (UV / TiO2 / O3)
Ultraviolet / peracetic acid (UV / PAA)
Hydrogen peroxide / ferrous ion (Fenton’s Reagent)
Ultraviolet / ferrous ion / hydrogen peroxide (photo-Fenton) (UV / Fe2+
/ H2O2)
Hydrodynamic cavitation
E-Beam
1.2.3 Ultraviolet / Hydrogen peroxide
In this process, UV light is applied to the water containing H2O2 to form OH• (Kommineni et
al., 1999) according to the equation below:
H2O2 → 2OH•
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Absorbance of UV by H2O2 increases at wavelengths below 254 nm and has a peak at a
wavelength of 240 nm. Therefore, in principle, medium pressure UV lamps produce a greater
number of hydroxyl radicals than low pressure lamps (Munter, 2001). However, overall UV
absorption by the organic and inorganic constituents of water may be higher for a medium
pressure UV lamp than a low pressure UV lamp, leaving less UV available for absorption by
the H2O2. Hence low pressure UV may be more energy-efficient for this application (KWR,
2011).
Generation of UV is energy-intensive at the doses applied for an AOP, particularly if the UV
transmittance (UVT) of the water is low. Only a small proportion of the H2O2 is consumed,
therefore removal of excess H2O2 is required. For this purpose the process is typically
followed by granular activated carbon (GAC); the GAC may also remove DBPs (Hofman-Caris
and Beerendonk, 2011).
Current status and applications
Ultraviolet / H2O2 has been used for water re-use and potable water applications. Proprietary
UV / H2O2 processes include Rayox and Sentinel (Calgon Carbon, 2017); UVPhox and
UVSwiftECT (Trojan, 2017); and MiPROphoto (Xylem, 2017). In the UK, Anglian Water has
installed a Trojan UV / H2O2 system at Hall Water Treatment Works, and other water
companies are known to have undertaken pilot trials.
1.2.4 Ozone / Hydrogen peroxide
Radicals, notably OH•, are formed to some extent by the decomposition reactions of ozone
when it is dissolved in water. The generation of OH• from ozone is enhanced by the
simultaneous introduction of H2O2 (Hoigné, 1998), hence the combination of H2O2 and O3
provides more effective oxidation than the individual use of O3 or H2O2 (Paillard et al., 1988).
Hydrogen peroxide reacts slowly with O3, but it dissociates in water to form hydro-peroxide
ion (HO2-) which reacts readily with O3 to produce the OH• (Hoigné, 1998) according to the
equation below:
H2O2 + H2O ↔ HO2- + H3O
+
O3 + HO2- → OH• + O2
- + O2
If the water contains bromide there is potential for bromate formation when using this process,
which can be minimised by adjusting the O3:H2O2 ratio and the pH (Von Gunten and Oliveras,
1998). Only a small proportion of the H2O2 is consumed during this process therefore
quenching of the excess H2O2 is required typically by GAC. In addition, treatment of O3 off-
gas is required.
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Current status and applications
The application of H2O2 to enhance ozonation has long been recognised and some
conventional ozone contact tanks have provision for H2O2 dosing. The concept has been
developed as an AOP, for which ozone doses are potentially much higher than normally
applied in a conventional ozone contact tank.
Xylem is the principal supplier of O3 / H2O2 processes and currently markets its proprietary
MiPro™, eco3 and Pro3mix® products. This company has built a 34.4 Ml/d plant for K-Water
in Sung-Nam South Korea for taste and odour removal. The process has been trialled by
Anglian Water at one of their treatment works (Scheideler and Holden, 2015).
1.2.5 Ozone / Ultraviolet
In this process, low or medium pressure UV is applied to ozonated water to form OH•.
Ultraviolet at 254 nm wavelength produces H2O2 as an intermediate, which then decomposes
to form OH• (Munter, 2001) according to the equation below:
O3 + H2O → O2 + H2O2
2O3 + H2O2 → 2 OH• + 3O2
H2O2 → 2 OH•
This combined process is more effective than O3 or UV applied separately. At an equal
oxidant concentration, using low pressure (monochromatic) UV lamps, O3 / UV is more
efficient at generating OH• than UV / H2O2 (the most commonly applied AOP for potable water
treatment, with which alternative AOPs are frequently compared) (Glaze et al., 1987; Munter,
2001) because O3 absorbs more UV at 254 nm than H2O2. However, UV / H2O2 may be more
favourable with medium pressure (polychromatic) UV lamps (Kommineni et al., 1999). Ozone
generation requires electrical energy and thus raises operating costs relative to UV / H2O2,
particularly if high concentrations of OH• are required (when the lower solubility of O3 than
H2O2 becomes a factor (Kommineni et al., 1999). The capital cost of ozone generation plant is
also high relative to the provision of storage and dosing plant for H2O2 (Grote, 2012).
There is a potential for bromate formation when using O3 / UV if the water contains bromide.
Treatment of O3 off-gas is also required and diffusion of O3 can result in mass transfer
limitations. UV is energy-intensive at the doses applied for an AOP and the energy will
increase based on water quality deterioration, such as if the UVT of the water is low.
Current status and applications
Ozone / UV has been used for groundwater treatment and remediation (for example in the US
(Patterson et al., 2013). The capital and operating costs are likely to be higher than UV / H2O2
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because of the O3 generation. However, many UK water companies have experience of O3
and/or UV as individual processes, and the combination might be considered on a case-by-
case basis.
1.2.6 Ozone / Ultraviolet / Hydrogen peroxide
In this process, O3 and H2O2 are dosed simultaneously (or O3 dosed into water containing
H2O2), into a chamber exposed to UV (Arslan et al., 2017; Kutz, 2007). Photolysis initiates
radical formation from O3 and H2O2. The radicals then promote further decomposition of
ozone, but also react with each other (Arslan et al., 2017):
O3 + H2O2 → OH• + O2 + HO2•
O3 + OH• HO2• + O2
O3 + HO2• OH• + 2O2
OH• + HO2• H2O + O2
This process has the potential to improve micropollutant removal relative to AOPs utilising two
of the three components, as was evident in (Dillon et al., 2011), but there are cost implications
of introducing a third component.
This is not the same process as commercialised by Xylem, the MiPROeco3 plus process, in
which MiPRO O3 / H2O2 treatment is immediately followed by UV; this is a two stage AOP
which utilises the residual H2O2 (from the O3 AOP stage) at the inlet of the UV, and provides
an extra AOP barrier.
Current status and applications
This process is commercially available, for example Esco’s CATADOX process (ESCO
International, 2017), which also incorporates a proprietary catalyst. Although the marketing of
CATADOX emphasises industrial wastewater treatment, drinking water treatment is listed as
a potential application. Xylem does not sell O3 / UV / H2O2 as a commercialised AOP unit but
could provide it as a bespoke system. This three-component AOP potentially provides greater
treatment efficacy relative to two-component systems, so might be an option in some
circumstances.
1.2.7 Ultraviolet / Hypochlorous acid
The photolysis of HOCl generates chlorine (Cl•) and OH• radicals, while the photolysis of
hypochlorite ion (OCl-) generates oxygen radicals (O•) according to the equation below:
HOCl → Cl• + OH•
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OCl ˉ→ Clˉ + O•
Cl2 + H2O → HOCl + HCl
Ultraviolet / Cl2 has consequently been investigated as an alternative to UV / H2O2, and has a
number of potential advantages (Rosenfeldt et al., 2013):
a) HOCl absorbs UV more strongly than H2O2, thus generating more radicals than an
equivalent quantity of H2O2;
b) HOCl and H2O2 are sources of, but also react with (scavenge), radicals. The nett
production of radicals is therefore the result of competing production/consumption
reactions. HOCl reacts with its product radicals more slowly than does H2O2, thus
scavenging fewer radicals than an equivalent quantity of H2O2;
c) Because of a) and b), less HOCl should be needed than H2O2 for effective treatment.
Any residual HOCl is potentially useful for final disinfection, and for both reasons the
requirement to quench excess HOCl may be avoided; and
d) HOCl is lower in cost than H2O2.
However, OCl- reacts with radicals faster than H2O2. Because of the pH dependency of HOCl
dissociation, this means that UV / Cl2 is expected to be more efficient as an AOP at pH < 7
than at pH > 7.
Current status and applications
Boal (2014) investigated the use of UV / Cl2 for groundwater remediation at two sites for the
removal of perchlorate, N-Nitrosodimethylamine (NDMA) and volatile organic carbon (VOCs),
as a potential alternative to the UV / H2O2 currently used. UV / Cl2 was found to achieve
treatment targets at half the operating cost of UV / H2O2 at one site, and c. 30% of the
operating cost at the other site. UV / Cl2 has been investigated at pilot scale for the removal of
2-Methylisoborneol (2MIB) and geosmin (Rosenfeldt et al., 2013; Springer and Kashinkunti,
2015). The first full-scale UV / Cl2 AOP plant was commissioned in late 2016 at the Terminal
Island Water Reclamation Plant, Los Angeles (Robinson, 2016). Pilot trials had compared UV
/ Cl2 with UV / H2O2 and O3 / H2O2 and concluded that UV / Cl2 was the least costly option,
primarily because chemical costs would be about 25% of those for UV / H2O2 (the latter would
have used sodium hypochlorite to quench residual H2O2).
No trials or full-scale potable water applications of UV / Cl2 have been identified in the UK.
Potential users may have concerns about formation of chlorinated DBPs in an AOP which
uses chlorine. The published case studies noted above did not identify such DBPs as a
problem, but this would have to be verified for any proposed application.
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1.2.8 Ultraviolet / Persulphate
Photolysis of persulphate ion ([S2O8]2-
) generates sulphate radicals (SO4•) according to the
equation below (Heidt, 1942) .
S2O82-
→ 2SO4•-
Hydroxyl radicals are also formed from sulphate radical anions:
SO4•- + H2O → SO4
2- + OH• + H
+
Ultraviolet / S2O8 has consequently been investigated as an alternative to UV / H2O2. In a
study by (Criquet and Leitner, 2009), the radicals generated by UV / S2O8 yielded a greater
mineralization of acetic acid than OH radicals. In addition the study suggested that this
process produces less DBP. Lutze (2013) compared UV / S2O8 with UV / H2O2 for its potential
to degrade micropollutants in water treatment. Lutze (2013) observed that sulphate radicals
generally react with micropollutants at a similar rate or slower than hydroxyl radicals, but there
are some compounds with which they react, albeit slowly, that don’t react with hydroxyl
radicals (for example perfluorinated carboxylic acids). Sulphate radicals were found to react
more slowly with natural organic matter than hydroxyl radicals, but to be inhibited by chloride
and bicarbonate ions.
Current status and applications
Evoqua market the Vanox™ UV / S2O8 process for industrial wastewater treatment
specifically targeting certain organics (e.g. urea) but also for removal of total organic carbon
(TOC) in general (Evoqua, 2017).
Ultraviolet / S2O8 has been investigated at laboratory scale for odour control (removal of MIB
and geosmin) (Xie et al., 2015) and various individual compounds or groups of compounds
(for example iodoacids) (Xiao et al., 2016).
No full-scale potable water applications of UV / S2O8 have been identified, and no UK trials
are known. Despite the limited information regarding the applicability of this AOP process, this
process might have potential if micropollutants resistant to other AOPs are encountered.
1.2.9 Ultraviolet / Titanium dioxide
The TiO2 electrode acts as a photocatalyst when exposed to UV at wavelengths below
380 nm (Tran et al., 2009). Energy from the light causes electrons to become excited and
jump from valence bands to conduction bands, leaving highly reactive ‘positively charged
holes’. These holes have a higher oxidation potential than that of OH•, and can either oxidise
directly or generate OH• from water molecules (Tran et al., 2009). The excited electrons can
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react with dissolved oxygen to generate superoxide anions (O2-), which can further react to
generate OH• (Azrague and Osterhus, 2009) according to the equation below:
TiO2 + → eˉ cb (TiO2) + h
+ vb (TiO2)
h+ vb (TiO2) + OHˉ → TiO2 + OH•
where cb is conduction band and vb is valence band.
The TiO2 catalyst can be immobilised or maintained in suspension. As the photocatalysed
reactions occur on the surface of the TiO2, surface area is an important factor in performance.
Immobilising the TiO2, for example, as a coating on the reactor vessel wall, avoids having to
separate and recover the catalyst from treated water, but limits the surface area. Dosing
particulate TiO2 substantially increases surface area but requires separation and recovery,
which adds additional stages to the process.
Factors that affect this AOP are organic load, catalyst concentration, UV exposure and light
intensity, reactor design, temperature and pH of solution. The use of excessive amounts of
catalyst in suspension may impede UV transmission and thus reduce process efficiency
(Gogate and Pandit, 2004).
Current status and applications
Various companies have commercialised UV / TiO2 systems.
An integrated system which combines a UV / TiO2 reactor with ceramic ultrafiltration for
continuous TiO2 recovery, ‘Photo-Cat®’, has been developed by the Canadian company
Purifics ES Inc (Purifics, 2017). It is available in units up to 120 MLD. Purifics have reference
sites for potable water, wastewater, remediation and industrial applications. There are no
known Purifics applications in the UK.
ATG have developed the Keratox process that combines a fixed TiO2 catalyst with UV (Atguv,
2017). The process is being promoted for the treatment of a wide range of micro-pollutants.
UK site trials are on-going as part of the UKWIR Chemicals Investigation Programme 2 (CIP2)
in relation to wastewater treatment.
Brightwater Environmental Ltd (Brightwater, 2017) has also developed a UV reactor with a
TiO2 coating, marketed primarily for disinfection. It is used in Europe and Asia for process
water, swimming pool and potable water disinfection although it also has been used in the UK
for disinfection of private water supplies. However, it does not have the validation required for
a UV disinfection process so is currently unlikely to be acceptable for public supply use in the
UK.
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Overall, UV / TiO2 is commercially available (Purifics, non-UK), or close to, commercial
availability (ATG) in forms that may be of interest to the UK public water treatment sector. At
least one UK water company has investigated UV / TiO2 at laboratory scale for the removal of
metaldehyde (Dillon et al., 2011), but no subsequent pilot trials have emerged using TiO2.
Having a fixed catalyst does simplify the process, potentially making Keratox a more attractive
proposition than Photo-Cat®. An AOP with no chemical addition may be of particular interest
to water companies in the UK as this would lower both the on going operational cost of
purchasing chemicals and the capital cost involved with ensuring suitable storage is available.
Ultraviolet / Titanium dioxide / Hydrogen peroxide
This process includes addition of H2O2 to the reaction occurring using TiO2 and UV (Yano et
al., 2005a; Garcia et al., 2007) according to the equation below:
TiO2 + → eˉ cb (TiO2) + h
+ vb (TiO2)
h+ vb (TiO2) + OHˉ → TiO2 + OH•
Yano et al. (2005a) found that addition of H2O2 to UV / TiO2 greatly increased the rate and
degree of decomposition of propyzamide relative to UV / TiO2 without H2O2. A more recent
study evaluated the effectiveness of UV / TiO2 in the degradation of 44 organic pesticides
(Miguel et al., 2012). This research included comparison with and without H2O2. It showed an
increase in degradation of the pesticides of up to 57% with H2O2.
Current status and applications
While this AOP is not at the stage of commercial application, there is evidence of performance
enhancement relative to UV / TiO2. Additional research will be needed to understand the
effect of H2O2 on decomposition of emerging micropollutants such as metaldehyde.
Quenching of H2O2 would have to be accounted for in the overall cost of the process.
1.2.10 Ultraviolet / Titanium dioxide / Ozone
The photocatalytic action of UV on TiO2 is enhanced by the addition of O3. The O3 provides a
source of hydroxyl radicals, by reaction with electrons on the surface of the TiO2 that have
been excited by UV (Mehrjouei et al., 2012):
TiO2 + → eˉ cb (TiO2) + h
+ vb (TiO2)
h+ vb (TiO2) + OHˉ → TiO2 + OH•
O3 + eˉ → O3•ˉ
O3•ˉ + H
+ → HO3
ˉ
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HO3ˉ → O2 + OH•
Giri et al. (2008) compared the efficacy of combinations of UV, TiO2 and O3 for degradation of
2,4-D, using a laboratory-scale batch UV reactor with immobilised TiO2 fibres. The initial
concentration of 2,4-D was 10 mg/l and each experiment proceeded for 2 hours, thus
conditions were not representative of potable water treatment. The degradation rate of 2,4-D
by UV / TiO2 / O3 (photocatalytic ozonation) was about five times higher than by UV / TiO2. It
was concluded that OH• were the major oxidant species for 2,4-D degradation and that UV /
TiO2 / O3 provided a source of OH• from the ozone decay induced by the UV / TiO2
Current status and applications
This AOP is not at the stage of commercial application but is currently at bench or pilot scale.
In the near future, this process may be feasible for degradation of recalcitrant organic
compounds. While adding ozonation to this process will increase the capital and operational
costs, the addition of ozone improves the transmittance of the water increasing the
effectiveness of the UV in performing the photo-catalysis (Wiley, 2010).
1.2.11 Ultraviolet / Peracetic acid
Peracetic acid exists in equilibrium with acetic acid, hydrogen peroxide and water according to
the equation below:
CH3COOH + H2O2 ↔ CH3COOOH + H2O
Exposure to UV splits the O-O bond to generate OH• (Caretti and Lubello, 2003):
CH3COOOH → CH3COO• + OH•
Current status and applications
Caretti and Lubello (2003) observed that UV/PAA, at pilot scale, was capable of achieving
economically ≥ 6 log inactivation of Total Coliforms in wastewater intended for irrigation,
whereas PAA or UV alone were not.
A disadvantage of PAA is that it adds biodegradable organic carbon, promoting biofilm growth
downstream (Beber de Souza et al., 2015). No potable water applications have been
identified.
1.2.12 Hydrogen peroxide / Ferrous ion (Fenton’s Reagent)
Fenton’s Reagent generates OH• as a product of the oxidation of ferrous ion to ferric ion by
H2O2 (Kommineni et al., 1999) according to the equation below:
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Fe2+
+ H2O2 → Fe3+
+ OH- + OH•
Ferric ion is reduced to ferrous ion by H2O2, thereby enabling further generation of OH•.
Fe3+
+ H2O2 → Fe2+
+ H+ + OOH•
The reaction is sensitive to pH. If the pH is too high, the ferric ion precipitates and the
resultant ferric hydroxide catalytically decomposes H2O2 to O2. The general requirement is for
initial pH to be in the range 3-5 (Peroxide., 2017). MacAdam and Parsons (2009) state that
maximum effectiveness is at pH 2.8-3.
Conventional Fenton’s reagent is a homogeneous process as all reactants are in solution.
The dosed iron must be separated, by raising pH to precipitate the iron as ferric hydroxide.
This separation might be avoided, or at least simplified, by attaching the iron to a solid support
material. Various support materials have been investigated to provide a heterogeneous
Fenton process, including minerals, resins and activated (Blanco et al., 2014).
He et al. (2016) have reviewed the catalytic reaction mechanisms of the heterogeneous
Fenton process, noting that it is not yet fully understood but classifying the activity in terms of
heterogeneous reactions on the surface of the support media and homogeneous reactions by
ions leached from the surface.
Current Status and applications
It is considered unlikely that homogeneous Fenton’s reagent is a practical process for potable
water treatment. The heterogeneous Fenton process is potentially more practical, but a fully
developed process has yet to emerge.
1.2.13 Ultraviolet / ferrous ion / Hydrogen peroxide (photo-Fenton)
Exposing Fenton’s Reagent to UV increases the rate of regeneration of ferric ions from
ferrous ions, and generates additional OH• (Al-Tawabini, 2003) according to the equation
below:
Fe3+
+ H2O2→ Fe2+
+ OOH• + H+
The above reaction occurs because ferric ion strongly absorbs UV light. UV intensity may be
reduced by precipitation of iron salts on the lamp surface (e.g. FePO4, FeCO3) and
transmittance by precipitation of Fe(OH)3 (US EPA, 1999).
Photo-Fenton AOP is multi-component, of which the overall performance for degrading any
particular compound is the sum of different reaction mechanisms, including direct oxidation by
H2O2, direct photolysis by UV and oxidation by OH•. Hydroxyl radicals may be generated by
H2O2 / UV, H2O2 / Fe2+
and Fe3+
/ UV.
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Current status and applications
It is considered unlikely that photo-Fenton is a practical process for potable water treatment.
Huston and Pignatello (1999) investigated the performance of photo-Fenton for degradation of
13 pesticides. They used substantially higher initial pesticide concentrations than would be
experienced in potable water treatment and observed > 95% degradation of all pesticides
after 30 minutes reaction time except for methoxychlor (79%) and malathion (94%), which
indicates that many common pesticides are susceptible to photo-Fenton.
1.2.14 Hydrodynamic cavitation
In relation to AOPs, hydrodynamic cavitation refers to the formation and subsequent
implosion of microbubbles in aqueous solution. The implosion results in the localised release
of heat which raises the temperature at the interface between bubble and water. The elevated
temperature can cause direct thermal degradation of organic compounds or the thermal
dissociation of water molecules into radicals (Benito et al., 2005) according to the equation
below:
H2O → H• + OH•
Performance can be enhanced by using hydrodynamic cavitation in combination with ozone,
hydrogen peroxide or UV (Dindar, 2016; Kommineni et al., 1999).
Microbubbles can be formed by the application of ultrasound (sonication), high voltage
discharge (pulse plasma cavitation) or by inducing acceleration/deceleration of liquid flow
(hydrodynamic cavitation) (Kommineni et al., 1999).
Current status and applications
Hydrodynamic cavitation has been demonstrated at large scale. The proprietary Hydrox
(hydrodynamic cavitation with optional H2O2and UV) and CAV-OX (hydrodynamic cavitation
with H2O2 and UV) processes were commercialised in the 1990s and implemented for
groundwater remediation (Kommineni et al., 1999; Eilers, 1994), but are no longer available.
WRc tested a pilot-scale combined ultrasonic / ozone reactor for removal of pesticides,
including metaldehyde, but the results were inconclusive as to the contribution of cavitation to
removal (Camm et al., 2013). No examples of implementation in the UK have been identified.
1.2.15 E-beam
When water is exposed to an electron beam, various oxidising species (including OH•) and
reducing species (including hydrogen atoms and free electrons) are generated. X-rays are
also generated by the electron beam generator, and the apparatus must be shielded. The
electron beam penetrates only a few centimetres into water (Kommineni et al., 1999).
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Current status and applications
This AOP has some industrial applications, including in the food and beverage sector. It
requires specialist operators, and is not considered applicable for potable water treatment.
1.3 Water company survey
A survey was designed to provide a comprehensive review of current use of AOPs at water
treatment works as well as those that will be potentially used over the next 5 – 10 years
(Appendix A). The survey was designed to review the different types AOPs used or
considered; the reasons (if applicable) for not using AOPs; the process parameters including
doses and water quality; and which DBP were being monitored. An additional section of the
survey was included regarding use of ozonation at treatment works. The rationale of this was
to enquire if the water companies are monitoring non-regulated DBPs.
The survey was sent out in March 2017 to the R&D managers of 15 water companies with a
request to complete the survey by 7th April 2017. For the first part of the survey, in total there
were 14 responses comprising 10 email responses, 1 phone call and 3 completed
questionnaires. Due to lack of response on the second part of the survey it was re-issued in
August 2017 at the request of DWI in order to increase the response rate. Of the 15
companies contacted, 7 returned the ozone section of the questionnaire (Appendix B) and 5
responded by email.
1.3.1 Current of future use of AOPs
Only three of the responses relating to AOP usage were in the form of completed
questionnaires (Appendix B).
The majority of the companies do not employ AOPs at treatment works and do not intend to
do so in the near future. Two companies have considered AOP treatment, including UV / H2O2
and O3 / H2O2, but do not plan full-scale implementation because of concerns about by-
products (THM formation potential, bromate). Several companies are hesitant to consider the
use of AOP due to the additional costs associated with UV and / or ozone processes. In other
cases, regulatory compliance can be achieved with existing (non-AOP) processes.
The AOP’s that are currently employed at full scale, have been piloted, or would at least be
considered are:
Ozone / H2O2
UV / H2O2
The operational parameters of these AOPs and basic water characteristics that came from the
survey are presented in Table 1.1 below.
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Table 1.1 Flow rates and AOP doses – UV/H2O2/O3
Site No.
Flow Rate
Scale H2O2 Dose
UV Dose O3
Dose Water type
Additional information
1 500 m3/h Full 5 mg/l 650 mJ/cm
2 X
Soft water
Lowland
Metaldehyde,
other
pesticides,
T&O
2 833 m3/h Full NA NA X
Hard
water
Lowland
To achieve
0.6 log
reduction
metaldehyde
3 40 m3/h Pilot
4 – 40
mg/l X
2 – 13
g/m3
Soft water
Surface
4 0.3 – 0.6
m3/h
Pilot 20 – 40
mg/l
1300 – 2600
mJ/cm2
X
Soft
Water
Surface
In addition to the surveys sent out to the water companies, Xylem and Trojan were contacted,
as they provide AOP systems and could provide insight to AOP technologies currently being
developed. WRc also contacted the Water Science & Technology department at Cranfield
University, due to their involvement in researching AOPs.
From these contacts, suppliers see potential in UV / Cl2 and UV / S2O8. There is on-going
research and development to improve efficiency of conventional UV lamps and in the use of
LEDs as an alternative source of UV. AOP technologies in an early stage of research include:
Alternative photocatalysts to TiO2;
Boron doped diamond electrodes; and
Dry and wet plasma.
The second part of the questionnaire requested information regarding DBPs from ozonation.
(Appendix B). Of the 12 companies that responded, 7 currently use ozone, with downstream
GAC. In terms of monitoring for DBPs other than bromate or THMs, one monitors for HAAs
while another monitors for chlorate at one site (albeit related to the use of sodium hypochlorite
used on the site rather than the ozone).
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1.4 Conclusions
A review of the literature on the type and use of AOPs in England and Wales and the survey
of water companies to establish current or potential future usage were carried out. Table 1.2
presents the status of each AOP and which were chosen for further review based on current
usage or feasible usage in the near future for drinking water applications.
Table 1.2 Summary of current and potential future usage of AOPs
AOP Overview Status Outcome
UV / H2O2 Worldwide applications for
potable water and water re-use.
Currently used in the UK.
In use in the UK Will be reviewed for
DBPs in next
objectives.
O3 / H2O2 Worldwide applications for
potable water. Has been trialled
in UK at pilot scale.
Possible use in
the UK in the near
future
Will be reviewed for
DBPs in next
objectives.
O3 / UV Available commercially, has
been used in US for
groundwater treatment and
remediation. UK experience as
individual processes. Including
O3 and UV is potentially
expensive.
Possible use in
the UK in the near
future
Will be reviewed for
DBPs in next
objectives.
O3 / UV /
H2O2
Available for industrial
wastewater applications, with
potential use for potable water.
May offer improved treatment
efficacy than a two-component
AOP. Including O3 and UV is
potentially expensive.
Possible use in
the UK in the near
future
Will be reviewed for
DBPs
in next objectives.
UV / Cl2 Potential users may have DBP
concerns because of Cl2. No
trials identified in UK. However,
available commercially in US.
May have operational cost
benefits relative to UV / H2O2.
Possible use in
the UK in the near
future
Will be reviewed for
DBPs in next
objectives.
UV / S2O8 Available commercially for
industrial wastewater treatment.
Tested at bench-scale for odour
treatment but no trials identified
in UK, but has potential due to
high oxidation level.
Possible use in
the UK in the near
future
Will be reviewed for
DBPs in next
objectives.
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AOP Overview Status Outcome
UV / TiO2 Commercially available outside
of UK, used for wastewater,
groundwater remediation and
water treatment applications.
Has only been investigated at
laboratory scale in UK. An AOP
with no chemical addition may
be of particular interest as would
represent lower costs.
Possible use in
the UK in the near
future
Will be reviewed for
DBPs in next
objectives.
UV / TiO2 /
H2O2
No commercial applications
found. Data from pilot and
bench-scale research in
wastewater. Process has been
researched for over 10 years.
No trials identified in UK.
Conceptually straightforward
extension of UV / TiO2, to
potentially enhance treatment
efficiency.
Possible use in
the UK in the near
future
Will be reviewed for
DBPs in next
objectives.
UV / TiO2 / O3 No commercial applications
found, reported experience is at
bench-scale or pilot scale. No
trials identified in UK. Adding O3
to UV / TiO2 would be
appreciably more expensive
than adding H2O2. Considered
unlikely to yield a cost-effective
process in the foreseeable
future.
Unlikely to be
used in UK in
near future
Will not be reviewed
in next objectives.
UV / PAA Pilot scale reviewed. Process
does not appear applicable for
potable water treatment
because of the residual PAA.
No trials identified in UK.
Unlikely to be
used in UK in
near future
Will not be reviewed
in next objectives.
Fenton’s
Reagent
Extensive research base exists,
and may have applications in
industrial wastewater treatment.
Process in its homogeneous
form is not suitable for potable
water treatment because of
acidic pH and requirement for
Unlikely to be
used in UK in
near future
Will not be reviewed
in next objectives.
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AOP Overview Status Outcome
separation of iron.
Heterogeneous process would
obviate need for separation, but
considered unlikely to yield a
practicable process in the
foreseeable future.
UV / Fe2+
/
H2O2
An extension of Fenton’s
Reagent, and for similar
reasons considered unlikely to
yield a practicable process in
the foreseeable future.
Unlikely to be
used in UK in
near future
Will not be reviewed
in next objectives.
Hydrodynamic
cavitation
Demonstrated at large scale
and implemented for
groundwater remediation in
1990s in US but that particular
proprietary process is no longer
available. A number of different
approaches to achieving
cavitation remain subjects of
research, but are considered
unlikely to yield a practicable
process in the foreseeable
future.
Unlikely to be
used in UK in
near future
Will not be reviewed
in next objectives.
E-beam Some industrial applications,
including in the food and drink
sector. It requires specialist
operators and is not considered
practicable for potable water
applications.
Unlikely to be
used in UK in
near future
Will not be reviewed
in next objectives.
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2. Objective 2: Review of chemical reactions and potential formation of Disinfection by-products
2.1 Introduction
As discussed in Section 1, eight different AOPs have been identified as currently or potentially
used in UK drinking water treatment works. These AOPs include:
UV / H2O2 ;
O3 / H2O2 ;
O3 / UV;
O3 / UV / H2O2;
UV / Cl2;
UV / S2O8
UV / TiO2; and
UV / TiO2 / H2O2.
The objective of this task is to describe the main types of reaction mechanisms that take place
for the above AOPs and the potential DBPs that could potentially be formed from these AOPs.
2.2 Radical Chain Reactions
The strong oxidising agents such as OH• generated by AOPs are produced by chemical
mechanisms known as radical chain reactions. The section below briefly outlines the
reactions involved in radical-type reactions in AOPs.
Radical chain reactions consist of three main reaction mechanisms (Clayden et al., 2001).
These include:
initiation;
propagation; and
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termination.
2.2.1 Initiation
At the initiation stage a molecule such as H2O2 or chlorine Cl2 is homolytically cleaved by
either heat or light to produce two radicals.
2.2.2 Propagation
The propagation stage involves radicals produced during initiation abstracting other
constituents in the solution producing further radicals, creating a chain reaction. At this stage
one radical is consumed and another radical formed.
2.2.3 Termination
Termination mechanisms involve the reaction of two radicals causing the chain reaction to
terminate, forming spin-paired molecules, which are more stable.
2.3 Advanced Oxidation Processes
The section below describes the eight different AOPs which were highlighted in Objective 1.
The mechanism of AOPs includes oxidation of contaminants in raw water, predominantly via
OH•. Therefore each AOP is separated into the most likely reaction mechanisms which
describes the chemistry involved in generating the more reactive OH•. Following on from the
reaction mechanisms to produce OH•, the likely DBPs that will occur in treated water following
reactions are between contaminants and the individual AOPs.
2.3.1 Ultraviolet / Hydrogen peroxide
Reaction mechanism
The photolysis of H2O2 leads to the initiation of OH•. There are two main mechanisms
generating OH• including the direct photolysis of H2O2 (Figure 2.1) and the photolysis of
hydroperoxide ion (HO2-) (Munter, 2001).
The direct photolysis of H2O2 involves the homolytic cleavage of H2O2 to initiate OH• (Munter,
2001); OH• are also produced via propagation chain reactions, as seen below (Jo, 2008).
Figure 2.1 Reaction mechanism for UV / H2O2 treatment
H2O2 → 2OH•
OH• + H2O2 HO2• + H2O
HO2• + H2O2 HO• + H2O + O2
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Hydrogen peroxide is also in equilibrium with HO2- and a hydrogen ion (H
+). The HO2
- also
absorbs UV radiation at 254 nm and undergoes photolysis also producing OH• (Munter,
2001).
Figure 2.2 Potential reaction mechanism for UV / H2O2 treatment
H2O2 ↔ H+ + HO2
-
HO2- → OH• + O•
-
Disinfection by-products
The main reaction mechanisms of UV / H2O2 are absorption of UV photons, which break
bonds in the contaminant and oxidise pollutants via OH•. The UV dose in the UV /
H2O2process is greater when compared to UV disinfection alone, this facilitates increased
breakage of bonds and production of OH• (IJpelaar et al., 2007).
One of the advantages of using the direct photolysis of H2O2 in raw water is that it does not
produce bromate (BrO3-) (Jo, 2008). Ultraviolet / H2O2 treatment has “been successfully used
for the destruction of chlorophenols and other chlorinated compounds”, although it is unclear
what the products of these reactions are. Atrazine, desethylatrazine and simazine are
reported to be mineralised via the UV / H2O2 process (Munter, 2001).
The pressure of UV irradiation is also reported to affect chemicals such as nitrate. If medium
pressure UV lamps are used, nitrate will be reduced to nitrite, but this reaction is not
anticipated to occur using low-pressure UV lamps (IJpelaar et al., 2007).
Like other AOPs, pH of raw water is a major factor which affects the rate of oxidation.
Increase in pH (alkaline conditions) increases the rate of OH• generation (Andreozzi et al.,
1999).
2.3.2 Ozone / Hydrogen peroxide
Reaction mechanism
The disinfection process using H2O2 and O3 is known as the peroxone process. This process
involves the oxidation of organic substances either via direct oxidation using O3 or via OH•
from O3 decomposition (Lenntech, 2017). Direct oxidation using O3 is a relatively slow
process compared to the more reactive and faster oxidation by OH• (US EPA, 1999). The rate
constants of OH• attack on organic molecules such as benzene, toluene, chlorobenzene,
trichloroethylene, tetrachloroethylene, n-butanol and tert-butanol are reported to be in the
range of 106 – 10
9 mol/l (M
-1) s
-1, while direct ozonation has rate constants for the same
chemicals in the range of 0.03 – 17 M-1
s-1
(Andreozzi et al., 1999).
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Figure 2.3 shows the reaction mechanism for oxidation of organic compounds via the
production of OH•. In aqueous solutions H2O2 dissociates into HO2- and a H
+. The HO2
- acts
as the initiator in the peroxone process as it reacts rapidly with O3 forming a chain reaction
producing OH• (Andreozzi et al., 1999; Collins and Cotton, 2009).
Figure 2.3 Reaction mechanism for O3 / H2O2 treatment
H2O2 H+ + HO2
-
HO2- + O3 OH• + O•
-
HO2• ↔ H+ + O2•
-
O2•- + O3 O2 + O3•
-
O3•- + H
+ HO3•
HO3• OH• + O2
Disinfection by-products
Compounds in raw water react via direct oxidation with aqueous O3 or by OH• (US EPA,
1999). There are various different DBPs, depending on the constituents of raw water; the
likely DBPs following the direct peroxone treatment process are listed in Table 2.1. Haloacetic
acids (HAAs) and trihaloacetic acids (THMs) are also present in finished water. The formation
of HAAs and THMs are reduced following peroxone and chloramination as primary and
secondary treatment processes, respectively (US EPA, 1999).
The pH of raw water is a major factor which affects the rate of oxidation; increase in pH
(alkaline conditions) increases the rate of OH• generation (Andreozzi et al., 1999).
Table 2.1 DBPs formed following peroxone treatment process (US EPA, 1999)
Type of chemical Disinfection By-product
Aldehydes
Formaldehyde
Acetaldehyde
Glyoxal
Methyl glyoxal
Acids
Oxalic acid
Succinic acid
Formic acid
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Type of chemical Disinfection By-product
Ethanoic acid
Aldo- and ketoacids Pyruvic acid
Brominated substancesa
Bromate ion
Bromoform
Brominated ethanoic acids
Bromopicrin
Brominated acetonitriles
Additional substances Hydrogen peroxide
a: In the presence of bromide ions (Br-).
2.3.3 Ozone / Ultraviolet
Reaction mechanism
The photolysis of O3 during advanced oxidation produces OH•. Figure 2.4 describes the type
of reactions occurring during O3 / UV treatment. Ozone absorbs UV radiation at 254 nm which
generates molecular oxygen (O2) and an oxygen in an excited singlet state (O(1D)). In an
aqueous solution O(1D) reacts with water (H2O) producing H2O2 as an intermediate, which
forms OH• under UV irradiation (hν) (Munter, 2001; Andreozzi et al., 1999; Malley, 2008).
Additionally, it is important to note that the H2O2 intermediate produced may also initiate OH•
via a peroxone process as described in Section 2.3.1.
Figure 2.4 Reaction mechanism for O3 / UV treatment
O3 → O2 + O(
1D)
O(1D) + H2O H2O2
H2O2 → 2OH•
Disinfection by-products
It is anticipated that OH• (as described above) is the main reactant with substances in raw
water, which has the potential to generate DBPs.
Table 2.2 summarises the main DBPs from ozonation of raw water (WHO, 2000). However, it
is not clear if all these DBPs are observed with the addition of UV irradiation.
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Table 2.2 DBPs from the ozonation of raw water
a: In the presence of natural organic matters (NOM), hypobromous acid generates various organobromine
compounds (Glaze et al., 1993).
b: (WHO, 2000).
c: In the presence of bromide ions (Br-) (WHO, 2000).
d: Ozonation of unsaturated organic compounds (Bailey, 1978).
e: Forms metal-ozone compounds (M+O3
-) (Bailey, 1978).
Some of the main by-products of O3 treatment process are aldehydes, which are reported to
increase with higher doses of O3 (Nawrocki et al., 2003). One study looking at the seasonal
variations of DBPs identified benzaldehyde as the only aromatic aldehyde in treated water
following ozonation (Zhong et al., 2017).
The main carboxylic acids observed following ozonation of natural organic matters (NOMs)
are formic, ethanoic and oxalic acids, while the main ketoacids DBPs are pyruvic, glyoxalic
and ketomalonic acids (Nawrocki et al., 2003). Higher levels of carboxylic acids are reported
Disinfection by-product
Bromoforma
Monobromoacetic acida
Dibromoacetic acida
Dibromoacetonea
Cyanogen bromidea
Chlorateb
Iodateb
Bromatec
Hydrogen peroxided
Hypobromous acidc
Epoxidesb
Ozonatese
Formaldehydeb
Acetaldehydeb
Glyoxalb
Methylglyoxalb
Ketoacidsb
Ketonesb
Carboxylic acidsb
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to be produced when compared to levels of aldehydes, such as formaldehyde, acetaldehyde,
glyoxal and methylglyoxal (Nawrocki et al., 2003). Zhong et al. (2017) also reported the
formation of carboxylic acids, fumaric acid, benzoic acid, protocatechuic acid and
3-hydroxybenzoic acid in the treated water at two treatments works.
One study identified that O3 / UV treatment process has the potential to mineralise 50% of
total organic carbon to carbon dioxide (CO2) and H2O at an O3 and UV dose of
0.62 ± 0.019 mg O3/ml and 1.61 W s/cm2, respectively (Chin and Bérubé, 2005).
2.3.4 Ozone / Ultraviolet / Hydrogen peroxide
Reaction mechanism
The addition of H2O2 to the photolytic reaction of O3 promotes the formation of OH• (Figure
2.5) (Malley, 2008; Munter, 2001).
Figure 2.5 Reaction mechanism for O3 / UV / H2O2 treatment
O3 → O2 + O(
1D)
O(1D) + H2O H2O2
H2O2 → 2OH•
The H2O2 facilitates additional propagation reactions, which generates more reactive oxygen
species, including OH• (Figure 2.6) (Malley, 2008; Munter, 2001).
Figure 2.6 Potential reaction mechanism for O3 / UV / H2O2treatment
OH• + H2O2 O2•- + H2O + H
+
O2•- + O3 O2 + O3•
-
O3•- + H
+ HO3•
HO3• OH• + O2
Disinfection by-products
Hydrogen peroxide is added to the O3 / UV process to accelerate the production of OH•; the
major reaction mechanism is via pollutants and OH•.
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Limited data were located on the formation of DBPs following the O3 / UV / H2O2 process. One
study investigating the oxidation of NOMs, identified an increase in aldehydes and carboxylic
acids in treated water and a decrease in HAAs and THMs. Bromate was also reported in
treated water following ozonation (Agbaba et al., 2016).
2.3.5 Ultraviolet / Hypochlorous acid
Reaction mechanism
The photolysis of HOCl involves the initiation of HOCl generating OH• and Cl•. Additionally,
HOC also dissociates into hypochlorite (OCl-) and H
+. The photolysis of OCl
- generates Cl•
and oxygen atom radical anions (O•-) in an initiation reaction mechanism, propagation of O•
-
with H2O leads to the generation of OH• (El-Kalliny, 2013). Figure 2.7 summarises the likely
reaction mechanisms.
Figure 2.7 Reaction mechanism for UV / Cl2 treatment
HOCl → OH• + Cl•
HOCl ↔ OCl- + H
+
OCl- → O• + Cl•
O•- + H2O OH• + OH
-
Disinfection by-products
Hypochlorous acid is reported to be a more effective disinfectant than hypochlorite ions and is
the more dominant species at pH <7.5 (WHO, 2000). As described above, the photolysis of
HOCl generates OH•, which is the main reactant for the oxidation contaminants in raw water.
Hypobromous acid is identified in treated water in the presence of OCl-, which is generated in
OH• production, and Br-. This can eventually lead to BrO3
- formation.
Table 2.3 summarises other potential DBPs following UV / Cl2 treatment (WHO, 2000).
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Table 2.3 DBPs from the UV / Cl2 of raw water
Disinfection by-product
Trihalomethanes
Haloacetic acids
Haloacetonitriles
Chloral hydrate
Chloropicrin
Chlorophenols
N-Chloramines
Halofuranones
Bromohydrins
Chlorate
Aldehydes
Cyanoalkanoic acids
Alkanoic acids
Benzene
Carboxylic acids
2.3.6 Ultraviolet / Persulphate
Reaction mechanism
In aqueous solutions persulphate salts dissociate into persulphate anions. Photolysis of
persulphate ([S2O8]2-
) directly produces sulphate radical anions (SO4•-), which are a highly
reactive species. Sulphate radical anions react with H2O in aqueous solutions and generate
OH• (Figure 2.8) (Ocampo, 2009).
Figure 2.8 Reaction mechanism for UV/[S2O8]2−
treatment
S2O82-
→ 2SO4•
-
SO4•- + H2O HSO4
- + OH
-
Disinfection by-products
Both SO4•- and OH• can directly react with pollutants (Ocampo, 2009). Bromate ions are
produced in the presence of Br- and SO4•
- in raw water via several radical chain reaction
mechanisms; however, levels of BrO3- have reported to decrease with increased pH (Fang
and Shang, 2012). No additional data were located on the potential DBPs from UV / S2O8
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treatment process, although one study highlighted that additional disinfection (such as
chlorination or hydrogen peroxide) will affect the levels and the types of DBPs in treated
water.
2.3.7 Ultraviolet / Titanium dioxide
Reaction mechanism
During disinfection, the semiconductor TiO2, is used as a photocatalyst. Figure 2.9 shows the
likely reaction mechanism of the UV / TiO2 treatment process. Titanium dioxide absorbs UV
radiation causing a series of complex reactions to produce OH•. The outer electrons of TiO2
(a semiconductor) are located in two energy bands, the valence band and conduction band.
UV wavelengths of approximately 385 nm have sufficient energy to promote a photo-excited
electron (ecb-) from the valence band into the conduction band. This transfer of an electron
creates a “positive hole” (h+) in the valence band.
Delocalised electrons in the conduction band and positive holes can undergo several
oxidation and reduction (redox) reactions. The conduction band electrons can react with O2
producing the superoxide radical (O2•-), while positive holes react with H2O producing OH•
(Gilmour, 2012; Stasinakis, 2008). The indirect oxidation of pollutants produces OH•. The
positive holes are also capable of direct oxidation of pollutants (Gilmour, 2012).
Figure 2.9 Reaction mechanism for UV/TiO2 treatment
TiO2 → ecb
- + h
+
ecb- + O2 O2•
-
h+ + H20 H
+ + OH•
Disinfection by-products
Organic compounds typically undergo degradation via oxidation reactions with valence band
holes and OH•. A variety of organic compounds are reported to undergo oxidation and
mineralisation to CO2 and H2O (Gilmour, 2012; Stasinakis, 2008).
Reduction in Total Organic Carbon (TOC) was reported after ultrafiltration and UV / TiO2
photocatalytic treatment. However, the level of reduction (40%) was likely have been
enhanced by the configuration of the experiment (samples were re-circulated for 24 hours)
(Richardson et al., 1996). The same study also identified chlorinated DBPs (halomethanes
and halonitriles) in treated water, following secondary chlorination. Concentrations of these
halogenated by-products were lower when compared to the levels following chlorination as
the only disinfectant. One organic by-product, 3-methyl-2,4-hexanedione, was tentatively
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identified in treated water from ultrafiltration and UV / TiO2 photocatalytic treatment
(Richardson et al., 1996).
2.3.8 Ultraviolet / Titanium dioxide /hydrogen peroxide
Reaction mechanism
The inclusion of both the photocatalyst (TiO2) and H2O2 in the UV / TiO2 / H2O2 process is
reported to enhance the production of OH•. Although the exact chemical mechanism of the
UV / TiO2 / H2O2 processes is unclear, below are the main anticipated reactions (Yano et al.,
2005b).
As shown in Section 2.3.1, the photolysis of H2O2 generates OH•, but at high H2O2
concentrations these radicals can also be “mopped up” by H2O2. As seen in Section 2.3.4
positive holes in the valence band of TiO2 also generate additional OH• (Bokhari et al., 2015;
Yano et al., 2005b).
In the presence of a photocatalyst, such as TiO2, UV irradiation aqueous solutions maintain
an equilibrium of electron migration between the valence and conduction bands (Gilmour,
2012). With the addition of H2O2, which is reported to be an effective “electron trapper”, this
shifts the equilibrium allowing a greater availability of positive holes in the valence band,
which maintains reactions generating OH• (Yano et al., 2005b).
Disinfection by-products
It is anticipated that pollutants react with the positive holes in the valence band of TiO2 and
with OH• radicals.
Limited data were located on potential DBPs following UV / TiO2 / H2O2 treatment. One study
reported that the herbicide, propyzamide decomposed into intermediates and only with
additional treatment of ultrasonic waves did it mineralise to CO2 and H2O (Yano et al., 2005b).
2.3.9 Other considerations
Water hardness
It is clear that the production of OH• is a key process required to oxidise and/or degrade
contaminants in raw water. However, the hardness of water can affect the rate of OH•
production. Bicarbonate (HCO3-) and carbonate anions (CO3
2-) act as scavengers and react
with OH•, producing carbonate radical anions and bicarbonate radicals (CO3•- and
HCO3•). As
well as reducing the production of the highly reactive OH•, reactions between carbonate
radical anions and bicarbonate radicals, and pollutants in raw water is reported to not be
“significant” (Jo, 2008). Therefore, the oxidation of pollutants is reduced in waters with higher
carbonate and bicarbonate levels.
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Inorganic anions
Anions such as chloride (Cl-) and bromide (Br
-) are also OH• scavengers, with Br
- reacting
more quickly. These ions “mop up” the OH• reducing the magnitude of oxidation of
contaminants in raw water.
Natural organic matters
In photolysis (UV) processes, it has been reported that NOM with higher UV absorbing
properties produce OH• at a higher rate than ozonation processes. However, NOMs such as
humic and fulvic compounds reduce the effectiveness of AOPs by acting as a OH• scavenger
and adsorb UV radiation (Jo, 2008).
2.4 Conclusion
There are eight AOPs that have been identified as currently or potentially being used in
England and Wales over the next ten years. The OH• formed are strong oxidising agents that
are readily produced in AOP radical reactions and will react with pollutants to produce various
DBPs.
Types of DBPs identified in treated water are dependent on factors such as the hardness of
the water, constituents present in the raw water (inorganic ions, bromine and NOM) and the
types/sequence of disinfection. Some AOPs mineralise pollutants to CO2 and H2O, while
others can generate DBPs, depending on the constituents of raw water. Common DBPs found
in treated water, following AOPs include:
aldehydes (formaldehyde, acetaldehyde, glyoxal and methyl glyoxal);
carboxylic acids (oxalic, succinic, formic and ethanoic acids);
ketoacids (pyruvic acid);
hydrogen peroxide;
haloacetic acids (monobromoacetic acid and dibromoacetic acid);
haloacetonitriles;
trihalomethanes (bromoform);
hypobromous acid;
bromate; and
chlorate.
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3. Objective 3: Systematic review of the formation of DBPs by AOPs
3.1 Introduction
Objective 3 of this project is to undertake a systematic review of the published and grey
literature issued since 1990 on the formation of by-products from the AOPs identified under
Objective 1.
This section describes the approach taken to carry out the review, and summarises the
findings for each of the included AOPs.
3.2 Search methodology
To ensure that as many relevant records are captured as possible and also to ensure quality
of the data retrieved a staged approach was followed, as shown below:
Development of search terms;
Literature screening and evaluation; and
Data extraction.
3.2.1 Development of search terms
Under Objective 1, several AOPs were identified either as being currently in use in England
and Wales, or of potential application in the future. These AOPs formed the basis of the
search terms (Table 3.1). Additional search parameters (Table 3.2) were used in conjunction
with those listed in Table 3.1 to identify DBPs formed from AOPs. Searching was restricted to
studies published after 1990 and in the English language.
Two databases were initially interrogated namely Scopus and Science Direct1. Each search
was customised for the database that was investigated. An example of a search string for one
database i.e. Scopus is given in Appendix D.
Using these terms, separate searches were undertaken for each AOP to identify the formation
of DBPs. Titles and abstract retrieved were stored in the reference management software
EndNote X8 for further evaluation.
1 A technical issue with Science Direct when using multiple search terms and wildcards meant that
robust searches using the data was not possible.
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Table 3.1 Search terms specifically related to AOP techniques
Type of AOP Search terms(a)
Generic terms AOP [OR] Advanced Oxid* [OR] Advanced Treatme*
Terms related
to O3 / H2O2
Hydrogen peroxide [OR] H2O2
[OR] Hydrogen dioxide [OR]
7722-84-1
[AND] Ozone [OR] O3 [OR] Triatomic
oxygen [OR] 10028-15-6
Terms related
to UV / H2O2
Hydrogen peroxide [OR] H2O2
[OR] Hydrogen dioxide [OR]
7722-84-1
[AND] UV [OR] ultraviolet
Terms related
to O3 / UV
Ozone [OR] O3 [OR] Triatomic
oxygen [OR] 10028-15-6
[AND] UV [OR] ultraviolet
Terms related
to O3 / UV /
H2O2
Hydrogen peroxide [OR]
H2O2 [OR] Hydrogen
dioxide [OR] 7722-84-1
[AND] Ozone [OR]
O3 [OR]
Triatomic
oxygen [OR]
10028-15-6
[AND] UV [OR] ultraviolet
Terms related
to UV / TiO2
UV [OR] ultraviolet [AND] Titanium dioxide [OR] TiO2 [OR]
Titanium oxide [OR] 13463-67-7
Terms related
to UV / TiO2 /
H2O2
UV [OR] ultraviolet [AND] Titanium
dioxide [OR]
TiO2 [OR]
Titanium
oxide [OR]
13463-67-7
[AND] Hydrogen peroxide [OR]
H2O2 [OR] Hydrogen
dioxide [OR] 7722-84-1
Terms related
to UV / Cl2
UV [OR] ultraviolet [AND] Hypochlorous acid [OR] OCl [OR]
7790-92-3
Terms related
to UV / S2O8
UV [OR] ultraviolet [AND] Persulphate [OR] persulfate [OR]
*S2O8
a.) Terms in brackets [ ] represent connecting phrases that vary between database, but are used to ensure the
correct use of the search terms in combination.
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Table 3.2 Search terms for the formation and occurrence of DBPs
Search terms related to the formation/occurrence of DBPs from AOPs
React* [OR] Form* [OR] Produc* [OR] Level* [OR] Occur* [OR] Generat*
[AND]
DBP [OR] disinfect* [OR] by-product* [OR] byproduct* [OR] by product*
Common search terms related to drinking water
[AND]
Water [OR] Drink* [OR] treat* [OR] WTW
3.2.2 Literature review and screening
A systematic selection of the publications retrieved from the literature search was carried out
by applying inclusion and exclusion criteria described in Table 3.3, to firstly the titles and then
abstracts of the retrieved papers.
A list of the keywords searched to exclude irrelevant publications is given in Appendix C.
Table 3.3 Inclusion and exclusion criteria used
Inclusion criteria Exclusion criteria
Articles that were published between 1990
and today.
Articles outside of these dates.
Articles that are published in English. Articles that are in other languages.
Articles concerning the formation of
disinfection by-products from the following
treatment processes:
O3 alone
O3 / H2O2
O3 / UV
UV / H2O2
O3 / UV / H2O2
UV / TiO2
UV / TiO2 / H2O2
UV / Cl2
UV / S2O8
Articles concerning the formation of
disinfection by-products from the following
treatment processes:
Ultraviolet and peracetic acid
Hydrogen peroxide and ferrous ion
(Fenton’s Reagent )
Ultraviolet and hydrogen peroxide and
ferrous ion (photo -Fenton )
Cavitation
E-beam
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Inclusion criteria Exclusion criteria
Articles concerning the formation or
occurrence of DBP following treatment with
the included processes.
Articles concerning the occurrence of DBP
following treatment with the excluded
processes.
Articles concerning the treatment of drinking
water.
Articles concerning the treatment of any
other products such as wastewater, food,
petroleum, solid waste or textiles.
Articles concerning the atmosphere, such as
ozone depletion, climate change or air
pollution.
Articles related to solar radiation or by-
products produced in the environment.
Articles concerning plants or plant health.
Articles pertaining to the removal of DBP from
drinking water subsequent to ozone or an
AOP.
Articles, reviews, evaluations and reports that
report original studies or provide reworking of
data (such as authoritative evaluations.
Retracted articles
Articles, reviews, evaluations and reports that
report original studies or provide reworking of
data (such as authoritative evaluations.
Articles that are based on opinion such as
editorials or commentaries.
Abstracts were used to exclude articles where the primary content was considered
inappropriate due to any of the following:
Experiments related to non-drinking water.
Data not including information about DBPs.
General discussions about DBPs but lacking specific DBP names.
3.2.3 Data extraction
The full publications for abstracts found to be relevant were retrieved and the relevant
information was extracted. The information of interest included the type of AOP used, the
experimental conditions and the doses applied, the type and concentration of DBPs detected
upon treatment and parameters describing the initial influent water quality. Other details found
to be pertinent to the interpretation of the results were also included.
Tables showing the numbers of papers excluded in each step of the assessment process, for
each AOP, are included in Appendix D.
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A tabulated summary of the reviewed literature (relating to AOPs and ozone) is provided in
Appendix E.
3.2.4 Ultraviolet and hydrogen peroxide
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.2. In summary, 14716 papers were initially identified, of which 25
remained after the exclusion process.
Findings
A summary of the DBP’s identified is given in Table 3.4. This AOP is the most commonly
used, therefore the number of DBPs referenced in research data is greater than for other
AOPs.
Table 3.4 List of DBPs found (UV / H2O2)
Name Name Name
2,4-dinitrophenol Bromodichloroacetamide Haloacetic acid
2-hydroxy-3-nitrobenzoic acid Bromodichloromethane Haloacetonitriles
2-hydroxy-5-nitrobenzoic acid Chloral hydrate Haloketone
2-methoxy-4,6-dinitrophenol Chlorate Halonitromethane
2-nitrohydroquinone Chlorite Methylglyoxal
3,5-dinitrosalicylic acid Chloroacetamide NDMA
4-hydroxy-3-nitrobenzoic acid Chloropicrin Nitrate
4-nitro-1,3-benzendiol Dibromoacetamide Oxalate
4-nitrobenzene-sulfonic acid Dibromoacetic acid Oxalic acid
4-nitrocatechol Dibromomethane Perchlorate
4-nitrophenol Dichloroacetamide Propanoic acid
4-nitrophtalic acid Dichloroacetic acid Tribromoacetic acid
5-nitrovanillin Dichloroacetonitrile Tribromomethane
Acetaldehyde Dichloronitromethane Trichloroacetamide
Acetate Dinoterb Trichloroacetonitrile FP
Acetic Acid Formaldehyde Trichloromethane
Aniline Formate Trichloronitromethane
Bromate
Trichloronitromethane FP
Bromoacetic acid Glyoxal Tricholoacetic acid
Bromochloroacetamide Haloacetamide FP
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3.2.5 Ozone and hydrogen peroxide
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.5. In summary, 13686 papers were initially identified, of which 12
remained after the exclusion process.
Findings
A summary of the DBP’s identified is given in Table 3.5.
Table 3.5 List of DBPs found (O3 / H2O2)
Names
Acetone
Aldehydes
Aniline
Bromate
Chlorobenzene
Glyoxal
Isopropyl alcohol
Nitrobenzene
Tertiary-butyl alcohol
Tertiary-butyl formate
3.2.6 Ozone and Ultraviolet
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.7. In summary, 11968 papers were initially identified, of which 10
remained after the exclusion process.
Findings
A total of 10 papers were evaluated. The main DBPs found from articles were common DBPs
found in previous tables, such as THM, HAA and aldehydes.
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3.2.7 Ozone and Ultraviolet and hydrogen peroxide
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.9. In summary, 11438 papers were initially identified, of which 5
remained after the exclusion process.
Findings
A summary of the DBP’s identified is given in Table 3.6.
Table 3.6 List of DBPs found (O3 / UV / H2O2)
Name
Acetaldehyde
Acetate
Aldehydes
Bromate
Carboxylic acids
Formaldehyde
Formate
Glyoxal
Haloacetic acids
Ketones
Methylglyoxal
Oxalate
Trihalomethane
3.2.8 Ultraviolet and hypochlorous acid
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.11. In summary, 10270 papers were initially identified, of which 7
remained after the exclusion process.
Findings
A summary of the DBP’s identified is given in Table 3.7.
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Table 3.7 List of DBPs found (UV and Hypochlorous acid)
Name
Bromate
Chloral hydrate
Chlorate
Chlorite
Chlorodiiodomethane
Chloroform
Chloropicrin
Dichloroacetonitrile
Dichloroiodomethane
HAA
Haloacetonitriles
Haloketone
Halonitromethane
Iodoform
p-chlorobenzoic acid (pCBA)
Perchlorate
THM
Trichloronitromethane
3.2.9 Ultraviolet and persulphate
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.13. In summary, 10048 papers were initially identified, of which 6
remained after the exclusion process.
Findings
A summary of the DBP’s identified is given in Table 3.8.
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Table 3.8 List of DBPs (UV and persulfate)
Name
Monobromoacetic acid
Dibromochloromethane
Dibromoacetonitrile
Dibromoacetic acid
Bromoform (TBM)
Bromochloroacetonitrile
Bromate (BrO3-)
3.2.10 Ultraviolet and titanium dioxide
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.15. In summary, 18598 papers were initially identified, of which 5
remained after the exclusion process.
Findings
A summary of the DBP’s identified is given in Table 3.9.
Table 3.9 DBPs found (UV and titanium dioxide)
Name
1,3-dihydroxybenzene
2,2-dihydroxy-4-methoxybenzophenone
2-hydroxybenzaldehyde
2-methylphenol
2-methylphenyl benzoate
4-methylphenol
Benzaldehyde
Benzoic acid
Benzyl alcohol
Phenols
THM
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3.2.11 Ultraviolet, titanium dioxide and hydrogen peroxide
Initial search
The outcome of the search and subsequent application of inclusion/exclusion criteria is
summarised in Table D.17. In summary, 6202 papers were initially identified, of which 4
remained after the exclusion process.
Findings
From the articles found relevant to this process, the only DBP found was phenol.
3.3 Outcome
A total of 78 DBPs were carried forward to Objective 4.
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4. Objective 4: Prioritisation and Toxicity Review
4.1 Prioritisation of DBPs
The systematic review of the literature outlined in Objective 3 identified 78 DBPs that may be
produced during the use of AOPs.
It is not possible or necessary to assess the toxicity of each of these DBPs within this project
as many of these DBPs have already been assessed by other organisations. Therefore, a
systematic prioritisation process was developed that excluded DBPs that have been
previously assessed by other organisations or in previous DWI reviews. This prioritisation
process is detailed in Figure 4.1.
An important feature of this process is that at each stage of the prioritisation process,
objective evidence is required to justify the exclusion of a DBP. Therefore, in the absence of
such evidence, a DBP cannot be excluded. This reduces the likelihood of prioritising DBPs for
which a large body of data already exists, ensuring the focus of this project is on those DBPs
that are formed by AOPs where the consequences of their formation in UK waters is largely
unknown.
Two DBPs formed by ozone alone were identified as ‘high priority’ and so these are
considered in Appendix G.
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Figure 4.1 Prioritisation of DBPs to identify those chemicals to be considered for
toxicological assessment
4.1.1 Prioritisation Activity 1: Has a WHO GDWQ or English and Welsh drinking water standard been established?
Of the 78 DBPs identified in the literature review, 19 were excluded as they were either:
Subject to World Health Organization (WHO) Guidelines for Drinking-water Quality
(GDWQ);
Reviewed by WHO, but it was determined that a guideline was not appropriate;
No
No
Yes
Yes
No
Yes
Disinfection By-Product (DBP)
Is the DBP formed under conditions that are of
relevance to UK treatment processes?
Exclude from further
assessment
Has the DBPs been quantified in drinking
water?
Exclude from further
assessment
Has DWI previously considered the DBP and
assessed the potential risk to human health?
Does TTC indicate that the DBP
is class I (low oral toxicity)?
Exclude from further
assessment Low priority grouping
No
Yes
Has a WHO GDWQ or English and Welsh
drinking water standard been established?
Exclude from further
assessment
Yes
No
Prioritisation
Activity 1
Prioritisation
Activity 2
Prioritisation
Activity 3
Prioritisation
Activity 4
Prioritisation
Activity 5
Expert review and exclusion of DBPs that are not considered to be of
relevance to this project
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Subject to a drinking water standard in England and Wales; or
Not subject to a drinking water standard per se, but subject to tiered guidance by DWI.
4.1.2 Prioritisation Activity 2: Has DWI previously considered the DBP and assessed the potential risk to human health?
Of the remaining DBPs, 22 had previously been considered within research funded by DWI.
However during such projects, a human health risk assessment was only carried out for 13 of
these DBPs. Therefore, these 13 were excluded from further evaluation.
4.1.3 Prioritisation Activity 3: Is the DBP formed under conditions that are of relevance to UK treatment processes?
Following further review of the literature from which the initial list of DBPs were identified,
24 DBPs were excluded from further evaluation as they were formed under conditions that are
not relevant to the UK.
4.1.4 Prioritisation Activity 4: If the DBPs were not detected in drinking water, does TTC indicate that the DBP is class I (low oral toxicity)?
Prioritisation Activity 4 was focussed on excluding those chemicals that had not been
detected in drinking water and that were not considered to be a concern, assessed using the
Threshold of Toxicological Concern (TTC) approach. In this process, each chemical that had
not been detected in drinking water was modelled in ToxTree, and if the model assigned it to
‘Class I’ (i.e. low oral toxicity) the DBP was excluded. However, no DBPs met this criteria, and
therefore, there were no exclusions on this basis.
4.1.5 Prioritisation Activity 5: Expert review and exclusion of DBPs that are not considered to be of relevance to this project
There are UKWIR/WRc Toxicity Datasheets available for 13 DBPs hence these were
excluded from the risk assessment (Table 4.1). However, a summary of the toxicity and fate
of each chemical in drinking water is provided in Section 4.3.11.
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Table 4.1 Thirteen DBPs excluded based on existing available toxicity data
Excluded DBP CAS RN UKWIR/WRc Toxicity Datasheet
2,4-Dinitrophenol,
4-Nitrophenol
51-28-5,
100-02-7 2,4-Dinitrophenol
Acetaldehyde 75-07-0 Acetaldehyde
Acetic acid,
Acetate
64-19-7,
71-50-1 Acetic acid
Acetone 67-64-1 Acetone
Aniline 62-53-3 Aniline
Benzoic acid 65-85-0 Benzoic acid
Bromochloroacetonitrile 83463-62-1 Bromochloroacetonitrile
Formate 71-47-6 Formic acid
Nitrobenzene 98-95-3 Nitrobenzene
Oxalate 144-62-7 Oxalic acid
Propanoic acid 79-09-4 Propanoic acid
4.1.6 Final list of DBPs
After applying the exclusion criteria specified in each prioritisation activity, nine DBPs were
identified (Table 4.2).
Table 4.2 Final list of DBPs for assessment in this project
DBP CAS Number
2-Hydroxy-5-nitrobenzoic acid 96-97-9
2-Methoxy-4,6-dinitrophenol 4097-63-6
2-Nitrohydroquinone 16090-33-8
3,5-Dinitrosalicylic acid 609-99-4
4-Hydroxy-3-nitrobenzoic acid 616-82-0
4-Nitrobenzene-sulfonic acid 138-42-1
4-Nitrocatechol 3316-09-4
4-Nitrophthalic acid 610-27-5
5-Nitrovanillin 6635-20-7
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4.2 Literature Search and Data Collation
4.2.1 Experimental toxicity data
Selection of information sources and search terms
Data on each DBP were collated from ToxPlanet, which covers over 100 databases and
authoritative bodies. When available, opinions from toxicology databases were primarily
considered, including the Hazardous Substances Databank (HSDB), or authoritative bodies
such as the US Agency for Toxic Substances and Disease Registry (ATSDR), the National
Toxicology Programme, US Environment Protection Agency (US EPA) etc.
In cases where data were scarce, primary literature, such as scientific publications, was
searched using Scopus and PubMed. The general search terms used for each of these
databases are provided in Appendix F. The search terms were adapted according to the
information source being interrogated. Synonyms and CAS numbers were also used where
appropriate.
Following preliminary searches, the titles and abstracts of the published data were screened
to select the relevant publications.
Data extraction
Retrieved literature was systematically and critically reviewed where possible, and relevant
data were extracted, including type of study, type and number of animals and toxicological
endpoint as well as the results presented.
4.2.2 Alternative approaches to deriving a Point of Departure (PoD)
As one of the exclusion criteria applied was the exclusion of DBPs with established drinking
water guidelines, it was anticipated that experimental toxicity data for the remaining DBPs
may be limited. Therefore, where no data were retrieved in the literature search, various
alternative methods were applied in order to determine a point of departure (PoD).
Identification of structural alerts and QSAR modelling
VEGA
Quantitative structure-activity relationship (QSAR) modelling software (VEGA) was used to
predict the toxicity of a chemical based on its chemical structure. The purpose of the software
is to relate the target chemical to results obtained for structurally similar chemicals, by
performing ‘trend analysis’ or ‘read across’. VEGA was also used to identify structural alerts
for sensitisation, mutagenicity, carcinogenicity and reproductive toxicity for each chemical.
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OECD QSAR toolbox
The OECD toolbox can be used to group chemicals based on their mechanism of action or
their structural similarity, to extract data for similar chemicals and fill data gaps using read
across, trend analysis or QSAR models. This approach is underpinned by a large database of
experimental studies. To undertake QSAR assessments, a step-wise approach of grouping
and refining potentially similar chemicals is used to identify those experimental studies that
could be used to predict the toxicity of the chemical under investigation.
Depending on the data available, repeat-dose predictions for PoDs such as a No Observed
(Adverse) Effect Level (NO(A)EL) or Lowest Observed (Adverse) Effect Level (LO(A)EL)
could be determined using the modelling software. However, due to the limited size of the
data sets behind some of the endpoints under investigation (oral repeat-dose and
reproductive/developmental toxicity); the predictions that have been developed may not be
robust. Therefore, caution should be applied in their use for the purposes of risk assessment.
Threshold of Toxicological Concern approach
The TTC approach is intended to be used as a screening tool for chemicals for which
substance-specific toxicity data are not available (European Food Safety and World Health,
2016; European Commission, 2009). The TTC values equating to low, moderate or high
toxicity (Cramer class I, II or III, respectively) have been established for substances of similar
chemical structure and likelihood of toxicity. These were based on extensive toxicity data,
from which NOAELs were derived. The 5th percentile NOAEL were divided by a factor of 100
to calculate the TTC value for each class. Substances, for which no toxicity data are available,
may be conservatively assessed by comparing the appropriate TTC value (based on the
chemical’s structure) with human exposure data. If the exposure is below the TTC value then
the likelihood of adverse health effects occurring is low.
The TTC values are as follows:
Cramer Class I
A TTC value of 30 µg/kg bw/day is derived for simple chemical structures that are known to
be efficiently metabolised to innocuous products; a low order of oral toxicity is anticipated.
Cramer Class II
A TTC value of 9 µg/kg bw/day is derived for intermediate structures that are less innocuous
than Class I but the chemical does not contain structures similar to those in Class III.
Cramer Class III
A TTC value of 1.5 µg/kg bw/day is derived for complex chemical structures that have no
indication of safety or may be metabolised to a reactive functional group; significant toxicity is
anticipated.
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The decision tree software, ToxTree, was used to generate Cramer Class data and also to
provide structural alerts that indicate genotoxic potential.
Structural alert for genotoxicity
For chemicals with structural alerts for genotoxicity, a TTC value of 0.0025 µg/kg bw/day was
derived. This value is considered to be ‘sufficiently protective’ for mutagenic compounds and
is associated with a 1 in 106 excess lifetime cancer risk (European Food Safety and World
Health, 2016; European Commission, 2009).
4.3 Toxicity Summary
4.3.1 2-Hydroxy-5-nitrobenzoic acid
Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
2-Hydroxy-5-nitrobenzoic acid has been classified as a ‘skin irritant, category 2; H315’ and
‘eye irritant, category 2; H319’ under European Globally Harmonised System (GHS)
Classification and Labelling regulations (PubChem, 2017g). No information on the study was
available. No sensitisation data are available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
The European Chemicals Agency (ECHA) registration document for 2-hydroxy-5-nitrobenzoic
acid reports a negative result in the Ames assay and in vitro mammalian chromosome
aberration test based on read across from a chemical of a similar structure (no further details
reported) (Vughs et al., 2016). A potential for DNA binding through the production of nitrenium
ions and reactive oxygen species (ROS) was also predicted and a structural alert for
genotoxic carcinogenicity was noted (no further data available). It was concluded that the
structure of 2-hydroxy-5-nitrobenzoic acid has ‘genotoxic potential’ but is not mutagenic
(Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
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VEGA
Based on the chemical structure, 2-hydroxy-5-nitrobenzoic acid is predicted to be mutagenic.
It is also predicted to be non-sensitising to the skin, carcinogenic and both a toxicant and non-
toxicant in developmental and reproductive activity models, although all these predictions are
deemed unreliable. The results of these findings are summarised in Table 4.3.
OECD toolbox
The OECD QSAR toolbox was applied to determine either a NO(A)EL or LO(A)EL for repeat
dose toxicity and for developmental and reproductive toxicity. Unfortunately, due to the limited
databases, the amount of data was insufficient to develop any predictions.
TTC
2-Hydroxy-5-nitrobenzoic acid is categorised as a Cramer Class III using ToxTree modelling
software. However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has
been identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.
Selection of PoD
No PoDs for 2-hydroxy-5-nitrobenzoic acid were available based on experimental data or
OECD toolbox predictions. Due to structural alerts for genotoxicity, the TTC value of
0.0025 µg/kg bw/day is considered the most appropriate for the risk characterisation.
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Table 4.3 Table 4.4 VEGA predictions for 2-hydroxy-5-nitrobenzoic acid
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules (experimental
Vs predicted)
Identified
structural
alerts
Sensitisation
(CAESAR)
Non-
sensitising Not optimal Strong Good Disagree -
Mutagenicity
(CAESAR, ISS) Mutagenic Appears reliable Strong Good Agree
SA27 nitro
aromatic
Mutagenicity
(KNN) Mutagenic Appears reliable Strong Good Agree -
Mutagenicity
(SarPy) Mutagenic Appears reliable Strong Good Agree SM52; SM189
Carcinogenicity
(CAESAR) Carcinogenic Not reliable
a Strong Not adequate Some disagree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Disagree
Carcinogenic
no: 33, 63, 64
Carcinogenicity
(ISS) Carcinogenic Not optimal Strong Not optimal Some disagree
SA27 nitro
aromatic
Carcinogenicity
(ISSCAN-CGX) Carcinogenic Not reliable Strong Not adequate Disagree
Carcinogenic
no: 21, 36, 42
Reproductive/developmental
toxicity (CAESAR) Toxicant Not reliable Moderate Not adequate Disagree -
Reproductive/developmental
toxicity (PG) Non-toxicant Not reliable Moderate Good Disagree -
a Model class assignment is uncertain
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4.3.2 2-Methoxy-4,6-dinitrophenol
Experimental toxicity data
Acute toxicity
Limited data are available. A lowest lethal dose (LDLo) of 40 000 µg/kg in the pigeon has
been reported following intraperitoneal exposure (RTECs, 2017a), however no further details
on the study were available.
Irritation and sensitisation
No data are available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
(Vughs et al., 2016) reviewed the toxicological properties of 2-methoxy-4,6-dinitrophenol
based on read across data. A potential for DNA binding was predicted, however details on the
structural alerts for this chemical were not available. In addition, a positive response in the
Ames assay, with and without metabolic activation was predicted (no further data available). It
was concluded that 2-methoxy-4,6-dinitrophenol is ‘potentially mutagenic’ in the Ames test;
however there were ‘insufficient data’ available to further assess genotoxic or carcinogenic
potential (Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 2-methoxy-4,6-dinitrophenol is predicted to be sensitising to
the skin. It is also predicted to be mutagenic, with two of the four models used being classed
as reliable. It is also predicted to be carcinogenic and as both a toxicant and non-toxicant in
developmental and reproductive activity models although these predictions were unreliable.
The results of these findings are summarised in Table 4.5.
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Table 4.5 VEGA predictions for 2-methoxy-4,6-dinitrophenol
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules (experimental
Vs predicted)
Identified
structural alerts
Sensitisation
(CAESAR) Sensitising Appears reliable Strong Good Agree -
Mutagenicity
(CAESAR) Mutagenic Appears reliable Strong Good Agree
SA27 nitro
aromatic
Mutagenicity
(ISS) Mutagenic Not optimal Strong Not adequate Disagree
SA27 nitro
aromatic
Mutagenicity
(KNN) Mutagenic Not reliable Strong Not adequate Some disagree -
Mutagenicity
(SarPy) Mutagenic Appears reliable Strong Good Agree SM95
Carcinogenicity
(CAESAR)
Non-
carcinogenic Not reliable
a Strong Not optimal Some disagree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenic no:
37,40, 63, 64
Carcinogenicity(ISS) Carcinogenic Not optimal Strong Not adequate Disagree SA27 nitro
aromatic
Carcinogenicity
(ISSCAN-CGX) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenic no:
42
Reproductive/developmental
toxicity(CAESAR) Toxic Not optimal Moderate Good Disagree -
Reproductive/developmental
toxicity (PG) Non-toxic Not reliable Strong Good Disagree -
a Predicted substance falls into a network that is populated by no compounds of the dataset.
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OECD toolbox
Using the OECD QSAR Toolbox, two NOELs and six LOELs were predicted for repeated
dose toxicity. These results are presented in Table 4.6. However, it should be noted that
these predictions, whilst falling within the prediction domain, and featuring acceptable
statistical measures of fit, are considered to be of low reliability due to the small size of the
dataset upon which they are based.
The experimental database for developmental and reproductive toxicity was too limited to
derive estimates for these endpoints.
Table 4.6 OECD Toolbox predictions for 2-methoxy-4,6-dinitrophenol
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NOEL
(rat or
mouse or
rabbit)
Ecosar None 4 Yes 0.942 123 000 µg/kg bw/day Low
LOEL
(rat or rabbit) Ecosar None 3 Yes 1.00 90 600 µg/kg bw/day Low
NOEL
(SD rat, oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Ecosar
Chemical elements
3 Yes 0.991 97 700 µg/kg bw/day Low
LOEL
(SD rat, oral
gavage or
diet)
Repeat dose
(HESS)
Repeat dose (HESS)
Ecosar
Chemical elements
3 Yes 1.00 90 700 µg/kg bw/day Low
LOEL
(SD rat, oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Ecosar
Chemical elements
3 Yes 1.00 94 300 µg/kg bw/day Low
LOEL
(SD rat, oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Structural similarity
(>70%)
3 Yes 1.00 94 300 µg/kg bw/day Low
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TTC
2-Methoxy-4,6-dinitrophenol is categorised as a Cramer Class III using ToxTree modelling
software. However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) was
identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.
Selection of PoD
No experimental PoDs were available for 2-methoxy-4,6-dinitrophenol. Based on the
modelled data, the following PoDs are proposed:
A NOEL of 97 700 µg/kg bw/day derived from the OECD toolbox,
A LOEL of 90 600 µg/kg bw/day derived from the OECD toolbox,
A TTC value of 0.0025 µg/kg bw/day.
The reliability of both the NOEL and LOEL values is considered to be ‘low’ due to the
limitation of the dataset behind their derivation so should be used with caution.
4.3.3 2-Nitrohydroquinone
Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
No data are available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
Vughs et al. (2016) reviewed the toxicological properties of 2-nitrohydroquinone based on
read across data. A potential for DNA binding through the production of nitrenium ions and
ROS was predicted and a structural alert for genotoxic carcinogenicity was noted (no further
data available). It was concluded that the structure of 2-nitrohydroquinone ‘suggests
genotoxic potential’ (Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
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Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 2-nitrohydroquinone is predicted to be sensitising to the
skin. It is also predicted to be mutagenic, with two of the four models used being reliable. It is
also predicted to be both a toxicant and non-toxicant in developmental and reproductive
activity models and carcinogenic, although the developmental and reproductive toxicity and
carcinogenicity predictions were unreliable. The results of these findings are summarised in
Table 4.7.
OECD toolbox
The OECD QSAR toolbox was applied to determine either a NO(A)EL or LO(A)EL for repeat
dose toxicity and for developmental and reproductive toxicity. Unfortunately, due to the limited
databases, the amount of data was insufficient to develop any predictions.
TTC
2-nitrohydroquinone is categorised as a Cramer Class III using ToxTree modelling software.
However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has been
identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.
Selection of PoD:
As no PoDs for 2-nitrohydroquinone were available based on experimental data or OECD
toolbox predictions, and structural alerts for genotoxicity have been reported, the TTC value
0.0025 µg/kg bw/day is considered the most appropriate PoD for risk characterisation.
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Table 4.7 VEGA predictions for 2-nitrohydroquinone
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules (experimental
Vs predicted)
Identified
structural alerts
Sensitisation
(CAESAR) Sensitising
Appears
reliable Strong Good Agree -
Mutagenicity
(CAESAR) Mutagenic
Appears
reliable Strong Good Agree
SA27 nitro
aromatic
Mutagenicity
(ISS) Mutagenic Not optimal Strong Not adequate Disagree
SA27 nitro
aromatic
Mutagenicity
(KNN) Mutagenic Not reliable Strong Not adequate Some disagree -
Mutagenicity
(SarPy) Mutagenic
Appears
reliable Strong Good Agree SM95
Carcinogenicity
(CAESAR)
Non-
carcinogenic Not reliable
a Strong Not optimal Some disagree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenicity no:
37, 40, 63, 64
Carcinogenicity (ISS) Carcinogenic Not optimal Strong Not adequate Disagree SA27 nitro
aromatic
Carcinogenicity
(ISSCAN-CGX) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenicity no:
42
Reproductive/developmental
toxicity (CAESAR) Toxicant Not optimal Moderate Good Disagree -
Reproductive/developmental
toxicity (PG) Non-toxicant Not reliable Strong Good Disagree -
a Predicted substance falls into a network that is populated by no compounds of the dataset.
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4.3.4 3,5-Dinitrosalicylic acid
Experimental toxicity data
Acute toxicity
Limited data are available. Oral median lethal doses (LD50) of 270 000 µg/kg bw (mouse) and
860 000 µg/kg bw (rat) have been reported (RTECs, 2017b), however no further details on
these studies are available.
Irritation and sensitisation
3,5-Dinitrosalicylic acid has been classified as a ‘skin irritant, category 2; H315’ and ‘eye
irritant, category 2; H319’ under European GHS Classification and Labelling regulations
(PubChem, 2017a). No information on the study was available. No sensitisation data are
available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
Vughs et al. (2016) reviewed the toxicological properties of 3,5-dinitrosalicylic acid based on
read across data. A potential for DNA binding through the production of nitrenium ions and
was predicted and a structural alert for genotoxic carcinogenicity was noted (no further data
available). It was concluded that the structure of 3,5-dinitrosalicylic acid ‘suggests genotoxic
potential’ (Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 3,5-dinitrosalicylic acid is predicted to be sensitising to the
skin and carcinogenic. Three of the four models predict it to be mutagenic; however, only one
of these predictions (ISS) is reliable. It is also predicted as both a toxicant and non-toxicant in
developmental and reproductive activity models; however, these predictions were unreliable.
The results of these findings are summarised in Table 4.8.
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Table 4.8 VEGA predictions for 3,5-dinitrosalicylic acid
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules
(experimental Vs
predicted)
Identified
structural alerts
Sensitisation
(CAESAR) Sensitising Appears reliable Strong Good Agree -
Mutagenicity
(CAESAR) Mutagenic Not reliable Strong Not adequate Disagree
SA27 nitro
aromatic
Mutagenicity
(ISS) Mutagenic Appears reliable Strong Good Agree
SA27 nitro
aromatic
Mutagenicity
(KNN) Mutagenic Not reliable Strong Not adequate Some disagree -
Mutagenicity
(SarPy)
Non-
mutagenic Not optimal Strong Not optimal Some disagree -
Carcinogenicity
(CAESAR) Carcinogenic Appears reliable Strong Good Agree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Appears reliable Strong Good Agree
Carcinogenicity
no: 64
Carcinogenicity
(ISS) Carcinogenic Appears reliable Strong Good Agree
SA27 nitro
aromatic
Carcinogenicity
(ISSCAN-CGX) Carcinogenic Appears reliable Strong Good Agree
Carcinogenicity
no: 42
Reproductive/developmental
toxicity (CAESAR) Toxic Not reliable Moderate Not adequate Disagree -
Reproductive/developmental
toxicity (PG) Non-toxic Not reliable Moderate Good Disagree -
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OECD toolbox
Using the OECD QSAR Toolbox, one NOEL and two LOELs were predicted for repeated
dose toxicity. These results are presented in Table 4.9. However, it should be noted that
these predictions, whilst falling within the prediction domain, and featuring acceptable
statistical measures of fit, are considered to be of low reliability due to the small size of the
dataset upon which they are based.
The experimental database for developmental and reproductive toxicity was too limited to
derive estimates for these endpoints.
Table 4.9 OECD Toolbox predictions for 3,5-dinitrosalicylic acid
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NOEL
(SD rat,
oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements
Structural similarity
(>60%)
3 Yes 0.991 31 800 µg/kg bw/day Low
LOEL
(rat, oral
gavage or
diet)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements 5 Yes 0.927 35 500 µg/kg bw/day Low
LOEL
(SD rat,
oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements
Structural similarity
(>60%)
3 Yes 1.00 29 600 µg/kg bw/day Low
TTC
3,5-Dinitrosalicylic acid is categorised as a Cramer Class III using ToxTree modelling
software. However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has
been identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.
Selection of PoD
No experimental toxicity PoDs for 3,5-dinitrosalicylic acid were available. Based on the
modelled data obtained, the following PoDs are proposed:
A NOEL of 31 800 µg/kg bw/day derived from the OECD toolbox,
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A LOEL of 29 600 µg/kg bw/day derived from the OECD toolbox,
A TTC value of A TTC value of 0.0025 µg/kg bw/day.
The reliability of both the NOEL and LOEL values is considered to be ‘low’ due to the
limitation of the dataset behind their derivation so should be used with caution.
4.3.5 4-Hydroxy-3-nitrobenzoic acid
Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
4-Hydroxy-3-nitrobenzoic acid has been classified as a ‘skin irritant, category 2; H315’ and
‘eye irritant, category 2; H319’ under European GHS Classification and Labelling regulations
(PubChem, 2017c). No information on the study was available. No sensitisation data are
available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
Vughs et al. (2016) reviewed the toxicological properties of 4-hydroxy-3-nitrobenzoic acid
based on read across data. A potential for DNA binding through the production of nitrenium
ions and ROS was predicted and a structural alert for genotoxic carcinogenicity was noted (no
further data available). It was concluded that the structure of
4-hydroxy-3-nitrobenzoic acid ‘suggests genotoxic potential’ (Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 4-hydroxy-3-nitrobenzoic acid is predicted to be mutagenic.
It is also predicted to be non-sensitising to the skin, carcinogenic and as both a toxicant and
non-toxicant in developmental and reproductive activity models, although these predictions
were unreliable. The results of these findings are summarised in Table 4.10.
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OECD toolbox
The OECD QSAR toolbox was applied to determine either a NO(A)EL or LO(A)EL for repeat
dose toxicity and for developmental and reproductive toxicity. Unfortunately, due to the limited
databases, the amount of data was insufficient to develop any predictions.
TTC
4-hydroxy-3-nitrobenzoic acid is categorised as a Cramer Class III using ToxTree modelling
software. However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has
been identified using ToxTree modelling software. Therefore, a TTC value of
0.0025 µg/kg bw/day is appropriate.
Selection of PoD
No PoDs for 2-hydroxy-5-nitrobenzoic acid were available based on experimental data or
OECD toolbox predictions. Due to structural alerts for genotoxicity, the TTC value of
0.0025 µg/kg bw/day is considered the most appropriate for the risk characterisation.
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Table 4.10 VEGA predictions for 4-hydroxy-3-nitrobenzoic acid
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules (experimental
Vs predicted)
Identified
structural alerts
Sensitisation
(CAESAR)
Non-
sensitising Not optimal Strong Good Disagree -
Mutagenicity
(CAESAR, ISS) Mutagenic Appears reliable Strong Good Agree
SA27 nitro
aromatic
Mutagenicity
(KNN) Mutagenic Appears reliable Strong Good Agree -
Mutagenicity
(SarPy) Mutagenic Appears reliable Strong Good Agree SM52
Carcinogenicity
(CAESAR) Carcinogen Not reliable
a Strong Not adequate Some disagree -
Carcinogenicity
(IRFMN/Antares) Carcinogen Not optimal Strong Not optimal Disagree
Carcinogenicity no:
33, 37, 63, 64
Carcinogenicity
(ISS) Carcinogen Not optimal Strong Not optimal Some disagree
SA27 nitro
aromatic
Carcinogenicity
(ISSCAN-CGX) Carcinogen Not reliable Strong Not adequate Disagree
Carcinogenicity no:
36, 42
Reproductive/developmental
toxicity(CAESAR) Toxic Not reliable Moderate Not adequate Disagree -
Reproductive/developmental
toxicity (PG) Non-toxic Not reliable Moderate Good Disagree -
a Model class assignment is uncertain
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4.3.6 4-Nitrobenzene-sulfonic acid
Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
4-Nitrobenzene-sulfonic acid has been classified as a ‘skin irritant, category 1, H314’ and ‘eye
irritant, category 1, H318’ under European GHS Classification and Labelling regulations
(PubChem, 2017d). No information on the study was available. No sensitisation data are
available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
Measured genotoxicity data are limited to a negative response in an Ames assay (with and
without metabolic activation (Kawai et al., 1987). No further details on this study were
available.
Vughs et al. (2016) reviewed the toxicological properties of 4-nitrobenzene-sulfonic acid
based on read across data. No structural alerts for mutagenicity of carcinogenicity were found
hence it was concluded that 4-nitrobenzene-sulfonic acid does not indicate any signs of
mutagenicity or genotoxicity (Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 4-nitrobenzene-sulfonic acid is predicted to be non-
sensitising to the skin although the reliability of the prediction was not optimal. It is also
predicted to be non-mutagenic, with two of the four models used being reliable. The models
for carcinogenicity have equivocal results and all predictions were either not reliable or not
optimal. It is also predicted as a non-toxicant in developmental and reproductive activity
models but again the models were not reliable. The results of these findings are summarised
in Table 4.11.
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Table 4.11 VEGA predictions for 4-nitrobenzene-sulfonic acid
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules (experimental
Vs predicted)
Identified
structural alerts
Sensitisation (CAESAR) Non-sensitising Not optimala Strong Good Agree -
Mutagenicity (CAESAR) Non- Mutagenic Appears
reliableb
Strong Good Agree -
Mutagenicity (ISS) Non-mutagenic Not reliable Strong Not adequate Some disagree -
Mutagenicity (KNN) Non-mutagenic Appears
reliableb
Strong Good Agree -
Mutagenicity (SarPy) Mutagenic Not reliableb Strong Not adequate Disagree -
Carcinogenicity (CAESAR) Non-carcinogenic Not reliablec
Strong Not optimal Some disagree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenicity
no: 63, 64
Carcinogenicity (ISS) Non-carcinogenic Not reliable Strong Not adequate Some disagree -
Carcinogenicity (ISSCAN-CGX) Carcinogenic Not reliable Strong Not adequate Disagree Carcinogenicity
no: 42
Reproductive/developmental
toxicity(CAESAR) Non-toxic Not reliable
c Moderate Good Disagree -
Reproductive/developmental
toxicity (PG) Non-toxic Not reliable
d Moderate Not optimal Disagree -
a Some atom centred fragments of the compound have not been found in compounds of the dataset or are rare fragments (1 inadequate fragment found).
b Experimental value is non-mutagenic.
c A prominent number of atom centred fragments of the compound have not been found in the compounds of the data set or are rare fragments (1 unknown
fragment and 1 infrequent fragment found). d
Some number of atom centred fragments of the compound have not been found in the compounds of the data set or are rare fragments (1 infrequent
fragment found).
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OECD toolbox
The database of experimental data for chemicals that are similar to 4-nitrobenzene-sulfonic
acid, and thus its appropriateness for developing predictions, is extremely limited. However,
the OECD Toolbox predicted a NOEL and a LOEL (Table 4.12). Although these predictions
meet various criteria for, they are considered to be of low reliability due to the small size of the
dataset upon which they are based.
Due to this small dataset, it has not been possible to develop any predictions for reproductive
endpoints.
Table 4.12 OECD Toolbox predictions for 4-nitrobenzene-sulfonic acid
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LOEL
(SD rat,
oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements 4 Yes 0.854 871 000 µg/kg bw/day Low
NOEL
(SD rat,
oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements 5 Yes 0.938 876 000 µg/kg bw/day Low
TTC
4-hydroxy-3-nitrobenzoic acid is categorised as a Cramer Class III, and no structural alerts for
genotoxicity have been identified using ToxTree modelling software. Therefore, a TTC value
of 1.5 µg/kg bw/day is appropriate.
Selection of PoD
No experimental toxicity PoDs for 4-nitrobenzene-sulfonic acid were available. Based on the
modelled data obtained, the following PoDs are proposed:
A NOEL of 876 000 µg/kg bw/day derived from the OECD toolbox,
A LOEL of 871 000 µg/kg bw/day derived from the OECD toolbox,
A TTC value of 1.5 µg/kg bw/day.
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The reliability of both the NOEL and LOEL values is considered to be ‘low’ due to the
limitation of the dataset behind their derivation so should be used with caution.
4.3.7 4-Nitrocatechol
Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
4-Nitrocatechol has been classified as a ‘skin irritant, category 2; H315’ and ‘eye irritant,
category 2; H319’ under European GHS Classification and Labelling regulations (PubChem,
2017e). No information on the study was available. No sensitisation data are available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
Vughs et al. (2016) reviewed the toxicological properties of 4-nitrocatechol based on read
across data. A potential for DNA binding was predicted, however details on the structural
alerts for this chemical were not available. It was concluded that 4-nitrocatechol is ‘probably
not’ mutagenic in an Ames assay; however, there were insufficient data available to assess
further genotoxic or carcinogenic potential (Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 4-nitrocatechol is predicted to be sensitising to the skin and
carcinogenic. It is also predicted to be mutagenic and both a toxicant and non-toxicant in
developmental and reproductive activity models although these predictions were unreliable.
The results of these findings are summarised in Table 4.13.
OECD toolbox
Using the OECD QSAR Toolbox two NOELs were predicted for repeated dose toxicity. These
results are presented in Table 4.14. However, it should be noted that these predictions, whilst
statistically falling within the prediction domain, and featuring acceptable statistical measures
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of fit, are considered to be of low reliability due to the small size of the dataset upon which
they are based.
The experimental database for developmental and reproductive toxicity was too limited to
derive estimates for these endpoints.
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Table 4.13 VEGA modelling software toxicity predictions for 4-nitrocatechol
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules (experimental
Vs predicted)
Identified
structural alerts
Sensitisation
(CAESAR) Sensitising Appears reliable Strong Good Agree -
Mutagenicity
(CAESAR, ISS) Mutagenic Not optimal Strong Not optimal Some disagree
SA27 nitro
aromatic
Mutagenicity
(KNN) Mutagenic Not reliable Strong Not adequate Some disagree -
Mutagenicity
(SarPy)
Non-
mutagenic Not reliable Strong Not adequate Disagree -
Carcinogenicity
(CAESAR) Carcinogenic Appears reliable Strong Good Agree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Appears reliable Strong Good Agree
Carcinogenicity
no: 63, 64
Carcinogenicity
(ISS) Carcinogenic Not optimal Strong Not optimal Some disagree
SA27 nitro
aromatic
Carcinogenicity
(ISSCAN-CGX) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenicity
no: 42
Reproductive/developmental
toxicity (CAESAR) Toxic Not reliable Moderate Not adequate Disagree -
Reproductive/developmental
toxicity (PG) Non-toxic Not reliable Moderate Not optimal Disagree -
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Table 4.14 OECD Toolbox predictions for 4-nitrocatechol
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NOEL
(F344 or SD
rat, oral
gavage)
Ecosar
Ecosar
Chemical elements
Structural similarity (>40%)
3 Yes 0.446 736 000 µg/kg bw/day Low
NOEL
(F344 rat,
oral gavage
or diet)
Ecosar
Ecosar
Chemical elements
Organic functional groups
6 Yes 0.826 840 000 µg/kg bw/day Low
TTC
4-Nitrocatechol is categorised as a Cramer Class III using ToxTree modelling software.
However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has been
identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.
Selection of PoD
No experimental toxicity PoDs for 4-nitrocatechol were available. Based on the modelled data
obtained, the following PoDs are proposed:
A NOEL of 736 000 µg/kg bw/day derived from the OECD toolbox,
A TTC value of 0.0025 µg/kg bw/day.
4.3.8 4-Nitrophthalic acid
Experimental toxicity data
Acute toxicity
No data are available.
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Irritation and sensitisation
4-Nitrophthalic acid has been classified as a ‘skin irritant, category 2; H315’ and ‘eye irritant,
category 2; H319’ under European GHS Classification and Labelling regulations (PubChem,
2017f). No information on the study was available. No sensitisation data are available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
Vughs et al. (2016) reviewed the toxicological properties of 4-nitrophthalic acid based on read
across data. A potential for DNA binding through the production of nitrenium ions and ROS
was predicted and a structural alert for non-genotoxic carcinogenicity was noted (no further
data available). It was concluded that the structure of 4-nitrophthalic acid suggests genotoxic
potential (Vughs et al., 2016).
Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 4-nitrophthalic acid is predicted to be sensitising to the skin
and mutagenic. It is also predicted to be carcinogenic and as both a toxicant and non-toxicant
in developmental and reproductive activity models although these predictions are unreliable.
The results of these findings are summarised in Table 4.15.
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Table 4.15 VEGA predictions for 4-nitrophthalic acid
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar
molecules
Concordance for
similar molecules
(experimental Vs
predicted)
Identified structural
alerts
Sensitisation
(CAESAR) Sensitising
Appears
reliable Moderate Good Agree -
Mutagenicity
(CAESAR, ISS) Mutagenic
Appears
reliable Strong Good Agree SA27 nitro aromatic
Mutagenicity
(KNN) Mutagenic
Appears
reliable Strong Good Agree -
Mutagenicity
(SarPy) Mutagenic
Appears
reliable Strong Good Agree
SM19, SM52, SM72,
SM104, SM118
Carcinogenicity
(CAESAR)
Non-
carcinogenic Not reliable
a Strong Not adequate Disagree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenicity no: 31,
32, 33, 63, 64
Carcinogenicity
(ISS) Carcinogenic Not optimal Strong Not optimal Some disagree
SA27 nitro aromatic,
SA42 phthalate
diesters and
monoesters
Carcinogenicity
(ISSCAN-CGX) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenicity no: 36,
41, 42
Reproductive/developmental
toxicity (CAESAR) Toxic
Appears
reliable Moderate Good Agree -
Reproductive/developmental
toxicity (PG) Non-toxic Not reliable Moderate Good Disagree -
a Predicted value falls into a network that is populated by no compounds of the dataset.
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OECD toolbox
The OECD QSAR toolbox was applied to determine either a NO(A)EL or LO(A)EL for repeat
dose toxicity and for developmental and reproductive toxicity. Unfortunately, due to the limited
databases, the amount of data was insufficient to develop any predictions.
TTC
4-nitrophthalic acid is categorised as a Cramer Class III using ToxTree modelling software.
However structural alerts for genotoxic (QSA27 nitro aromatic) and non-genotoxic (QSA42
phthalate diesters and monoesters) carcinogenicity have been identified. Therefore, a TTC
value of 0.0025 µg/kg bw/day is appropriate.
Selection of PoD
No PoDs for 2-hydroxy-5-nitrobenzoic acid were available based on experimental data or
OECD toolbox predictions. Due to structural alerts for genotoxicity, the TTC value of 0.0025
µg/kg bw/day is considered the most appropriate for the risk characterisation.
4.3.9 5-Nitrovanillin
Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
5-Nitrovanillin has been classified as a ‘skin irritant, category 2; H315’ and ‘eye irritant,
category 2; H319’ under European GHS Classification and Labelling regulations (PubChem,
2017b). No information on the study was available. No sensitisation data were located.
Chronic toxicity
No data are available.
Mutagenicity/genotoxicity
Vughs et al. (2016) reviewed the toxicological properties of 5-nitrovanillin based on an ECHA
registration document formed from read-across predictions, whereby negative results in the
Ames assay and an in vitro mammalian chromosome aberration test were noted. A potential
for DNA binding through the production of nitrenium ions and ROS was also predicted and a
structural alert for genotoxic carcinogenicity was noted (no further data available). It was
concluded that the structure of 5-nitrovanillin has ‘genotoxic potential’ but is not mutagenic
(Vughs et al., 2016).
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Reproductive/developmental toxicity
No data are available.
Alternative approaches to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 5-nitrovanillin is predicted to be non-sensitising to the skin
and mutagenic. It is also predicted to be carcinogenic and as both a toxicant and non-toxicant
in developmental and reproductive activity models, although these predictions are unreliable.
The results of these findings are summarised in Table 4.17.
OECD toolbox
Using the OECD QSAR Toolbox, one LOEL and one NOEL were predicted for repeated dose
toxicity. These results are presented in Table 4.16. However, it should be noted that these
predictions, whilst statistically falling within the prediction domain, and featuring acceptable
statistical measures of fit, are considered to be of low reliability due to the small size of the
dataset upon which they are based.
The experimental database for developmental and reproductive toxicity was too limited to
derive estimates for these endpoints.
Table 4.16 OECD Toolbox predictions for 5-nitrovanillin
En
dp
oin
t
Pro
file
Su
b-c
ate
go
ris
ati
on
pro
file
s
Nu
mb
er
of
ca
teg
ory
me
mb
ers
In d
om
ain
?
R2
sta
tis
tic
Res
ult
Reli
ab
ilit
y
LOEL
(F344 or SD
rat, oral
gavage or
diet)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements 5 Yes 0.927 166 000 µg/kg bw/day Low
NOEL
(F344 or SD
rat, oral
gavage)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements 5 Yes 0.871 279 000 µg/kg bw/day Low
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TTC
4-Nitrophthalic acid is categorised as a Cramer Class III using ToxTree modelling software.
However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has been
identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.
Selection of PoD
No experimental toxicity PoDs for 5-nitrovanillin were available. Based on the modelled data
obtained, the following PoDs are proposed:
A NOEL of 279 000 µg/kg bw/day derived from the OECD toolbox,
ALOEL of 166 000 µg/kg bw/day derived from the OECD toolbox,
A TTC value of 0.0025 µg/kg bw/day.
The reliability of both the NOEL and LOEL values is considered to be ‘low’ due to the
limitation of the dataset behind their derivation so should be used with caution.
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Table 4.17 VEGA predictions for 5-nitrovanillin
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for
similar molecules
(experimental Vs
predicted)
Identified structural
alerts
Sensitisation (CAESAR) Non-
sensitising
Appears
reliable Strong Good Agree -
Mutagenicity (CAESAR) Mutagenic Appears
reliable Strong Good Agree SA27 nitro aromatic
Mutagenicity (ISS) Mutagenic Not reliablea Strong Not adequate Disagree
SA11 simple aldehyde,
SA27 nitro aromatic
Mutagenicity (KNN) Non-
mutagenic Not optimal Strong Good Some disagree -
Mutagenicity (SarPy) Mutagenic Appears
reliable Strong Good Agree SM52
Carcinogenicity (CAESAR) Non-
carcinogenic Not optimal
a Strong Good Disagree -
Carcinogenicity
(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Some disagree
Carcinogenicity no: 33, 37,
63, 64
Carcinogenicity (ISS) Carcinogenic Not reliable Strong Not adequate Disagree SA11 simple aldehyde,
SA27 nitro aromatic
Carcinogenicity (ISSCAN-CGX) Carcinogenic Not reliablea Strong Not adequate Disagree Carcinogenicity no: 36, 42
Reproductive/developmental
toxicity (CAESAR) Toxic Not reliable
a Moderate Not adequate Disagree -
Reproductive/developmental
toxicity (PG) Non-toxic Not reliable
a Moderate Good Disagree -
aSome atom centred fragments of the compound have not been found in the compounds of the dataset or are rare fragments (1 infrequent fragment found).
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4.3.10 Summary
A PoD for all DBPs has been determined using a variety of methods, a summary of which is
presented as Table 4.18. Limited experimental data were available for each DBP and so
alternative approached to derive a PoD using modelled toxicity data has been applied. Where
possible, modelled NOELs and LOELs have been derived and TTC values have been
determined based on each DBP’s chemical structural alerts. Due to the low reliability of the
modelling due to the limited databases, the TTC approach was recommended to be
precautionary.
Table 4.18 Summary of PoD for each DBP
DBP PoD (µg/kg bw/day)
TTC (µg/kg bw/day) NOEL LOEL
2-Hydroxy-5-nitrobenzoic acid - - 0.0025
2-Methoxy-4,6-dinitrophenol 97 700 90 600 0.0025
2-Nitrohydroquinone - - 0.0025
3,5-Dinitrosalicylic acid 31 800 29 600 0.0025
4-Hydroxy-3-nitrobenzoic acid - - 0.0025
4-Nitrobenzene-sulfonic acid 876 000 871 000 1.5
4-Nitrocatechol 736 000 - 0.0025
4-Nitrophthalic acid - - 0.0025
5-Nitrovanillin 279 000 166 000 0.0025
4.3.11 Summaries of other DBPs for which Toxicity Datasheets exist
The following chemicals were also identified as DBPs as part of this project’s objective (see
Section 4.1.5 for further details). As toxicity data for these chemicals was already collated and
available to DWI through the UKWIR/WRc Toxicity Datasheet subscription service, it was
agreed that a comprehensive risk assessment for these chemicals was not required.
However, a summary of each chemical’s toxicity profile and, where appropriate, a
health-based guidance value (HBGV) is provided.
2,4-Dinitrophenol and 4-nitrophenol
2,4-Dinitrophenol (and the structurally similar chemical 4-nitrophenol) is highly water soluble.
It causes moderate to high acute oral toxicity in experimental animals, and anticipated signs
of toxicity following short-term human exposure include gastrointestinal irritation, muscle
cramps and increased basal metabolism. Chronic human exposure is associated with
irreversible cataracts. Both 2,4-dintrophenol and 4-nitrophenol are skin irritants and
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4-nitrophenol has been classed as a potential skin sensitiser. 2,4-Dinitrophenol has a
cytotoxic mode of action, and genotoxic studies have provided equivocal results.
The US Environmental Protection Agency (EPA) reviewed over 100 cases of cataracts arising
in patients using 2,4-dinitrophenol therapeutically and determined a LOAEL of
2 mg/kg bw/day. The US EPA applied an uncertainty factor (UF) of 1000 (10 to account for
intra-species variation, 10 to account for the use of subchronic rather than chronic data, and
10 for the use of a LOAEL) to the LOAEL to derive an oral Reference Dose (RfD) of
0.002 mg/kg bw/day (2 µg/kg bw/day).
Acetaldehyde
Acetaldehyde is a volatile chemical that is highly water soluble. It causes low acute oral
toxicity in experimental animals and anticipated signs of toxicity following short-term human
exposure include central nervous system depression, reduced respiratory rate and pulmonary
oedema. Acetaldehyde has been classed as an irritant (in particular to the respiratory tract
following inhalation); however, there is no evidence to suggest that it is a skin sensitiser. The
overall data indicate the acetaldehyde is genotoxic.
As limited chronic toxicity data for acetaldehyde are available, the European Scientific
Committee for Food (SCF) derived a Tolerable Daily Intake (TDI) of 0.1 mg/kg bw/day
(100 µg/kg bw/day) based on results from a 2-year oral rat study and a 3-generation oral rat
study which both used methaldehyde (formaldehyde) as the test substance (no further details
available).
Acetic acid and acetate
Acetic acid (and the conjugate base, acetate) is a volatile chemical that is highly water
soluble. It causes low acute oral toxicity in experimental animals and anticipated signs
following short-term human exposure include corrosion and irritation of the gastro-intestinal
tract and reduced pulmonary function. Chronic human oral exposure is associated with kidney
damage and liver cirrhosis. Acetic acid is classified as a skin irritant. Skin sensitisation is rare,
but some cases have been reported. Overall, there is some evidence that it is genotoxic in
vivo.
Due to the widespread use of acetic acid in food, and the endogenous occurrence in
mammalian metabolism, the Joint Food and Agriculture/World Health Organization (WHO)
Expert Committee on Food Additives (JECFA) and the European Food Safety Authority
(EFSA), concluded that it was not necessary to derive a HBGV.
Acetone
Acetone is a volatile chemical that is highly water soluble. It causes low acute oral toxicity in
experimental animals and anticipated signs of toxicity following short-term human exposure
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include gastro-intestinal irritation, sedation, headache, ataxia, hypothermia and convulsions.
Chronic human exposure is associated with metabolic acidosis, ketosis and eventual liver and
kidney damage. Acetone has been classed as an eye irritant. There is no evidence to suggest
that it is a skin sensitiser. The overall data indicate the acetone is not genotoxic.
In a 13-week toxicity study, F344/N rats were administered acetone via drinking water at
concentrations of 0, 2500, 5000, 10 000, 20 000 or 50 000 mg/l (average doses were reported
to be 0, 200, 400, 900, 1700 and 3400 mg/kg bw/day for males, and 0, 300, 600, 1200, 1600
and 3100 mg/kg bw/day for females, respectively). A NOAEL of 900 mg/kg bw/day was
identified based on nephropathy. The US EPA applied an UF of 1000 (10 to account for intra-
species variation, 10 to account for inter-species variation and 10 to account for a limited
database) to this NOAEL to derive an oral RfD of 0.9 mg/kg bw/day (900 µg/kg bw/day).
Aniline
Aniline is a semi-volatile chemical that is highly water soluble. It causes low to moderate acute
oral toxicity in experimental animals and anticipated signs following short-term human
exposure include methaemoglobinaemia and haemolysis. Chronic human oral exposure is
associated with anaemia, weight loss, hypoxia and cutaneous lesions. Aniline has been
classed as a skin and eye irritant and a skin sensitiser. The overall genotoxicity data for
acetone are equivocal.
In a 104-week dietary carcinogenicity study, F344 rats were administered aniline
hydrochloride at aniline-equivalent doses of 0, 7, 22 or 72 mg/kg bw/day. A LOAEL of 7 mg/kg
bw/day was identified based on an increased incidence of chronic capsulitis (inflammation of
ligaments) in females at all dose levels when compared with controls. By applying an UF of
1000 (10 to account for intra-species variation, 10 to account for inter-species variation and
10 to account for the use of a LOAEL) to the LOAEL, a TDI of 0.007 mg/kg bw/day can be
derived (7 µg/kg bw/day).
Benzoic acid
Benzoic acid is a non-volatile chemical that is highly water soluble. It causes low acute oral
toxicity in experimental animals, and anticipated signs following short-term human exposure
include loss of balance and vision, stomach pains and gastro-intestinal irritation. It is also
reported to provoke recurrences of asthmas and skin conditions in individuals that are prone
to the conditions. No chronic human exposure data are available. Benzoic acid has been
classed as a skin and eye irritant. There is no evidence to suggest that it is a skin sensitiser.
Whilst no in vivo genotoxicity data are available, the overall in vitro data indicate that benzoic
acid is not genotoxic.
In a 16-week dietary toxicity study, rats were administered benzoic acid at concentrations of
0, 5000 or 10 000 mg/kg diet (equivalent to 0, 250 and 500 mg/kg bw/day, respectively). As
no significant effects were reported throughout the study, a NOAEL of 500 mg/kg bw/day
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(highest dose tested) was identified. The EFSA applied an UFof 100 (10 to account for intra-
species variation, 10 to account for inter-species variation) to this NOAEL to derive an
Acceptable Daily Intake (ADI) of 5 mg/kg bw/day (5000 µg/kg bw/day).
Bromochloroacetonitrile
Bromochloroacetonitrile is a semi-volatile chemical that is highly water soluble. No acute
toxicity data are available and chronic oral exposure data are limited to a single-dose mouse
comparative study, whereby an increased incidence in lung tumours were observed when
compared to mice administered other haloacteonitriles (no further details are available).
Bromochloroacetonitrile has been classed as an eye irritant. There are no data to suggest it is
a skin sensitiser. Whilst limited in vivo genotoxicity data are available, the overall in vitro data
indicate that benzoic acid is genotoxic.
In a developmental oral (gavage) toxicity study, bromochloroacetonitrile was administered to
pregnant Long-Evans rats at dose levels of 0, 5, 25, 45 or 65 mg/kg bw/day on days 6 to 18 of
gestation. A developmental LOAEL of 5 mg/kg/day was identified based on increased
incidences of cardiovascular foetal abnormalities. However, it should be noted that caution
must be applied to the interpretation of these results, as tricaprylin was used as a vehicle to
administer bromochloroacetonitrile, and tricaprylin is also associated with embryotoxic and
developmental effects. By applying an UFof 1000 (10 to account for intra-species variation, 10
to account for inter-species variation and 10 for the use of a LOAEL and the limited database)
to the LOAEL, a TDI of 0.005 mg/kg bw/day is derived (5 µg/kg bw/day).
Formate
Formic acid (and the conjugate base, formate) is a semi-volatile chemical that is miscible in
water. It causes low acute oral toxicity in experimental animals and anticipated signs following
short-term exposure include salivation, a burning sensation in the mouth, vomiting, ulceration
of gastric membranes and circulatory pain. No chronic human exposure data could be located
and experimental animal data are limited to inhalation studies. Formic acid has been classed
as a skin and eye irritant. There is no evidence to suggest it is a skin sensitiser. Overall the
data indicate that formic acid is not genotoxic.
JECFA derived an ADI of 3 mg/kg bw/day (3000 µg/kg bw/day) for formic acid and formate
(for their sum and individually); however, the basis for this derivation was not reported.
Nitrobenzene
Nitrobenzene is a volatile chemical that is soluble in water. It causes low acute oral toxicity in
experimental animals and anticipated signs following short-term human exposure include
methaemoglobinaemia, cyanosis, headache and dyspnoea. No data on chronic human
exposure were located, however multiple repeat-dose experimental data in rats report clinical
signs including ataxia and lethargy, and microscopic lesions to the brain. Nitrobenzene is not
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classified as an irritant or a skin sensitiser. Overall, the data indicate that nitrobenzene may
be weakly genotoxic.
In the WHO Guidelines for Drinking-water Quality (GDWQ), a formal guideline value was not
established because nitrobenzene was ‘rarely found in drinking water at concentrations of
health concern’. However, short-term health based value and hence a short-term TDI was
derived by WHO. This is based on a 28-day oral (gavage) toxicity study in F344 rats that were
administered nitrobenzene at doses of 0, 5, 25 or 125 mg/kg bw/day. A LOAEL of 5 mg/kg
bw/day was identified based on spongiotic changes to the cerebellum. WHO applied an UFof
1000 (10 to account for intra-species variation, 10 to account for inter-species variation and
10 to account for the use of a LOAEL) to the LOAEL to derive a TDI of 0.005 mg/kg bw/day.
WHO noted in this derivation that nitrobenzene exposure may result in
methaemoglobinaemia, which is a particular concern for bottle-fed infants. However, WHO
stated that ‘available data were inadequate’ to derive a value for this endpoint.
Oxalate
Oxalic acid (and its conjugate base, oxalate) is a non-volatile chemical that is highly water
soluble. It causes low to moderate acute oral toxicity in experimental animals and anticipated
signs following short-term human exposure include immediate corrosive damage to the mouth
and gastrointestinal tract, gastrointestinal irritation, depression of the nervous system and
convulsions. Chronic human oral exposure is associated with excessive formation of calcium
oxalate, leading to bladder calculi and renal damage. Oxalic acid has been classified as an
eye and skin irritant. There is no evidence to suggest it is a skin sensitiser. No in vivo
genotoxicity data for are available, however the limited in vitro data available indicate that
oxalic acid is not genotoxic.
In a 2-year dietary carcinogenicity study, rats were administered oxalic acid at dose levels of
0, 0.1, 0.5, 0.8 or 1.2% (equivalent to 0, 60, 300, 480 and 720 mg/kg bw/day in males and 0,
40, 250, 400 and 600 mg/kg bw/day in females, respectively). A LOAEL of 40 mg/kg bw/day
(lowest dose administered) was identified based on hepatocellular hypertrophy. By applying
an UFof 100 (10 to account for intra-species variation, 10 to account for inter-species
variation), a TDI of 0.4 mg/kg bw/day is derived (400 µg/kg bw/day). As the LOAEL was
considered to be based on a relatively minor effect (enlargement of liver cells), no additional
UFwas applied to account for the use of a LOAEL.
Propanoic acid
Propanoic acid is an involatile chemical that is miscible with water. It causes low acute oral
toxicity in experimental animals. No short-term or chronic human exposure data could be
located; however repeat dose studies in experimental animals have reported gastro-intestinal
hyperplasia and ulceration (20-week dietary rat study, effects observed at 270 or
2700 mg/kg bw/day) and diffuse epithelial hyperplasia of the oesophagus (100-day dietary
dog study, effects observed in 3/8 dogs at 1832 mg/kg bw/day). Propanoic acid is classified
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as a skin and eye irritant. There is no evidence to suggest it is a skin sensitiser. Overall, data
indicate that propanoic acid is not genotoxic.
JECFA set an ADI of “not limited” for propanoic acid and confirmed that there are no safety
concerns for its current levels of intake, based on its use as a flavouring agent.
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5. Objective 5: Risk Assessment
5.1 Hazard Identification
During the hazard identification phase, the type and nature of potential adverse effects
(hazards) are identified (see Section 4.3 for further details).
5.2 Hazard Characterisation
Hazard characterisation encompasses a qualitative or quantitative description of inherent
toxicological properties of the DBP. Health based guidance values such as an ADI or TDI are
used to provide an estimate of the amount of chemical that can be ingested over a lifetime
without appreciable risk to health.
5.2.1 Proposed PoDs
The PoD, usually in the form of a NO(A)EL or LO(A)EL is identified from the literature search
or determined from the alternative methods applied i.e. modelling. If no PoD was derived, the
TTC value has been used.
5.2.2 Selection of proposed Uncertainty Factors (UF)
In general, a default UFof 100 is typically used, consisting of a factor of 10 for inter-species
variability (4 for toxicokinetics and 2.5 for toxicodynamics) and 10 to account for intra-species
differences (3.2 for toxicokinetics and 3.2 for toxicodynamics) (WHO, 2001). However, in
some cases, such default factors may not be applicable, or additional UFs may need to be
considered. In cases where the TTC value was identified as the most appropriate PoD,
uncertainty factors are not required. A summary of the considerations for the UFs used in this
hazard characterisation is presented in Table 5.1.
Table 5.1 Uncertainty Factor considerations
Assessment
Factor
Possible
Range Comment
Inter-species
differences 1-10
UF used to account for difference in sensitivity between species:
10 is proposed if animal data are used
Intra-species
differences 1-10
UF used to account for differences in sensitivity between
individuals:
10 is proposed to account for human variability
QSAR data 3-10
UF used to account for use of QSAR data:
3 is proposed if a NO(A)EL is used
10 is proposed if a LO(A)EL is used*
* In some cases the NO(A)EL and LO(A)EL are similar. In such situations the additional UF is used as worse-case
scenario to be sufficiently protective. It is noted that this approach may be over-conservative
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5.2.3 Derivation of proposed TDI
The TDI is calculated by using equation:
5.3 Exposure Assessment
During the exposure assessment phase, the maximum measured concentration of the DBP in
drinking water is converted to an intake value. This is achieved by using default assumptions
on bodyweight and volume of water ingested for different receptors to allow the intake to be
expressed on a bodyweight basis. The following assumptions are used:
60 kg adult drinking 2 litres per day,
10 kg child drinking 1 litres per day,
5 kg infant drinking 0.75 litres per day.
The concentrations of DBPs used in this assessment were identified by Vughs et al. (2016). In
this paper, artificial water based on ultrapure water, KNO3 and extracts of NOM2 were treated
with medium pressure (MP) UV to simulate the work of Kolkman et al. (2015). The
concentrations of nitrate and NOM are representative of what can occur in natural raw waters.
Kolkman et al. (2015) had reported the formation of 84 DBPs following treatment of similar
artificial water with MP UV, of which 22 had also been detected in samples from a full-scale
MP UV / H2O2 AOP plant at a water treatment works. Following a comparison of reference
standards, retention times and MS/MS fragmentation, Vughs et al. (2016) confirmed the
identity of 14 DBPs that were previously reported by Kolkman et al. (2015). Five of the 14
identified DBPs were excluded from further evaluation based on the prioritisation criteria
(Section 4.1).
Vughs et al. (2016) fractionated the DBPs into 8 fractions using HPLC for analysis by LC-
Orbitrap Mass Spectroscopy. As part of the identification process, each DBP was semi-
quantified by comparing the relative abundance of the chemical to the known concentration of
the internal standards used in the analysis. As such, the unit of quantification for each
chemical is referred to as ‘µg/l internal standard equivalents’ (ITSD eq.).
Only data for the five highest concentrations of DBPs in each fraction were presented, the
concentrations of which all exceeded 0.015 µg/l ITSD eq. These DBPs were considered to be
2 10.4 mg/l nitrate; 2.5 mg/l C (Standard fulvic acid solution using Pony Lake NOM obtained from
International Humic Substances Society).
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the ‘most intensive’ by-products detected i.e. were present at the highest concentrations. All
such DBPs were identified, with the exception of one chemical (m/z; 316.1413, concentration;
0.0349 µg/L ITSD eq.) (Vughs et al., 2016).
It should also be noted that the DBP concentrations were detected following the use of AOPs
but prior to GAC treatment. Research has shown that the mutagenic response observed in
Ames assays using water treated by AOPs no longer occurs following GAC filtration, implying
that the nitrogenated DBPs to which the mutagenic is partially attributed may be removed by
GAC. Therefore, the exposure assessments conducted here represent a worst case scenario.
5.4 Risk Characterisation
During risk characterisation, the estimated intake of a DBP via drinking water is compared
with HBGVs. Where possible, the risk of each DBP has been characterised against both a
modelled TDI and a TTC value.
5.5 Risk Communication
To aid risk communication, the margin of exposure (MOE) approach is commonly used. The
MOE is defined as the ratio of a defined PoD for an adverse effect to the estimated exposure.
For this project, an MOE has been calculated for adult, child and infant exposure, calculated
using the following equation (WHO, 2009):
The MOE approach has been endorsed by WHO; for effects with a biological threshold, an
MOE of at least 100 would be considered acceptable, and for effects without a threshold, an
acceptable MOE of greater than 10 000 has been suggested (WHO, 2009; COC, 2006). In
general however, the magnitude of the MOE gives an indication of the level of concern, for
example; the larger the MOE, the smaller the potential risk.
5.6 2-Hydroxy-5-nitrobenzoic acid
5.6.1 Hazard identification
Limited experimental data for 2-hydroxy-5-nitrobenzoic acid were available. Modelling
software identified structural alerts for genotoxicity.
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5.6.2 Hazard characterisation
Proposed PoDs
No modelled PoD for 2-hydroxy-5-nitrobenzoic acid could be derived. Based on the data
obtained in Section 4.3.1, a TTC value of 0.0025 µg/kg bw/day is considered an appropriate
PoD.
5.6.3 Exposure assessment
The maximum concentration of 2-hydroxy-5-nitrobenzoic acid measured in drinking water was
0.0562 µg/l ITSD eq. (Vughs et al., 2016). Based on default factors the daily intake would be:
0.00187 μg/kg bw/day for an adult,
0.00562 μg/kg bw/day for a child,
0.00843 μg/kg bw/day for an infant.
5.6.4 Risk characterisation
TDI
No TDI for 2-hydroxy-5-nitrobenzoic acid could be derived.
TTC
The maximum intake of 2-hydroxy-5-nitrobenzoic acid via drinking water by adults
(0.00187 μg/kg bw/day is less than the TTC value (0.0025 µg/kg bw/day) and therefore,
adverse health effects are not anticipated in adults.
The maximum intake in children and infants (0.00562 to 0.00843 µg/kg bw/day) is greater
than the TTC value. Therefore, additional research into the occurrence in drinking water and
toxicological properties of this DBP may be prudent.
5.6.5 Risk communication
No MOE for 2-hydroxy-5-nitrobenzoic acid could be derived.
5.7 2-Methoxy-4,6-dinitrophenol
5.7.1 Hazard identification
Limited experimental data for 2-methoxy-4,6-dintrophenol were available. Modelling software
identified structural alerts for sensitisation and genotoxicity.
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5.7.2 Hazard characterisation
Proposed PoDs
The NOEL and LOEL modelled in Section 4.3.2 are very similar hence the lowest value was
selected as the PoD, namely the LOEL of 90 600 µg/kg bw/day. The reliability of these values
is considered to be ‘low’ due to the limitation of the dataset so should be used with caution.
Therefore the TTC approach using a TTC value of 0.0025 µg/kg bw/day will also be used in
the risk assessment.
Selection of proposed UFs
The proposed UFs for use with the PoD selected are as follows:
10 for inter-species variability
10 for intra-species variability
10 for the use of a modelled LOEL
Total UF used = 1000
Derivation of proposed TDI
The proposed TDI is 90.6 µg/kg bw/day.
5.7.3 Exposure assessment
The maximum concentration of 2-methoxy-4,6-dinitrophenol measured in drinking water was
0.0454 μg/l ITSD eq (Vughs et al., 2016). Based on default factors the daily intake would be:
0.0015 μg/kg bw/day for an adult,
0.0045 μg/kg bw/day for a child,
0.0068 μg/kg bw/day for an infant.
5.7.4 Risk characterisation
TDI
The maximum intake of 2-methoxy-4,6-dinitrophenol via drinking water by adults, children and
infants (0.00151 to 0.00681 μg/kg bw/day) is less than the proposed TDI (90.6 μg/kg bw/day).
Therefore it is not anticipated that any adverse public health effects will occur following
exposure to 2-methoxy-4,6-dinitrophenol via drinking water. The TDI and hence the risk
characterisation should be used with caution due to the limitations in the dataset used to
derive the LOEL.
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TTC
The maximum intake of 2-methoxy-4,6-dinitrophenol via drinking water by adults
(0.0015 μg/kg/day) is less than the TTC value (0.0025 µg/kg bw/day), and therefore, adverse
health effects are not anticipated in adults.
The maximum intake by children and infants (0.00454 to 0.00681 μg/kg bw/day) exceeds the
TTC value. Therefore, additional research into the occurrence in drinking water and
toxicological properties of this DBP may be prudent.
Risk communication
Although it is possible to calculate MOEs for 2-methoxy-4,6-dinitrophenol, it is not
recommended due to the uncertainty and lack of reliability in the TDI .
5.8 2-Nitrohydroquinone
5.8.1 Hazard identification
Limited experimental data for 2-nitrohydroquinone were available. Modelling software
identified structural alerts for sensitisation and genotoxicity.
5.8.2 Hazard characterisation
Proposed PoDs
No modelled PoD for 2-nitrohydroquinone could be derived. Based on the data obtained in
Section 4.3.3, a TTC value of 0.0025 µg/kg bw/day is considered an appropriate PoD.
5.8.3 Exposure assessment
The concentration of 2-nitrohydroquinone was measured by Vughs et al. (2016) but was not
reported as it was not considered to be an ‘intensive by-product’. However, as the
concentration of each ‘intensive by-product’ is reported to exceed 0.015 µg/l ITSD eq, it is
therefore assumed that the concentration of ‘non-intensive by products’ would be <0.015 µg/l
ITSD eq. (see Section 5.3 for further information).Therefore, for the purpose of this project, a
maximum concentration of 0.015 µg /l will be used. However it should be noted that this value
may be an over-conservative representation of 2-nitrohydroquinone in typical drinking water.
Based on default factors the daily intake would be,
0.0005 μg/kg bw/day for an adult,
0.0015 μg/kg bw/day for a child,
0.00225 μg/kg bw/day for an infant.
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5.8.4 Risk characterisation
TDI
No TDI for 2-nitrohydroquinone could be derived.
TTC
The maximum intake of 2-nitrohydroquinone via drinking water by adults, children and infants
(0.0005 to 0.00225 μg/kg bw/day) is less than the TTC value (0.0025 µg/kg bw/day), and
therefore, adverse health effects are not anticipated.
5.8.5 Risk communication
No MOE for 2-nitrohydroquinone could be derived.
5.9 3,5-Dinitrosalicylic acid
5.9.1 Hazard identification
Limited experimental data for 3,5-dinitrosalicylic acid were available. Modelling software
identified structural alerts for sensitisation, genotoxicity and carcinogenicity.
5.9.2 Hazard characterisation
Proposed PoDs
Based on the data obtained in Section 4.3.4, a modelled LOEL of 29 600 µg/kg bw/day has
been selected as the most conservative modelled PoD. The reliability of this LOEL is
considered to be ‘low’ due to the limitation of the dataset so should be used with caution.
Therefore the TTC approach using a TTC value of 0.0025 µg/kg bw/day will also be used in
the risk assessment.
Selection of proposed UFs
The proposed UFs for use with the PoD selected are as follows:
10 for inter-species variability
10 for intra-species variability
10 for the use of a modelled LOEL
Total UF used = 1000
Derivation of proposed TDI
The proposed TDI is 29.6 µg/kg bw/day.
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5.9.3 Exposure assessment
The maximum concentration of 3,5-dinitrosalicylic acid measured in drinking water was
0.0073 μg/l ITSD eq. (Vughs et al., 2016). Based on default factors the daily intake would be,
0.00024 μg/kg bw/day for an adult,
0.00073 μg/kg bw/day for a child,
0.0011 μg/kg bw/day for an infant.
5.9.4 Risk characterisation
TDI
The maximum intake of 3,5-dinitrosalicylic acid via drinking water by adults, children and
infants (0.00024 to 0.0011 µg/kg bw/day) is less than the proposed TDI (29.6 µg/kg bw/day).
Therefore it is not anticipated that any adverse public health effects will occur following
exposure to 3,5-dinitrosalicylic acid via drinking water. The TDI and hence the risk
characterisation should be used with caution due to the limitations in the dataset used to
derive the LOEL.
TTC
The maximum intake of 3,5-dinitrosalicylic acid via drinking water by adults, children and
infants (0.00024 to 0.0011 µg/kg bw/day) is less than the TTC value (0.0025 µg/kg bw/day),
and therefore adverse health effects are not anticipated.
5.9.5 Risk communication
Although it is possible to calculate MOEs for 3,5-dinitrosalicylic acid, it is not recommended
due to the uncertainty and lack of reliability in the TDI .
5.10 4-Hydroxy-3-nitrobenzoic acid
5.10.1 Hazard identification
Limited experimental data for 4-hydroxy-3-nitrobenzoic acid were available. Modelling
software identified structural alerts for genotoxicity.
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5.10.2 Hazard characterisation
Proposed PoDs
No modelled PoD for 4-hydroxy-3-nitrobenzoic acid could be derived. Based on the data
obtained in Section 4.3.5 therefore, a TTC value of 0.0025 µg/kg bw/day is considered an
appropriate PoD.
5.10.3 Exposure assessment
The maximum concentration of 4-hydroxy-3-nitrobenzoic acid measured in drinking water was
0.0422 μg/l ITSD eq. (Vughs et al., 2016). Based on default factors the daily intakes would be:
0.00141 μg/kg bw/day for an adult,
0.00422 μg/kg bw/day for a child,
0.00633 μg/kg bw/day for an infant.
5.10.4 Risk characterisation
TDI
No TDI for 4-hydroxy-3-nitrobenzoic acid could be derived.
TTC
The maximum intake of 4-hydroxy-3-nitrobenzoic acid via drinking water by adults
(0.00141 μg/kg bw/day) is less than the TTC value (0.0025 µg/kg bw/day), and therefore,
adverse health effects following adult exposure to this level of 2-hydroxy-5-nitrobenzoic acid
are not anticipated.
The maximum intake in children and infants (0.00422 to 0.00633 μg/kg bw/day) is greater
than the TTC value. Therefore, additional research into the occurrence in drinking water and
toxicological properties of this DBP may be prudent.
5.10.5 Risk communication
No MOE for 4-hydroxy-3-nitrobenzoic acid could be derived.
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5.11 4-Nitrobenzene-sulfonic acid
5.11.1 Hazard identification
Limited experimental data for 4-nitrobenzene-sulfonic acid were available. Modelling software
identified structural alerts for carcinogenic endpoints, however the results were equivocal and
all predictions were either not reliable or not optimal.
5.11.2 Hazard characterisation
Proposed PoDs
The NOEL and LOEL modelled in Section 4.3.6 are very similar hence the lowest value was
selected as the PoD, namely the LOEL of 871 000 µg/kg bw/day. The reliability of these
values is considered to be ‘low’ due to the limitation of the dataset so should be used with
caution. Therefore the TTC approach using a TTC value of 1.5 µg/kg bw/day will also be used
in the risk assessment.
Selection of proposed UFs
The proposed UFs for use with the PoD selected are as follows:
10 for inter-species variability
10 for intra-species variability
10 for the use of a modelled LOEL
Total UF used = 1000
Derivation of proposed TDI
The proposed TDI is 871 µg/kg bw/day.
5.11.3 Exposure assessment
The concentration of 4-nitrobenzene-sulfonic acid was measured by Vughs et al. (2016) but
was not reported as it was not considered to be an ‘intensive by-product’. However, as the
concentration of each ‘intensive by-product’ is reported to exceed 0.015 µg/l ITSD eq, it is
therefore assumed that the concentration of ‘non-intensive by products’ would be <0.015 µg/l
ITSD eq. (see Section 5.3 for further information). Therefore, for the purpose of this project, a
maximum concentration of 0.015 μg/l will be used, however it should be noted that this value
may be an over-conservative representation of 4-nitrobenzene-sulfonic acid in typical drinking
water. Based on default factors the daily intake would be:
0.0005 μg/kg bw/day for an adult,
0.0015 μg/kg bw/day for a child,
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0.00225 μg/kg bw/day for an infant.
5.11.4 Risk characterisation
TDI
The maximum intake of 4-nitrobenzene-sulfonic acid via drinking water by adults, children and
infants (0.0005 to 0.00225 μg/kg bw/day) is less than the proposed TDI (871 µg/kg bw/day).
Therefore it is not anticipated that any adverse public health effects will occur following
exposure to 4-nitrobenzene-sulfonic acid via drinking water. The TDI and hence the risk
characterisation should be used with caution due to the limitations in the dataset used to
derive the LOEL.
TTC
The maximum intake of 4-nitrobenzene-sulfonic acid via drinking water by adults, children and
infants (0.0005 to 0.00225 μg/kg bw/day) is less than the TTC value (1.5 µg/kg bw/day), and
therefore adverse health effects are not anticipated.
5.11.5 Risk communication
Although it is possible to calculate MOEs for 4-nitrobenzene-sulfonic acid, it is not
recommended due to the uncertainty and lack of reliability in the TDI.
5.12 4-Nitrocatechol
5.12.1 Hazard identification
Limited experimental data for 4-nitrocatechol were available. Modelling software identified
structural alerts for sensitisation, as well as genotoxic and carcinogenic endpoints.
5.12.2 Hazard characterisation
Proposed PoDs
Based on the data obtained in Section 4.3.7, a modelled NOEL of 736 000 µg/kg bw/day has
been selected as the most conservative modelled PoD. The reliability of these values is
considered to be ‘low’ due to the limitation of the dataset so should be used with caution.
Therefore the TTC approach using a TTC value of 0.0025 µg/kg bw/day will also be used in
the risk assessment.
Selection of proposed UFs
The proposed UFs for use with the PoD selected are as follows:
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10 for inter-species variability
10 for intra-species variability
5 for the use of a modelled NOEL
Total UF used = 500
Derivation of proposed TDI
The proposed TDI is 1472 µg/kg bw/day.
5.12.3 Exposure assessment
The maximum concentration of 4-nitrocatechol measured in drinking water was 0.027 μg/l
ITSD eq. (Vughs et al., 2016). Based on default factors the daily intake would be,
0.0009 μg/kg bw/day for an adult,
0.0027 μg/kg bw/day for a child,
0.00405 μg/kg bw/day for an infant.
5.12.4 Risk characterisation
TDI
The maximum intake of 4-nitrocatechol via drinking water by adults, children and infants
(0.00090 to 0.00405 μg/kg bw/day) is less than the proposed TDI (1472 µg/kg bw/day).
Therefore it is not anticipated that any adverse public health effects will occur following
exposure to 4-nitrocatechol via drinking water. The TDI and hence the risk characterisation
should be used with caution due to the limitations in the dataset used to derive the NOEL.
TTC
The maximum intake of 4-nitrocatechol via drinking water by adults (0.00090 μg/kg bw/day) is
less than the TTC value (0.0025 µg/kg bw/day) and therefore, adverse health effects following
adult exposure to this level of 4-nitrocatechol via drinking water are not anticipated in adults.
The maximum intake in children and infants (0.00270 to 0.00405 μg/kg bw/day) exceeds the
TTC value. Therefore, additional research into the occurrence in drinking water and
toxicological properties of this DBP may be prudent.
5.12.5 Risk communication
Although it is possible to calculate MOEs for 4-nitrocatechol, it is not recommended due to the
uncertainty and lack of reliability in the TDI.
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5.13 4-Nitrophthalic acid
5.13.1 Hazard identification
Limited experimental data for 4-nitrophthalic acid were available. Modelling software identified
structural alerts for sensitisation and genotoxicity.
5.13.2 Hazard characterisation
Proposed PoDs
No modelled PoD for 4-nitrophthalic acid could be derived. Based on the data obtained in
Section 4.3.8, a TTC value of 0.0025 µg/kg bw/day is considered an appropriate PoD.
5.13.3 Exposure assessment
The maximum concentration of 4-nitrophthalic acid measured in drinking water was
0.0007 μg/l ITSD eq. (Vughs et al., 2016). Based on default factors daily intakes would be,
0.00002 μg/kg bw/day for an adult,
0.00007 μg/kg bw/day for a child,
0.00011 μg/kg bw/day for an infant.
5.13.4 Risk characterisation
TDI
No TDI for 4-nitrophthalic acid could be derived.
TTC
The maximum intake of 4-nitrophthalic acid via drinking water by adults, children and infants
(0.00002 to 0.00011 μg/kg/day) is less than the TTC value (0.0025 µg/kg bw/day). Therefore,
adverse health effects following exposure to 4-nitrophthalic acid via drinking water are not
anticipated.
5.13.5 Risk communication
No MOE for 4-nitrophthalic acid could be derived.
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5.14 5-Nitrovanillin
5.14.1 Hazard identification
Limited experimental data for 5-nitrovanillin were available. Modelling software identified
structural alerts for genotoxicity.
5.14.2 Hazard characterisation
Proposed PoDs
Based on the data obtained in Section 4.3.9, a modelled LOEL of 166 000 µg/kg bw/day has
been selected as the most conservative modelled PoD. The reliability of these values is
considered to be ‘low’ due to the limitation of the dataset so should be used with caution.
Therefore the TTC approach using a TTC value of 0.0025 µg/kg bw/day will also be used in
the risk assessment.
Selection of proposed UFs
The proposed UFs for use with the PoD selected are as follows:
10 for inter-species variability
10 for intra-species variability
10 for the use of a low-reliably modelled LOEL
Total UF used = 1000
Derivation of proposed TDI
The proposed TDI is 166 µg/kg bw/day.
5.14.3 Exposure assessment
The concentration of 5-nitrovanillin was measured by Vughs et al. (2016) but was not reported
as it was not considered to be an ‘intensive by-product’. However, as the concentration of
each ‘intensive by-product’ is reported to exceed 0.015 µg/l ITSD eq, it is therefore assumed
that the concentration of ‘non-intensive by products’ would be <0.015 µg/l ITSD eq. (see
Section 5.3 for further information). Therefore, for the purpose of this project, a maximum
concentration of 0.015 µg /l will be used, however please note that this value may be an over-
conservative representation of 5-nitrovanillin in typical drinking water. Based on default factors
daily intakes would be,
0.0005 μg/kg bw/day for an adult,
0.0015 μg/kg bw/day for a child,
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0.00225 μg/kg bw/day for an infant.
5.14.4 Risk characterisation
TDI
The maximum intake of 5-nitrovanillin via drinking water by adults, children and infants
(0.00050 to 0.00225 μg/kg bw/day) is less than the proposed TDI (166 µg/kg bw/day).
Therefore adverse health effects following exposure to 5-nitrovanillin via drinking water are
not anticipated. The TDI and hence the risk characterisation should be used with caution due
to the limitations in the dataset used to derive the LOEL.
TTC
The maximum intake of 5-nitrovanillin via drinking water by adults, children and infants is less
than the TTC value (0.0025 µg/kg bw/day), and therefore adverse health effects following
exposure to 5-nitrovanillin via drinking water are not anticipated.
5.14.5 Risk communication
Although it is possible to calculate MOEs for 5-nitrovanillin, it is not recommended due to the
uncertainty and lack of reliability in the TDI.
5.15 Summary and Conclusions
A summary of the risk characterisation for the DBPs is presented in Table 5.2. Where
possible, a PoD based on a modelled data and the TTC approach was used in order to
provide a weight of evidence approach to the risk assessment. When comparing the TDI
derived from modelled data and the TTC values for each DBP, a large difference in
magnitude was observed. This difference is largely based on the method of prediction behind
each approach.
The modelled PoDs have been derived using the OECD toolbox, based on existing data for
repeated dose toxicity and reproductive/developmental toxicity of chemicals with structural
similarities to the DBP in question. The lack of data in the data sets used for the predictions,
the complexity of endpoints and the limited number of chemicals with structural similarity to
the DBPs in question all contribute to the low reliability of the modelled PoDs.
Threshold of toxicological concern values however, are calculated based on NOAELs derived
for the three classes of chemicals, namely Cramer class I, II or III. The 5th percentile of the
NOAEL is divided by a factor of 100 to derive the TTC value. Application of the TTC approach
when chemical-specific data are not available is a pragmatic approach that allows the safety
evaluation of chemicals and it is a form of risk characterisation that balances uncertainties
inherent in extrapolation of TTC values to an unknown substances, against the level of human
exposure.
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Eight DBPs were noted to have structural alerts for mutagenicity and therefore are considered
to be potentially genotoxic. It is generally accepted that genotoxic chemicals exhibit no
threshold for their mutagenic potential (Fukushima, 2010). Therefore, it is widely
recommended that exposure levels be kept to as low as reasonably practicable, and thus it is
considered impossible to define a ‘safe’ level of exposure (Humfrey, 2007) As such, a TTC
value of 0.0025 µg/kg bw/day is used as it is thought to be of ‘negligible risk’ in the event that
a substance may later be defined as carcinogenic (European Commission, 2009; Humfrey,
2007). Whist the TTC approach has been criticised as being ‘overly conservative’ (Delaney,
2007), particularly in terms of calculating impurities in pharmaceuticals (European
Commission, 2009), it is considered to be an appropriate method for risk characterisation for
chemicals with limited existing data.
Overall, in cases where modelled PoDs were derived, the estimated exposure values for each
DBP were below the proposed TDI, indicating that the exposure to these DBPs via drinking
water is not anticipated to cause adverse health effects. However, due to the limitations in the
toxicity databases on which each PoD was based, caution should be used in their
interpretation.
Analysis of the chemical structure of 4-nitrobenzene-sulfonic acid did not identify any
mutagenic structural alerts, and carcinogenic VEGA predictions for carcinogenicity were
equivocal and unreliable. The estimated exposure of 4-nitrobenzene-sulfonic acid in drinking
water did not exceed the proposed TDI or the TTC value, therefore, it is considered to be of
low concern to public health.
When characterising each DBP against the genotoxic TTC value of 0.0025 µg/kg bw/day, the
estimated exposure of four DBPs (2-hydroxy-5-nitrobenzoic acid, 2-methoxy-4,6-
dinitrophenol, 4-hydroxy-3-nitrobenzoic acid and 4-nitrocatechol) exceed the threshold value
for children and infants, but not adults. Therefore for such chemicals additional research on
their occurrence in drinking water and the hazard potential would be prudent.
Of the remaining DBPs that were identified as potentially genotoxic (2-nitrohydroquinone,
3,5-dinitrosalicylic acid, 4-nitrophthalic acid and 5-nitrovanillin), the estimated exposure levels
were below the TTC value and hence adverse health effects are not anticipated.
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Table 5.2 Summary of risk characterisation of DBPs based on their estimated daily
intake
DBP
TDI
(µg/kg
bw/day)
TTC
(µg/kg
bw/day)
Estimated Daily Intake
(TDI)
Estimated Daily Intake
(TTC)
Adult Child Adult Adult Child Infant
2-Hydroxy-5-nitrobenzoic
acid - 0.0025 - - - Below Above Above
2-Methoxy-4,6-
dinitrophenol 90.6 0.0025 Below Below Below Below Above Above
2-Nitrohydroquinone - 0.0025 - - - Below Below Below
3,5-Dinitrosalicylic acid 29.6 0.0025 Below Below Below Below Below Below
4-Hydroxy-3-nitrobenzoic
acid - 0.0025 - - - Below Above Above
4-Nitrobenzene-sulfonic
acid 871 1.5 Below Below Below Below Below Below
4-Nitrocatechol 1472 0.0025 Below Below Below Below Above Above
4-Nitrophthalic acid - 0.0025 - - - Below Below Below
5-Nitrovanillin 166 0.0025 Below Below Below Below Below Below
- No data; modelled NO(A)EL/LO(A)EL could not be derived
Below; estimated daily intake is below the proposed TDI/TTC value, adverse health effects are not anticipated
Above; estimated daily intake is above the proposed TDI/TTC value, adverse health effects cannot be excluded
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6. Objective 6: Review of analytical methods for detecting disinfection by-products from advanced oxidation processes
6.1 Introduction
The systematic review in Objective 3 identified 78 DBPs that are produced during the use of
AOPs.
A systematic prioritisation process outlined in Objective 4 identified nine DBPs that were
potentially formed in water following AOP processes and for which a human health risk
assessment was carried out. These compounds were prioritised and grouped into similar
functional group moieties e.g. Nitrobenzene diols
The following Table 6.1 shows the DBPs to be reviewed.
Table 6.1 DBPs assessed
Disinfection by-product CAS RN Group
2-Hydroxy-5-nitrobenzoic acid 96-97-9 Hydroxynitrobenzoic acids
2-Methoxy-4,6-dinitrophenol 4097-63-6 Dinitrophenols
2-Nitrohydroquinone 16090-33-8 Nitrobenzene diols
3,5-Dinitrosalicylic acid 609-99-4 Dinitrophenols
4-Hydroxy-3-nitrobenzoic acid 616-82-0 Hydroxynitrobenzoic acids
4-nitrobenzene-sulfonic acid 138-42-1 Miscellaneous
4-Nitrocatechol 3316-09-4 Nitrobenzene diols
4-nitrophthalic acid 610-27-5 Miscellaneous
5-nitrovanillin 6635-20-7 Miscellaneous
6.2 Literature Review
A literature review was undertaken to identify the most common analytical techniques used to
quantify the concentration of the compounds present in drinking water. Data sources used
included the World Health Organisation, European Commission, Defra and the United States
Environmental Protection Agency and the following:
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Researchgate
ChemSpider
PubMed
PubChem
The review aimed to identify the most common analytical technique for identifying the DBPs,
including a summary of the methodology. Where possible, standards and reagents used to
assist in the quantification of the compound are listed as well as the type of equipment used.
Depending on the analytical method identified, and date of the literature, a limit of detection is
reported for compound assessment.
The method of isotopic substitution, employed by Vughs et al. (2016) using 15
N to substitute 14
N in the sample, provides a reliable and quantitative result. However, the level of equipment
and expertise involved make it impractical for frequent analyses. The methods described
below have been accepted as the industry standards for rapid qualitative analyses and are
easier to replicate in the field.
6.3 Method Reviews
6.3.1 Dinitrophenol
Introduction
Nitrogenous DBPs (N-DBP) are formed in drinking water treatment processes, during the
reaction with NOM.
The two compounds assessed in this section are 2-methoxy-4,6-dinitrophenol and 3,5-
dinitrosalicylic acid (Figure 6.1).
Figure 6.1 Structures of compounds
2-methoxy-4,6-
dinitrophenol
3,5-dinitrosalicylic
acid
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Analytical methodology
Principle of method
Quantification of N-DBPs is based on modifications of US EPA method 551.1.
Samples of water are extracted with methyl tert-butyl ether (MtBE ) prior to analysis using gas
chromatography – mass spectroscopy (GC-MS) coupled with an electron capture detector
(ECD) using a HP-5 capillary column (30 m x 0.25 mm x 0.25 µm). Recently, pentane has
been introduced as an extraction solvent owing to safety concerns. The injector and detector
temperature were 200°C and 290°C, respectively, and the nitrogen carrier gas had a flow rate
of 30 ml/min and pressure of 69.8 kPa. The temperature program for the N-DBP analyses
was as follows: hold at 37°C for 10 min, ramp to 50°C at 5°C/min and hold for 5 min, and
finally ramp to 260°C at 15°C/min and hold for 10 min.
Standards and reagents
Pure analytes are added to the AOP treated water sample,. These are added to generate a
calibration curve to quantify the concentration of the AOP treated water sample being tested.
A laboratory blank is also used as a control sample to ensure interferences are not
encountered.
Standards are available from:
Sigma-Aldrich 48027 – MtBE
D0550 Sigma Aldrich – 3,5-dinitrosalicylic acid
AKOS000282909 AKos – 2-methoxy-4,6-dinitrophenol
Pentane, acetone, methanol, sodium chloride and sodium sulphate can also be purchased
from standard laboratory suppliers.
Equipment
Gas chromatography with detection by an ECD or GC-MS if concentrations are sufficient.
Non-polar methyl polysiloxane (silica-fused) capillary column, at 30 m x 0.25 mm x 0.25 µm.
Oven set to 200°C, detection temperature at 290°C. An alternative column can be used which
incorporates a 6% chemically bonded cyanopropylphenyl to the methyl polysiloxane, oven
temperatures are the same (Hodgeson et al., 1990).
Limit of detection
The method detection limit should be 0.1 mg/l for dinitrophenols (ChemSpider, 2017). No data
could be found for detection of N-DBPs.
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6.3.2 Hydroxynitrobenzoic Acids
Introduction
Nitrobenzoic acids (nitrosalicylic acids) are by-products from the oxidation of drinking water
treatment processes (H2O2).
The two compounds assessed in this section are 2-hydroxy-5-nitrobenzoic acid and 4-
hydroxy-3-nitrobenzoic acid (Figure 6.2).
Figure 6.2 Structures of compounds
2-hydroxy-5-
nitrobenzoic acid
4-hydroxy-3-
nitrobenzoic acid
6.3.3 Analytical methodology
Principle of method
The method below is applicable to salicylic acid compounds having a content of 0.1 mg/l
(Lide, 1998).
On heating the AOP treated water sample in the presence of a reducing sugar (such as
glucose, fructose) the colour of the solution changes from yellow to orange/red. One of the
nitro groups is reduced to the amine at temperatures above 90°C after 5 to 15 minutes.
Analysis is completed using a colorimeter (spectrophotometer) with a wavelength between
500 and 560 nm. The ideal wavelength is 540 nm (green light).
Standards and reagents
Pure analytes are added to the AOP treated water sample. These are added to generate a
calibration curve to quantify the concentration of the AOP treated water sample being tested.
A laboratory blank is also used as a control sample to ensure interferences are not
encountered.
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Standards are available from:
Sigma-Aldrich 247871 – 2-hydroxy-5-nitrobenzoic acid
Sigma-Aldrich 228575 – 4-hydroxy-3-nitrobenzoic acid
Equipment
Colorimeter and standard laboratory glassware.
6.3.4 Limit of detection
Compounds should be detected above 0.1 mg/l (LoD). This methodology is neither robust nor
reliable to accurately quantify an LoD.
6.4 Nitrobenzene diol
Introduction
The two compounds assessed in this section are 2-nitrohydroquinone and 4-nitrocatechol
(Figure 6.3).
Figure 6.3 Structures of compounds
2-nitrohydroquinone 4-nitrocatechol
Analytical methodology
Principle of method
This method is applicable for nitrobenzene derivatives. The sample is extracted using an
organic solvent (dichloromethane) and analysed by GC analysis. Flame ionisation or MS may
also be used for detection.
Firstly the sample is extracted with dichloromethane at pH 11 and then a separate extraction
at pH 2 followed by evaporation of dichloromethane to increase the sample concentration.
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Analysis is completed using a gas-phase chromatograph, coupled with a mass spectrometer
(Agency for toxic substances and disease registry, 1995). A non-polar column, as supplied by
SGE, with dimensions of 50 m x 0.32 mm x 0.25 µm. Injector and detector temperatures of
250°C and 280°C are used; the oven is set to 60°C, programmed to increase by 2°C/min to
230°C and maintained for a minimum of 20 minutes. Volume injected is 10 µl.
Standards and reagents
Analytical grade dichloromethane can be purchased from Sigma-Aldrich (24233-M).
Standards are available from:
FR-2180 RD Chemicals – 2-nitrohydroquinone
11450063 Fisher Scientific – 4-nitrocatechol
Equipment
Gas chromatograph coupled with detection by mass spectroscopy (GC-MS).
Non-polar capillary columns, typically 50 m x 0.32 mm x 0.25 µm.
Standard laboratory glassware.
Limit of detection
Water sample detection limits have been reported as 1.9 µg/l (Hodgeson et al, 1990).
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6.4.2 Miscellaneous Compound
Introduction
The three compounds assessed in this section of the report are 4-nitrobenzene sulfonic acid,
4-nitrophthalic acid and 5-nitrovanillin (Figure 6.4) (ChemSpider, 2017).
Figure 6.4 Structures of compounds
4-nitrobenzene
sulfonic acid 4-nitrophthalic acid 5-nitrovanillin
There are limited data available for analytical methods associated with determination of the
above compound concentrations within water samples.
Analytical methodology
Principle of method
Although not identical in structure, these compounds contain the nitro grouping, similar to the
dinitrophenols. Gas chromatography traces exist for all three compounds (Figure 6.5). As with
the phenols, it should be possible to extract the compounds into the organic phase using a
relatively polar solvent such as dichloromethane (NCBI, 2017).
Analysis is completed by gas chromatography coupled with detection by mass spectroscopy.
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Figure 6.5 GC-MS trace for 4-nitrobenzene sulfonic acid
Standards and reagents
Data lacking.
Equipment
Gas chromatograph, mass spectrometer detector, non-polar capillary column. Standard
laboratory glassware.
6.4.3 Limit of detection
Data lacking.
6.4.4 Availability of standards
ACM138421 Alfa Chemistry – 4-nitrobenzene sulfonic acid
274755 Sigma Aldrich – 4-nitrophthalic acid
N28000 Sigma Aldrich – 5-nitrovanillin
6.5 Conclusions
Analytical methods for the prioritised nine DBPs that were potentially formed in water
following AOP processes and for which a human health risk assessment was carried out have
been investigated. Some methods are well developed such as nitrobenzene diols and
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dinitrophenols whereas other methods for compounds such as the hydroxynitrobenzoic acids,
4-nitrobenzene sulfonic acid, 4-nitrophthalic acid and 5-nitrovanillin will need further
development to ensure they are robust and reliable. Additionally, problems with limits of
detection for these methods may not be low enough to detect the concentrations of these
compounds in drinking water. Advances in chromatography during the past twenty years has
allowed for better quantification of hydroxynitrobenzoic acids without the need to use less
accurate colorimetric spectrophotometry. However these methods are yet to be verified as
industry standards.
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7. Objective 7: Sampling and analysis strategy for future research projects
7.1 Introduction
As evident from Objective 3, a range of potential DBPs may arise as a result of the use of
AOP treatment. Under Objective 4, these identified DBPs were subject to a prioritisation
process to identify those DBPs that were considered of potential relevance to UK drinking
water, had not been identified in research with more ‘conventional’ water treatment, and as
such, were considered to be of highest priority subject to a high-level risk assessment. The
prioritised compounds comprise of nine DBPs, which were identified in studies carried out by
Vughs et al. (2016) and Kolkman et al. (2015). These studies investigated the potential
generation of DBPs after UV/H2O2. However, it was found that these DBPs were no longer
present after GAC treatment, which was located downstream of the AOP process and was
intended to quench residual H2O2.
The two UV / H2O2 plants currently operated in England and Wales also have GAC
downstream of the AOP as part of the normal practice (to quench residual H2O2). Therefore,
based on the limited data currently available, it may be a reasonable expectation that the
concentrations of DBPs formed via UV / H2O2 will be reduced by GAC, assuming its effective
operation. However, it should be emphasised that this is based on limited data and further
monitoring may be required to validate this assumption.
7.2 Removal of prioritised DBPs
The prioritised compounds comprise of nine DBPs, which were identified in studies carried out
by Vughs et al. (2016) and Kolkman et al. (2015). Vughs et al. (2016) used genotoxicity as an
indicator for DBPs formed by UV / H2O2, and isolated compounds that contributed to the
genotoxicity. During the study it was observed that the genotoxicity was no longer present
after GAC adsorption, implying that the DBPs had been removed. The analytical strategy
outlined below would help confirm both formation and removal of these DBPs.
7.3 Outline of strategy
The data reviews in the previous objectives have identified a number of gaps in the available
information. Therefore, prior to instigating a full sampling programme, a number of preliminary
steps are required to ensure that the sampling programme is fit-for-purpose. This report
considers a number of developmental stages that need to be undertaken prior to the sampling
strategy. A preliminary approach to sampling is also provided; however, the details of this
strategy are contingent upon the outcome of the development stages below:
Analytical method development
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Identification of sites for sampling
Communication
Sampling strategy.
7.4 Analytical method development
The purpose of this section is to recommend a strategy that develops a more encompassing
analytical method applicable to the nine prioritised DBPs described in Table 7.1. All nine
compounds have standards available for purchase from a variety of suppliers and a further
review of literature has shown a methodology capable of detecting all these chemicals using
similar analytical procedure.
During this method development, ‘spiked’ water samples would be utilised over a range of
concentrations and calibration curves would be developed for each standard. This
methodology would be repeated to ensure that detection limits (LODs) are repeatable and
standardised for anticipated DBP formation during AOP treatment.
The nine DBPs identified during the prioritisation process are shown in Table 7.1.
Table 7.1 DBPs for further assessment
DBP CAS RN Structure
2-Hydroxy-5-nitrobenzoic acid 96-97-9
2-Methoxy-4,6-dinitrophenol 4097-63-6
2-Nitrohydroquinone 16090-33-8
3,5-Dinitrosalicylic acid 609-99-4
4-Hydroxy-3-nitrobenzoic acid 616-82-0
4-nitrobenzene-sulfonic acid 138-42-1
4-Nitrocatechol 3316-09-4
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DBP CAS RN Structure
4-Nitrophthalic acid 610-27-5
5-Nitrovanillin 6635-20-7
Kolkman et al. (2015) used a liquid chromatography / high resolution mass spectroscopy (LC /
HR-MS) approach to analyse a variety of DBPs possibly formed during AOP treatment of
drinking water. This method has shown to be effective in matching reference standards of
DBPs to the DBPs found in an artificial water sample that was treated by medium pressure
UV – specifically the nine compounds listed above have all been identified with this method.
For the analysis, a quadrupole time of flight (QToF) mass spectrometer was utilised as better
structural elucidation could be obtained than using a LC-Orbitrap analyser, i.e. where
compounds are isomers of each other and higher resolution assists in structure determination.
The work from Kolkman et al. (2015) did not report any LOD, but the literature values
described in Objective 6 using standard GC-MS analysis should be realisable, i.e. 2-
nitrohydroquinone was reported to be detected at 1.9 µg/l (Hodgeson et al, 1990). Repeated
testing of standard ‘spiked’ water samples will establish the actual LODs and development of
the analytical method can be used to adjust the methodology to reduce the LOD as far as
possible.
Should the monitoring of DBPs show they are not present or present in limited concentrations,
pre-concentration of samples can be undertaken. Use of such analytical process can be
employed to back calculate the concentration of the DBP present and further assist in
developing the actual LOD for the nine DBPs of potential concern.
Once the methodology has been satisfactorily developed, a range of conditions can be
progressed with ‘spiked’ DBPs in a variety of water sources (e.g. hard water, soft water). The
recovery of these spikes will have been optimised, such that, confidence in the analysis of
actual water samples will be robust and reflect ‘real’ drinking water samples for the general
public.
Suggested sample bottles from an external laboratory are amber glass jars. In discussion with
the laboratory no preservatives for these types of compounds would be required as the
stability of the samples would be up to 28 days. This information requires verification and
validation should a sampling programme be developed.
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7.5 Identification of sites for sampling
It is recognised that the use of AOPs are not commonplace in England and Wales at the
present time. Although earlier investigations indicate that this may remain the position of
water companies for the near future, should the use of AOPs become commonplace, it is
critical to understand the circumstances where their use may favour the formation of DBPs.
Those sites that favour their formation can be considered ‘high risk’ in the sense that
consumers may potentially be exposed to higher concentrations of DBPs than consumers at
sites where DBP formation is lower. Sampling at these ‘high risk’ sites would allow the
investigation of the risk of exposure to the DBPs, to determine whether or not there is likely to
be a concern to human health, and thus determine whether regulatory action would be
required.
The review of the literature on the formation of DBPs following AOPs has revealed significant
gaps in the available data on the understanding of their formation in water conditions relevant
to the UK; therefore, prior to full-scale sampling, it is recommended that bench-scale analysis
is conducted with different water conditions to determine the best approach to identify these
‘high-risk’ sites.
7.5.1 Bench-scale pre-sampling study
Bench-scale pre-sampling would be conducted whereby changes to water conditions, such as
pH and other parameters that may influence the formation of potential DBPs, are
systematically investigated to determine those conditions that favour DBP formation. Each of
the following parameters (and any other parameters that may influence DBP formation) would
be sequentially adjusted in water prior to treatment with a bench-scale AOP unit and the
DBPs in the water post-treatment will be quantified:
pH
Conductivity
Water hardness
TOC
DOC
Nitrate
7.5.2 Identification of ‘high risk’ sites for sampling
As stated above, sites that favour the formation of the DBPs can be considered ‘high risk’ as
consumers may potentially be exposed via their drinking water.
The information collated in the bench-scale tests can be used to inform which drinking water
treatment works that employ AOPs are likely to be ‘high risk’ sites. For example, if it is
established that ‘high’ TOC levels result in increased DBP formation, further investigation
should be conducted where it is known that TOC levels are atypically high. Those sites that
are identified as such are subsequently included in the sampling programme.
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The scale of any survey will be subject to resourcing constraints. With the current gaps in
knowledge on the number of parameters that can influence AOP formation, it is not currently
possible to recommend a set number of sites to sample; however, the number of ‘high risk’
sites should be selected to ensure that all parameters (pH, conductivity etc.) that are
established as increasing DBP formation are represented.
In terms of the current use of AOPs, whereby only two sites are in operation across England
and Wales, the results of the bench-scales may provide information on whether one of these
sites is likely to favour DBP formation over the other. Should this be the case, intensive
sampling could be conducted at this site.
By way of controls and validation of the bench-scale tests, it is also recommended that two
sites are selected that would be considered ‘low risk’ by bench-scale tests. After three
sampling periods, if the results of these ‘low risk’ sites are consistent with the bench-scale
tests (i.e. concentrations of DBPs at these sites are lower than their high-risk counterparts),
these sites can be removed from the sampling programme, and more frequent sampling can
be conducted at ‘high risk’ sites.
7.6 Communication
In order to conduct a successful sampling regime, coordination between the operations team
on site, the water sampler and the analytical centre is essential. The following strategy should
be applied to maximise the effectiveness of the suggested sampling protocol:
1. A sampling protocol should be prepared that clearly states the sample point(s) and the
sampling procedure that will cover various aspects of the sampling such the volume of
water to be collected, the types of bottles to be used and the handling conditions of
those bottles (for example, storing in cold conditions), and the intended times and dates
of sampling at each site.
a. These documents should be written in plain English and easy to follow by all
parties involved.
b. The sampling protocol will be subject to versioning controls, to ensure that any
changes to the protocol are logged and all parties are using the most up-to-date
protocol.
2. An inventory form should be prepared identifying the sample points, label for sample
bottles and water quality determinand. This inventory form will also serve as a chain-of-
custody to ensure that all samples can be ‘tracked’ through the sampling procedure.
3. Designated operational team members will be identified, as will named individuals in
the analytical laboratory and the water treatment works.
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a. Each of these individuals will have copies of the sampling protocol and any
subsequent revisions to these protocols.
b. Each individual will also provide a contact telephone number and email address,
as well as the contact details of a nominated stand-in, to ensure effective
communication.
c. A minimum of 24 hours prior to sampling, the sampler will contact the water
treatment works to confirm the logistics of the intended sampling and
arrangements for prompt analysis of the samples.
4. Regular and direct communication between the designated personnel will be ensured
to highlight any issues or circumstantial changes which may influence the
commencement of the sampling. The use of nominated stand-in personal will be
applied whenever necessary to minimise the risk of ‘missed’ sampling due to
unforeseen changes in circumstances.
7.7 Sampling strategy for AOP treatment works
The European Drinking Water Directive sets out a minimum frequency for sampling based on
the volume of water distributed each day. In the UK, it was suggested that two levels of
monitoring under the Directive be undertaken; audit and check monitoring. For audit
monitoring, four samples per year are suggested to measure the general microbial quality of
the water and treatment effectiveness. Check monitoring is carried out using higher sampling
frequencies and is usually employed for monitored for pesticides and for water supplies of
10 000 m3/day. In this case, a minimum of 34 samples is suggested. In all cases, the samples
should be representative of the quality of water supplied during the course of a year
(Ratnayaka et al., 2009).
The primary interest of sampling in this survey is to confirm the presence of the DBPs after
AOP treatment. Therefore, it is not strictly necessary to follow the minimum sampling
frequencies laid out within the Drinking Water Directive; however, they do offer a useful basis
to determine an appropriate minimum number of samples, based on volume of water treated.
As a secondary consideration, it is also important to understand whether the DBPs are being
removed after GAC treatment. Therefore, sampling should be conducted after the AOP unit to
monitor the formation of potential DBPs, with some concurrent sampling also occurring after
GAC treatment to ensure the effectiveness of the GAC in removing the DBPs (if formed). The
rationale for sampling at these two points is two-fold:
firstly, sampling immediately after the AOP unit should allow for the detection of these
DBPs at their highest concentrations in water; therefore, should a consumer drink this
water, these would represent a ‘worst-case’ for exposure. Comparison of the
concentration of the DBPs at this point in the treatment process with any health-based
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guidance values would allow a determination of the risk to these consumers in an
‘extreme’ case; and
sampling after the GAC should act as a confirmation of the effectiveness of this
treatment process in reducing these DBPs, and, assuming that GAC does reduce their
concentrations, allow for a more realistic assessment of consumer exposure. The
frequency of sampling after GAC may vary depending on the efficiency of this unit in
removing DBPs.
The sampling strategy below should be followed at least for one full calendar year to allow for
any seasonal variability of the surface water quality. The strategy should be reviewed
regularly and at least after one year as more data become available. The following sampling
strategy is suggested to reflect the minimum frequencies and volumes mentioned above. AOP
treatment is typically not continuously operated.
Monitor DBP formation during AOP operation (before the GAC).
a. Samples should be collected from the AOP treated stream twice a month, as a
minimum, while the AOP is in operation.
b. A control sample should be collected from the raw water prior to entering the AOP
system. This is to understand the water quality entering the AOP system and detect
any pre-existance of DBP in the raw water prior to the AOP.
c. During seasonal changes (such as high rainfall occurrences) additional samples should
be collected as the nature of organics in surface water can exhibit seasonal variation. In
addition, agricultural run-off may contribute to nitrate concentration in the surface water.
The frequency of sampling should be increased to a daily sampling programme for one
week, or the duration of the event (whichever is shorter). These results should then be
assessed and three possible scenarios considered:
i) if the event has ended, or the apparent event has no influence on DBPs
formation, sampling can be reduced to twice per month;
ii) if the sampling event is continuing beyond one week, such that the DBP
concentrations are elevated, but there is no evidence of a significant variation in
the day-to-day concentrations of DBPs, sampling can be reduced to twice per
week, with a reassessment of the sampling frequency occurring after four weeks;
or
iii) if the sampling event is continuing beyond one week, such that the DBP
concentrations are elevated, and there is evidence of a significant variation in the
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day-to-day concentrations of DBPs, daily sampling should continue until the
concentrations of DBPs return to ‘normal’.
Monitor performance of the GAC unit in removing DBPs:
a. if DBPs are not detected after the AOP, there is no requirement for sampling of the
GAC treated stream; and
b. if DBPs are detected after the AOP, then twice weekly sampling of the GAC product
stream is recommended and should commence with immediate effect. It is anticipated
that GAC would reduce the DBPs. Any detection of DBPs may suggest the failure of
the GAC for removal of the DBPs and therefore trigger a more rigorous sampling
regime. This may ultimately result in termination of AOP and replacement of the GAC.
Prior to the sampling, the external laboratory will be informed of the analysis required
(detailed further in Section 7.6). The analytical centre will provide adequate sampling bottles
containing appropriate preservative chemicals in accordance with the analytical method used
for detecting the requested DBPs. Transport of the solution bottles should be completed in
cool boxes with ice packs and to minimise the risk of Legionella, samples should be kept in
the dark. A range of experimental parameters would be established with the external
laboratory with initial LODs being established during experimental analyses (detailed further in
Section 7.4).
7.8 Conclusions and Suggestions
A range of potential DBPs may arise as a result of the use of AOP treatment. However, the
identified DBPs went through a prioritisation process as part of Objective 4. Nine DBPs were
identified requiring further consideration.
As part of Objective 1 it was identified that currently only two plants are using AOP within
England and Wales. The research undertaken has identified that both of these plants
currently employ the use of GAC.
Based on the data currently available, it may be a reasonable expectation that, following
formation of these potential DBPs via AOP treatment, their concentrations in drinking water
will subsequently be reduced by GAC adsorption, assuming effective operation of the GAC.
This conclusion is based on limited data and further monitoring may be required to validate it.
Prior to instigating a full sampling programme, a number of preliminary steps are required to
ensure that the sampling programme is fit-for-purpose. Further analytical method
development is required using ‘spiked’ water samples to optimise detection limits in UK
drinking water and ensure that results are repeatable. This includes optimisation of calibration
curves and further refinement of LODs.
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There is also a lack of understanding as to the conditions that may favour the formation of
these DBPs. Prior to full-scale sampling, bench-scale analysis should conducted with different
water conditions to determine these conditions. This information can then be used to
determine sites where, should AOPs be employed, there is a reasonable expectation that
these DBPs will be formed. These sites should be the primary focus of the sampling survey.
Once the survey sites have been identified, a number of approaches can be taken. A one-
year, bimonthly sampling strategy is proposed, and has been broadly described in this report.
However, due to a number of unresolved questions, this approach may need to be adjusted
once bench-scale results are known. The approach of sampling over the course of one year
allows for the determination of any seasonal variability of the surface water quality that may
influence the formation of these DBPs.
Within this sampling programme, sampling at each water treatment works will be conducted
over a range of times of the day (morning, afternoon, evening) to address this question. To
fully understand the effects of changes in water conditions that may potentially affect DBP
formation (such as high rainfall events), a sampling programme has also been recommended
to determine the influence of these events.
Sampling in this manner allows for the majority of samples being collected immediately after
AOP treatment. Assuming this represents the highest concentration of DBPs in water this
represents a ‘worst-case’ by which to estimate exposure to the consumer. Sampling after
GAC has also been proposed to confirm the effectiveness of this treatment in reducing DBP
concentrations.
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References
Acero, J.L., Haderlein, S.B., Schmidt, T.C., Suter, M.J.F. and Von Gunten, U. (2001) MTBE oxidation
by conventional ozonation and the combination ozone/hydrogen peroxide: Efficiency of the processes
and bromate Formation. Environmental Science and Technology, 35, 4252-4259.
Adedapo, R. (2005) Disinfection By-Product Formation in Drinking Water Treated with Chlorine
Following UV Photolysis & UV/H2O2.
Agbaba, J., Molnar, J., Tubić, A., Watson, M., Maletić, S. and Dalmacija, B. (2015) Effects of water
matrix and ozonation on natural organic matter fractionation and corresponding disinfection by-products
formation. Water Science and Technology: Water Supply, 15, 75-83.
Agbaba, J., Jazić, J.M., Tubić, A., Watson, M., Maletić, S., Isakovski, M.K. and Dalmacija, B. (2016)
Oxidation of natural organic matter with processes involving O3, H2O2 and UV light: Formation of
oxidation and disinfection by-products. RSC Advances, 6, 86212-86219.
Agency for toxic substances and disease registry (1995) Toxicological Profile for Polycyclic Aromatic
Hydrocarbons (PAHs),(update) PB/95/264370. Atlanta: US Department of Health and Human Services.
US Department of Health Human Services.
Al-Tawabini, B. (2003) Treatment of water contaminated with Di-N-Butyl Phthalate by photo-Fenton
process. Global Nest: the Int J, 5, 23-28.
Alizadeh Fard, M., Aminzadeh, B. and Vahidi, H. (2013) Degradation of petroleum aromatic
hydrocarbons using TiO2 nanopowder film. Environmental technology, 34, 1183-1190.
Amy, G., Bull, R., Craun, G.F., Pegram, R., Siddiqui, M. and Organization, W.H. (2000) Disinfectants
and disinfectant by-products. Environmental Health Criteria 216. World Health Organization.
Andreozzi, R., Caprio, V., Insola, A. and Marotta, R. (1999) Advanced oxidation processes (AOP) for
water purification and recovery. Catalysis Today, 53, 51-59.
Andrews, S.A. and Huck, P.M. (1994) Using Fractionated Natural Organic Matter to Quantitate Organic
Byproducts of Ozonation. Ozone: Science & Engineering, 16, 1-12.
Aquilina, G., Benigni, R., Bignami, M., Calcagnile, A., Dogliotti, E., Falcone, E. and Carere, A. (1984)
Genotoxic activity of dichlorvos, trichlorfon and dichloroacetaldehyde. Pesticide Science, 15, 439-442.
Arslan, A., Topkaya, E., Özbay, B., Özbay, I. and Veli, S. (2017) Application of O3/UV/H2O2 oxidation
and process optimization for treatment of potato chips manufacturing wastewater. Water and
Environment Journal, 31, 64-71.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 125
Atguv (2017) Available from: https://atguv.com/atg-uv-applications/drinking-water/
Azrague, K. and Osterhus, S. (2009) Persistent organic pollutants (POPs) degradation in natural waters
using a V-UV/UV/TiO2 reactor. Water Science and Technology: Water Supply, 9, 653-660.
Bailey, J.C. (1978) Ozonation in organic chemistry, New York, London, Academic Press.
Barceló, D. and Petrovic, M. (2008) Emerging contaminants from industrial and municipal waste:
removal technologies, Springer.
Beber de Souza, J., Queiroz Valdez, F., Jeranoski, R.F., Vidal, C.M.d.S. and Cavallini, G.S. (2015)
Water and wastewater disinfection with peracetic acid and uv radiation and using advanced oxidative
process PAA/UV. International Journal of Photoenergy, 2015.
Benito, Y., Arrojo, S., Hauke, G. and Vidal, P. (2005) Hydrodynamic cavitation as a low-cost AOP for
wastewater treatment: Preliminary results and a new design approach. WIT Transactions on Ecology
and the Environment, 80.
Blanco, M., Martinez, A., Marcaide, A., Aranzabe, E. and Aranzabe, A. (2014) Heterogeneous Fenton
catalyst for the efficient removal of Azo dyes in water. American Journal of Analytical Chemistry, 5, 490.
Boal, A. Groundwater Remediation Using a Chlorine/Ultraviolet Advanced Oxidation Process. 2014
NGWA Groundwater Summit, 2014. Ngwa.
Bokhari, T.H., Abbas, W., Munir, M., Bukhari, I.H. and Khan, M.K. (2015) Impact of UV/TiO2/H2O2 on
degradation of disperse red F3BS. Chemistry - An Asian Journal 27, 282-287
Bond, T., Goslan, E.H., Jefferson, B., Roddick, F., Fan, L. and Parsons, S.A. (2009) Chemical and
biological oxidation of NOM surrogates and effect on HAA formation. Water research, 43, 2615-2622.
Borikar, D., Mohseni, M. and Jasim, S. (2015) Evaluation and Comparison of Conventional and
Advanced Oxidation Processes for the Removal of PPCPs and EDCs and Their Effect on THM-
Formation Potentials. Ozone: Science and Engineering, 37, 154-169.
Brightwater (2017) Available from: www.bwater.eu
Calgon Carbon (2017) Available from: www.calgoncarbon.com
Caretti, C. and Lubello, C. (2003) Wastewater disinfection with PAA and UV combined treatment: a pilot
plant study. Water Research, 37, 2365-2371.
Čehovin, M., Medic, A., Scheideler, J., Mielcke, J., Ried, A., Kompare, B. and Žgajnar Gotvajn, A.
(2017) Hydrodynamic cavitation in combination with the ozone, hydrogen peroxide and the UV-based
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 126
advanced oxidation processes for the removal of natural organic matter from drinking water. Ultrasonics
Sonochemistry, 37, 394-404.
ChemEXPERT™ (2017) CCRIS - Chemical Carcinogenesis Research Information System.
Dichloroacetaldehyde.
ChemSpider (2017) Available from: http://www.chemspider.com/About.aspx
Chin, A. and Bérubé, P.R. (2005) Removal of disinfection by-product precursors with ozone-UV
advanced oxidation process. Water Research, 39, 2136-2144.
Chu, W., Gao, N., Yin, D., Krasner, S.W. and Mitch, W.A. (2014) Impact of UV/H2O2 pre-oxidation on
the formation of haloacetamides and other nitrogenous disinfection byproducts during chlorination.
Environmental Science and Technology, 48, 12190-12198.
Clayden, J., Greeves, N., Warren, S. and Wothers, P. (2001) Organic Chemistry, Oxford University
Press Inc., New York.
COC (2006) Comparative Risk Assessment: Application of the MOE Approach for Communicating the
Risks of Exposure to Genotoxic Carcinogens. Committee on the Carcinogenicity of Chemicals in Food,
Consumer Products and the Environment.
Collins, J. and Cotton, C. (2009) Advanced Oxidation Processes for Contaminant Destruction: Selecting
between Ozone-Peroxide or UV-Peroxide. Arizona: Malcolm Pirnie, Inc.
Cortés, S., Ormad, P., Puig, A. and Ovelleiro, J.L. (1996) Study of the advanced oxidation processes of
chlorobenzenes in water. Ozone: Science and Engineering, 18, 291-298.
Criquet, J. and Leitner, N.K.V. (2009) Degradation of acetic acid with sulfate radical generated by
persulfate ions photolysis. Chemosphere, 77, 194-200.
Czaplicka, M., Jaworek, K. and Bąk, M. (2015) Study of photodegradation and photooxidation of p-
arsanilic acid in water solutions at pH = 7: kinetics and by-products. Environmental Science and
Pollution Research, 22, 16927-16935.
Delaney, E.J. (2007) An impact analysis of the application of the threshold of toxicological concern
concept to pharmaceuticals. Regulatory Toxicology and Pharmacology, 49, 107-124.
Deng, L., Huang, C.H. and Wang, Y.L. (2014) Effects of combined UV and chlorine treatment on the
formation of trichloronitromethane from amine precursors. Environmental Science and Technology, 48,
2697-2705.
Derks, J. (2010) Performance comparison of LP vs. MP mercury vapour lamps.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 127
Dillon, G., Hall, T., Jonsson, J., Murrell, K., Shepherd, D., Song, J. and Stanger, M. (2011) Treatment
for New and Emerging Pesticides. UKWIR.
Dindar, E. (2016) An Overview of the Application of Hydrodinamic Cavitation for the Intensification of
Wastewater Treatment Applications: A Review. Innovative Energy & Research, 5.
Dotson, A.D., Keen, V.S., Metz, D. and Linden, K.G. (2010) UV/H2O2 treatment of drinking water
increases post-chlorination DBP formation. Water Research, 44, 3703-3713.
Eilers, R. (1994) Hydrodynamic Cavitation Oxidation Destroys Organics. Environmental Protection
Agency.
El-Kalliny, A. (2013) Photocatalytic Oxidation in Drinking Water Treatment Using Hypochlorite and
Titanium Dioxide. Master of Science in Chemistry, Ain Shams University, Egypt.
EPA (1995) Dichlorvos; Notice of Preliminary Determination to Cancel Certain Registrations and Draft
Notice of Intent to Cancel. Federal Register, 60.
ESCO International (2017) Available from: http://www.escouk.com/processes/catadox-process/
European Commission (2009) Risk assessment methodologies and approaches for genotoxic and
carcinogenic substances European Commission.
European Food Safety, A. and World Health, O. (2016) Review of the Threshold of Toxicological
Concern (TTC) approach and development of new TTC decision tree. EFSA Supporting Publications,
13, 1006E-n/a.
Evoqua (2017) Available from: www.evoqua.com
Fang, J.-Y. and Shang, C. (2012) Bromate Formation from Bromide Oxidation by the UV/Persulfate
Process. Environmental Science & Technology, 46, 8976-8983.
Fischer, G.W., Schneider, P. and Scheufler, H. (1977) [Mutagenicity of dichloroacetaldehyde and 2,2-
dichloro-1,1-dihydroxy-ethanephosphonic acid methyl ester, possible metabolites of the
organophosphate pesticide Trichlorphon]. Chem Biol Interact, 19, 205-13.
Frimmel, F.H., Hesse, S. and Kleiser, G. (2000) Technology-related characterization of hydrophilic
disinfection by-products in aqueous samples. ACS Publications.
Fukushima, S. (2010) Carcinogenic risk assessment: are there dose thresholds for carcinogens? Asian
Pac J Cancer Prev, 11, 19-21.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 128
Garcia, J., Oliveira, J., Silva, A., Oliveira, C., Nozaki, J. and De Souza, N. (2007) Comparative study of
the degradation of real textile effluents by photocatalytic reactions involving UV/TiO 2/H 2 O 2 and
UV/Fe 2+/H 2 O 2 systems. Journal of Hazardous Materials, 147, 105-110.
Gerrity, D., Mayer, B., Ryu, H., Crittenden, J. and Abbaszadegan, M. (2009) A comparison of pilot-scale
photocatalysis and enhanced coagulation for disinfection byproduct mitigation. Water research, 43,
1597-1610.
Gilmour, C.R. (2012) Water Treatment using Advanced Oxidation Processes: Application Perspectives.
Masters in Engineering Science, Department of Chemical and Biochemical Engineering, The University
of Western Ontario, London, Ontario, Canada.
Giri, R., Ozaki, H., Takanami, R. and Taniguchi, S. (2008) Heterogeneous photocatalytic ozonation of
2, 4-D in dilute aqueous solution with TiO2 fiber. Water Science and Technology, 58, 207-216.
Glaze, W.H., Kang, J.-W. and Chapin, D.H. (1987) The chemistry of water treatment processes
involving ozone, hydrogen peroxide and ultraviolet radiation.
Glaze, W.H., Weinberg, H.S. and Cavanagh, J.E. (1993) Evaluating the Formation of Brominated DBPs
During Ozonation. American Water Works Association, 85, 96-103.
Gogate, P.R. and Pandit, A.B. (2004) A review of imperative technologies for wastewater treatment I:
oxidation technologies at ambient conditions. Advances in Environmental Research, 8, 501-551.
Grote, B. Application of Advanced Oxidation Processes (AOP) in Water Treatment. 37th Annual Qld
Water Industry Operations Workshop 2012.
He, J., Yang, X., Men, B. and Wang, D. (2016) Interfacial mechanisms of heterogeneous Fenton
reactions catalyzed by iron-based materials: A review. Journal of Environmental Sciences, 39, 97-109.
Heidt, L.J. (1942) The photolysis of persulfate. The Journal of Chemical Physics, 10, 297-302.
Hodgeson, J., Cohen, A. and Munch, D. (1990) Determination of Chlorination Disinfection Byproducts,
Chlorinated Solvents, and Halogenated Pesticides/herbicides in Drinking Water by Liquid-liquid
Extraction and Gas Chromatography with Electron Capture Detection. Environmental Protection
Agency, Cincinnati, USA.
Hofman-Caris, C. and Beerendonk, E. (2011) New concepts of UV/H2O2 oxidation. KWR Watercycle
Research Institute, Nieuwegein, the Netherlands.
Hoigné, J. (1998) Chemistry of aqueous ozone and transformation of pollutants by ozonation and
advanced oxidation processes. Quality and treatment of drinking water II. Springer.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 129
Humfrey, C.D.N. (2007) Recent Developments in the Risk Assessment of Potentially Genotoxic
Impurities in Pharmaceutical Drug Substances. Toxicological Sciences, 100, 24-28.
Huston, P.L. and Pignatello, J.J. (1999) Degradation of selected pesticide active ingredients and
commercial formulations in water by the photo-assisted Fenton reaction. Water Research, 33, 1238-
1246.
Ijpelaar, G.F., Groenendijk, M., Hopman, R. and Kruithof, J.C. (2002) Advanced oxidation technologies
for the degradation of pesticides in ground water and surface water. Water Science and Technology:
Water Supply.
IJpelaar, G.F., Harmsen, D.J.H. and Heringa, M. (2007) UV disinfection and UV/H2O2 oxidation: by-
product formation and control. Techneau.
James, C.P. (2013) Advanced oxidation processes for wastewater reuse-removal of micropollutants.
Jasim, S.Y., Ndiongue, S., Alshikh, O. and Jamal, A.T. (2012) Impact of Ozone and Hydrogen Peroxide
vs. UV and Hydrogen Peroxide on Chlorine Residual. Ozone: Science and Engineering, 34, 16-25.
Jo, C.H. (2008) Oxidation of Disinfection Byproducts and Algae-related Odourants by UV/H2O2. Doctor
of Philosophy in Civil and Environmental Engineering, Virginia Polytechnic Institute and State
University.
Jo, C.H., Dietrich, A.M. and Tanko, J.M. (2011a) Simultaneous degradation of disinfection byproducts
and earthy-musty odorants by the UV/H 2 O 2 advanced oxidation process. Water research, 45, 2507-
2516.
Jo, C.H., Dietrich, A.M. and Tanko, J.M. (2011b) Simultaneous degradation of disinfection byproducts
and earthy-musty odorants by the UV/H2O2 advanced oxidation process. Water Research, 45, 2507-
2516.
Kawai, A., Goto, S., Matsumoto, Y. and Matsushita, H. (1987) [Mutagenicity of aliphatic and aromatic
nitro compounds. Industrial materials and related compounds]. Sangyo Igaku, 29, 34-54.
Kleiser, G. and Frimmel, F. (2000) Removal of precursors for disinfection by-products (DBPs)—
differences between ozone-and OH-radical-induced oxidation. Science of the Total Environment, 256,
1-9.
Kolkman, A., Martijn, B.J., Vughs, D., Baken, K.A. and van Wezel, A.P. (2015) Tracing nitrogenous
disinfection byproducts after medium pressure UV water treatment by stable isotope labeling and high
resolution mass spectrometry. Environmental science & technology, 49, 4458-4465.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 130
Kommineni, S., Zoeckler, J., Stocking, A., Liang, S., Flores, A. and Kavanaugh, M. (1999) Advanced
Oxidation Processes. Technologies for the Removal of Methyl Tertiary Butyl Ether (MTBE) from
Drinking Water: Air Stripping, Advanced Oxidation Processes, Granular Activated Carbon, Synthetic
Resin Sorbents. Second ed.
Kommineni, S., Zoeckler, J., Stocking, A., Liang, S., Flores, A. and Kavanaugh, M. (2008) Advanced
oxidation processes. national water research institute.
Krasner, S.W., Weinberg, H.S., Richardson, S.D., Pastor, S.J., Chinn, R., Sclimenti, M.J., Onstad, G.D.
and Thruston, A.D. (2006) Occurrence of a new generation of disinfection byproducts. Environmental
science & technology, 40, 7175-7185.
Krasner, S.W. (2009) The formation and control of emerging disinfection by-products of health concern.
Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering
Sciences, 367, 4077-4095.
Krasner, S.W., Mitch, W.A., Westerhoff, P. and Dotson, A. (2012) Formation and control of emerging C-
and N-DBPs in drinking water. Journal: American Water Works Association, 104.
Kutz, M. (2007) Environmentally conscious materials and chemicals processing, John Wiley & Sons.
KWR (2011) New Concepts of UV/H2O2 Oxidation.
Lamsal, R., Walsh, M.E. and Gagnon, G.A. (2011) Comparison of advanced oxidation processes for
the removal of natural organic matter. Water research, 45, 3263-3269.
Lekkerkerker-Teunissen, K. (2012) Advanced oxidation and managed aquifer recharge: A synergistic
hybrid for organic micropollutant removal.
Lenntech (2017) Water Treatment: Disinfectants Peroxone [Online]
Lide, D.R. (1998) Handbook of chemistry and physics, 87 edn. Boca Raton, FL: CRC Press).
Murakami, M., Taketomi, Y., Miki, Y., Sato, H., Hirabayashi, T., and Yamamoto, K.(2011). Recent
progress in phospholipase A₂ research: from cells to animals to humans. Prog. Lipid Res.
Liu, W., Andrews, S.A., Stefan, M.I. and Bolton, J.R. (2003) Optimal methods for quenching H 2 O 2
residuals prior to UFC testing. Water Research, 37, 3697-3703.
Lutze, H. (2013) Sulfate radical based oxidation in water treatment. Dissertation Dr. rer. nat. Duisburg-
Essen. https://duepublico. uni-duisburg-essen. de/servlets/DerivateServlet/Derivate-35021/Lutze_Diss.
pdf. Accessed 13 Febr.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 131
MacAdam, J. and Parsons, S.A. (2009) An investigation into advanced oxidation of three
chlorophenoxy pesticides in surface water. Water Science and Technology, 59, 1665-1671.
Malley, J.P., Jr. (2008) Advanced Oxidation Process Basics and Emerging Applications in Water
Treatment. IUVA News, July 2008.
Mehrjouei, M. (2012) Advanced oxidation processes for water treatment: reactor design and case
studies.
Mehrjouei, M., Müller, S. and Möller, D. (2012) Synergistic effect of the combination of immobilized
TiO2, UVA and ozone on the decomposition of dichloroacetic acid. Journal of Environmental Science
and Health, Part A, 47, 1073-1081.
Metz, D.H., Meyer, M., Dotson, A., Beerendonk, E. and Dionysiou, D.D. (2011) The effect of UV/H2O2
treatment on disinfection by-product formation potential under simulated distribution system conditions.
Water Research, 45, 3969-3980.
Miguel, N., Ormad, M.P., Mosteo, R. and Ovelleiro, J.L. (2012) Photocatalytic degradation of pesticides
in natural water: Effect of hydrogen peroxide. International Journal of Photoenergy, 2012.
Mo, J., Jiang, J., Peng, L., Xie, R. and Jiang, W. (2015) Study on degradation of humic acids by
UV/O3/H2O2 processes. Fresenius Environmental Bulletin, 24, 2017-2025.
Munter, R. (2001) Advanced oxidation processes–current status and prospects. Proc. Estonian Acad.
Sci. Chem, 50, 59-80.
Nawrocki, J., Świetlik, J., Raczyk-Stanisławiak, U., Dąbrowska, A., Biłozor, S. and Ilecki, W. (2003)
Influence of Ozonation Conditions on Aldehyde and Carboxylic Acid Formation. Ozone: Science &
Engineering, 25, 53-62.
NCBI (2017) National Center for Biotechnology Information - PubChem Database, Available from:
https://pubchem.ncbi.nlm.nih.gov/
Neng, N.R. and Nogueira, J.M.F. (2010) Determination of short-chain carbonyl compounds in drinking
water matrices by bar adsorptive micro-extraction (BAμE) with in situ derivatization. Analytical and
Bioanalytical Chemistry, 398, 3155-3163.
Ocampo, A.M. (2009) Persulfate Activation by Organic Compounds. Doctor of Philosophy, Washington
State University.
Onstad, G.D., Weinberg, H.S. and Krasner, S.W. (2008) Occurrence of halogenated furanones in U.S.
drinking waters. Environmental Science and Technology, 42, 3341-3348.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 132
Paillard, H., Brunet, R. and Dore, M. (1988) Optimal conditions for applying an ozone-hydrogen
peroxide oxidizing system. Water Research, 22, 91-103.
Patterson, C.L., Cadena, F., Sinha, R., Ngo‐Kidd, D.K., Ghassemi, A. and Radha Krishnan, E. (2013)
Field Treatment of MTBE‐Contaminated Groundwater Using Ozone/UV Oxidation. Groundwater
Monitoring & Remediation, 33, 44-52.
Peroxide., U. (2017) Fenton's Reagent General Chemistry Using H2O2. (accessed June 2017) [Online]
Pisarenko, A.N., Stanford, B.D., Snyder, S.A., Rivera, S.B. and Boal, A.K. (2013) Investigation of the
use of chlorine based advanced oxidation in surface water: Oxidation of natural organic matter and
formation of disinfection byproducts. Journal of Advanced Oxidation Technologies, 16, 137-150.
PubChem (2017a) 3,5-DINITROSALICYLIC ACID [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/11873
PubChem (2017b) 5-Nitrovanillin [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/81134
PubChem (2017c) 4-HYDROXY-3-NITROBENZOIC ACID [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/12033
PubChem (2017d) 4-NITROBENZENESULFONIC ACID [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/8740
PubChem (2017e) 4-nitrocatechol [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/3505109
PubChem (2017f) 4-Nitrophthalic acid [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/69121
PubChem (2017g) 5-Nitrosalicylic acid [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/7318
PubChem (2017h) DICHLOROACETALDEHYDE [Online] Available from:
https://pubchem.ncbi.nlm.nih.gov/compound/6576
Purifics (2017) Available from: www.purifics.com
Ratnayaka, D.D., Brandt, M.J. and Johnson, M. (2009) Twort's Water Supply 6th Edition, IWA
Publishing, 231.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 133
Richardson, S.D., Thruston, A.D., Jr., Collette, T.W., Patterson, K.S., Lykins, B.W. and Ireland, J.C.
(1996) Identification of TiO2/UV Disinfection Byproducts in Drinking Water. Environmental Science and
Technology, 30, 3327-3334.
Richardson, S.D., Thruston Jr, A.D., Caughran, T.V., Chen, P.H., Collette, T.W., Schenck, K.M., Lykins
Jr, B.W., Rav-Acha, C. and Glezer, V. (2000) Identification of new drinking water disinfection by-
products from ozone, chlorine dioxide, chloramine, and chlorine. Water, Air, and Soil Pollution, 123, 95-
102.
Rieder, S., Hofstetter, T. and Von Gunten, U. (2007) The new generation of disinfection byproducts
(DBPs). Citeseer.
Robinson, K. (2016) UV/Chlorine AOP for Potable Reuse: Lower Cost Option. Water Reuse in Texas.
Rosenfeldt, E., Boal, A.K., Springer, J., Stanford, B., Rivera, S., Kashinkunti, R.D. and Metz, D.H.
(2013) Tech Talk--Comparison of UV-mediated Advanced Oxidation (PDF). Journal-American Water
Works Association, 105, 29-33.
RTECs (2017a) Registry of Toxic Effects of Chemical Substances (RTECs). Phenol, 2,4-dinitro-6-
methoxy-. ChemEXPERT® [Online]
RTECs (2017b) Registry of Toxic Effects of Chemical Substances (RTECs). Salicylic acid, 3,5-dinitro-.
ChemEXPERT® [Online]
Sarathy, S.R., Stefan, M.I., Royce, A. and Mohseni, M. (2011) Pilot-scale UV/H 2O 2 advanced
oxidation process for surface water treatment and downstream biological treatment: Effects on natural
organic matter characteristics and DBP formation potential. Environmental Technology, 32, 1709-1718.
Scheideler, J. and Holden, B. Improving UV advanced oxidation processes for the removal of pesticides
by an upstream ozonation process Asia-Pacific Wastewater Treatment and Reuse Conference, 2015.
Shah, A.D. and Mitch, W.A. (2012) Halonitroalkanes, halonitriles, haloamides, and N-nitrosamines: A
critical review of nitrogenous disinfection byproduct formation pathways. Environmental Science and
Technology, 46, 119-131.
Sharpless, C.M., Page, M.A. and Linden, K.G. (2003) Impact of hydrogen peroxide on nitrite formation
during UV disinfection. Water research, 37, 4730-4736.
Springer, J. and Kashinkunti, R. (2015) UV/Cl2 AOP Pilot Study. OAWWA Conference.
Stasinakis, A.S. (2008) Use of Selected Advanced Oxidation Processes (AOPs) for Watewaster
Treatment - A Mini Review. Global NEST Journal, 10, 376-385.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 134
Toor, R. and Mohseni, M. (2007) UV-H2O2 based AOP and its integration with biological activated
carbon treatment for DBP reduction in drinking water. Chemosphere, 66, 2087-2095.
Tran, H., Evans, G., Yan, Y. and Nguyen, A. (2009) Photocatalytic removal of taste and odour
compounds for drinking water treatment. Water Science and Technology: Water Supply, 9, 477-483.
Trojan (2017) Available from: www.trojanuv.com
Upelaar, G., Meijers, R., Hopman, R. and Kruithof, J. (2000) Oxidation of Herbicides in Groundwater by
the Fenton Process: A Realistic Alternative for O3/H2O2 Treatment? Ozone: science & engineering,
22, 607-616.
US EPA (1999) Alternative Disinfectants and Oxidants Guidance Manual. Office of Water (4607):
United States Environmental Protection Agency.
Von Gunten, U. and Oliveras, Y. (1998) Advanced oxidation of bromide-containing waters: bromate
formation mechanisms. Environmental science & technology, 32, 63-70.
Vughs, D., Baken, K., Kolkman, A., Martijn, A. and de Voogt, P. (2016) Application of effect-directed
analysis to identify mutagenic nitrogenous disinfection by-products of advanced oxidation drinking
water treatment. Environmental Science and Pollution Research, 1-14.
Wang, D., Bolton, J.R., Andrews, S.A. and Hofmann, R. (2015) Formation of disinfection by-products in
the ultraviolet/chlorine advanced oxidation process. Science of the Total Environment, 518-519, 49-57.
Wang, Y., Le Roux, J., Zhang, T. and Croué, J.-P. (2014) Formation of brominated disinfection
byproducts from natural organic matter isolates and model compounds in a sulfate radical-based
oxidation process. Environmental science & technology, 48, 14534-14542.
Wang, Z., Lin, Y.L., Xu, B., Xia, S.J., Zhang, T.Y. and Gao, N.Y. (2016) Degradation of iohexol by
UV/chlorine process and formation of iodinated trihalomethanes during post-chlorination. Chemical
Engineering Journal, 283, 1090-1096.
WHO (2000) Environmental Health Criteris 216: Disinfectants and Disinfectant By-products. Geneva:
World Health Organization.
WHO (2001) Guidance Document for the Use of Data in Development of Chemical-Specific Adjustment
Factors (CSAFs) for Interspecies Differences and Human Variability in Dose/Concentration–Response
Assessment. World Health Organisation.
WHO (2009) A Risk-Based Decision Tree Approach for the Safety Evaluation of Residues of Veterinary
Drugs. World Health Organisation.
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 135
Wiley, J. (2010) White’s handbook of chlorination and alternative disinfectant. New York: Black and
Veatch Corporation.
Wu, T. and Englehardt, J.D. (2016) Mineralizing urban net-zero water treatment: Field experience for
energy-positive water management. Water Research, 106, 352-363.
Wu, Z., Fang, J., Xiang, Y., Shang, C., Li, X., Meng, F. and Yang, X. (2016) Roles of reactive chlorine
species in trimethoprim degradation in the UV/chlorine process: Kinetics and transformation pathways.
Water Research, 104, 272-282.
Xiao, Y., Zhang, L., Zhang, W., Lim, K.-Y., Webster, R.D. and Lim, T.-T. (2016) Comparative evaluation
of iodoacids removal by UV/persulfate and UV/H2O2 processes. Water Research, 102, 629-639.
Xie, P., Ma, J., Liu, W., Zou, J., Yue, S., Li, X., Wiesner, M.R. and Fang, J. (2015) Removal of 2-MIB
and geosmin using UV/persulfate: contributions of hydroxyl and sulfate radicals. Water research, 69,
223-233.
Xue, Y., Dong, W., Wang, X., Bi, W., Zhai, P., Li, H. and Nie, M. (2016) Degradation of sunscreen agent
p-aminobenzoic acid using a combination system of UV irradiation, persulphate and iron(II).
Environmental Science and Pollution Research, 23, 4561-4568.
Xylem (2017) Available from: www.xylem.com
Yang, X., Sun, J., Fu, W., Shang, C., Li, Y., Chen, Y., Gan, W. and Fang, J. (2016) PPCP degradation
by UV/chlorine treatment and its impact on DBP formation potential in real waters. Water Research, 98,
309-318.
Yano, J., Matsuura, J.-i., Ohura, H. and Yamasaki, S. (2005a) Complete mineralization of propyzamide
in aqueous solution containing TiO2 particles and H2O2 by the simultaneous irradiation of light and
ultrasonic waves. Ultrasonics sonochemistry, 12, 197-203.
Yano, J., Matsuura, J., Ohura, H. and Yamasaki, S. (2005b) Complete mineralization of propyzamide in
aqueous solution containing TiO2 particles and H2O2 by the simultaneous irradiation of light and
ultrasonic waves. Ultrason Sonochem, 12, 197-203.
Zhong, X., Cui, C. and Yu, S. (2017) Seasonal evaluation of disinfection by-products throughout two
full-scale drinking water treatment plants. Chemosphere, 179, 290-297.
Zoschke, K., Dietrich, N., Börnick, H. and Worch, E. (2012) UV-based advanced oxidation processes
for the treatment of odour compounds: Efficiency and by-product formation. Water Research, 46, 5365-
5373.
DWI
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© WRc plc 2018 136
Zúñiga-Benítez, H., Aristizábal-Ciro, C. and Peñuela, G.A. (2016) Heterogeneous photocatalytic
degradation of the endocrine-disrupting chemical Benzophenone-3: Parameters optimization and by-
products identification. Journal of Environmental Management, 167, 246-258.
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Appendix A Water company survey
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Appendix B Water company responses
B1 Company 1
1. Current Use of Advanced Oxidation Processes (AOPs)
1.1. Is your company currently employing AOPs at any
drinking water treatment works?
Yes ☒ Please proceed to Question 1.2
No ☐ Please proceed to Question 2
1.2. At how many drinking water treatment works does your
company currently employ AOPs?
…………………………….
For each works employing an AOP, please complete the following table. This table can be
copied/duplicated multiple times if required.
1.3. Description of currently used AOP process (please copy and paste this table as many times as
required)
1.3.1. Please describe the AOP. Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☒
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
1.3.2. Please describe the main treatment
objective(s) of the AOP (e.g.
metaldehyde, other pesticides).
Metaldehyde, clopyralid and general pesticides
……………………………….
1.3.3. Please describe the main driver for
the selection of this AOP (e.g.
achieving the treatment objective,
cost, reducing DBP formation).
At the time only company with process guarantee for
metaldehyde was offering UV /H2O2
……………………………….
1.3.4. Is this installation a permanent or
trial installation?
Trial/Pilot plant ☐
Permanent ☒
1.3.5. When was this system installed?
……March 2015…………. (month/year)
1.3.6. What are the typical dose rate(s) or
dose range(s) for the AOP?
works to 0.6 log reduction metaldehyde
1.3.7. What is the flow rate?
up to 20 mld……….
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1.3.8. Please describe the characteristics
of the water at this works.
Hardwater ☒
Softwater ☐
Groundwater ☐
Upland surface water ☐
Lowland surface water ☒
Other ☐ Please describe below
………………………………
1.3.9. Please describe the typical summer
and winter water quality
characteristics of this water (as
measured at, or as close as possible)
to the inlet of the AOP.
Summer:
pH 7.6
Alkalinity: 160 .mg/l CaCO3
Turbidity: …………0.1… ……NTU
Bromide: …………150 ………μg/l Br-
TOC: ………………4.0……………...mg/l
UVT: …………………87…………%
or
UV254abs:…………………………cm-1
Winter
pH
Alkalinity: …………155…………mg/l CaCO3
Turbidity: …………0.1…………….NTU
Bromide: …………177…………….μg/l Br-
TOC: ………………5.2……………mg/l
UVT: ………………86……………….%
or
UV254abs:………………………….cm-1
DWI
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1.3.10. Please identify the DBPs you are
encountering in the final water at this
works and approximate
concentration ranges.
1.3.11. Have you noticed periods of
increase or decrease in DBPs (e.g.
seasonal)?
1.3.12. Please describe what measures, if
any, are being used to control these
DBPs.
1.3.13. Do you have a procedure in place
for responding to elevated
concentrations of DBPs? (What is
considered elevated?)
1.3.14. Which methods are used to
identify/analyse the DBP?
1.3.15. Was an analysis performed to
identify potential DBPs prior to
installation of the AOP?
1.3.16. Have concentrations of DBPs
changed since installation?
Some brominated THM
……………………………….……………………………….
.
Seasonal with water temperature.
……………………………….……………………………….
Roughing GAC regeneration to aid precursor removal
……………………………….……………………………….
Yes when total THM approaches 50µg/l….
……………………………….……………………………….
……………………………….……………………………….
Standard laboratory method, tried multisensor online with no
success……………………………….……………………………….
Site is new and designed from day 1 with AOP…………….
……………………………….……………………………….
Yes lower due to change in GAC regeneration frequency.
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
2. Future Use/Anticipated Use of Advanced Oxidation Processes (AOPs)
For each AOP that may potentially be used in the future, please complete the following table. This table
can be copied/duplicated multiple times if required.
2.1. Please tick, as appropriate, any of the following trials if
your company is undertaking such research using AOPs.
Bench-scale ☒
Laboratory-scale ☐
2.2. If you ticked either option in question 2.1, please describe
the AOPs you are currently investigating.
Ozone/Hydrogen peroxide ☒
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
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Other ☐ Please describe below
………………………………
2.3. Do you anticipate installing AOPs at your drinking water
treatment works within the next five years?
Yes ☐ Please proceed to Question 2.3.1
No ☒ Please proceed to Question 2.4
2.3.1. Please describe which AOPs you expect to install and
the rationale behind that choice of AOP.
Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
Rationale for choice
………………………………
2.4. Do you anticipate installing AOPs at your drinking water
treatment works within the next ten years?
Yes ☒ Please proceed to Question 2.4.1
No ☐ Please proceed to Question 3
2.4.1. Please describe which AOPs you expect to install and
the rationale behind that choice of AOP.
Ozone/Hydrogen peroxide ☒
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
Rationale for choice
reuse of existing ozone plant……
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3. Ozonation by-products:
WTW Name**
Volume
output
(MLD)
Water
Source *
Reason for O3 use.
(pesticide removal,
disinfection)
O3 Dose
(mg/l)
Does the
works have
GAC? (Y/N)
Are DBP monitored?
(Exclude Bromate and THM).
Which and concentration (µg/L)
Other comments
Site 1 45 L Pesticide removal 1.0 Y No Ozone split pre plant/post filters
Site 2 30 L Pesticide removal Y No Ozone split pre plant/post filters
Site 3 16 L Pesticide removal 1.1 Y No Ozone split pre plant/post filters
Site 4 24 L Pesticide removal 1.8 Y No Ozone split pre plant/post filters
Site 5 60 L Pesticide removal 1.2 Y No Ozone split pre plant/post filters
Site 6 330 L Pesticide removal 1.6 Y No Ozone split pre plant/post filters
Site 7 250 L Pesticide removal 1.3 Y No Ozone split pre plant/post filters
Site 8 90 L Pesticide removal 1.5 Y No Ozone split pre plant/post filters
Site 9 45 L Pesticide removal 1.4 Y No Ozone split pre plant/post filters
Site 10 24 L Pesticide removal 1.2 Y No Post membrane ozone only
Site 11 30 L Pesticide removal 1.8 Y No Ozone split pre plant/post filters
Site 12 60 L Pesticide removal 1.6 Y No Ozone split pre plant/post filters
* G – ground; U – upland; L – lowland.
** Either site name or Site 1, Site 2, etc.
DWI
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Thank you for your time in completing this questionnaire. If you have any additional information that
you would like to share, or wish to elaborate on any responses to these questions further, please
enter this information in comment box below.
4. Additional comments
Sites 3,4, 5 and 10 are direct abstraction others are reservoir sites
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B2 Company 2
1. Current Use of Advanced Oxidation Processes (AOPs)
1.1. Is your company currently employing AOPs at any
drinking water treatment works?
Yes ☐ Please proceed to Question 1.2
No ☒ Please proceed to Question 2
1.2. At how many drinking water treatment works does your
company currently employ AOPs?
………………none…………….
For each works employing an AOP, please complete the following table. This table can be
copied/duplicated multiple times if required.
1.3. Description of currently used AOP process (please copy and paste this table as many times as
required)
1.3.1. Please describe the AOP. Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
1.3.2. Please describe the main treatment
objective(s) of the AOP (e.g. metaldehyde,
other pesticides).
……………………………….
1.3.3. Please describe the main driver for the
selection of this AOP (e.g. achieving the
treatment objective, cost, reducing DBP
formation).
……………………………….
1.3.4. Is this installation a permanent or trial
installation?
Trial/Pilot plant ☐
Permanent ☐
1.3.5. When was this system installed?
………………………………. (month/year)
1.3.6. What are the typical dose rate(s) or dose
range(s) for the AOP?
……………………………….
1.3.7. What is the flow rate?
……………………………….
1.3.8. Please describe the characteristics of the
water at this works.
Hardwater ☐
Softwater ☐
Groundwater ☐
Upland surface water ☐
Lowland surface water ☐
Other ☐ Please describe below
………………………………
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1.3.9. Please describe the typical summer and
winter water quality characteristics of this
water (as measured at, or as close as
possible) to the inlet of the AOP.
Summer:
pH
Alkalinity: ………………………..mg/l CaCO3
Turbidity: …………………………NTU
Bromide: …………………………μg/l Br-
TOC: ……………………………...mg/l
UVT: ………………………………%
or
UV254abs:…………………………cm-1
Winter
pH
Alkalinity: …………………………mg/l CaCO3
Turbidity: ………………………….NTU
Bromide: ………………………….μg/l Br-
TOC: ………………………………mg/l
UVT: ……………………………….%
or
UV254abs:………………………….cm-1
1.3.10. Please identify the DBPs you are
encountering in the final water at this works
and approximate concentration ranges.
1.3.11. Have you noticed periods of increase or
decrease in DBPs (e.g. seasonal)?
1.3.12. Please describe what measures, if any,
are being used to control these DBPs.
1.3.13. Do you have a procedure in place for
responding to elevated concentrations of
DBPs? (What is considered elevated?)
1.3.14. Which methods are used to
identify/analyse the DBP?
1.3.15. Was an analysis performed to identify
potential DBPs prior to installation of the
AOP?
1.3.16. Have concentrations of DBPs changed
since installation?
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
……………………………….……………………………….
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2. Future Use/Anticipated Use of Advanced Oxidation Processes (AOPs)
For each AOP that may potentially be used in the future, please complete the following table. This table
can be copied/duplicated multiple times if required.
2.1. Please tick, as appropriate, any of the following trials if
your company is undertaking such research using AOPs.
Bench-scale ☐
Laboratory-scale ☐
2.2. If you ticked either option in question 2.1, please describe
the AOPs you are currently investigating.
Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
2.3. Do you anticipate installing AOPs at your drinking water
treatment works within the next five years?
Yes ☐ Please proceed to Question 2.3.1
No ☒ Please proceed to Question 2.4
2.3.1. Please describe which AOPs you expect to install and
the rationale behind that choice of AOP.
Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
Rationale for choice
………………………………
2.4. Do you anticipate installing AOPs at your drinking water
treatment works within the next ten years?
Yes ☐ Please proceed to Question 2.4.1
No ☐ Please proceed to Question 3
Don’t know
2.4.1. Please describe which AOPs you expect to install and
the rationale behind that choice of AOP.
Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
Rationale for choice
………………………………
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3. Ozonation by-products:
WTW Name**
Volume
output
(MLD)
Water
Source *
Reason for O3 use.
(pesticide removal,
disinfection)
O3 Dose
(mg/l)
Does the
works have
GAC? (Y/N)
Are DBP monitored?
(Exclude Bromate and THM).
Which and concentration (µg/L)
Other comments
Site 1 45 Lowland
river pesticide
Main
ozone Run
to residual
of 0.1mg/l
y Chlorate primarily due to
hypochlorite use Pre and main ozone
Site 2 68
Lowland
River or v
small
reservoir
pesticide
Run to
residual of
0.1mg/l
y N Main ozone prior to GAC
Site 3 22 Lowland
reservoir pesticide
Run to
residual of
0.1mg/l
y N Main ozone prior to GAC
Site 4 22 Lowland
reservoir pesticide
Run to
residual of
0.1mg/l
y N Main ozone prior to GAC
* G – ground; U – upland; L – lowland.
** Either site name or Site 1, Site 2, etc.
DWI
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Thank you for your time in completing this questionnaire. If you have any additional information that
you would like to share, or wish to elaborate on any responses to these questions further, please
enter this information in comment box below.
4. Additional comments
DWI
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B3 Company 3
1. Current Use of Advanced Oxidation Processes (AOPs)
1.1. Is your company currently employing AOPs at any
drinking water treatment works?
Yes ☐ Please proceed to Question 1.2
1.2. At how many drinking water treatment works does
your company currently employ AOPs?
1
For each works employing an AOP, please complete the following table. This table can be
copied/duplicated multiple times if required.
1.3. Description of currently used AOP process (please copy and paste this table as many times as
required)
1.3.1. Please describe the AOP. Hydrogen peroxide/UV (pre GAC)
c5.0mg/l of H2O2, 450-650mj/cm2 UV dose.
1.3.2. Please describe the main treatment objective(s) of
the AOP (e.g. metaldehyde, other pesticides).
Other pesticides & Geosmin/MIB.
1.3.3. Please describe the main driver for the selection
of this AOP (e.g. achieving the treatment
objective, cost, reducing DBP formation).
Uncertainty at the time over metaldehyde risk,
more absolute barrier (in combination with GAC)
to general pesticide risk from horticultural
catchment.
Secondary benefit that it would potentially
address seasonal geosmin/MIB events in the
raw water (generally related to algal blooms).
1.3.4. Is this installation a permanent or trial
installation?
Permanent
1.3.5. When was this system installed? July 2012
1.3.6. What are the typical dose rate(s) or dose range(s)
for the AOP?
450-650mj/cm2, 5.0mg/l H2O2
1.3.7. What is the flow rate? c5.5 - 12MLD
1.3.8. Please describe the characteristics of the water at
this works.
Softwater
Lowland surface water
Eutrophic reservoir source with horticultural
catchment
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1.3.9. Please describe the typical summer and winter
water quality characteristics of this water (as
measured at, or as close as possible) to the inlet
of the AOP.
All available sample results from 01/01/2012 to
date used to calculate average concentrations:
[*Filtered water (immediately prior to AOP)
++ Raw Water]
Average concentrations Summer (April –
September inclusive):
*pH – 6.14
*Turbidity – <current laboratory LOD (0.22NTU)
*Bromate – 1.84ug/l
++Bromide – 151.3ug/l
*TOC – 1.84mg/l
*UV Transmittance at 254nm – 94.45%
Average concentrations Winter (October – March
inclusive):
*pH – 6.52
*Turbidity – <current laboratory LOD (0.22NTU)
*Bromate – 1.78ug/l
++Bromide – 129.43ug/l
*TOC – 2.02mg/l
*UV Transmittance at 254nm – 94.58%
1.3.10. Please identify the DBPs you are encountering
in the final water at this works and approximate
concentration ranges.
All available sample results since the AOP was
commissioned in July 2012 reviewed:
Bromate – All results below laboratory LOD
HAAs:
Bromochloroacetic Acid (BCA) – zero to 2.4ug/l
Bromodichloroacetic Acid (MBA) – zero to 0.7ug/l
Dalapon – zero to 0.2ug/l
Dibromoacetic Acid (DBA) – zero to 4.7ug/l
Dibromochloroacetic Acid – zero to 1.5ug/l
Dichloroacetic Acid – zero to 2.7ug/l
Monobromoacetic Acid (MBA) – zero to 0.5ug/l
Monochloroacetic Acid – zero to 1.0ug/l
Tribromoacetic Acid – zero to 2.2ug/l
Trichloroacetic Acid – zero to 1.0ug/l
Total HAAs – zero to 13.3
THMs:
Bromodichloromethane – 0.1 to 37.3ug/l
Dibromochloromethane – 0.1 to 27.7ug/l
Tribromomethane – 0.1 to 36.1ug/l
Trichloromethane – 0.2 to 9.3ug/l
Total THMs – 0.9 to 77.4ug/l
DWI
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1.3.11. Have you noticed periods of increase or
decrease in DBPs (e.g. seasonal)?
Yes.
Higher concentrations are evident during the
summer. Decreases in DBP concentrations are
observed following GAC regeneration.
1.3.12. Please describe what measures, if any, are
being used to control these DBPs.
Process optimisation to remove DBP precursors
and reduce the formation potential in final water.
Management of water age within distribution
network.
1.3.13. Do you have a procedure in place for
responding to elevated concentrations of DBPs?
(What is considered elevated?)
The Company’s internal action limit for THMs is
75 ug/l (individual result), action plan for all
zones where average is >50ug/l.
1.3.14. Which methods are used to identify/analyse the
DBP?
GCMS (by head space)
1.3.15. Was an analysis performed to identify potential
DBPs prior to installation of the AOP?
Yes, genotoxicity testing with KWR, DBP
formation (system mimic method) undertaken
with Trojen (HAA and THM). Post installation /
stabilisation of GAC further DBPFP testing
undertaken for TTHMs (max formation potential
method).
Bromate and biological stability testing
undertaken as part of pilot work.
Plus we have an ongoing operational monitoring
programme.
1.3.16. Have concentrations of DBPs changed since
installation?
Yes, generally reduced/no significant increase in
bromate.
Note: The AOP was commissioned in
conjunction with a GAC process stage (minimum
20 min EBCT). Reduction is associated with
GAC process. All data we have suggested no
significant impact of AOP operated in the manner
we do (low pressure, relatively low peroxide
dose) and with good quality/low DOC water prior
to application of AOP. I expect different results in
different operating conditions. The PhD by Bram
Martijn provides an interesting insight into by-
product formation at the PWNT sites (but this is a
chlorine free environment).
Average final water sample results reviewed for
four years prior to, and four years post
commissioning.
Pre commissioning (July 2008 to June 2012
inclusive):
Bromate – All results below LOD (0.6ug/l at time)
Total HAAs – 3.79ug/l
Total THMs – 45.3ug/l
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Post commissioning (July 2012 to June 2016
inclusive):
Bromate – All results below LOD (2.4ug/l at time)
Total HAAs – 3.36ug/l
Total THMs – 32.6ug/l
2. Future Use/Anticipated Use of Advanced Oxidation Processes (AOPs)
For each AOP that may potentially be used in the future, please complete the following table. This table
can be copied/duplicated multiple times if required.
2.1. Please tick, as appropriate, any of the following
trials if your company is undertaking such research
using AOPs.
None currently but we have a good
understanding from previous pilot work and full
scale experience what to expect.
2.2. If you ticked either option in question 2.1, please
describe the AOPs you are currently investigating.
Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
2.3. Do you anticipate installing AOPs at your drinking
water treatment works within the next five years?
No ☐ Please proceed to Question 2.4
2.3.1. Please describe which AOPs you expect to install
and the rationale behind that choice of AOP.
Ozone/Hydrogen peroxide ☐
UV/Hydrogen peroxide ☐
Ozone/UV/Hydrogen peroxide ☐
Titanium dioxide/UV ☐
Other ☐ Please describe below
………………………………
Rationale for choice
………………………………
2.4. Do you anticipate installing AOPs at your drinking
water treatment works within the next ten years?
Yes ☐ Please proceed to Question 2.4.1
DWI
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2.4.1. Please describe which AOPs you expect to install
and the rationale behind that choice of AOP.
UV/Hydrogen peroxide ☐
Other ☐ Please describe below
Possible emergence of harder to treat pesticides
may lead to wider application of AOP
Rationale for choice:
Experience, confidence, disinfection and AOP,
relative cost provided you have good pre-
treatment to provide suitable quality of water into
the AOP reactor and some downstream
remediation in the form of GAC.
3. Ozonation by-products:
WTW Name**
Volume
output
(MLD)
Water
Source *
Reason for O3 use.
(pesticide removal,
disinfection)
O3 Dose
(mg/l)
Does the
works have
GAC? (Y/N)
Are DBP monitored?
(Exclude Bromate and THM).
Which and concentration (µg/L)
Other comments
* G – ground; U – upland; L – lowland.
** Either site name or Site 1, Site 2, etc.
DWI
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© WRc plc 2018 159
Thank you for your time in completing this questionnaire. If you have any additional information that you
would like to share, or wish to elaborate on any responses to these questions further, please enter this
information in comment box below.
4. Additional comments
An investigation into the impact of UV/H2O2 advanced oxidation and subsequent GAC treatment on disinfection
byproduct (DBP) formation potential in two of Company 3’s drinking water treatment works was completed by
Trojan technologies in 2013. Specifically, six samples were collected from the Site1 treatment works and six
samples from a pilot system operating at the Site2 treatment works. The samples were sent to Trojan
Technologies’ lab in London, Canada, where the DBP formation tests were performed. Chlorine incubation was
performed on each of the samples plus two blank samples to provide a 0.5 ppm free chlorine residual after a four
day hold time. Each of the samples was then analyzed in triplicate for haloacetic acid compounds and
trihalomethane compounds.
In general, the results indicated that UV/H2O2 treatment does not increase THMs, while subsequent GAC
treatment provides a slight decrease. For HAAs it’s not quite as clear. For the Site1 samples a significant
decrease in HAAs after UV/H2O2 was observed primarily due to monochloroacetic acid (MCAA) reduction.
Significant reductions were also observed after GAC treatment. For the Site2 samples, an increase in HAAs was
observed following UV/H2O2 due to both MCAA and dichloroacetic acid (DCAA). Again, carbon reduced the levels
to below the pre-UV levels. The post GAC samples were all collect at half the full scale EBCT to understand a
worst case scenario if we choose to apply this technology with limited downstream GAC.
SITE1
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I don’t send the Site2 pilot plant data as I feel the GAC at this site was not fully biological due to the intermittent
operation of the pilot plant at this time.
A study of genotoxicity was also performed with KWR on the Site1 pilot facility. The summary of this research
was that there was a mild genotoxic effect observed in water throughout the treatment train. This did not improve
or worsen across the AOP/GAC at pilot scale.
Company3 performed DBPFP tests looking at THMs. This showed no significant change in TTHM values post
AOP (<<5%) and moderate reduction post GAC (c25%).
Sampling Point Total THMFP (µg/l) DOC (mg/l)
Site1 – Filtered (pre AOP) 119,23 2
Site1 - GAC Inlet (Post AOP peroxide/UV) 118,67 1,8
Site1 - GAC No.1 Mid Bed 85,63 1,2
SITE1
DWI
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B4 Company 4 (Ozone only)
WTW Name** Volume output
(MLD) Water Source *
Reason for O3 use.
(pesticide removal,
disinfection)
O3 Dose
(mg/l)
Does the
works have
GAC? (Y/N)
Are DBP monitored?
(Exclude Bromate
and THM). Which
and concentration
(µg/L)
Other comments
Site 1 (Pre and
Inter) 125 Lowland river Disinfection/Pesticide 1.5 / 0.1 -
None (Other than
THM / Bromate)
Site 2 (Pre and
Inter) 80 – 100 Lowland river Disinfection/Pesticide 1.5 / 0.1 -
Site 3 (Pre and
Inter) 60 Lowland river Disinfection/Pesticide 1.5 / 0.1 -
Do not use inter
dosing point
during summer
months.
Site 4 (Pre and
Inter) 40 Lowland river Disinfection/Pesticide 1.5 / 0.1 -
* G – ground; U – upland; L – lowland.
** Either site name or Site 1, Site 2, etc.
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B5 Company 5 (Ozone only)
WTW Name**
Volume
output
(MLD)
Water
Source *
Reason for O3 use.
(pesticide removal,
disinfection)
O3 Dose
(mg/l)
Does the
works have
GAC? (Y/N)
Are DBP monitored?
(Exclude Bromate and THM).
Which and concentration
(µg/L)
Other comments
Site 1 35-45 ML/d L Pesticide removal 100 Y No See additional comments
below
Site 2 45-65 ML/d L/GW Pesticide removal 100 Y No See additional comments
below
* G – ground; U – upland; L – lowland.
** Either site name or Site 1, Site 2, etc.
Currently no sampling is undertaken for additional DBPs. A proposal is being drawn up to implement additional sampling at the relevant sites.
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B6 Company 6 (Ozone only)
WTW Name**
Volume
output
(MLD)
Water
Source *
Reason for O3 use.
(pesticide removal,
disinfection)
O3 Dose
(mg/l)
Does the
works have
GAC? (Y/N)
Are DBP monitored?
(Exclude Bromate and THM).
Which and concentration
(µg/L)
Other comments
Site 1 650 L pesticide 1.5 Y No Pre and Main Ozone
Site 2 600 L pesticide 1.5 Y No Main
Site 3 650 L pesticide 1.5 Y No Main
Site 4 160 L pesticide 1.5 Y No Main
All the above are SSF works
Site 5 50 L pesticide 1.5 Y No Pre
Site 6 90 L pesticide 1.5 Y No Pre and Main Ozone
Site 7 80 L pesticide 1.5 Y No Pre and Main Ozone & SSF
Site 8 70 L pesticide 1.5 Y No Pre
Site 9 80 L pesticide 1.5 Y No Pre and Main Ozone
* G – ground; U – upland; L – lowland.
** Either site name or Site 1, Site 2, etc.
All Works output flows are approximate, given daily output is subject to variation.
It should be noted that ozone has benefits to water quality other than pesticide removal, such as colour, taste and odour, algal toxins, bacteria, virus and
protozoan disinfection, increase in biodegradability of organics in water, improvements in particle capture on filters and GAC adsorbers, improvement of
coagulation process etc.
Ozone is not currently combined with UV or H2O2 (which is widely taken to be the definition of an AOP).
The first four works on the list have SSF and no chemical coagulation. The bottom 5 have chemical coagulation.
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B7 Company 7 (Ozone only)
WTW Name**
Volume
output
(MLD)
Water
Source *
Reason for O3 use.
(pesticide removal,
disinfection)
O3 Dose
(mg/l)
Does the
works have
GAC? (Y/N)
Are DBP monitored?
(Exclude Bromate and THM).
Which and concentration
(µg/L)
Other comments
Site 1
Max 46
Av 25
Min 8
U
To breakdown
organics for
subsequent removal
by GAC
103mg/l
on 181l/s
flow
Y HAAs – mean 52 ug/l
Works investment for front end
Coagulation, Clarification &
DAF. Due on line 2018. Ozone
will be decommissioned &
removed from site
Site 2
Max 0.24
MLD
Av 0.15MLD
U
To breakdown
organics for
subsequent removal
by GAC
14.5mg/l Y HAAs – mean 58 ug/l Aerators in final water tank as
additional reduction in THM.
* G – ground; U – upland; L – lowland.
** Either site name or Site 1, Site 2, etc.
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Appendix C Inclusion and exclusion criteria used in the literature review
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Table C.1 Inclusion and exclusion criteria applied to the selection of relevant papers for the each AOP
Inclusions Exclusions
In Any Field In Title
Name of the AOP: Ozone AND Hydrogen Peroxide Ultraviolet AND Hydrogen Peroxide Ultraviolet AND Ozone and Hydrogen Peroxide etc.
Wastewater OR Waste water
Chemical Compound of the AOP: O3 AND H2O2 UV AND H2O2 UV AND O3 AND H2O2 etc.
Retracted
Words:
AOP OR Advanced Oxidation
Bacteria NOT by product NOT by-product NOT byproduct
Words:
By product OR by-product OR byproduct
Cryptosporidium NOT by product NOT by-product NOT byproduct
Words:
Disinfection by product OR Disinfection by-product OR Disinfection byproduct OR DBP
E. coli NOT by product NOT by-product NOT byproduct
In Keywords
Wastewater OR Waste water NOT by product NOT by-product NOT byproduct
Bacteria NOT by product NOT by-product NOT byproduct
Cryptosporidium NOT by product NOT by-product NOT byproduct
E. coli NOT by product NOT by-product NOT byproduct
In Any Field
Solar
Pathogen
Leachate
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Inclusions Exclusions
Patent
Waste Management
Petroleum
Pulp
Textile
Activated sludge
Pulse
Fouling
Atomic layer deposition
Food
Air pollution
Vegetable
Solid waste
Implant
Hospital
Membrane filtration NOT by product NOT by-product NOT byproduct
Microwave NOT by product NOT by-product NOT byproduct
Plasma NOT by product NOT by-product NOT byproduct
Clinical NOT by product NOT by-product NOT byproduct
Virus NOT by product NOT by-product NOT byproduct
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Table C.2 List of words used for the exclusion of irrelevant papers for ozonation
Exclusions words
Alga X
Atmosphere
Troposphere
Stratosphere
Sun X
Solar X
Air pollution X
Journal - Vet
Journal - plant
Fouling X
Membrane
Biological X
Cryptosporidium X
E. coli X
Iron or ferrous X
Swimming pool
Ballast water
Potable reuse
Electrolysis
Seawater
‘X’: Word is present in title or keywords
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Appendix D Search strings and outcomes of searches, for formation of DBPs
D1 Ultraviolet and hydrogen peroxide
Table D.1 Search string for formation of DBPs from UV / H2O2 using Scopus
Information
source
Scopus
Date accessed 15th May 2017
Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR (("Hydrogen peroxide"
OR "H2O2" OR "Hydrogen dioxide" OR CASREGNUMBER(7722-84-1)) AND (UV
OR ultraviolet))) AND (react* OR form* OR produc* OR level* OR occur* OR
generat*) AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR
"by-product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND
(LIMIT-TO (LANGUAGE,"English"))
Number of
records
retrieved
14716
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
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Table D.2 Summary of numbers of papers identified, excluded and assessed (UV /
H2O2)
Total number of articles 14716
Steps Inclusions Exclusions
1 Articles that contained “UV” or “Ultraviolet”
in any field
4741 Articles that contained
neither “UV” or “Ultraviolet”
in any field
9975
2 Articles that contained “H2O2” or “Hydrogen
peroxide” in any field
1652 Articles that contained
neither “H2O2” or
“Hydrogen peroxide” in any
field
3089
3 Articles that contained “Advanced oxidation”
or “AOP” in any field
695 Articles that contained
neither “Advanced
oxidation” or “AOP” in any
field
957
4 Articles that contained “byproduct” or “by-
product” or “by product” in any field
181 Articles that contained
neither “byproduct” or “by-
product” or “by product” in
any field
514
4.1 Articles in step 4 that contained “disinfection
byproduct” or “disinfection by-product” or
“disinfection by product” in any field
Articles in step 4 that contained “formation”
54 Articles in step 4 that
contained neither
“disinfection byproduct” or
“disinfection by-product” or
“disinfection by product” in
any field
127
4.2 Articles in step 4 that contained “formation” 103 Articles in step 4 that did
not contain “formation”
78
5 Combination of 4.1 and 4.2 excluding
duplicated results
92 Combination of 4.1 and 4.2
excluding duplicated
results
89
6 Articles included by reading abstracts 25 Articles excluded by
reading abstracts
67
Final
list
Total articles Included 25 Total articles Excluded 14691
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D2 Ozone and hydrogen peroxide
Table D.3 Search string for formation of DBPs from hydrogen peroxide and ozone
treatment using Scopus
Information
source
Scopus
Date accessed 11th May 2017
Search terms ((“AOP” OR “Advanced Oxid*” OR “Advanced Treatme*”) OR (“Hydrogen peroxide”
OR “H2O2” OR “Hydrogen dioxide” OR CASREGNUMBER(7722-84-1)) AND
(“Ozone” OR “O3” OR “Triatomic oxygen” OR CASREGNUMBER(10028-15-6)))
AND (react* OR form* OR produc* OR level* OR occur* OR generat*) AND (water
OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-product*" OR
"byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-TO
(LANGUAGE,"English"))
Number of
records
retrieved
8150
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language 0restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
Table D.4 Search string for formation of DBPs from hydrogen peroxide and ozone
treatment using Science Direct
Information
source
Science Direct
Date accessed 11th
May 2017
Search terms ((“AOP” OR “Advanced Oxid*” OR “Advanced Treatme*”) OR (“Hydrogen peroxide”
OR “H2O2” OR “Hydrogen dioxide”) AND (“Ozone” OR “O3” OR “Triatomic
oxygen”)) AND (react* OR form* OR produc* OR level* OR occur* OR generat*)
AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-
product" OR "byproduct" OR "by product")
Number of
records
retrieved
5079
Specific
exclusions
Date restriction: 1990 to present
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Information
source
Science Direct
applied to
search
Table D.5 Summary of numbers of papers identified, excluded and assessed (O3 /
H2O2)
Total number of articles 13686
Steps Inclusions Exclusions
1 Articles that contained “O3” or
“Ozone” and “H2O2” or “Hydrogen
peroxide” in any field
882 Articles that contained:
“O3” or “Ozone” but not
“H2O2” or “Hydrogen
peroxide”
“H2O2” or “Hydrogen
peroxide” but not “O3” or
“Ozone”
in any field
12804
2 Articles that contained “Advanced
oxidation” or “AOP” in any field
356 Articles that contained
neither “Advanced
oxidation” or “AOP” in any
field
526
2.1 Articles in step 2 that contained
“formation” in any field
23 Articles in step 2 that did
not contain “formation” in
any field
333
2.2 Articles in step 2 that contained
“disinfection byproduct” or
“disinfection by-product” or
“disinfection by product” or “DBP” in
any field
16 Articles in step 2 that did
not contain “disinfection
byproduct” or “disinfection
by-product” or “disinfection
by product” or “DBP” in any
field
340
3 Combination of 2.1 and 2.2 excluding
duplicated results
23 Duplicated articles after
combination of 2.1 and 2.2
16
4 Remaining articles after exclusion 18 Articles excluded based on
list of words in Table D.20
5
5 Articles included by reading abstracts 12 Articles excluded by
reading abstracts
6
Final list Total articles Included 12 Total articles Excluded 13674
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D3 Ozone and Ultraviolet
Table D.6 Search string for formation of DBPs from ozone and UV treatment using
Scopus
Information
source
Scopus
Date accessed 15th May 2017
Search terms ((“AOP” OR “Advanced Oxid*” OR “Advanced Treatme*”) OR ((“Ozone” OR “O3”
OR “Triatomic oxygen” OR CASREGNUMBER(10028-15-6))) AND (UV OR
ultraviolet)) AND (react* OR form* OR produc* OR level* OR occur* OR generat*)
AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-
product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-
TO (LANGUAGE,"English"))
Number of
records
retrieved
11968
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
Table D.7 Summary of numbers of papers identified, excluded and assessed
(O3 / UV)
Total number of articles 11968
Steps Inclusions Exclusions
1 Articles that contained “UV” or
“Ultraviolet” in any field
4912 Articles that contained
neither “UV” or “Ultraviolet”
in any field
7056
2 Articles that contained “O3” or
“Ozone” in any field
1620 Articles that contained
neither “UV” or “Ultraviolet”
in any field
3292
3 Articles that contained “AOP” or
“Advanced oxidation” in any field
418 Articles that contained
“AOP” or “Advanced
oxidation” in any field
1202
4 Articles that contained “byproduct” or
“by-product” or “by product” in any
field
108 Articles that contained
neither “byproduct” or “by-
product” or “by product” in
any field
179
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Total number of articles 11968
Steps Inclusions Exclusions
4.1 Articles in step 4 that contained
“disinfection byproduct” or
“disinfection by-product” or
“disinfection by product” in any field
30 Articles in step 4 that
contained neither
“disinfection byproduct” or
“disinfection by-product” or
“disinfection by product” in
any field
78
4.2 Articles in step 4 that contained
“formation”
60 Articles in step 4 that did
not contain “formation”
48
5 Combination of 4.1 and 4.2 excluding
duplicated results
65 Duplicated articles after
combination of 4.1 and 4.2
25
6 Remaining articles after exclusion 54 Articles excluded based on
list of words in Table D.20
11
7 Articles included by reading abstracts 10 Articles excluded by
reading abstracts
44
Final list Total articles Included 10 Total articles Excluded 11958
D4 Ozone and Ultraviolet and hydrogen peroxide
Table D.8 Search string for formation of DBPs from hydrogen peroxide and onzone
and UV treatment using Scopus
Information
source
Scopus
Date accessed 17th May 2017
Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR (("Hydrogen peroxide"
OR "H2O2" OR "Hydrogen dioxide" OR CASREGNUMBER(7722-84-1)) AND
(“Ozone” OR “O3” OR “Triatomic oxygen” OR CASREGNUMBER(10028-15-6))
AND (UV OR ultraviolet))) AND (react* OR form* OR produc* OR level* OR occur*
OR generat*) AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect*
OR "by-product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND
(LIMIT-TO (LANGUAGE,"English"))
Number of
records
retrieved
11438
Specific
exclusions
applied to
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
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Information
source
Scopus
search
Table D.9 Summary of numbers of papers identified, excluded and assessed
(UV / H2O2)
Total number of articles 11438
Steps Inclusions Exclusions
1 Articles that contained
“UV” or “Ultraviolet” in
any field
4873 Articles that contained
neither “UV” or
“Ultraviolet” in any field
6565
2 Articles that contained
“O3” or “Ozone” in any
field
2265 Articles that contained
neither “UV” or
“Ultraviolet” in any field
2608
3 Articles that contained
“H2O2” or “Hydrogen
peroxide” in any field
405 Articles that contained
neither “H2O2” or
“Hydrogen peroxide” in
any field
1860
4 Articles that contained
“Advanced oxidation” or
“AOP” in any field
232 Articles that contained
neither “Advanced
oxidation” or “AOP” in
any field
173
5 Articles that contained
“byproduct” or “by-
product” or “by product”
in any field
53 Articles that contained
neither “byproduct” or
“by-product” or “by
product” in any field
179
5.1 Articles in step 5 that
contained “disinfection
byproduct” or
“disinfection by-product”
or “disinfection by
product” or “DBP” in
any field
14 Articles in step 5 that
contained neither
“disinfection byproduct”
or “disinfection by-
product” or “disinfection
by product” or “DBP” in
any field
39
5.2 Articles in step 5 that
contained “formation”
29 Articles in step 5 that did
not contain “formation”
24
6 Combination of 5.1 and
5.2 excluding
duplicated results
42 Duplicated articles after
combination of 5.1 and
5.2 and articles that
1
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Total number of articles 11438
Steps Inclusions Exclusions
contained “Wastewater”
or “waste water” in title
or keywords*
7 Articles included by
reading abstracts
5 Articles excluded by
reading abstracts
37
Final list Total articles Included 5 Total articles Excluded 11433
D5 Ultraviolet and hypochlorous acid
Table D.10 Search string for formation of DBPs from UV and hypochlorous acid
using Scopus
Information
source
Scopus
Date accessed 17th May 2017
Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR ((UV OR ultraviolet)
AND (“Hypochlorous acid” OR “OCl” OR CASREGNUMBER(7790-92-3)))) AND
(react* OR form* OR produc* OR level* OR occur* OR generat*) AND (water OR
drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-product*" OR
"byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-TO
(LANGUAGE,"English"))
Number of
records
retrieved
10270
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
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Table D.11 Summary of numbers of papers identified, excluded and assessed
(UV / HOCl)
Total number of articles 10270
Steps Inclusions Exclusions
1 Articles that contained “UV” or
“Ultraviolet” in any field
8656 Articles that contained
neither “UV” or “Ultraviolet”
in any field
1614
2 Articles that contained “Hypochlorous
acid” or “Chlorine” or “HOCl” or “ClO”
or “HClO” or “Cl” in any field
374 Articles that contained
neither “Hypochlorous acid”
or “HClO” or “ClO” in any
field
8282
3 Articles that contained “Advanced
oxidation” or “AOP” in any field
106 Articles that contained
neither “Advanced oxidation”
or “AOP” in any field
268
4 Articles that contained “byproduct” or
“by-product” or “by product” in any field
55 Articles that contained
neither “byproduct” or “by-
product” or “by product” in
any field
51
4.1 Articles in step 4 that contained
“disinfection byproduct” or “disinfection
by-product” or “disinfection by product”
or “DBP” in any field
32 Articles in step 4 that
contained neither
“disinfection byproduct” or
“disinfection by-product” or
“disinfection by product” or
“DBP” in any field
23
4.2 Articles in step 4 that contained
“Formation” in any field
33 Articles in step 4 that did not
contain “Formation” in any
field
22
5 Combination of 4.1 and 4.2 excluding
duplicated results
40 Duplicated articles after
combination of 4.1 and 4.2
25
6 Articles that did not contain
“wastewater” or “waste water” in title or
keywords
38 Articles that contained
“wastewater” or “waste
water” in title or keywords
2
7 Articles included by reading abstracts 7 Articles excluded by reading
abstracts
31
Final list Total Inclusions 7 Total Exclusions 10263
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D6 Ultraviolet and persulphate
Table D.12 Search string for formation of DBPs from UV and persulphate using
Scopus
Information
source
Scopus
Date accessed 17th May 2017
Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR ((UV OR ultraviolet)
AND (Persulphate OR Persulfate OR “*S2O8”))) AND (react* OR form* OR produc*
OR level* OR occur* OR generat*) AND (water OR drink* OR treat* OR WTW) AND
(DBP OR disinfect* OR "by-product*" OR "byproduct*" OR "by product*") AND
PUBYEAR > 1989 AND (LIMIT-TO (LANGUAGE,"English"))
Number of
records
retrieved
10048
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
Table D.13 Summary of numbers of papers identified, excluded and assessed
(UV / S2O8)
Total number of articles 10048
Steps Inclusions Exclusions
1 Articles that contained “UV” or
“Ultraviolet” in any field
3223 Articles that did not contain
“UV” or “Ultraviolet” in any
field
6825
2 Articles that contained “Persulphate” or
“Persulfate” or “S2O8” in any field
137 Articles that contained
neither “Persulphate” or
“Persulfate” or “S2O8”in any
field
3086
3 Articles that contained “Advanced
oxidation” or “AOP” in any field
54 Articles that contained
neither “Advanced oxidation”
or “AOP” in any field
83
3.1 Articles in step 3 that contained
“formation”
17 Articles in step 3 that did not
contain “formation”
37
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Total number of articles 10048
Steps Inclusions Exclusions
3.2 Articles in step 3 that contained
“byproduct” or “by-product” or “by
product”
20 Articles in step 3 that
contained neither
“byproduct” or “by-product”
or “by product”
34
3.2.1 Articles in step 3.2 that contained
“disinfection” or “DBP”
3 Articles in step 3.2 that
contained neither
“disinfection” or “DBP” in
any field
17
4 Combination of 3.1 and 3.2 and 3.2.1
excluding duplicated results
30 Duplicated articles after
combination of 3.1 and 3.2
and 3.2.1
10
5 Articles included by reading abstracts 6 Articles excluded by reading
abstracts
24
Final list Total Inclusions 6 Total Exclusions 10042
D7 Ultraviolet and titanium dioxide
Table D.14 Search string for formation of DBPs from UV and titanium dioxide
treatment using Scopus
Information
source
Scopus
Date accessed 17th May 2017
Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR ((“Titanium dioxide”
OR “TiO2” OR “Titanium oxide” OR CASREGNUMBER(13463-67-7)) AND (UV OR
ultraviolet))) AND (react* OR form* OR produc* OR level* OR occur* OR generat*)
AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-
product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-
TO (LANGUAGE,"English"))
Number of
records
retrieved
16484
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
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Table D.15 Summary of numbers of papers identified, excluded and assessed
(UV / TiO2)
Total number of articles 18598
Steps Inclusions Exclusions
1 Articles that contained “UV” or
“Ultraviolet” in any field
8464 Articles that contained
neither “UV” or “Ultraviolet”
in any field
10134
2 Articles that contained “Titanium
dioxide” or “TiO2” in any field
2527 Articles that contain neither
“Titanium dioxide” or “TiO2”
in any field
5937
3 Articles that contained “Advanced
oxidation” or “AOP” in any field
246 Articles that contained
neither “Advanced
oxidation” or “AOP” in any
field
2281
4 Articles that contained “byproduct” or
“by-product” or “by product” in any
field
57 Articles that contained
neither “byproduct” or “by-
product” or “by product” in
any field
189
4.1 Articles in step 4 that contained
“disinfection” or “DBP” in any field
16 Articles in step 4 that did
not contain “disinfection” or
“DBP” in any field
41
4.2 Articles in step 4 that contained
“formation” in any field
27 Articles in step 4 that did
not contain “formation” in
any field
30
5 Combination of 4.1 and 4.2 excluding
duplicated results
32 Duplicated articles after
combination of 4.1 and 4.2
11
6 Articles that did not contain
“wastewater” “or “waste water” in title
or keywords
29 Articles that contained
“wastewater” or “waste
water” in title or keywords
3
7 Articles included by reading abstracts 5 Articles excluded by
reading abstracts
24
Final list Total Inclusions 5 Total Exclusions 18593
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D8 Ultraviolet and titanium dioxide and hydrogen peroxide
Table D.16 Search string for formation of DBPs from UV, titanium dioxide and
hydrogen peroxide treatment using Scopus
Information
source
Scopus
Date accessed 17th May 2017
Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR (“Titanium dioxide”
OR “TiO2” OR “Titanium oxide” OR CASREGNUMBER(13463-67-7)) AND (UV OR
ultraviolet) AND (“Hydrogen peroxide” OR “H2O2” OR “Hydrogen dioxide” OR
CASREGNUMBER(7722-84-1))) AND (react* OR form* OR produc* OR level* OR
occur* OR generat*) AND (water OR drink* OR treat* OR WTW) AND (DBP OR
disinfect* OR "by-product*" OR "byproduct*" OR "by product*") AND PUBYEAR >
1989 AND (LIMIT-TO (LANGUAGE,"English"))
Number of
records
retrieved
6202
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
Table D.17 Summary of numbers of papers identified, excluded and assessed
(UV / TiO2 / H2O2)
Total number of articles 6202
Steps Inclusions Exclusions
1 Articles that contained “UV” or “Ultraviolet” in any field
2776 Articles that contained neither “UV” or “Ultraviolet” in any field
3426
2 Articles that contained “Titanium dioxide” or “TiO2” in any field
776 Articles that contain neither “Titanium dioxide” or “TiO2” in any field
2000
3 Articles that contained “Hydrogen peroxide” or “H2O2” in any field
235 Articles that contain neither “Hydrogen peroxide” or “H2O2” in any field
541
4 Articles that contained “Advanced oxidation” or “AOP” in any field
84 Articles that contained neither “Advanced oxidation” or “AOP” in any field
151
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Total number of articles 6202
Steps Inclusions Exclusions
4.1 Articles in step 4 that contained “formation” in any field
18 Articles in step 4 that did not contain “formation” in any field
66
4.2 Articles in step 4 that contained “byproduct” or “by-product” or “by product” in any field
19 Articles in step 4 that contained neither “byproduct” or “by-product” or “by product” in any field
65
4.2.1 Articles in step 4.2 that contained “disinfection” or “DBP” in any field
3 Articles in step 4.2 that did not contain “disinfection” or “DBP” in any field
16
5 Combination of 4.1 and 4.2 and 4.2.1 excluding duplicated results
24 Duplicated articles after combination of 4.1 and 4.2 and 4.2.1
16
6 Articles that did not contain “wastewater” or “waste water” in title or keywords
22 Articles that contained “wastewater” or “waste water” in title or keywords
2
7 Articles included by reading abstracts
4 Articles excluded by reading abstracts
20
Final list Total Inclusions 4 Total Exclusions 6198
D9 Ozone
Table D.18 Search string for formation of DBPs from ozone treatment using Scopus
Information
source
Scopus
Date accessed 10th
May 2017
Search terms (Ozone OR "O3" OR "Triatomic oxygen" OR CASREGNUMBER (10028-15-6)) AND
(react* OR form* OR produc* OR level* OR occur* OR generat*) AND (water OR
drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-product*" OR
"byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-TO
(LANGUAGE,"English"))
Number of
records
retrieved
17455
Specific
exclusions
applied to
search
Date restriction: 1990 to present (PUBYEAR > 1989)
Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))
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Table D.19 Search string for formation of DBPs from ozone treatment using Science
Direct
Information
source
Science Direct
Date accessed 11th
May 2017
Search terms (Ozone OR "O3" OR "Triatomic oxygen") AND (react* OR form* OR produc* OR
level* OR occur* OR generat*) AND (water OR drink* OR treat* OR WTW) AND
("DBP" OR disinfect* OR "by-product" OR "byproduct" OR "by product")
Number of
records
retrieved
23887
Specific
exclusions
applied to
search
Date restriction: 1990 to present
Table D.20 Additional ‘In Any Field’ Exlusion Words
Exclusion Words
Solar
Pathogen
Leachate
Patent
Waste Management
Petroleum
Pulp
Textile
Activated sludge
Pulse
Fouling
Atomic layer deposition
Food
Air pollution
Vegetable
Solid waste
Implant
Hospital
Membrane filtration NOT by product NOT by-product NOT byproduct
Microwave NOT by product NOT by-product NOT byproduct
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Exclusion Words
Plasma NOT by product NOT by-product NOT byproduct
Clinical NOT by product NOT by-product NOT byproduct
Virus NOT by product NOT by-product NOT byproduct
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Appendix E Summary of reviewed literature
Table E.1 DBP formation from UV / H2O2 process
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
H2O2 at 0, 5, 10 mg/L MP-reactor 850 mJ/cm2 LP-reactor
1140 mJ/cm2
River water pre-treated by coagulation,
microstraining and sand filtration
UVT: >80 - 74% nitrate: 8.65 - 16 mg/l
DOC: 3.36 - 4 mg/l bicarbonate: 137 -
151mg/l
Nitrite Nitrite AOC formation is enhanced in the
presence of hydrogen peroxide
63
436 - 504 (MP)
Nitrite formation using LP lamps was
negligible regardless of the hydrogen
peroxide dose. It was higher using MP
lamps in the absence of the hydrogen
peroxide.
10 - 15 (LP) In the absence of hydrogen peroxide,
AOC formation using MP lamps is twice as
high as AOC formation using LP
lamps.
UV: 3000 mJ/cm2
H2O2 10-20 mg /L
Surface raw water THM-FP 54 Blank water: THM - FP: 198, 258
2
DCAA-FP 292 Blank water: DCAA - FP: 168, 220
TCAA-FP 149 Blank water: TCAA - FP: 475, 345
UV: 500 mJ/cm2
THM-FP 238
DCAA-FP 297
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
H2O2 10-20 mg /L
TCAA-FP 317
250 min UV irradiation H2O2: 4 - 16 mg/l
River surface water THM-FP Experiment on preoxidation by AOP,
followed by chlorination, to
investigate removal potential of DBP PRECURSORS
6
DOC: 2.03 mg/l 110% at 4 mg/l H2O2
pH: 7.6 107 - 124% at 8 mg/l H2O2
105% at 16 mg/l H2O2
UV 3000 mJ/cm2 + 13 mg/L H2O2
pH: 7.5, 7.8, Turb (FTU): 4.2, 3.1
Nitrite 0.8 mg/l Initial nitrate concentration in raw
water influences post-AOP nitrite
concentrations. Water quality for two samples provided but
it is not specified which one the results
refer to.
22
UV 1000 mJ/cm2 + 13 mg/L H2O2
Bromide: 103, 204 Nitrite 0.25 mg/l
UV 2000 mJ/cm2 + 4.2 mg/L
H2O2
Bromate: <0.2 Nitrite 1.15 mg/l
UV 1000 mJ/cm2 + 4.2 mg/L
H2O2
Nitrate: 2.3, 9.8 Nitrite 0.6 mg/l
AOC: 11, 37
Blend of surface river water (30%) and
dechlorinated municipal drinking water (70%)
TOC: 3.61 mg/l UVT: 89.9%
THM-FP initial: 42 THM-FP THM-FP, FA, AA
Considerable transformation of
NOM (reduction of aromaticity, higher
biodegrability) No relevant reduction
in DBP formation
28
LP 0.09 kWh/m3 + 10 mg/L
Formaldehyde initial: 7 Formaldehyde 52,16,14
LP 0.18 kWh/m3 +
Acetic Acid initial: 8 Acetic Acid 56,19,16
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
10 mg/L potential Considerable increase in
biodegradable carbon content of effluent
MP 0.18 kWh/m3 + 10 mg/L
45,12,13
MP 0.54 kWh/m3 + 10 mg/L
43,19,20
UV=678 mJ/cm2 H2O2=3
mg/L
Post MF effluent (total hardness 332.9 mg/l as
CaCO3)
NDMA 0.196 THMs were the only pollutants that
couldn’t be removed by at least 98% at the optimal UV and H2O2
dose applied
62
UV=739 mJ/cm2 H2O2=3
mg/L
THM 25
UV=1845 mJ/cm2 H2O2=3
mg/L
Post RO effluent (total hardness <29 mg/l as
CaCO3)
NDMA 0.198
UV=1861 mJ/cm2 H2O2=3
mg/L
THM 34
UV=1200 mJ/cm2; H2O2=6
mg/L
No info on water quality Trichloromethane 60 - 500 Trichloromethane 49 - 410 No substantial difference in
degradation is observed between
presence and absence of H2O2
39
Tribromomethane 90 Tribromomethane 1
Dibromomethane 80 Dibromomethane 16
Bromodichloromethane 80 - 550 Bromodichloromethane
54 - 534
Tribromoacetic acid 160 Tribromoacetic acid
2
Dibromoacetic acid 190 Dibromoacetic acid
38
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
Dichloroacetic acid 190 Dichloroacetic acid
190
bromoacetic acid 200 bromoacetic acid 200
Tricholoacetic acid 180 Tricholoacetic acid
180
H2O2 - 23 mg/l
UV - 1140 mJ/cm2
2.83 mg/l DOC; 0.092 cm-1 UV254 abs; <5 mg/l
CaCO3 alkalinity; >35 OH.
THMFP (raw) 325 THMFP 77 % reduction
(Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-
93 1996)
23
HAAFP 62% reduction
THM 75 Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.
AOPs tend to decrease aromaticity, hence greater effect
on THMFP is expected.
HAAFP (raw) 168 HAA 64
MP UV 1800 mJ/cm2
H2O2 - 1 - 4.8 mg/l
2 treated river water sources
THM Source 2: >10 THM-FP 30% - 110% Source 1: increasing THMFP with
increasing pH. The impacts of the two AOPs were similar, except at pH 6.5,
where UV/Cl increased THMFP
more than UV/H2O2.
29
Source 1, pre-chlorinated: Alkalinity 85-92 mg/l CaCO3, TOC 1.5 mg/l, UV254abs 0.02 cm-
1, turbidity 0.02-0.04, bromide 2-3 mg/l
HAA Source 2: 13 HAA-FP 20% - 110%
Haloacetonitriles 5
Haloketone No formation observed.
Chloropicrin No formation observed. Source 2: decreasing HAAFP with
increasing pH. The impacts of the two AOPs were similar, except at pH 6.5,
where UV/Cl
Source 2, NOT pre-chlorinated: Alkalinity 123
mg/l CaCO3, TOC 3.5 mg/l, UV254abs 0.04 cm-
1, turbidity 0.2 NTU, bromide 2-3 mg/l
Chlorite
Chlorate
Perchlorate
Bromate 0.1 - 2 (UV/Cl)
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
pH = 6.5, 7.5 and 8.5 increased HAAFP more than UV/H2O2.
H2O2 - 4 - 12 mg/l
Dilute humic acid in drinking water, 1.1-3.4
mg/l DOC.
THMFP 44 - 58.3 (initial)
10% - 25% FP
FP test was 20 mg/l FAC dose and 48
hours contact time. Comparison to
formation potential without treatment
35
UV - 300-1800
mJ/cm2
HAAFP 33.7 - 44.1 (initial)
No change
UV dose not stated
H2O2- 20 - 30 mg/l
COD reduction as in a pilot DPR system.
Followed by chlorination to a residual of 2-4 mg/l
DCAA 15.7 Water contained approximately 100
µg/l bromide.
37
TCAA 1.6
LP UV 800-2000
mJ/cm2 / 10
mg/l H2O2 MP UV 200-500 mJ/cm
2
/ 10 mg/l H2O2
AOPs applied to water after conventional
treatment and after conventional treatment + GAC. Mean TOC after
conventional treatment = 1.9 mg/l; after GAC = 0.9
mg/l.
THMFP Conventionally treated water: c. 90 µg/l in
spring and c. 220 µg/l in autumn.
Approximately 50% higher than without
AOP. Conventionally + GAC treated water: c. 50 µg/l in spring and c. 75 µg/l
in autumn. Approximately 100% higher than without
AOP.
Chlorination: dose sufficient chlorine to achieve residual of 0.6-1.2 mg/l after 3
days.
40
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
HAAFP Conventionally treated water:
52 µg/l on average. 34 µg/l without
AOP. Conventionally + GAC treated water: 20 µg/l on average.
14 µg/l without |AOP.
10 mg/l H2O2 /LP UV 600 mJ/cm
2
Groundwater: TOC 5.8 mg/l, UV254abs 0.23 cm-
1, Alkalinity 753 mg/l CaCO3, 623 µg/l bromide, pH 8.
Total aldehydes 26 Raw: 11.2 43
Formaldehyde 10 Raw: 6.6
Acetaldehyde 12 Raw: 2.6
Glyoxal 3 Raw: 1.5
Methylglyoxal 1 Raw: 0.5
Total carboxylic acids 70 Raw: < 10
Oxalate 40
Acetate 20
Formate 10
Bromate < 5 Raw: < 5
THMFP 390 Chlorination: 7 day. Raw: 305
HAAFP 275 Chlorination: 7 day. Raw: 348
10 mg/l H2O2 /LP UV
3000 mJ/cm
2
Total aldehydes 49 Raw: 11.2
Formaldehyde 32 Raw: 6.6
Acetaldehyde 7 Raw: 2.6
Glyoxal 8 Raw: 1.5
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
Methylglyoxal 2 Raw: 0.5
Total carboxylic acids 160 Raw: < 10
Oxalate 90
Acetate 50
Formate 20
Bromate < 5 Raw: < 5
THMFP 456 Chlorination: 7 day. Raw: 305
HAAFP 456 Chlorination: 7 day. Raw: 348
5 mg/l H2O2 / 1000 mJ/cm
2
Lake water treated in pilot plant by
coagulation/clarification/filtration. H2O2 / UV applied after filtration. Raw water: DOC 1.6 mg/l; alkalinity
83 mg/l CaCO3, hardness 99 mg/l.
THMFP 90.5 Chlorination test: apply range of chlorine dose ,
measure residuals and THMs after 5
days (targets: initial chlorine residual 1 - 2 mg/l; residual after 5
days ≥ 0.2 mg/l). Note: chlorine relied
upon to quench H2O2. No control
(without either AOP) reported.
51
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
10 mg/l H2O2 / LP UV 585 mJ/cm
2
Filtered water from three water treatment plants, two treating river water, one treating lake water.
DOC 2.3 - 2.7 mg/l; DON 0.24 - 0.49 mg/l; bromide 21 - 139 μg/l; iodide <10 -
15 μg/l.
Haloacetamide FP (chloroacetamide + dichloroacetamide +
bromochloroacetamide +
dibromoacetamide + trichloroacetamide +
bromodichloroacetamide)
1 - 2 Chlorination: 24 h, 1 mg/l residual.
Chlorine relied upon to quench H2O2. Raw: 2.7 - 5.9 μg/l (17 - 37
nM). UV doses < 585
mJ/cm2, and H2O2
doses 2 - 50 mg/l also explored: Reducing UV dose increased formation. Optimum H2O2 dose in range
10 - 15 mg/l; formation increased at lower doses, and higher doses either had no additional
benefit or resulted in increased formation. Dichloroacetamide
was most prevalent (> 50% of total formation).
1
10 mg/l H2O2 / LP UV 585 mJ/cm
2
Filtered water from a water treatment plant
treating lake water. DOC 2.5 mg/l; DON 0.49 mg/l; bromide 21 μg/l; iodide
<1 μg/l.
DichloroacetonitrileFP 3.7 Chlorination: 24 h, 1 mg/l residual.
Chlorine relied upon to quench H2O2.
Raw: 7.4 μg/l.
Trichloroacetonitrile FP <0.1
Dichloronitromethane FP
0.12
Trichloronitromethane FP
0.31
H2O2 - 10.5 mg/l - 105.5
mg/l
Synthetic water 3 mg/l TOC
pH 8.3 20 +/- 1 C
thiosulphate quenching THMs
90.5 A comparison of 3 different inorganic H2O2 quenching
chemicals: sodium hypochlorite, sodium thiosulphite, sodium
5
hypochlorite quenching THMs
85.6
sulphite 88.6
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
quenching THMs sulphite with an alternative (Bovine
catalase). Standardised
conditions for AOP and chlorination to
simulate a distribution network.
thiosulphate quenching HAAs
59.1
hypochlorite quenching HAAs
58.7
sulphite quenching HAAs
56.4
thiosulphate Aldehydes
LDL
hypochlorite Aldehydes
LDL
sulphite Aldehydes
LDL
LP UV (19.5-585 mJ/cm2, 254 nm),
H2O2 (2-20 mg/l x 10 minutes), UV with
H2O2 (585 mJ/cm2, 10
mg/l).
Raw and inter-stage treated water from 3
surface water sources in China, selected for
difference in DOC and DOC:DON ratio.
Site: MH, high SUVA SUVA: 4.5L/mg.m in raw
water, 3.4L/mg.m in filtered water
DOC: 3.7mg/l in raw water, 2.3mg/l in filtered
water Site: SY, low SUVA
SUVA: 2.4L/mg.m in raw water, 1.6L/mg.m in
filtered water DOC: 6.1mg/l in raw
water, 2.7mg/l in filtered water
Site: ZQ, low SUVA SUVA: 2.6L/mg.m in raw
HAcAms (H2O2 10mg/l, followed by
chlorination)
2.7 - 5.9 Concluded that UV/H2O2 pre trt may be more effective in reducing HAcAms in low-SUVA waters. Colimated beam
apparatus for batch tests with UV and UV with H2O2. Chlorine dose calculated to quench residual
H2O2, and a residual of 1 +/- 0.5 mgCl2/l
after 24 hours, adjusted to pH 7.5.
12
HAcAms (H2O2 alone) DOM changed from high to lower molecular weight
matter
HAcAms (UV combined with H2O2)
HAcAms concentration
decreased with increased UV
dose, for a given dose of H2O2,
due to increased hydroxyl radicals and destruction of pre-cursors. At a given UV dose,
HAcAms concentration
decreased with
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
water, 1.7L/mg.m in filtered water
DOC: 5.9mg/l in raw water, 2.5mg/l in filtered
water DON: 0.62mg/l in raw
water, 0.49mg/l in filtered water
For all waters, UV irradiation alone, followed
by chlorination, had no significant effect on precursors or in the ultimate formation of
HAcAms compared to chlorination alone.
increasing H2O2 dose (0-20 mg/l), but increased at greater H2O2
doses (scavenging of
hydroxyl radicals).
UV / Clorination:
UV at 3 mg/L, H2O2
at 5 mg/L
Removal of personal care products using
UV/Chlorine and UV/Hydrogen peroxide and formation of DBPs
after chlorination. Three sources of water were tested. One of the tested water samples
was ammonia-rich. The water sources were previously treated
through coagulation, flocculation,
sedimentation and sand filtration. Reaction time with AOP: 1.5 or 3 min.
treated water was sampled and quenched with sodium sulfite and
clorinated for 24 h at 0.9 + 0.1 mg/l free chlorine
Chloral hydrate The higher radical exposure in the
UV/Chlorine AOP over UV/H2O2 AOP
likely resulted in alteration of dissolved organic matters and thus enhanced the formation potentials
of CH, HKs and TCNM but reduced
the formation potential of HANs .
On the other hand, in the ammonia rich
water, the formation potentials of THMs,
HKs and TCNM were slightly higher and the formation potentials
of CH and HANs were lower during the
32
Haloketone
trichloronitromethane
Haloacetonitriles
Halonitromethane
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
residual. sub-sequent post-chlorination with
UV/chlorine AOP than with UV/H2O2 AOP.
Meuse: H2O2 at 10 mg/L; UV
dose at 550 mJ/cm2;
GAC treatment at flow of 5 L/h Ohio river: H2O2 at
10mg/L; UV dose at 400
mJ/cm2; GAC at flow
of 57 L/h Comparison study: H2O2 at 10mg/L;
Different UV reactors of MP, LP and
DBD
Studied genotoxic activity of 3 surface waters
before and after treatment with UV/H2O2 and after subsequent GAC, for MP and LP
lamps. To detect gene mutations, the Ames II
assay and for a complementary assay
detecting chromosomal damage, the Comet assay in HepG2 liver cells were used. No
genotoxic activity was observed after UV/H2O2 in the Comet assay and
in the Ames II TAMix strain with and without S9
under all applied conditions. An increase in genotoxic activity in the
Ames II TA98 strain both with and without S9 was measured in three tested
waters after MP UV/H2O2. After LP and
DBD UV/H2O2 a lower or no increase was
observed in genotoxic activity. GAC post
treatment effectively reduced the formed genotoxic activity to
Genotoxity Reduced level with the use of
GAC
64
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
control levels for all but one study and to below
the level of the pre-treated water in the other study; no health risks are
expected as long as UV/H2O2 is followed by
GAC adsorption.
23mg/l H2O2
1140mJ/cm2 UV
2.83mg/l DOC; 0.092cm-1 UV254abs; <5mg/l
CaCO3 alkalinity: >35 OH.
THMFP (raw) 325 THMFP 77 (Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-
93 1996) % Mineralisation of TOC: UV < O3 <
H2O2/O3 < UV/H2O2 < UV/O3
(3:6:10:23:31) % reduction in
THMFP: UV < O3 < H2O2/O3 < UV/O3 <
UV/H2O2 (15:69:70:75:77) % reduction in
HAAFP: UV < O3 < H2O2/O3 < UV/O3 <
UV/H2O2 (0:8:31:52:62)
Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.
AOPs tend to decrease aromaticity, hence greater effect
on THMFP is expected.
23
HAAFP (raw) 168 HAAFP 62
No specified Artificial raw water Identified DBPs: - - High mutagenicity 47
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
doses; Lamp
specifications: MP lamp,
3 kW, irradiation path=19.5
mm
[NOM]=2.5 mg C/l [NO3-]=10.4 mg/l
4-nitrophenol - observed, but it could not be related to any
N-DBP group; 81 DBPs were formed
in total, but only 14 identified; Relative
concentrations detected expressed in
the paper as ng/L ISTD eq;
4-nitrocatechol -
4-nitro-1,3-benzendiol -
2-nitrohydroquinone -
2-hydroxy-5-nitrobenzoic acid
-
4-hydroxy-3-nitrobenzoic acid
High concentration' (unspecified)
2-hydroxy-3-nitrobenzoic acid
-
2,4-Dinitrophenol -
5-Nitrovanillin -
4-Nitrobenzene-sulfonic acid
-
4-Nitrophtalic acid High concentration' (unspecified)
2-Methoxy-4,6-dinitrophenol
High concentration' (unspecified)
3,5-Dinitrosalicylic acid High concentration' (unspecified)
Dinoterb High concentration' (unspecified)
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 198
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
UV: 500 - 2000
mJ/cm^2 H2O2: 1 - 5
mg/l Treatment followed by coagulation-filtration, in some cases
pre-ozonation)
Upper and lower-bound parameters of waters
tested Turbidity: 0.96-6.59 NTU
DOC: 2.78-7.70 mg/L UV_254: 0.0548-0.206
cm^-1 Alkalinity: 87-250 mg/l as
CaCO3 Hardness: N/A-227 mg/l
as CaCO3 Iron: N/A-0.58 mg/l
Manganese: N/A-2.1 mg/l
THM-FP ~70 - ~670 UV/H2O2 + does not reduce DOC and
SUVA significantly more than
conventional treatment alone
UV/H2O2 + conv treat, generate
significantly more THM-FP than conventional
treatment alone (in one instance 203%
more)
50
UV: 0 - 150 mJ/cm^-2 H2O2: 0 - 10 mg/l
Ultrapure water with addition of:
TOC: 2.8 mg/l Ca: 29.1 mg/l CO3: 90 mg/l pH: 6.3, 8.3
Nitrate 0.02 mg N/l (pH: 8.3, H2O2 dosed)
0.018 mg N/l (pH: 8.3, H2O2 not dosed) 0.02 mg N/l (150
mJ/cm^-2, H2O2 not dosed)
0.06 mg N/l (150 mJ/cm^-2, H2O2
dosed)
- - Slightly more nitrite formed with 10 mg/l H2O2 than 5 mg/l. About 25% more
nitrite formed at pH 8.3 than at pH 6.5.
4
LP UV lamp (laboratory
scale). 18.5 g L-1
H2O2 Ozone 2.2
gO3/h
pH 7.0. Water type not stated, but assume
distilled or de-ionised water.
8.9 mmol L-1 p-arsanic acid treated.
Aniline *by product of p-arsanic acid
is removed after 30 min irrad.
Degradation of PPA was pseudo first
order kinetic reaction with linear
relationship ln (c/co) as a function of time.
Rate constants of decomposition were calculated, UV/O3 >
O3 > UV/H2O2 > H2O2 > UV.
Decomposition of p-arsanilic acid (PPA),
44
Acetic acid 70
Propanoic acid 20
Oxalic acid
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 199
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
kinetics and by-products.
68 mg/l H2O2 / LP
UV 48,000 - 186,000 mJ/cm
2
Solution of l-glutamic acid at 7.5 mg/l (= 3 mg/l
DOC).
DCAAFP 60 Chlorination: 4 h, 35
oC. Untreated = 0
μg/l
8
TCAAFP 27 Chlorination: 4 h, 35
oC. Untreated = 0
μg/l
DCAAFP 31 Chlorination: 4 h, 35
oC. Untreated = 6
μg/l
TCAAFP 22 Chlorination: 4 h, 35
oC. Untreated = 51
μg/l
DCAAFP 66 Chlorination: 4 h, 35
oC. Untreated =
374 μg/l
TCAAFP 103 Chlorination: 4 h, 35
oC. Untreated =
188 μg/l
5 mg/l H2O2 / LP/MP UV 500 mJ/cm2
Effluent of sand filtration unit at drinking water
works. Quality: Br = 49.7 mg/l;
hardness = 111 mgCaCO3/l; TOC 1.51
mg/l; UV254abs = 0.035 cm
-1
THMFP THMFP 65 - 66 Chlorination: 24 h, 1 mg/l residual.
Untreated = 47 μg/l
41
10 mg/l H2O2 /
LP/MP UV 1000
mJ/cm2
THMFP THMFP 92 - 97
5 mg/l H2O2 / LP/MP UV 500 mJ/cm2
HAAFP HAAFP 39 - 45 Chlorination: 24 h, 1 mg/l residual.
Untreated = 39 μg/l
10 mg/l H2O2 /
LP/MP UV
HAAFP HAAFP 48
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 200
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
1000 mJ/cm2
5 mg/l H2O2 / LP/MP UV 500 mJ/cm2
THMFP THMFP 39 Chlorination: 24 h, 1 mg/l residual.
Untreated = 22 μg/l
10 mg/l H2O2 /
LP/MP UV 1000
mJ/cm2
THMFP THMFP 49 - 53
5 mg/l H2O2 / LP/MP UV 500 mJ/cm2
HAAFP HAAFP 24 - 30
10 mg/l H2O2 /
LP/MP UV 1000
mJ/cm2
HAAFP HAAFP 23 - 30
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 201
Table E.2 DBP formation from O3 / H2O2
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
O3:H2O2 molar ratio = 4:1 and 2:1
No Info THMFP 90% initial Concentration
9
O3:H2O2 molar ratio = 1:1 and 1:2
100% initial Concentration
H2O2 - 23 mg/l / O3 - 4
mg/l
2.83 mg/l DOC; 0.092 cm-1 UV254 abs; <5 mg/l
CaCO3 alkalinity; >35 OH.
THMFP 98 Raw water THMFP = 325 μg/l
23
HAAFP 116 Raw water HAAFP = 168 μg/l
(Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-93 1996). Precursors of THMs tend to be
aromatic, precursors of HAAs tend to be
aliphatic. AOPs tend to decrease
aromaticity, hence greater effect on
THMFP is expected.
H2O2 - 1-7 mg/l / O3 - 2-14 mg/l
Dilute humic acid in drinking water, 1.1-3.4
mg/l DOC.
THMFP 20 - 31 FP test was 20 mg/l FAC dose and 48
hours contact time. Untreated THMFP =
44 -58.3 μg/l
35
HAAFP 21 - 25 FP test was 20 mg/l FAC dose and 48
hours contact time. Untreated HAAFP =
33.7 -44.1 μg/l
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 202
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
0.2 mg/l H2O2 / 2 mg/l O3
Lake water treated in pilot plant by
coagulation/clarification/filtration. H2O2 / O3
applied either to raw water or to clarified
water. Raw water: DOC 1.6 mg/l; alkalinity 83
mg/l CaCO3, hardness 99 mg/l.
THMFP 27.2 Chlorination test: apply range of chlorine dose ,
measure residuals and THMs after 5
days (targets: initial chlorine residual 1 - 2 mg/l; residual after 5
days ≥ 0.2 mg/l). Note: chlorine relied
upon to quench H2O2. No control
(without either AOP) reported.
51
0.34 mg H2O2/mg O3 (0.5 M/M).
2 and 4 mg/l O3.
Three types of raw water from Switzerland. All prefiltered (0.45um), buffered to pH 7 or 8.
Water spiked with bromide (to achieve 50 ug/l) and MTBE (176 ug/l). Temp 5 to 20 C.
pH7
Principle aim to investigate
degradation of MTBE by ozone and OH
radicals. Sub-aim, to compare formation of
bromate from ozonation with ozone combined with H2O2.
Concluded that,
compared to ozonation, H2O2 reduced bromate
formation but did not eliminate it: a
combination of reaction of bromide
with molecular ozone and hydroxyl radicals.
H2O2 reduces hypobromous acid
(HOBr) limiting formation of bromate.
33
low alkalinity & low DOC Bromate 8.8
high alkalinity & high DOC
Bromate 12.5
high alkalinity & low DOC Bromate 5.6
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 203
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
Solutions of 8.9 mmol L-1 p-arsanic
acid treated. LP UV lamp (laboratory scale). 18.5 g L-1 H2O2 dosed at 5
min intervals to batch reactor.
Ozone 2.2 gO3h-1.
pH 7.0. Water type not stated, but assume
distilled or de-ionised water.
Aniline Degradation of PPA was pseudo first
order kinetic reaction with linear
relationship ln (c/co) as a function of time.
Rate constants of decomposition were calculated, UV/O3 >
O3 > UV/H2O2 > H2O2 > UV.
Decomposition of p-arsanilic acid (PPA),
kinetics and by-products.
Intermediates included nitrophenol,
azobenzenes and phenylazophenol
44
Nitrobenzene
0-1.5 gO3/g TOC; 0.5 O3:H2O2
molar ratio; ozonation time 60(?)
0-1.5 gO3/g TOC; 0.5 O3:H2O2
molar ratio; ozonation
Wastewater with residual chlorobenzene: pH=9.4;
TOC=1150mg/l; COD=3920 mg/L
Synthetic solution: pH=8.4; TOC=250mg/l;
COD=792 mg/L Wastewater with residual chlorobenzene: pH=9.4;
TOC=1150mg/l; COD=3920 mg/L
Chlorobenzene ~ 80-100% Chlorebenzene
removal (ozonation time
30)
Better removal by O3/H2O2 compared
to O3 alone Low reduction in TOC
and COD indicate only incomplete
mineralisation to CO2 (Lists 4 possible Chlorobenzene
removal %'s, have chosen the 2 that
53
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 204
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
time 30(?) Synthetic solution: pH=8.4; TOC=250mg/l;
COD=792 mg/L
Better removal by O3/H2O2 compared to O3 alone Low reduction
in TOC and COD indicate only incomplete
mineralisation to CO2
best relate to the info above, assuming the
stated ozonation time)
23mg/l H2O2
4mg/l O3
2.83mg/l DOC; 0.092cm-1 UV254abs; <5mg/l
CaCO3 alkalinity: >35 OH.
THMFP 325 (Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-
93 1996) % Mineralisation of TOC: UV < O3 <
H2O2/O3 < UV/H2O2 < UV/O3
(3:6:10:23:31) % reduction in
THMFP: UV < O3 < H2O2/O3 < UV/O3 <
UV/H2O2 (15:69:70:75:77) % reduction in
HAAFP: UV < O3 < H2O2/O3 < UV/O3 <
UV/H2O2 (0:8:31:52:62)
Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.
AOPs tend to decrease aromaticity, hence greater effect
23
HAAFP 168
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 205
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
on THMFP is expected.
Unspecified Unspecified Bromate varying the chemical ratio of O3 to H2O2 is
effective at minimizing bromate
formation. In addition, research has
demonstrated that bromate formation is
reduced by approximately 20
percent at a slightly acidic pH (~6.5),
when compared to the ambient pH.
59
Tertiary-butyl formate
Tertiary-butyl alcohol
Acetone
Aldehydes
Glyoxal
Isopropyl alcohol
O3: 0.8 - 4.4 mg/l
H2O2: 0.02 - 0.25 mg/l Treatment followed by coagulation-filtration, in some cases
pre-ozonation
Upper and lower-bound parameters of waters
tested Turbidity: 0.96-6.59 NTU
DOC: 2.78-7.70 mg/L UV_254: 0.0548-0.206
cm^-1 Alkalinity: 87-250 mg/l as
CaCO3 Hardness: N/A-227 mg/l
as CaCO3 Iron: N/A-0.58 mg/l
Manganese: N/A-2.1 mg/l
THM-FP ~30 - ~320 O3/H2O2 + conven treatment does not reduce DOC and
SUVA significantly more than
conventional treatment alone
O3/H2O2 + conven treatment reduces
THM-FP significantly compared to conventional
treatment alone
50
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 206
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
H2O2: 8.8 mg/l
O3: 2.4 mg/l
Reported parameters for three samples:
DOC:2.2 mg/l;Br-:~250 µg/l; pH:7.8 + 1.5µg/l of 7
herbicides
DOC: 2.2 mg/l;Br-:~125 µg/l; pH:7.4
DOC: 0.8 mg/l;Br-:~70 µg/l; pH:5.5
Bromate 5 Study on herbicides removal efficacy
52
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 207
Table E.3 DBP formation from O3 / UV
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
O3 - 4 mg/l UV - 1140 mJ/cm2
2.83 mg/l DOC; 0.092 cm-1 UV254 abs; <5 mg/l
CaCO3 alkalinity; >35 OH.
Raw water THMFP 325 THMFP THM-FP % reduction 75
(Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-
93 1996)
23
HAAFP HAA-FP % reduction 52
Raw water HAAFP 168 THM 81 Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.
AOPs tend to decrease aromaticity, hence greater effect
on THMFP is expected.
HAA 81
O3 - 2 - 12 mg/l
UV - 300-1800
mJ/cm2
Dilute humic acid in drinking water, 1.1-3.4
mg/l DOC.
THMFP 44 - 58.3 (initial)
80% - 65% FP
FP test was 20 mg/l FAC dose and 48
hours contact time. Comparison to
formation potential without treatment
35
HAAFP 33.7 - 44.1 (initial)
55% - 70% FP
UV -270 mJ/cm2, O3
- 8 mg/l
Raw water quality: TOC 1.8 mg/l, alkalinity 3.7 mg/l CaCO3, pH 6.6,
UV254abs 0.074 cm-1.
THM 140 THMFP From 140 to 275
Chlorination: 10 - 20 mg/l residual for 8
days.
38
HAA 160 HAAFP From 160 to 364
UV - 810 mJ/cm2, O3
- 26 mg/l
THM 50 THMFP from 50 to 275
HAA 90 HAAFP From 90 to 340
2.9 mg/l O3 / LP UV 600
mJ/cm2
Groundwater: TOC 5.8 mg/l, UV254abs 0.23 cm-
1, Alkalinity 753 mg/l CaCO3, 623 µg/l
Total aldehydes 73 Raw: 11.2 43
Formaldehyde 33 Raw: 6.6
Acetaldehyde 5 Raw: 2.6
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 208
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
bromide, pH 8. Glyoxal 28 Raw: 1.5
Methylglyoxal 6 Raw: 0.5
Total carboxylic acids 534 Raw: < 10
Oxalate 260
Acetate 220
Formate 60
Bromate 51 Raw: < 5
THMFP 330 Chlorination: 7 day. Raw: 305
HAAFP 330 Chlorination: 7 day. Raw: 348
2.9 mg/l O3 / LP UV 3000
mJ/cm2
Total aldehydes 24 Raw: 11.2
Formaldehyde 10 Raw: 6.6
Acetaldehyde 3 Raw: 2.6
Glyoxal 10 Raw: 1.5
Methylglyoxal 1 Raw: 0.5
Total carboxylic acids 456 Raw: < 10
Oxalate 220
Acetate 170
Formate 60
Bromate 35 Raw: < 5
THMFP 250 Chlorination: 7 day. Raw: 305
HAAFP 190 Chlorination: 7 day. Raw: 348
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 209
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
H2O2 - 10.5 mg/l - 105.5
mg/l
Synthetic water 3 mg/l TOC
pH 8.3 20 +/- 1 C
thiosulphate quenching THMs
90.5 A comparison of 3 different inorganic H2O2 quenching
chemicals: sodium hypochlorite, sodium thiosulphite, sodium
sulphite with an alternative (Bovine
catalase). Standardised
conditions for AOP and chlorination to
simulate a distribution network.
5
hypochlorite quenching THMs
85.6
sulphite quenching THMs
88.6
thiosulphate quenching HAAs
59.1
hypochlorite quenching HAAs
58.7
sulphite quenching HAAs
56.4
thiosulphate Aldehydes
LDL
hypochlorite Aldehydes
LDL
sulphite Aldehydes
LDL
LP UV lamp (laboratory
scale). 18.5 g L-1
H2O2 Ozone 2.2
gO3/h
pH 7.0. Water type not stated, but assume
distilled or de-ionised water.
8.9 mmol L-1 p-arsanic acid treated.
Aniline *by product of p-arsanic acid
is removed after 30 min irrad.
Degradation of PPA was pseudo first
order kinetic reaction with linear
relationship ln (c/co) as a function of time.
Rate constants of decomposition were calculated, UV/O3 >
O3 > UV/H2O2 > H2O2 > UV.
Decomposition of p-
44
Acetic acid 70
Propanoic acid 20
Oxalic acid
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 210
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
arsanilic acid (PPA), kinetics and by-
products.
1140mJ/cm2 UV
4mg/l O3
2.83mg/l DOC; 0.092cm-1 UV254abs; <5mg/l
CaCO3 alkalinity: >35 OH.
THMFP (raw) 325 THMFP 75 (Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-
93 1996) % Mineralisation of TOC: UV < O3 <
H2O2/O3 < UV/H2O2 < UV/O3
(3:6:10:23:31) % reduction in
THMFP: UV < O3 < H2O2/O3 < UV/O3 <
UV/H2O2 (15:69:70:75:77) % reduction in
HAAFP: UV < O3 < H2O2/O3 < UV/O3 <
UV/H2O2 (0:8:31:52:62)
Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.
AOPs tend to decrease aromaticity, hence greater effect
on THMFP is expected.
23
HAAFP (raw) 168 HAAFP 52
UV=193/200/205
O3=0.085 mg/l
Pure and Raw reservoir water
Bromate 25 (in pure water) 43
nitrate=10 mg/l;
bromine=100 μg/l
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 211
Table E.4 DBP formation from O3 / UV / H2O2
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
2.9 mg/l O3 10 mg/l H2O2
LP UV 600 mJ/cm2
Groundwater: TOC 5.8 mg/l, UV254abs 0.23 cm-
1, Alkalinity 753 mg/l CaCO3, 623 µg/l bromide, pH 8.
Total aldehydes 70 Raw: 11.2 43
Formaldehyde 47 Raw: 6.6
Acetaldehyde 9 Raw: 2.6
Glyoxal 11 Raw: 1.5
Methylglyoxal 3 Raw: 0.5
Total carboxylic acids 450 Raw: < 10
Oxalate 190
Acetate 190
Formate 60
Bromate 31 Raw: < 5
THMFP 175 Chlorination: 7 day. Raw: 305
HAAFP 110 Chlorination: 7 day. Raw: 348
2.9 mg/l O3 10 mg/l H2O2
LP UV 3000 mJ/cm
2
Total aldehydes 90 Raw: 11.2
Formaldehyde 49 Raw: 6.6
Acetaldehyde 14 Raw: 2.6
Glyoxal 22 Raw: 1.5
Methylglyoxal 6 Raw: 0.5
Total carboxylic acids 500 Raw: < 10
Oxalate 190
Acetate 250
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 212
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
Formate 70
Bromate 23 Raw: < 5
THMFP 360 Chlorination: 7 day. Raw: 305
HAAFP 360 Chlorination: 7 day. Raw: 348
H2O2 - 10.5 mg/l - 105.5
mg/l
Synthetic water 3 mg/l TOC
pH 8.3 20 +/- 1 C
thiosulphate quenching THMs
90.5 A comparison of 3 different inorganic H2O2 quenching
chemicals: sodium hypochlorite, sodium thiosulphite, sodium
sulphite with an alternative (Bovine
catalase). Standardised
conditions for AOP and chlorination to
simulate a distribution network.
5
hypochlorite quenching THMs
85.6
sulphite quenching THMs
88.6
thiosulphate quenching HAAs
59.1
hypochlorite quenching HAAs
58.7
sulphite quenching HAAs
56.4
thiosulphate Aldehydes
LDL
hypochlorite Aldehydes
LDL
sulphite Aldehydes
LDL
O3: 190mg/h UV: 15W H2O2: 20mg/l
Solution: humic acid 20mg/l, pH ranging 4 -
8.5
~80% UV_254 removal; 17% TOC
removal ~90% UV_254
removal; >30% TOC removal
Study on NOM (humic acid) removal
54
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 213
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
efficiency for the four processes
Acidic pH shows slightly favourable for
Humic acid degradation
6, 10, 15 W
(UV) 60, 118, 190 mg/h (O3) 5, 10, 20,
40, 80 mg/l (H2O2)
Humic acid concentration: 20 mg/l
pH: 4, 5.5, 7, 8.5 UVT: 89.3%
Trihalomethane - - - The results showed that after
UV/O3/H2O2 treatment, the
molecular weight of humic acid and
unsaturated bonds decreased while
small molecules of aldehydes, ketones
and acids increased. The chemical
structure of the humic acids changed a lot after the advanced oxidation process (UV/O3/H2O2). Especially the
unsaturated C=C decreased
considerably, whereas, the C=O
and C-O increased a lot.
Hydroxyl radicals can further oxidize HA
into acids and esters.
54
Haloacetic acids
Ketones
Aldehydes
DWI
Report Reference: DWI 12852.02/16700-0 March 2018
© WRc plc 2018 214
Table E.5 DBP formation from UV / Cl2
AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
LPUV= 5400 mJ/cm2 /
Cl=9.8 mg/L
Synthetic water with increased polyamine
conc (10 mg/l) and pH=7
trichloronitromethane 3.08 TCNM formation resulted slightly
higher under low pH TCNM formation
potential according to precursor tested
follows trend MA>DMA>polyamine
11
LPUV= 5400 mJ/cm2 /
Cl=4.2 mg/L
0.83
LP 3020 mJ/cm2 / Cl
12.5 µM
Drinking water from WTPs spiked with iohexol
dichloroiodomethane 67.5 Experiment of pH influence also carried
out
30
LP 3020 mJ/cm2 / Cl
12.5 µM
chlorodiiodomethane 18.4
LP 3020 mJ/cm2 / Cl
12.5 µM
iodoform 18
LP 3020 mJ/cm2 / Cl
200 µM
dichloroiodomethane 10.5
LP 3020 mJ/cm2 / Cl
200 µM
chlorodiiodomethane 5.7
LP 3020 mJ/cm2 / Cl
200 µM
iodoform 3.6
LP 890 mJ/cm2 / Cl
- 200 µM
Unspecified, supposedly synthetic solution with
10µM trimethoprim
Comparison of chlorination and
UV/Cl for degradation of TMP and
investigation of by-
31
pH=6.1 Chloroform > 5
Chloral hydrate > 4
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
Dichloroacetonitrile > 0.5 products formation
Trichloronitromethane > 0
pH=8.8 Chloroform > 22
Chloral hydrate > 5
Dichloroacetonitrile > 0.9
Trichloronitromethane > 0
LP UV 3900 mJ/cm2 / Cl - 0 - 50 mg/l
Pre-chlorinated river water (78 mg/l Ca; 138 mg/l CaCO3 alkalinity;
2.6 mg/l TOC; UV254abs 0.045 cm-1; turbidity < 0.5 NTU). pH = 6, 7.5
and 9.
THM 14 With no UV: TTHM = 14 μg/l, HAA5 = 17
μg/l, HAA9 = 27 μg/l, TOX = 97 μg/l
No mineralisation of TOC evident, but UV254abs was
reduced (33% by UV alone; with 5-50 mg/l FAC: 80-90% at pH6, 65-80% at pH7.5, 60-75% at pH9) by the AOP reducing the aromaticity of the organic matter.
27
HAA5 37
HAA9 42
TOX 56
MP UV 1800 mJ/cm2 / Cl = 2-10 mg/l
Source 1, treated river water, pre-chlorinated: Alkalinity 85-92 mg/l
CaCO3, TOC 1.5 mg/l, UV254abs 0.02 cm-1,
turbidity 0.02-0.04, bromide 2-3 mg/l. pH =
6.5, 7.5 and 8.5
THM 14 - 17 THM-FP 45 - 52 THM without AOP: 18 μg/l. THMFP without
AOP: 30 - 40 μg/l THMFP increased with increasing pH.
29
HAA 10 - 15 HAA-FP 40 - 90 HAA without AOP: 10 - 15 μg/l. HAAFP
without AOP: 30 - 40 μg/l
Haloacetonitriles 1.5 - 4 HANFP 6 - 13 HAN without AOP: 1 μg/l. HANFP without
AOP: 3 - 4 μg/l
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
Haloketone No formation observed.
Chloropicrin No formation observed.
Chlorite > 99% pre-existing chlorite removed
Chlorate Up to 17% by mass of the chlorine consumed in the UV/Cl AOP was converted to chlorate.
Perchlorate Pre-existing concentration unchanged
Bromate 0.1 - 2 (UV/Cl)
Source 2, treated lake water, NOT pre-
chlorinated: Alkalinity 123 mg/l CaCO3, TOC 3.5
mg/l, UV254abs 0.04 cm-1, turbidity 0.2 NTU,
bromide 2-3 mg/l. pH = 6.5, 7.5 and 8.5
THM 5 - 10 THMFP 100 - 120 THM without AOP: 3 μg/l. THMFP without
AOP: 50 - 85 μg/l
HAA 4 - 15 HAAFP 65 - 135 HAA without AOP: < 1 μg/l. HAAFP without
AOP: 50 - 70 μg/l HAAFP decreasing with increasing pH. The impacts of the
two AOPs were similar, except at pH
6.5, where UV/Cl increased HAAFP
more than UV/H2O2.
Haloacetonitriles 1.5 - 5 HANFP 4 - 28 HAN without AOP: 0 μg/l. HANFP without
AOP: 2 - 8 μg/l
Haloketone No formation observed.
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
Chloropicrin No formation observed.
UV ? mJ/cm2 / Cl = 3 mg/L
Removal of personal care products using
UV/Chlorine and UV/Hydrogen peroxide and formation of DBPs
after chlorination. Three sources of water were tested. One of the tested water samples
was ammonia-rich. The water sources were previously treated
through coagulation, flocculation,
sedimentation and sand filtration. Reaction time with AOP: 1.5 or 3 min.
treated water was sampled and quenched with sodium sulfite and
clorinated for 24 h at 0.9 + 0.1 mg/l free chlorine
residual.
Chloral hydrate The higher radical exposure in the
UV/Chlorine AOP over UV/H2O2 AOP
likely resulted in alteration of dissolved organic matters and thus enhanced the formation potentials
of CH, HKs and TCNM but reduced
the formation potential of HANs .
On the other hand, in the ammonia rich
water, the formation potentials of THMs,
HKs and TCNM were slightly higher and the formation potentials
of CH and HANs were lower during the
sub-sequent post-chlorination with
UV/chlorine AOP than with UV/H2O2 AOP.
32
Haloketone
Trichloronitromethane
Haloacetonitriles
Halonitromethane
Unspecified p-chlorobenzoic acid (pCBA)
pCBA is an intermediate product
during the chlorination of
pesticides. High reactivity with
hydroxyl radicals (,OHpCBAk = 5·109
M-1s-1). Pseudo first-order reaction
58
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AOP Treatment
Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within the
paper Ref
behaviour for pCBA reacting with OH
radicals using the UV chlorine process.
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Table E.6 DBPs formation from UV / S2O8
AOP Treatment Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP treatment
(µg/l)
Final DBP
formed
Final DBP concentration
(µg/l)
Other details reported within the paper
Ref
UV ? mJ/cm2 / S208(2-) = 10
mM
Synthetic water Bromate (BrO3-) The performance of UV/S2O8(2─) was
investigated on a synthetic water. In addition, a model
was developed and an attempt was made to fit the model to the experimental
results of bromate formation. It was stated that
UV/S2O8(2─) has no significant tendency to form
BrO3(─) in presence of Br(─) and natural organic matter.
66
LP UV: 12kW (no further info)
S2O8 = 5 - 10mM
50 mL solutions with: 0.02 mM p-aminobenzoi
acid (approx) different concentrations
of NO3 CO3 Cl PO4 and NOM per sample
Degradation efficiency of p-aminobenzoi acid by
UV/Fe/persulfate Even low concentrations of carbonate and sulfat
considerably slowed kinetics (possible
reactions proposed) Very high efficiency
reported for UV/Fe/S2O8 on p-aminobenzoic acid
48
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AOP Treatment Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP treatment
(µg/l)
Final DBP
formed
Final DBP concentration
(µg/l)
Other details reported within the paper
Ref
UV ? Mj/cm2 / PAS = 100 uM
TOC: 2.25 mg/l Br: 200 ug/l
pH: 7.5 T: 20 C
Bromoform (TBM) 7 Actually used CuFe2O4 catalyst rather than UV but by-
products should still be applicable
6
Dibromoacetic acid 2
Monobromoacetic acid 2
Dibromoacetonitrile 2
Bromochloroacetonitrile 4
Dibromochloromethane 7
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Table E.7 DBP formation from UV / TiO2
AOP Treatment Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Other details reported within the paper
Ref
UV = 7000mJ/cm2 THM 24
100 mg/L TiO2 (5 kWh) Raw 1 - CAP canal (0.046 cm^-1
UV_254)
150 µg TTHM/l
400 mg/L TiO2 (2 kWh) Raw 2 Cap Canal (0.049 cm^-1
UV_254)
220 µg TTHM/l
400 mg/L TiO2 (10-20 kWh)
Raw 1 Salt River (0.110 cm^-1
UV_254)
130 µg TTHM/l
400 mg/L TiO2 (20 kWh) Raw 2 Salt River (0.110 cm^-1
UV_254)
180 µg TTHM/l
400 mg/L TiO2 (10 kWh)+4 mg/l Cl
Raw 2 Cap Canal 200 µg TTHM/l
400 mg/L TiO2 (5-10 kWh)+4 mg/l Cl
Raw 2 Salt River 260 µg TTHM/l
UV = 291 W/m2 1.5 g TiO2 dissolved in
200 mL
Synthetic groundwater phenols >400 Synthetic groundwater with initial BTEX concentration of
1000 µg/L removal efficiency of petroleum aromatic
hydrocarbons
26
Xenon light 35 mJ/m^2 TiO2: 0.2, 0.85 1.5 g/l
H2O2: 50, 100, 150 mg/l
pH: 3, 6, 9 2,2-dihydroxy-4-methoxybenzophenone
300 min treatment time 34
Benzaldehyde
1,3-dihydroxybenzene
4-Methylphenol
Benzoic acid
2-Methylphenol
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AOP Treatment Condition/Dose
Summary of relevant water conditions
DBPs Formed by AOP process
DBP concentrations formed during AOP
treatment (µg/l)
Other details reported within the paper
Ref
2-Hydroxybenzaldehyde
2-Methylphenyl benzoate
Benzyl alcohol
50mg/l TiO2; powder immobilised on glass
beads; unquantified UV
Injection of benzene, toluene, ethylbenzene and xylene to review
DBPs
Phenols Decomposition of BTEX compounds generates
phenols as by-products. The phenols are themselves degradable by the AOP.
10
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Table E.8 DBP formation from Ozonation
AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
O3 - 4 mg/l 2.83 mg/l DOC; 0.092 cm-1 UV254 abs; <5 mg/l
CaCO3 alkalinity; >35
OH.
THMFP 101 Unozonated THMFP = 326 μg/l
23
HAAFP 155 Unozonated HAAFP = 168 μg/l
(Chlorination method =
Summers RS et al, JAWWA 81 (7) pp 80-93 1996). Precursors of
THMs tend to be aromatic,
precursors of HAAs tend to be aliphatic. AOPs
tend to decrease aromaticity, hence greater effect on
THMFP is expected.
Raw water THMFP = 325
mg/l; HAAFP = 168
mg/l.
4 mg/l Raw water quality: TOC
1.8 mg/l, alkalinity 3.7 mg/l CaCO3,
pH 6.6, UV254abs 0.074 cm
-1
THMFP 150 µg/l Chlorination: 10 - 20 mg/l residual
for 8 days. THMFP without
ozone = 275 µg/l. Increasing ozone
dose up to 24 mg/l did not result in
any further change in THMFP.
38
HAAFP 190 µg/l
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
2.9 mg/l Groundwater: TOC 5.8 mg/l,
UV254abs 0.23 cm-1,
Alkalinity 753 mg/l CaCO3,
623 µg/l bromide, pH 8.
Total aldehydes 74 Raw: 11.2 43
Formaldehyde 32 Raw: 6.6
Acetaldehyde 5 Raw: 2.6
Glyoxal 29 Raw: 1.5
Methylglyoxal 7 Raw: 0.5
Total carboxylic acids 320 Raw: < 10
Oxalate 160
Acetate 100
Formate 60
Bromate 14 Raw: < 5
THMFP 370 Chlorination: 7 day. Raw: 305
HAAFP 420 Chlorination: 7 day. Raw: 348
0.5 mg O3/ mg DOC (2.06mg/l)
River surface water
82% (18% reduction)
Experiment on preoxidation by
AOP, followed by chlorination, to
investigate removal potential
of DBP PRECURSORS
6
1 mg O3/ mg DOC (2.12mg/l)
DOC: 2.3 mg/l THM-FP 76% (24% reduction)
1.5 mg O3/ mg DOC (2.12mg/l)
pH: 7.6 68% (32% reduction)
Unspecified Bottled water Butanone 39.7 Focus of paper was
demonstration of analytical method.
45
Acetone 30.6
Formaldehyde 16.6
Acetaldehyde 15
Propanal 5.8
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
Unspecified From three pairs of
treatment works, where
each pair treated same raw water but
one works used ozone
and the other didn't. DBPs reported here are those for
which the implication is that ozone increases formation potential.
1-bromo-1,1-dichloropropa
none FP
3 After chlorination of chloramination
(unspecified conditions). Haloketone.
55
1,1,3,3-tetrachloropropanone FP
1-bromo-1,3,3-
trichloropropanone FP
1,1-dibromo-3,3-
dichloropropanone FP
1,3-dibromo-1,3-
dichloropropanone FP
1,1,3-tribromo-3-
chloropropanone FP
dichloroacetaldehyde FP
10 - 16 After chlorination of chloramination
(unspecified conditions).
Haloaldehyde.
1,1,3,3-tetrabromopropanone FP
Chloropricrin FP
After chlorination of chloramination
(unspecified conditions).
Halonitromethane.
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
Unspecified Known reaction
products of ozone with
NOM
Phenols 56
Aldehydes
Carboxylic acids
Aldonic acids
Keto acids
Unspecified Unspecified Chloropricrin FP
1 - 5 160 - 380% greater formation
than without ozone.
57
2 and 4 mg/l O3.
Three types of raw water from
Switzerland. All prefiltered
(0.45um), buffered to pH
7 or 8. Bromide = 50
μg/l.
Principle aim to investigate
degradation of MTBE by ozone and OH radicals.
Sub-aim, to compare
formation of bromate from ozonation with
ozone combined with H2O2.
Concluded that,
compared to ozonation, H2O2 reduced bromate formation but did not eliminate it: a combination of
reaction of bromide with
molecular ozone and hydroxyl
33
low alkalinity & low DOC
Bromate 15.1
high alkalinity & high DOC
Bromate 20.7
high alkalinity & low DOC
Bromate 12
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
radicals. H2O2 reduces
hypobromous acid (HOBr) limiting
formation of bromate.
LP UV lamp (laboratory
scale). 18.5 g L-1
H2O2 Ozone 2.2
gO3/h
pH 7.0. Water type not
stated, but assume
distilled or de-ionised water. 8.9 mmol L-1 p-arsanic acid
treated.
Aniline *by product of p-arsanic acid
is removed after 30 min
irrad.
Degradation of PPA was pseudo first order kinetic
reaction with linear relationship
ln (c/co) as a function of time.
Rate constants of decomposition
were calculated, UV/O3 > O3 >
UV/H2O2 > H2O2 > UV.
Decomposition of p-arsanilic acid (PPA), kinetics
and by-products.
44
Acetic acid 70
Propanoic acid 20
Oxalic acid
4mg/l O3 2.83mg/l DOC; 0.092cm-1 UV254abs;
<5mg/l CaCO3 alkalinity: >35
OH.
THMFP 325000 (Chlorination method =
Summers RS et al, JAWWA 81 (7)
pp 80-93 1996) % Mineralisation of TOC: UV < O3
< H2O2/O3 < UV/H2O2 <
UV/O3 (3:6:10:23:31) % reduction in
THMFP: UV < O3
23
HAAFP 168000
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
< H2O2/O3 < UV/O3 < UV/H2O2
(15:69:70:75:77) % reduction in
HAAFP: UV < O3 < H2O2/O3 <
UV/O3 < UV/H2O2
(0:8:31:52:62) Precursors of
THMs tend to be aromatic,
precursors of HAAs tend to be aliphatic. AOPs
tend to decrease aromaticity, hence greater effect on
THMFP is expected.
Ozone followed by
chloramination (unspecified conditions)
Groundwater Trihaloacetaldehydes HNM 6.9 . Additional new DBPs found:
haloquinones;halocyclopentenoic
acids;nitrosamines derived from alkaloids and nitrosamides; halonitriles.
20
Halonitrimethanes Trihalogenatacetaldehydes
w/o bio-filter 16 (site specific)
Chloroacetaldehyde
Ozone followed by biofiltration (unspecified conditions)
High-bromide source
(unspecified type)
Trichloronitromethane
Iodinated THMs
Chloral Hydrate
Dichloroacetaldehyde 13
Ozone Low-bromide Bromonitromethane
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
(unspecified conditions)
source (unspecified
type)
Di- and Tri-halogenated halonitromethanes (HNMs)
(Hi br) 5.7, (low Br) 2.9
Dihalogenated acetaldehydes 5-12
Ozone (unspecified conditions)
16 drinking water plant influents;
Most of the plants were impacted by
algae or WWTP
effluents in their
catchments
Mean DOC: 3.3 mg/l
Mean DON: 0.29 mg/l as N
THM 4.3 - 167 (36) THMFP 57-492 (158) Filtration following ozonation has
showed high removal of
FP for trihalogenated acetaldehydes, chloropicrin and
NDMA; Ozonation tended to incread FP of trihalogenated acetaldehydes and cyanogen
halides, while tended to
reduce NDMA FP
25
Trihalogenated acetaldehydes ND - 19 (4.5) Trihalogenated
acetaldehydes FP
7.4-85 (30)
Dihalogenated acetaldehydes ND - 11 (ND) Dihalogenated
acetaldehydes FP
ND-7.1 (2.1)
Dihalogenated HANs ND - 9.9 (4) Dihalogenated HANs FP
0.9-12 (3.4)
Cyanogen halides ND - 8.4 (2.6) Cyanogen halides FP
ND-34 (11)
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
Chloropicrin ND - 7.6 (0.5) Chloropicrin FP
ND-5.9 (0.9)
Dihalogenated nitromethanes ND - 2.0 (ND) Dihalogenated
nitromethanes FP
ND-3.6 (<0.1)
NDMA ND - 20 (ND) NDMA FP ND-261 (22)
Ozone (unspecified conditions)
0.6 mg/l chlorate
Bromate 60
Bromohydrins
Chloral hydrate
Chlorate 10 - 106
O3: 2 - 10 mg/l Unspecified, reference
given
Bromate No bromate formed below about 3 mg/l
dose; at higher doses,
bromate concentration (ug/l) follows regression equation:
[Br (ug/l)]=8.28*[O3 (mg/l)] - 25.9
Other potential ozone DBPs listed but not quantified
(other than statement that
approximately 4 x more carboxylic
acids than aldehydes
produced under equal conditions).
3
Aldehydes
Carboxylic acids
Ketones
Brominated THMs
Phenols
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
Acetic acids
Cyanogen halides
Nitromethanes
Acetonitriles
Unspecified Three sources: Ozonated
water from one full-scale treatment
works and one pilot plant;
distilled water spiked with humic and fulvic acid
extracted from river water.
Aldehydes: Formaldehyde Acetaldehyde
Propanal Butanal
2-methyl propenal pentanal
3-methyl butanal hexanal heptanal octananl nonanal
undecanal dodecanal tridecanal
benzaldehyde
Paper reported DBPs detected
but not concentrations.
(Only DBPs confirmed by
analysis against standards are given here).
46
Ketones: acetone
2-butanone 3-methyl-2-butanone
2-pentanone 3-hexanone 2-hexanone
3-methyl cyclopentanone 6-methyl-5-hepten-2-one 6-hydroxy-2-hexanone
Paper reported DBPs detected
but not concentrations.
2-methyl propanoic acid; butanoic acid; 3-methyl butanoic acid; pentanoic acid;
hexanoic acid; heptanoic acid octanoic acid
Paper reported DBPs detected
but not
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
nonanoic acid decanoic acid undecanoic acid dodecanoic acid tridecanoic acid
tetradecanoic acid pentadecanoic acid hexadecanoic acid heptadecanoic acid
octadecanoic acid phenylacetic acid benzoic acid ethanedioic acid propanedioic acid butanedioic acid tert-butyl maleic acid
pentanedioic acid hexanedioic acid heptanedioic acid octanedioic acid nonanedioic acid decanedioic acid
undecanedioic acid tridecanedioic acid phthalic acid isophthalic acid terephthalic
acid 1,2,4-benzenetricarboxylic acid 1,3,5-benzenetricarboxylic acid 1,2,4,5-
benzenetetracarboxylic acid
concentrations.
Keto-acids: 3-keto-butanoic acid
3-methyl-2-keto-butanoic acid
Paper reported DBPs detected
but not concentrations.
Nitriles: benzeneacetonitril
heptanenitrile
Paper reported DBPs detected
but not concentrations.
Di-carbonyls: glyoxal
2-ketopropanal (methylglyoxal) 2,3-butanedione (dimethlyglyoxal)
5-keto-hexanal
Paper reported DBPs detected
but not concentrations.
Halo-alkanes/alkenes: 2,3-dichlorobutane
hexachlorocyclopentadiene
Chlorinated or chloraminated at 2
- 3 mg/l, contact time not specified.
Haloaldehydes: chloroacetaldehyde
trichloroacetaldehyde (chloral hydrate)
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AOP Treatment Condition/
Dose
Summary of relevant
water conditions
DBPs Formed by AOP process
DBP concentration
s formed during AOP treatment
(µg/l)
Final DBP formed
Final DBP concentration
(µg/l)
Other details reported within
the paper Ref
dichloroacetaldehyde
Haloketones: 1,1-dichloropropanone 1,3-dichloropropanone
1,1,1-trichloropropanone 1,1,3,3-tetrabromopropanone
Haloacids: chloroacetic acid bromoacetic acid
dichloroacetic acid trichloroacetic acid
bromochloroacetic acid dibromoacetic acid
2-chloropropanoic acid 2,2-dichloropropanoic acid
Haloacetonitriles: dichloroacetonitrile
bromochloroacetonitrile dibromoacetonitrile
Haloalcohols: 2-bromoethanol
Halo-nitro-methanes: dibromonitromethane
trichloronitromethane (chloropicrin) tribromonitromethane (bromopicrin)
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Table E.9 References
1 Chu et al. (2014) 29 Wang et al. (2015) 50 Borikar et al. (2015)
2 Toor and Mohseni (2007) 30 Wang et al. (2016) 51 Jasim et al. (2012)
3 Rieder et al. (2007) 31 Wu et al. (2016) 52 Upelaar et al. (2000)
4 Sharpless et al. (2003) 32 Yang et al. (2016) 53 Cortés et al. (1996)
5 Liu et al. (2003) 33 Acero et al. (2001) 54 Mo et al. (2015)
6 Kleiser and Frimmel (2000) 34 Zúñiga-Benítez et al. (2016) 55 Krasner et al. (2006)
7 Wang et al. (2014) 35 Čehovin et al. (2017) 56 Onstad et al. (2008)
8 Bond et al. (2009) 36 Wu and Englehardt (2016) 57 Shah and Mitch (2012)
9 Frimmel et al. (2000) 37 (36 and 37 are the same paper) 58 Mehrjouei (2012)
10 Alizadeh Fard et al. (2013) 38 Chin and Bérubé (2005) 59 Kommineni et al. (2008)
11 Deng et al. (2014) 39 Jo et al. (2011b) 60 Amy et al. (2000)
12 Chu et al. (2014) 40 Metz et al. (2011) 61 Adedapo (2005)
20 Krasner (2009) 41 Dotson et al. (2010) 62 James (2013)
21 Jo et al. (2011a) 42 Zoschke et al. (2012) 63 Derks (2010)
22 Ijpelaar et al. (2002) 43 Agbaba et al. (2016) 64 Hofman-Caris and Beerendonk (2011)
23 Lamsal et al. (2011) 44 Czaplicka et al. (2015) 65 Barceló and Petrovic (2008)
24 Gerrity et al. (2009) 45 Neng and Nogueira (2010) 66 Lutze (2013)
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25 Krasner et al. (2012) 46 Richardson et al. (2000) 67 Lekkerkerker-Teunissen (2012)
26 Alizadeh Fard et al. (2013) 47 Vughs et al. (2016) 68 Agbaba et al. (2015)
27 Pisarenko et al. (2013) 48 Xue et al. (2016)
28 Sarathy et al. (2011) 49 Andrews and Huck (1994)
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Appendix F Literature Review
F1 Generic search terms
Table F.1 Generic search terms used within Scopus
Search terms
(CASREGNUMBER(xxx) OR CHEMNAME(xxx) OR CHEM(xxx))
AND
(oral OR gavage OR intuba! OR diet OR feed OR capsule) AND (“health-based guidance val!” OR “acceptable
daily intake” OR “tolerable daily intake” OR “no observed adverse effect level” OR “benchmark dose” OR “lethal
dose” OR “margin of safety” OR “margin of exposure” OR toxic! OR epidem! OR carcin! OR tumor! OR tumour! OR
reproduc! OR development! OR foetox! OR fetotox! OR genotox! OR mutagen! OR cytotoxic! OR immunotox! OR
neurotox! OR “in vitro” OR “in vivo”) AND (LIMIT-TO (LANGUAGE, "English"))
Table F.2 Generic search terms used within PubMed
Search terms
(xxx[EC/RN Number] OR xxx)
AND
(oral[All Fields] OR gavage[All Fields] OR intuba*[All Fields] OR diet[All Fields] OR feed[All Fields] OR capsule[All
Fields]) AND ("health-based guidance val*"[All Fields] OR "acceptable daily intake"[All Fields] OR "tolerable daily
intake"[All Fields] OR "no observed adverse effect level"[All Fields] OR "benchmark dose"[All Fields] OR "lethal
dose"[All Fields] OR "margin of safety"[All Fields] OR "margin of exposure"[All Fields] OR toxic[All Fields] OR
toxicolo*[All Fields] OR epidemiol*[All Fields] OR carcinog*[All Fields] OR tumor[All Fields] OR tumour[All Fields]
OR tumorogen*[All Fields] OR tumourogen![All Fields] OR reproduc*[All Fields] OR development*[All Fields] OR
foetox*[All Fields] OR fetotox*[All Fields] OR genotox*[All Fields] OR mutagen*[All Fields] OR cytotoxic*[All Fields]
OR immunotox*[All Fields] OR neurotox*[All Fields] OR "in vitro"[All Fields] OR "in vivo"[All Fields]) AND
("english"[Language])
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Table F.3 Results from literature searches in Scopus and PubMed search
Chemical Search terms - Scopus
Number
of
records
retrieved
Search terms - Pubmed
Number
of
records
retrieved
2-Hydroxy-5-
nitrobenzoic acid
(CASREGNUMBER(96-97-
9) OR CHEMNAME(“2-
Hydroxy-5-nitrobenzoic
acid”) OR CHEM(“2-
Hydroxy-5-nitrobenzoic
acid”))
4 (96-97-9 [EC/RN Number] OR “2-
Hydroxy-5-nitrobenzoic acid”)
0
2-Methoxy-4,6-
dinitrophenol
CASREGNUMBER(4097-
63-6) OR CHEMNAME(2-
Methoxy-4,6-dinitrophenol)
OR CHEM(2-Methoxy-4,6-
dinitrophenol))
0 (4097-63-6 [EC/RN Number] OR 2-
Methoxy-4,6-dinitrophenol)
0
2-
Nitrohydroquinone
(CASREGNUMBER(16090-
33-8) OR CHEMNAME(2-
Nitrohydroquinone) OR
CHEM(2-
Nitrohydroquinone))
0 (16090-33-8 [EC/RN Number] OR
2-Nitrohydroquinone)
0
3,5-Dinitrosalicylic
acid
(CASREGNUMBER(609-
99-4) OR
CHEMNAME(“3,5-
Dinitrosalicylic acid”) OR
CHEM(“3,5-Dinitrosalicylic
acid”))
3 (609-99-4 [EC/RN Number] OR
“3,5-Dinitrosalicylic acid”)
3
4-Hydroxy-3-
nitrobenzoic acid
(CASREGNUMBER(616-
82-0) OR CHEMNAME(“4-
Hydroxy-3-nitrobenzoic
acid”) OR CHEM(“4-
Hydroxy-3-nitrobenzoic
acid”))
0 (85-38-1 [EC/RN Number] OR “2-
Hydroxy-3-nitrobenzoic acid”)
6
4-Nitrobenzene-
sulfonic acid
(CASREGNUMBER(138-
42-1) OR CHEMNAME(“4-
Nitrobenzene-sulfonic
acid”) OR CHEM(“4-
Nitrobenzene-sulfonic
acid”))
4 (138-42-1 [EC/RN Number] OR 4-
Nitrobenzene-sulfonic acid)
8
4-Nitrocatechol (CASREGNUMBER(3316-
09-4) OR CHEMNAME(4-
Nitrocatechol) OR
CHEM(4-Nitrocatechol))
10 (3316-09-4 [EC/RN Number] OR 4-
Nitrocatechol)
1
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Chemical Search terms - Scopus
Number
of
records
retrieved
Search terms - Pubmed
Number
of
records
retrieved
4-Nitrophthalic
acid
(CASREGNUMBER(610-
27-5) OR CHEMNAME(4-
Nitrophthalic acid) OR
CHEM(4-Nitrophthalic
acid))
0 (610-27-5 [EC/RN Number] OR 4-
Nitrophthalic acid)
7
5-Nitrovanillin (CASREGNUMBER(6635-
20-7) OR CHEMNAME(5-
Nitrovanillin) OR CHEM(5-
Nitrovanillin))
0 (6635-20-7 [EC/RN Number] OR 5-
Nitrovanillin)
1
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Appendix G Ozone DBP Assessment
G1 Introduction
As part of this project, DBPs formed following O3 treatment alone were also identified.
Following the prioritisation process, two DBPs were categorised as being ‘high priority’ (Table
G.1) and so the toxicity of these chemicals in drinking water has been reviewed as part of this
addendum.
Table G.1 High priority DBPs formed by ozone
DBP CAS Number
1-Bromo-1,1-dichloropropanone 1751-16-2
Dichloroacetaldehyde 79-02-7
G2 Toxicity Summary
G2.1 1-Bromo-1,1-dichloropropanone
G2.1.1 Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
No data are available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
No data are available.
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Reproductive/developmental toxicity
No data are available.
G2.1.2 Alternative approached to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, 1-bromo-1,1-dichloropropanone is predicted to be
sensitising to the skin and mutagenic whereas the the predictions for carcinogenicity and
reproductive/developmental toxicity were equivocal. However these should be treated with
caution as all of the predictions are considered to be unreliable. The results of these findings
are summarised inTable G.2.
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Table G.2 VEGA predictions for 1-bromo-1,1-dichloropropanone
Model Prediction Reliability of
Assessment
Similarity with
molecules of known
experimental value
Accuracy of
prediction for
similar molecules
Concordance for similar
molecules (experimental
Vs predicted)
Identified structural alerts
Sensitisation (CAESAR) Sensitising Not reliable
Moderate Good Agree -
Mutagenicity(CAESAR) Mutagenic Not reliable Strong Good Agree -
Mutagenicity (ISS) Non-mutagenic Not reliable
Moderate No adequate Disagree
Mutagenicity (KNN) Mutagenic Not reliablea
Strong Good Agree
Mutagenicity (SarPy) Mutagenic Not reliablea
Strong Good Agree SM93, SM106
Carcinogenicity (CAESAR) Carcinogenic Not reliablea,b
Moderate Good Some disagree -
Carcinogenicity (IRFMN/Antares) Carcinogenic Not reliablea
Moderate Not adequate Disagree Carcinogenic no: 57, 58, 59
Carcinogenicity (ISS) Non-
carcinogenic Not reliable
a Moderate Good Some disagree -
Carcinogenicity (ISSCAN-CGX) Non-
carcinogenic Not reliable
a Moderate Not optimal Disagree -
Reproductive/developmental
toxicity (CAESAR) Toxicant Not reliable
c,d No Good Disagree -
Reproductive/developmental
toxicity (PG) Non-toxicant Not reliable
e Moderate Good Disagree -
a A prominent number of atom centred fragments of the compound have not been found in the compounds of the dataset or are rare fragments (1 unknown
fragment found) b
Predicted substance falls into a network that is populated by no compounds of the dataset c 1 descriptor for this compound has values outside the descriptor range of the compounds of the dataset
d A prominent number of atom centred fragments of the compounds have not been found in the compounds of the dataset or are rare fragments (2 unknown
fragments found) e
A prominent number of atom centred fragments of the compounds have not been found in the compounds of the dataset or are rare fragments (1 infrequent fragment found).
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OECD toolbox
Using the OECD QSAR Toolbox, one NOAEL was predicted for repeated dose toxicity (Table
G.3). However, it should be noted that this prediction, whilst falling within the prediction
domain, and featuring an acceptable statistical measure of fit, is considered to be of low
reliability due to the small size of the dataset upon which it is based.
The experimental database for developmental and reproductive toxicity was too limited to
derive estimates for this endpoint.
Table G.3 OECD Toolbox predictions for 1-bromo-1,1-dichloropropanone
En
dp
oin
t
Init
ial
Pro
file
r
Su
b-c
ate
go
ris
ati
on
pro
file
s
Nu
mb
er
of
ca
teg
ory
me
mb
ers
In d
om
ain
?
R2
sta
tis
tic
Re
su
lt
Re
lia
bil
ity
NOAEL
(mice, oral
gavage,
drinking
water or diet)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements
Structural similarity
6 Yes 0.876 404 000 µg/kg bw/day Low
TTC
1-Bromo-1,1-dichloropropanone is categorised as a Cramer Class III, using ToxTree
modelling software. Therefore, a TTC value of 1.5 µg/kg bw/day is appropriate.
G2.1.3 Selection of PoD
No experimental PoDs were available for 1-bromo-1,1-dichloropropanone. Based on the
modelled data, the following PoDs are proposed:
A NOAEL of 404 000 µg/kg bw/day derived from the OECD toolbox,
A TTC value of 1.5 µg/kg bw/day.
The reliability of both the NOEL and LOEL values is considered to be ‘low’ due to the
limitation of the dataset behind their derivation so should be used with caution.
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G2.2 Dichloroacetaldehyde
G2.2.1 Experimental toxicity data
Acute toxicity
No data are available.
Irritation and sensitisation
Dichloroacetaldehyde has been classified as a ‘skin irritant, category 1; H314’ and ‘eye
irritant, category 1; H318’ under European GHS (PubChem, 2017h). No information on the
study was available. No sensitisation data are available.
Chronic toxicity
No data are available.
Mutagenicity/carcinogenicity
Both negative and positive results for mutagenicity have been reported in vitro for
dichloroacetaldehyde.
Negative results for mutagenicity include an unscheduled DNA synthesis assay in human
epithelial-like cells at 6-6000 mMol (ChemEXPERT™, 2017), and a genetic mutation assay in
Chinese hamster (V79) cells at 0.12-1.2 mMol (Aquilina et al., 1984). Positive results for
dichloroacetaldeyhe have been reported by EPA (1995) and Fischer et al. (1977), however,
no further details on these studies are available.
Reproductive/developmental toxicity
No data are available.
G2.2.2 Alternative approached to deriving a PoD
Modelled toxicity data
VEGA
Based on the chemical structure, dichloroacetaldehyde is predicted to be non- sensitising to
the skin. It is also predicted to be mutagenic, with three of the four models used considered to
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be reliable. The predictions for carcinogenicity and reproductive/developmental toxicity were
equivocal and also considered to be either not optimal or not reliable. The results of these
findings are summarised in Table G.4
OECD toolbox
Using the OECD QSAR Toolbox, one LOAEL was predicted for repeated dose toxicity. This
result is presented in Table G.5. However, it should be noted that this prediction, whilst falling
within the prediction domain is considered to be of low reliability due to the small size of the
dataset upon which it is based and the measure of fit is relatively poor.
The experimental database for developmental and reproductive toxicity was too limited to
derive estimates for these endpoints.
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Table G.4 VEGA predictions for dichloroacetaldehyde
Model Prediction Reliability of Assessment
Similarity with molecules of known experimental value
Accuracy of prediction for
similar molecules
Concordance for similar molecules
(experimental Vs predicted)
Identified structural alerts
Sensitisation (CAESAR) Non-
sensitising Not reliable
a Moderate Good Disagree -
Mutagenicity (CAESAR) Mutagenic Appears reliable
Strong Good Agree SA8 aliphatic halogens
Mutagenicity (ISS) Mutagenic Appears reliable
Strong Good Agree SA8 aliphatic halogens, SA11
simple aldehyde
Mutagenicity (KNN) Mutagenic Not optimal Strong Not optimal Agree -
Mutagenicity (SarPy) Mutagenic Appears reliable
Strong Good Agree SM106
Carcinogenicity (CAESAR) Non-
carcinogenic Not optimal Strong Good Disagree -
Carcinogenicity (IRFMN/Antares)
Carcinogen Not optimal Strong Not optimal Some disagree Carcinogenicity alert no: 57
Carcinogenicity(ISS) Carcinogen Appears reliable
Strong Good Agree SA8 aliphatic halogens, SA11simple aldehyde
Carcinogenicity (ISSCAN-CGX) Non
carcinogen Not reliable Strong Not adequate Disagree -
Reproductive/developmental toxicity (CAESAR)
Toxicant Not reliableb,c
No Good Disagree -
Reproductive/developmental toxicity (PG)
Non toxicant Not reliable Moderate Good Disagree -
a A prominent number of atom centred fragments of the compound have not been found in the compounds of the dataset or are rare fragments (1 unknown
fragment found) b
1 descriptor for this compound has values outside the descriptor range of the compounds of the dataset c A prominent number of atom centred fragments of the compounds have not been found in the compounds of the dataset or are rare fragments (2 infrequent
fragments found
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Table G.5 OECD Toolbox predictions for dichloroacetaldehyde E
nd
po
int
Init
ial
Pro
file
r
Su
b-c
ate
go
ris
ati
on
pro
file
s
Nu
mb
er
of
ca
teg
ory
me
mb
ers
In d
om
ain
?
R2
sta
tis
tic
Re
su
lt
Re
lia
bil
ity
LOAEL
(B6C3F1
mice, F344
rats or
Wistar rats)
Repeat dose
(HESS)
Repeat dose (HESS)
Chemical elements
Structural similarity
3 Yes 0.588 276 000 µg/kg bw/day Low
TTC
Dichloroacetaldehyde is categorised as a Cramer Class III using ToxTree modelling software.
However a structural alert for genotoxic carcinogenicity (QSA8 aliphatic halogen) was
identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.
G2.3 Selection of PoD
No experimental PoDs were available for dichloroacetaldehyde. Based on the modelled data,
the following PoDs are proposed:
A LOAEL of 276 000 µg/kg bw/day derived from the OECD toolbox,
A TTC value of 0.0025 µg/kg bw/day.
The reliability of both the NOEL and LOEL values is considered to be ‘low’ due to the
limitation of the dataset behind their derivation so should be used with caution.
G3 Risk Assessment
G3.1 1-Bromo-1,1-dichloropropanone
G3.1.1 Hazard identification
No experimental data for 1-bromo-1,1-dichloropropanone were available, and modelled data
predictions were considered to be unreliable.
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G3.1.2 Hazard characterisation
Proposed PoDs
Based on the data obtained in Section G2.1 a NOAEL of 404 000 µg/kg bw/day has been
selected as the modelled PoD. The reliability of this value is considered to be ‘low’ due to the
limitation of the dataset so should be used with caution. Therefore the TTC approach using a
TTC value of 1.5 µg/kg bw/day will also be used in the risk assessment.
Selection of proposed UFs
The proposed UF for use with the PoD selected is as follows:
10 for inter-species variability
10 for intra-species variability
5 for the use of a modelled NOAEL
Total UF used = 500
Derivation of proposed TDI
The proposed TDI is 808 µg/kg bw/day.
G3.1.3 Exposure assessment
The maximum concentration of 1-bromo-1,1-dichloropropanone measured in drinking water
was reported as <3 µg/L (Krasner et al., 2006). For the purpose of this project, a maximum
concentration of 3 µg/L will be used, however it should be noted that this value may be an
over-conservative representation of 1-bromo-1,1-dichloropropanone in typical drinking water.
Based on default factors the daily intake would be:
0.10 μg/kg bw/day for an adult,
0.30 μg/kg bw/day for a child,
0.45 μg/kg bw/day for an infant.
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G3.1.4 Risk characterisation
TDI
The maximum intake of 1-bromo-1,1-dichloropropanone via drinking water by adults, children
and infants (0.10 to 0.45 μg/kg bw/day) is less than the proposed TDI (808 μg/kg bw/day).
Therefore it is not anticipated that any adverse public health effects will occur following
exposure to 1-bromo-1,1-dichloropropanone via drinking water. The TDI and hence the risk
characterisation should be used with caution due to the limitations in the dataset used to
derive the NOAEL.
TTC
The maximum intake of 1-bromo-1,1-dichloropropanone via drinking water by adults, children
and infants is less than the TTC value (1.5 µg/kg bw/day), and therefore, adverse health
effects are not anticipated.
G3.1.5 Risk communication
The MOEs for Although it is possible to calculate MOEs for 1-bromo-1,1-dichloropropanone, it
is not recommended due to the uncertainty and lack of reliability in the TDI .
G3.2 Dichloroacetaldehyde
G3.2.1 Hazard identification
Limited experimental data for dichloroacetaldehyde were available, with equivocal in vitro
mutagenic effects reported. Modelling software identified structural alerts for sensitisation and
genotoxicity.
G3.2.2 Hazard characterisation
Proposed PoDs
Based on the data obtained in Section G2.2 a LOEL of 276 000 µg/kg bw/day has been
selected as the most conservative modelled PoD. The reliability of this value is considered to
be ‘low’ due to the limitation of the dataset so should be used with caution. Therefore the TTC
approach using a TTC value of 0.0025 µg/kg bw/day will also be used in the risk assessment.
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Selection of proposed UFs
The proposed UF for use with the PoD selected is as follows:
10 for inter-species variability
10 for intra-species variability
10 for the use of a modelled LOEL
Total UF used = 1000
Derivation of proposed TDI
The proposed TDI is 276 µg/kg bw/day.
G3.2.3 Exposure assessment
The maximum concentration of dichloroacetaldehyde measured in drinking water was 14 µg/l
(Krasner et al., 2006). This was at a groundwater treatment works which applied ozonation
and chloramination, but did not have GAC; Krasner et al. (2006) concluded that “it should be
possible to minimise formation of haloaldehydes at ozone plants through the use of biological
filtration” (i.e. GAC). Based on default factors the daily intake would be:
0.47 μg/kg bw/day for an adult,
1.4 μg/kg bw/day for a child,
2.1 μg/kg bw/day for an infant.
G3.2.4 Risk characterisation
TDI
The maximum intake of dichloroacetaldehyde via drinking water by adults, children and
infants (0.47 to 2.1 μg/kg bw/day) is less than the proposed TDI (276 μg/kg bw/day).
Therefore it is not anticipated that any adverse public health effects will occur following
exposure to dichloroacetaldehyde via drinking water. The TDI and hence the risk
characterisation should be used with caution due to the limitations in the dataset used to
derive the LOEL.
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TTC
The maximum intake of dichloroacetaldehyde in adults, children and infants exceeds the TTC
value. Therefore, additional research into the occurrence in drinking water and toxicological
properties of this DBP may be prudent.
G3.2.5 Risk communication
Although it is possible to calculate MOEs for dichloroacetaldehyde, it is not recommended due
to the uncertainty and lack of reliability in the TDI.
G4 Summary and Conclusions
A summary of the risk characterisation for the high priority DBPs is presented in Table G.6.
Analysis of the chemical structure of 1-bromo-1,1-dichloropropanone did not identify any
mutagenic structural alerts, and VEGA predictions for sensitisation, mutagenicity and
carcinogenicity were unreliable. The estimated exposure of 1-bromo-1,1-dichloropropanone in
drinking water did not exceed the proposed TDI or the TTC value, therefore, it is considered
to be of low concern to public health.
Dichloroacetaldehye was noted to have a structural alert for mutagenicity and therefore is
considered to be potentially genotoxic. Experimental in vitro data for mutagenicity is equivocal
however. When characterising dichloroacetaldehyde against the genotoxic TTC value of
0.0025 µg/kg bw/day, the estimated exposures for adults, children and infants exceeds the
threshold values. Therefore, additional research the occurrence of dichloroacetaldehyde in
drinking water and the hazard potential would be prudent.
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Table G.6 Summary of risk characterisation ozone DBPs
DBP
TDI
(µg/kg
bw/da
y)
TTC
(µg/kg
bw/day)
Estimated Daily
Intake (TDI)
Estimated Daily
Intake (TTC)
Adu
lt
Chil
d
Ad
ult
Adu
lt
Chi
ld
Infa
nt
1-Bromo-1,1-
dichloropropan
one
808 1.5 Belo
w
Belo
w
Bel
ow
Belo
w
Bel
ow
Bel
ow
Dichloroacetald
ehyde 276 0.0025
Belo
w
Belo
w
Bel
ow
Abo
ve
Ab
ove
Abo
ve
Below; estimated daily intake is below the proposed TDI/TTC value, adverse health effects are not
anticipated.
Above; estimated daily intake is above the proposed TDI/TTC value, adverse health effects cannot be
excluded.