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Destruction of disinfection byproducts and their precursors in swimming pool water bycombined UV treatment and ozonation

Cheema, Waqas Akram; Kaarsholm, Kamilla Marie Speht; Andersen, Henrik Rasmus

Publication date:2016

Document VersionPublisher's PDF, also known as Version of record

Link back to DTU Orbit

Citation (APA):Cheema, W. A., Kaarsholm, K. M. S., & Andersen, H. R. (2016). Destruction of disinfection byproducts and theirprecursors in swimming pool water by combined UV treatment and ozonation. Abstract from 2016 IUVA WorldCongress, vancouver, Canada.

https://orbit.dtu.dk/en/publications/bfd91b9b-d6c7-4312-94e8-b6a2a949570a

#12 - Byproduct Formation and Control

Destruction of disinfection byproducts and their precursors in swimming pool water by combined

UV treatment and ozonation

Waqas A. Cheema1, 2

, Kamilla MS Hansen1, Henrik R. Andersen

1

1Technical University of Denmark, Denmark

2 National University of Sciences & Technology, Pakistan

Abstract

Both UV treatment and ozonation are used to reduce different types of disinfection byproducts (DBP) in

swimming pools. UV treatment is most common as it is particularly efficient in removing the repulsive

chlorine like smelling chloramines (combined chlorine). UV treatment of a pool water increased chlorine

reactivity and formation of chlor-organic DBP such as trihalomethanes. Based on the similar selective

reactivity of ozone and chlorine we hypothesized that the created reactivity towards chlorine by UV

treatment of dissolved organic matter in pool water might also be expressed as an increased reactivity

towards ozone and that ozonation might saturate the chlorine reactivity created by UV treatment and

mitigate the increased DBP formation. By experimentally treating pool water samples, we found that UV

treatment makes pool water highly reactive to ozone. The created reactivity towards chlorine decreases

dose dependently with ozone dosage prior to contact with chlorine. Furthermore, the kinetics of ozone in

UV treated pool water changed drastically from a half-life in excess of 20 min to complete consumption

in less than 2 min. We discovered that ozonation in UV treated pool water induced formation of some

DBPs that are not commonly reported in pool water where trichloronitromethane is noteworthy as it is

genotoxic. Therefore, we performed repeated treatment experiments consisting of combined UV/ozone

treatment interchanged with chlorination for 24 h the genotoxicity created during the ozone treatment was

removed by the UV treatments. Based on the experimental results, a treatment system is proposed with a

UV system placed in a side stream to the recirculation flow followed by an ozone dosing point and a

small reaction chamber with a volume that allow 1-2 min reaction time before returning to the main

recirculation flow. This side-stream UV/ozone treatment will improve the swimming pool water quality.

Destruction of disinfection byproducts and their precursors in swimming pool water by combined UV treatment and ozonation

Waqas A. Cheema1,2, Kamilla M.S. Hansen1, Henrik R. Andersen1

1Technical University of Denmark, Denmark 2National University of Sciences and Technology, Pakistan

2016 IUVA World Congress

31 January- 03 February 2016

Vancouver, British Columbia,

Canada

2

Cl2Filter

Conventional treatments Disinfection By-Products

UV/Ozone Ozone UV Introduction

Chlorine + Dissolved Matter

Disinfection By-Products (DBPs) Inorganic e.g. Chloramines

Organic e.g. Trihalomethanes (THMs) Haloacetonitriles (HANs) Haloacetic acids (HAAs)

Particles: Hair, Skin cells

Dissolved matters: Sweat, Urine, Lotion, Shampoo, Make-up

Bacteria & virus

3

Disinfection By-Products

Compound Abbreviation Chemical structure

Trihalomethanes (THMs)

Chloroform TCM CHCl3

Bromodichloromethane BDCM CHBrCl2

Dibromochloromethane DBCM CHBr2Cl

Bromoform TBM CHBr3

Haloacetonitriles (HANs)

Dichloroacetonitrile DCAN CHCl2CN

Bromochloroacetanotile BCAN CHBrClCN

Miscellaneous

Trichloronitromethane TCnitro CCl3NO2

Dichloropropanone DCprop CHCl2COCH3

Trichloropropanone TCprop CCl3COCH3


4

Toxicity estimation

• The toxicity of the different groups

Haloacetonitriles (HANs) > Haloacetic acids (HAAs) > Trihalomethanes (THMs)

• Calculated for water samples by:

• EC50 taken from Plewa et al. 2008

i

i

EC

CToxicity

,50

Hansen et al., 2013


5

Emerging treatment technologies

Particles DOC + chlorine DBPs

Ozonation UV treatment


Can ozonation be effective to remove reactivity of organic matter towards chlorine?

Can UV treatment be effective to remove the DBPs?

6

UV treatment

0 10 20 300.0

0.2

0.4

0.6

0.8

1.0

1.2Morning

Evening

With UV (4 Lamps) Without UV

Experiment day no.

Con

centr

atio

n (m

g/L

)

Combined chlorine

Kristensen et al., 2010

Advantage (established) UV treatment followed by Cl2 decreased combined Cl2

Cl2

Filter UV


Disadvantage ( still need to be established) UV treatment followed by Cl2 Increased chloro-organic byproducts

7

Experimental setup

24 hr 25 C

Residual Chlorine 1±0.3 mg/L

Water samples

Swimming Pool

Sampling Treatment Analysis

UV

Purge & trap GC/MS


8

Control,Cl2 UV½d,Cl2 UV2d,Cl2 UV10d,Cl2

0.0

0.5

4%

5%5.3%

21%

Br-tTHM

tTH

M (

mm

ol/L)

Results

Control,Cl 2 UV½d,Cl2 UV2d,Cl2 UV10d,Cl2

0

12

Cl 2

co

nsu

mp

tio

n (

mg

/L)


Increasing UV dose followed by Cl2 no effect on Total THMs

UV treatment followed by Cl2 increased Cl2 reactivity

Increasing UV dose followed by Cl2 increased Br-THMs

Cl2 consumption Total Trihalomethane

9

COOHCH3 CH

Cl

CH3 CH3C

O

CH2

.OHCOOHCHCH3

Cl

CH3

OH

HOBr

HOBr

HOBr

CH2

Cl

CH3

COOH

CH3

CH3 CH

COOHCH

CH3

CH3

CH3C

O

CH2

Br-

Br-

.OH

Cl

CH2

Cl

Cl-

OH

Cl

CH3

Br-

COOHCH3 CH

Cl

CH

Cl

Cl

Br

CH

Cl

BrBr

COOHCH3 CH

Cl

CH3 CH3C

O

CH2

.OH

COOHCHCH3

Cl

CH3

CH2

Cl

CH3

OH

Br-Cl-DBP Formation Theory

UV Irradiation

COOH

COOH

CH2

CH

CH3CHCH

CH2

C CH2 CHCH2C

C

Cl

Cl

Br

OH

OBr

Br

OH

CH2

Cl

Cl2 Addition

Further reaction


Spiliotopoulou et al., (2015)

10

Initi

al 2

Contr

ol,Cl

UV 2

UV,C

lUV 2

UV,C

lUV 2

UV,C

l

0.0

0.2

0.4

0.61st cycle 2nd cycle 3rd cycle

2.7%2.5% 2.5%

3.1%

2.9%

3.3%

3.0%

3.5%

tTH

M (

µm

ol/L)

0 20 40 60 80

0.0

0.2

0.4

0.6

0.8

1.0Chloroform

Bromodichloromethane

Dibromochloromethane

Bromoform

2 4

Time (min)

EED (kWh/m3)6 8

C/C

0

Effect of repeated treatments


Hansen et al., (2013)

UV treatment decreased total THM

UV treatment followed by Cl2 increased total THM

Total Trihalomethane UV photolysis

Increased bromine substitution increasing UV photolysis

11

Ozone in pools

Oxidation of pollutants

I. Direct reaction

II. Radical reaction

H2O + O3 → O2 + 2 HO•

DOC + HO• → DOCradical oxidized

DOC + O3 → DOCselectively oxidized Fast consumption of ozone Decrease chlorine reactivity of pollutants Low ozone life time no reaction with bromide

Slow consumption of ozone Ozone converts to hydroxyl radicals with time Radical attack of inactive carbon increased

chlorine reactivity Long ozone life time oxidation of bromide to

bromate


Hansen et al.,(2016)

12

Experimental setup

O3


Water samples

Swimming Pool


24 hr 25 C

Purge & trap GC/MS


13

0 1st 2nd 3rd 0 1st 2nd 3rd

0.0

0.5

1.0

1.5

2.0Pool water Polluted pool water

Cl 2

-co

nsu

mp

tio

n (

mg

/L)

Cl2 consumption


Ozonation of polluted pool water decreased Cl2 reactivity

Ozonation of pool water increased Cl2 reactivity

Artificial body fluid


Polluted pool water

+ +

14

0 1st

2nd

3rd

0 1st

2nd

3rd

0.0

0.2

0.4

0.6

0.8

Polluted pool waterPool water

tTH

M (

µm

ol/L

)

Total Trihalomethane

Ozonation of polluted pool water decreased total THM

Ozonation of pool water increased total THM


Polluted pool water direct ozone reaction short ozone life time


15

UV and ozone treatments Summary

DOC

O3

DBPs

Cl2

Fast-reactive

UV

Rad

ical

oxid

ati

on

Dir

ect

oxid

ati

on

Lo

w e

xp

osu

re

Hig

h

exp

osu

re

Slow-reactive

UV/Ozone Ozone UV Introduction UV Ozone

16

Proposed system design

Cl2

Filter O3UV

R


17

Experimental setup

UV O3


Water samples

Purge & trap GC/MS

Swimming Pool


24 hr 25 C


18

Control,Cl 2 UV,Cl 2 O3,Cl2 UV/O3,Cl2

0

2

4

6

Cl 2

co

ns

um

pti

on

(m

g/L

)


Cl2 consumption

Single Treatments

Repeated UV treatments

Repeated O3 treatments

Control,Cl2 1st

cycle 2nd

cycle 3rd

cycle0

2

4

6

Cl 2

co

ns

um

pti

on

(m

g/L

)

Repeated UV/O3 treatments

Control,Cl 2 1st

cycle 2nd

cycle 3rd

cycle0

2

4

6

Cl 2

co

ns

um

pti

on

(m

g/L

)

Repeated UV treatments increased Cl2 consumption

Repeated O3 treatments had no effect on Cl2 consumption

Repeated UV/O3 treatments decreased Cl2 consumption

Control,Cl 2 1st

cycle 2nd

cycle 3rd

cycle0

2

4

6

Cl 2

co

ns

um

pti

on

(m

g/L

)

19 Control,Cl 2 1

st cycle 2

nd cycle 3

rd cycle

0.0

0.1

0.2

0.3

0.4

Tri

ha

lom

eth

an

e (

µm

ol/

L)

Control,Cl 2 1st

cycle 2nd

cycle 3rd

cycle0.00

0.15

0.30

0.45

Tri

ha

lom

eth

an

e (

µm

ol/

L)

Control,Cl2 UV,Cl2 O3,Cl2 UV/O3,Cl2

0.0

0.1

0.2

0.3

Tri

ha

lom

eth

an

e (

mo

l/L)

Total Trihalomethane

Single Treatments


Control,Cl 2 1st

cycle 2nd

cycle 3rd

cycle0.0

0.1

0.2

0.3

0.4

0.5

Tri

ha

lom

eth

an

e (

µm

ol/

L)

Repeated UV treatments increased THM concentration

Repeated O3 treatments had no effect on THM concentration

Repeated UV/O3 treatments decreased THM concentration




20


0.000

0.035

0.070

tHA

N (

µm

ol/L

)

Total Haloacetonitrile


Control,Cl 2 1st

cycle 2nd

cycle 3rd

cycle0.00

0.05

0.10

0.15

tHA

N (

µm

ol/L

)

Control,Cl 2 1st

cycle 2nd

cycle 3rd

cycle0.00

0.03

0.06

0.09

0.12

tHA

N (

µm

ol/L

)

Control,Cl2 1st cycle 2nd cycle 3rd cycle0.00

0.02

0.04

0.06

0.08

0.10

tHA

N (

µm

ol/L)

Single Treatments

Repeated UV treatments increased tHAN concentration

Repeated O3 treatments had no effect on tHAN formation

Repeated UV/O3 treatments decreased tHAN formation




21


0

2

4

6

TC

nitro

(µ

g/L

)

Trichloronitromethane


Control,Cl2 1st cycle 2nd cycle 3rd cycle0

2

4

6

8

TC

nitro

(µ

g/L

)

Control,Cl2 1st cycle 2nd cycle 3rd cycle0.0

3.5

7.0

TC

nitro

(µ

g/L

)


2

4

6

TC

nitro

(µ

g/L

)

Single Treatments

Repeated UV treatments increased TCnitro concentration

Repeated O3 treatments increased TCnitro concentration

Repeated UV/O3 treatments decreased TCnitro conc.




22


0

1

2

3

4

Genoto

xic

ity (

x10

-4)

Predicted toxicity



1

2

3

4

5

Genoto

xici

ty (

x10

-4)


1

2

3

4

Genoto

xic

ity (

x10

-4)


1

2

3

4

Genoto

xic

ity (

x10

-4)

Single Treatments

Repeated UV treatments increased toxicity

Repeated O3 treatments increased toxicity

Repeated UV/O3 treatments decreased toxicity




23

Gladsaxe muncipality pool


24

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