METRONIDAZOLE IN A UV-TIO2
PHOTOCATALYTIC SYSTEM: FATE,
REMOVAL AND MINERALIZATION
*Associate Professor
Department of Civil Engineering,
Indian Institute of Technology Madras,
Chennai, Tamilnadu – 600 036, India
Tel: +91-44-2257 4267; E-mail: [email protected]
Authored by
Neghi. N & Mathava Kumar*
INTRODUCTION - ANTIBIOTICS
Antibiotics - treat/prevent bacterial infections
Increasing trend in the consumption of antibiotics 2000-2010:-
Brazil - 68%, Russia -19%, India - 66%,China - 37%, South Africa - 219%(CDDEP,2015)
US10% of the world’s antibiotic consumption
Global antibiotic use by class
Broad spectrum penicillins
Cephalosporins
Macrolides
Trimethoprim and combinations
Quinolones
Aminoglycosides
Nitroimidazoles (Metronidazole falls under this class)2
ANTIBIOTICS IN THE ENVIRONMENT
3
Consumers
Excretion &
other activities
PPCP along
with
Wastewater
Wastewater
treatment units
Centralized
De-Centralized
DOC removal
by biological
process
Removal by
biological
process
PPCP in
effluent
PPCP into
Soil
PPCP into
SW
PPCP in
sludge
PPCP into
Ecosystem
PPCP into GW
ANTIBIOTICS IN THE ENVIRONMENT
4
Reference: www.saveantibiotics.org
ANTIBIOTICS IN THE ENVIRONMENT
5
Industrial wastewaters (Formulation)
Hospital Wastewaters
Aqua culture wastewaters
Meat processing units
Live-stock units
Feed manufacturing/growth supplement producing
units
6
Vanishing Vulture’s Poisoned animal carcass
feeding with Diclofenac
ANTIBIOTICS IN THE ENVIRONMENT
ANTIBIOTICS IN THE ENVIRONMENT
Develop antibiotic resistance in aquatic environments
Affect building blocks of the ecosystem processes
WHO report - different antibacterial resistant strains -
FS 194 -Updated April 2015
http://www.who.int/mediacentre/factsheets/fs194/en/
Detection range observed to be more in pharmaceutical
production plant effluents7
ANTIBIOTICS IN WATER AND WASTEWATER
8
Source/Point of Origin
Collection System
Wastewater treatment units
Point of Disposal
Away from disposal points
Sampling
Sampling
Increase in
antibiotics
concentration
WHY TO REMOVE ANTIBIOTICS..????
9
Close the Loop in water use pattern
Water
withdrawl
Water
Supply
Wastewater
Collection
Wastewater Treatment
Water Recharge
into Ground
2-(2-methyl-5-nitroimidazol-1-yl)ethanol, (C6H9N3O3)
Water Solubility 10 mg/mL
Log Kow 0.1 (hydrophilic)
Vapor pressure 3.1 x 10-7 mm Hg at 25oC
18% of drug excreted unchanged from human body
METRONIDAZOLE(MNZ)
10
INTRODUCTION - PHOTOCATALYSIS
Photocatalysis One of the AOP’s
h + + H2O → H+ + OH−
h + + OH− → HO•
O2 + e− →.O2−
H2O2 + e − → HO• + OH-
11
ATTRIBUTES OF PHOTOCATALYTIC SYSTEM
Ideal photocatalyst -TiO2
HO· generated in the system - non-selective- high oxidation potential (E0 = 2.8V/SHE)
UV-C band of light - ability to handle the antibiotic resistant genes in real time wastewater
Difficulties
Post separation of the catalyst
Operation under continuous-mode
Support catalyst - overcome the difficulties
Support medium - Activated charcoal, Stainless steel plate, Alumina.
12
BACKGROUND
13
OBJECTIVES
Feasibility of MNZ removal by photocatalytic system
with TiO2 and GAC
Quantify the roles of catalysts and UV power on MNZ
removal
Correlate MNZ removal with economic analysis to
identify best suitable experimental condition
Long term goal Create a system for continuous-
mode photocatalysis for antibiotics removal
14
BATCH PHOTOCATALYTIC REACTOR
15
UV POWER SUPPLY
PROBES CONNECTED TO pH/ORP/Temp
METER
ELECTRONIC STIRRER
DOUBLE WALLED CYLINDRICAL
GLASS REACTOR WITH WORKING VOLUME OF 1.9 L
METRONIDAZOLE AND TiO2 IN SUSPENSION
PHOTOGRAPHIC VIEW OF THE REACTOR
16
EXPERIMENTAL CONDITION
17
Initial MNZ
concentration
(mg/L)
UV Power
(W)
Catalyst
dosage
(g/L)
Type of
catalyst
Comments
15
-
- -
Blank
16 Photolytic
studies32
15
-
2.5 TiO2
Photocatalytic
studies16
32
15-
2.5 GACAdsorption
studies32
ANALYTICAL TECHNIQUES
I. MNZ and its metabolites - HPLC/ LC-MS
II. Organic carbon constituents of samples - TOC
III. Surface morphology of the catalyst and the support
chosen – SEM
IV. Elemental composition of the catalyst/ adsorbent –
EDS
V. pH/Temperature/Oxidation-Reduction Potential of the
system - Benchtop multi-parameter analyzer
VI. COD analysis - Standard Methods (APHA, 2002)
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19
MNZ REMOVAL BY CHOSEN PROCESSES
20
0,0
0,2
0,4
0,6
0,8
1,0
1,2
0 20 40 60 80 100 120
C/C0
Time(min)
16W
32W
TiO2 adsorption
TiO2+16W
TiO2+32W
GAC adsorption
GAC+32W
ORP TREND
21
0
100
200
300
400
0 20 40 60 80 100 120
OR
P (
mV
))
Time (min)
16W
32W
TiO2+16W
TiO2+32W
GAC+32W
22
23,6
33,8
61,1 62,4
52,9
21,715,6
23,9
42,4
94,1 96,4
77,5
32,5
18,7
0
20
40
60
80
100
16W 32W TiO2+
16W
TiO2 +
32W
GAC +
32W
GAC
adsorption
TiO2
adsorption
At 60 min
At 120 min
COMPARISON OF MNZ REMOVAL
ENERGY CONSUMPTION ANALYSIS
23
Rate of Reaction:
Energy Consumption:
ENERGY CONSUMPTION OF THE SYSTEM
FOR DIFFERENT PROCESS
24
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
16W 32 W TiO2+16W TiO2+32W GAC+32W GAC
adsorption
TiO2
adsorption
Energy Consumed* (KWh)
EEO (KWh m-3 order-1)
RESULTS OF BATCH ANALYSIS
25
Comments
Removal
(%) after 60
min
Removal (%)
after 120 minRate constant
‘k1’
(min-1)
Energy
Consumed*
(KWh)
EEO (KWh
m-3
order-1)MNZ COD MNZ COD
Blank 1.4 4.0 1.4 4.0 0.000 0.000 0.000
16W 23.6 15.3 23.9 17.5 0.002 0.032 0.144
32W 33.8 16.9 42.4 31.1 0.004 0.064 0.141
TiO2+16W 61.1 56.3 94.1 72.2 0.022 0.172 0.077
TiO2+32W 62.4 60.0 96.4 80.7 0.026 0.204 0.080
GAC+ 32W 52.9 - 77.5 - 0.012 0.214 0.129
GAC
adsorption
21.7 - 32.5 - 0.002 0.096 0.296
TiO2
adsorption
15.6 48.8 18.7 61.2 0.001 0.150 0.877
Energy consumed by (a) electronic overhead stirrer - 70/42 W (I/O), (b) UV Lamps - 16 W each, and
(c) orbital shaker for adsorption studies - 48 W were included for energy consumption analysis.
DEGRADATION OF 15 PPM OF MNZ IN
PHOTOCATALYTIC SYSTEM
26
MNZ
removal
COD
reduction
TOC
removal
Series1 96,4 80,7 66,5
96,480,7
66,5
Rem
ov
al
in p
ercen
t
SEM ANALYSIS OF ADSORPTION OF
MNZ ONTO TIO2 & GAC
27
(a) TiO2 before
treatment
(b) TiO2 after
treatment
(c) GAC before
treatment
(d) GAC after
treatment
LC-MS ANALYSIS
28
29
LC-MS ANALYSIS
CONCLUSIONS
Highest MNZ removal with 32 W UV power
and 2.5 g L-1 TiO2 in 120 min.
Removal of MNZ using GAC as a photocatalyst
was remarkably higher than that of GAC used as
an adsorbent.
The concept of electrical energy consumed per
order, i.e. EEO - ideal parameter for the economic
analysis.
30
31
Upgraded-Setup for PPCP Removal Research
32
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INTRODUCTION - METRONIDAZOLE
Antibacterial (Gram –ve anaerobic bacteria) and antiprotozoal
drug
Clinical application- principal treatment for H.pylori infections,
giardiasis, trichomoniasis - Additive in poultry and fish feeds to
eliminate parasites
Activation of the compound - formation of cytotoxic intermediates
- DNA, protein damage - carcinogenicity
Highly soluble in water and poorly biodegradable - entry into
surface and groundwater resources
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MATERIALS
• MNZ(99.9%) Sigma Aldrich
• Anatase form TiO2 Sigma Aldrich
Average size range ~25 nm
Surface area = 45-55 m2/g
Density = 3.9 g mL-1 at 25°C
• Granular activated carbon SDFCL, India
SBET = 1010 m2 g-1
VT ~ 0.532 cm3 g-1
37