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: mathav@iitm.ac.in

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)

18

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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Hapeshi, E., Achilleos, A., Vasquez, M.I., Michael, C., Xekoukoulotakis, N.P.,

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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

36

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