Environ Monit Assess (2010) 168:489–497DOI 10.1007/s10661-009-1129-9

Trihalomethane formation potential in treatedwater supplies in urban metro city

Aziz Hasan · Neeta Pradip Thacker · Jagdish Bassin

Received: 10 December 2008 / Accepted: 27 July 2009 / Published online: 13 August 2009© Springer Science + Business Media B.V. 2009

Abstract Trihalomethane (THM) formation po-tential (TFP) is very useful test to assess the levelof the formation of trihalomethanes in worst casescenario. Organics in water have the potential togenerate harmful disinfection by-products (DBPs)such as THMs, as a result of their reaction withdisinfectant chlorine used in drinking water. DBPsare increasingly recognized as cancerous agents.TFP of postchlorinated treated water were inves-tigated at six water treatment plants (WTPs) inDelhi City (India). The present paper presentsthe current trends of TFP so that prevention andcontrol measures can be initiated by the reg-ulating agencies responsible for drinking watersupply. Liquid–liquid extraction method, followed

A. Hasan · N. P. Thacker (B)Analytical Instruments Division, NationalEnvironmental Engineering Research Institute,Nehru Marg, Nagpur, 440 020, Indiae-mail: np_thacker@neeri.res.inURL: www.neeri.res.in

A. Hasane-mail: azizhasan@live.in

J. BassinDelhi Zonal Laboratory, National EnvironmentalEngineering Research Institute, CSIR Building,A-93/94, Phase I, Naraina Industrial Area,New Delhi, 110 028, Indiae-mail: jk_bassin@neeri.res.in

by qualitative and quantitative estimation by gaschromatograph equipped with electron capturedetector, had been used for the determination ofTHMs in water samples collected at the outlet justbefore supplying to the consumers during 2000–2007. The TFP values from 2004 onward of allWTPs did not exceed the WHO guideline valueof ≤1.

Keywords THM · TFP · DBP · pH ·Temperature · Residual chlorine

Introduction

Ensuring the accessibility of safe drinking wa-ter is a major concern throughout the world.Health risks may arise from consumption of wa-ter contaminated with infectious agents, toxicchemicals, and radiological hazards. Chlorine isone of the most common disinfectant agentsused in water disinfection process in India. Thegoal of the water disinfection is to protect thewater in the distribution systems against mi-crobial contamination and to prevent and con-trol regrowth of microorganism in the waterdistribution system. Dissolved organic matter(DOM) and its potential to form disinfection by-products (DBPs), like trihalomethanes (THMs)and others during water treatment, are themajor disadvantages of chlorination process.

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Chlorine, which exists as hypochlorous acid andhypochlorite in water, reacts with natural DOM,such as humic and fulvic acids to form THMs(Gallard and von Gunten 2002; Ristoiu et al.2009). In the presence of bromides in source wa-ters, hypobromous acid is formed when chlorineis used as disinfectant (Westerhoff et al. 2004).Hypobromous acid reacts with natural DOMand forms brominated and mixed chlorobromoby-products (Pourmoghaddas et al. 1993), suchas bromoform, bromodichloromethane (BDCM),and dibromochloromethane (DBCM; Trusselland Umphres 1978; Rook et al. 1978). It is gen-erally accepted that bromine reacts faster thanchlorine with natural DOM (Guo and Lin 2009).The distribution of chlorinated, brominated, andmixed chlorobromo by-products depends on theratios of HOCl/Br−, Br−/DOM, and Br−/freechlorine (Shukairy et al. 2001; Rebhun et al.2002). THMs formation in water is a function ofseveral factor including temperature, pH, contacttime, concentration of bromides, residual chlo-rine, and natural DOM (Thacker et al. 1999;Golfinopoulos and Arhonditsis 2002; Nikolaouet al. 2004; Ye et al. 2009). Trihalomethane for-mation potential (TFP) determines the THM-forming potential in the chlorinated water so asto evaluate water treatment processes or watersources or for predicting THM concentration indistribution.

DBPs are increasingly being recognized as anissue of high risk to human health as they giverise to renal, bowel, and other cancers and repro-ductive disorders (Arora et al. 1997; King et al.2000; Woo et al. 2002; Bull 2003). Recently, ithas been reported that THMs suspect to causeliver and kidney damage, retarded fetus growth,birth defects, and possibly miscarriage (Wrightet al. 2004; Ristoiu et al. 2009). The rapid growthof Delhi, due to the growing influx of populationinto the urban city from the neighboring statesand also from the other parts of the country, hasresulted in significant increase in drinking waterdemand. The access to safe drinking water inDelhi is 96.24% (Basil 2004), which is throughwater treatment plants (WTPs; 629 MGD)and ranny wells (81 MGD; Economic Survey ofDelhi 2007–2008). There are six WTPs situatedat different parts in the city. The surface water

Table 1 WHO guideline values for THMs (2006)

Disinfectant Guideline value Remarksby-products (μg L−1)

Trihalomethanes – The sum of theratio of theconcentrationof each to itsrespectiveguideline valueshould notexceed 1

Bromoform 100CDBM 100BDCM 60a

Chloroform 300aFor substances that are considered to be carcinogenic

is treated by conventional treatment process (co-agulation, flocculation, rapid sand filtration, andchlorination).

The occurrence of THMs in chlorinated watersin India has been reported earlier (Satyanarayanaand Chandrasekhar 1996; Thacker et al. 1996,1997, 2002). World Health Organization (WHO2006) has regulated the health related guidelinevalues (GV) for such compounds in drinking wa-ter (Table 1). The city of Delhi has an averagerainfall of 714 mm and the day temperature rangesfrom 7◦C to 44◦C. The level of THMs is expectedto vary due to the extreme climatic conditions andthe combined surface and groundwater sources ofsome of WTPs.

The present study reports the quality of treatedwater supply monitored during 2000 to 2007 inDelhi for TFP as chloroform (CHCl3), BDCM(CHCl2Br), DBCM (CHBr2Cl), and bromoform(CHBr3). Monitoring of final water supply forTFP can reveal the current trends so that theprevention and control measures can be initiatedby the regulating agencies.

Experimental

Sampling sites, sample collection,and preservation

The postchlorinated treated water samples fromBhagirathi, Sonia Vihar, Wazirabad, Nangloi,

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Wazirabad

Haiderpur

Bhagirathi

Nangloi

Okhla

Chandrawal

Sonia Vihar

WTP

Fig. 1 Location of water treatment plants at Delhi

Okhla, and Haiderpur WTPs (Fig. 1) were col-lected at the outlets, just before supplying tothe consumers. Water samples were collectedfrom Sonia Vihar only in the year 2007 as itwas a new WTP. All the plants have a conven-tional method of treatment, comprising coagula-tion, sedimentation, filtration, and chlorination.The water samples were collected with minimumaeration and in especially available containers,designed for volatile organics to minimize the lossof THMs during transit. Samples were collected

Table 2 Gas chromatograph conditions for analysis ofTHMs

Item Condition

Gas chromatograph Perkin-Elmer Sigma 3Bwith Ni63 ECD

Column Packed columnOven temperature (◦C) 65Injector temperature (◦C) 125Detector temperature (◦C) 300Carrier gas NitrogenCarrier gas flow (mL/min) 25

each year for four consecutive seasons, namelysummer, monsoon, postmonsoon, and winter. Allthe samples were collected in duplicate and, afterproper preservation and pretreatment, were im-mediately transported to the main laboratory atNagpur. Samples were analyzed within 14 days ofcollection.

THM and TFP analysis

The THM/TFP analyses in water samples werecarried out following the 20th edition of Standard

Table 3 QA/QC data and LOD established for THMs

Parameter Chloroform CDBM BDCM Bromoform

Recovery 98 96 84 97(%)

Standard 0.90 0.05 0.05 0.33deviation

Relative 2.93 0.15 0.23 1.11standarddeviation(%)

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Table 4 Minimum detection limits and range of linearityof THMs

Compounds Minimum Range of linearitydetectionlimits (ng L−1)

Chloroform 45 45 ng L−1 to 880 μg L−1

BDCM 20 20 ng L−1 to 900 μg L−1

CDBM 65 65 ng L−1 to 900 μg L−1

Bromoform 100 100 ng L−1 to 1,000 μg L−1

methods for the examination of water and wastewa-ter, published by APHA, AWWA, WEF (1998).Liquid–liquid extraction method, followed byqualitative and quantitative estimation by gaschromatograph (GC) equipped with electron cap-ture detector (ECD), had been used for the de-termination of THMs in aqueous samples. TheGC-ECD conditions used for analysis are given inTable 2.

Quality assurance (QA) and quality control(QC) data and limit of detection (LOD) wereestablished for each of THMs, namely chloroform,CDBM, BDCM, and bromoform analyzed in fieldsamples (Table 3). The minimum detection limitof the method for chloroform, CDBM, BDCM,and bromoform and the range of linearity arereported in Table 4.

As per approved standard methods, TFP is theconcentration of THMs formed in water buffered

at pH 7, containing an excess of free chlorinewith a chlorine residual of 1 to 5 mg L−1 afterbeing held for 7 days at 25◦C APHA, AWWA andWEF (1998). TFP is reported as a single value asmicrograms per liter as CHCl3.

TFP, μg L−1 as CHCl3 = A + 0.728B + 0.574C

+ 0.472D

where

A = microgram CHCl3 per literB = microgram CHBrCl2 per literC = microgram CHBr2Cl per literD= microgram CHBr3 per liter

Results and discussion

Out of 149 numbers of samples analyzed, themaximum TFP values of 283.5, 459.9, 274.2, 335.5,268.2, and 26.86 μg L−1 were found, respec-tively, in the final treated water of Bhagirathi,Haiderpur, Nangloi, Okhla, Wazirabad, andSonia Vihar (Fig. 2). Relatively high values ofTFP were found during summer season, whichmay be due to increase in temperature of waterbodies.

Fig. 2 Identified TFP aschloroform levels invarious WTPs at Delhiduring 2000–2007

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Fig. 3 Relativedistribution oftrihalomethanes of eachwater treatments plants

Fig. 4 Identifiedchloroform levels invarious WTPs at Delhiduring 2000–2007

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Fig. 5 Identified BDCMlevels in various WTPs atDelhi during 2000–2007

The chloroform, BDCM, DBCM, and bromo-form were measured in all WTP, and their relativedistributions are shown in Fig. 3. This indi-cates that chloroform was the predominant THMspecies in the water samples, which agrees withthe previous finding (Thacker et al. 2000; Paimet al. 2007). The chloroform levels (377, 311, and371.5 μg L−1) were found above the WHO GV in

three samples from the Haiderpur WTP collectedin the second half of the year 2000 and the first andthird quarter of the year 2002 (Fig. 4). Correlatedwith the season, the BDCM level (113.3 μg L−1)was found above the WHO GV in water sample ofHaiderpur WTP collected in the second half of theyear 2000. Also, in the second and third quarterof the year 2002, the treated water samples of

Fig. 6 Identified DBCMlevels in various WTPs atDelhi during 2000–2007

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Fig. 7 Identifiedbromoform levels invarious WTPs at Delhiduring 2000–2007

Okhla WTP showed higher BDCM values (69and 110.2 μg L−1, respectively) than WHO GV(Fig. 5). The DBCM and bromoform levels werefound below the WHO GV in all water samplesfrom all WTPs (Figs. 6 and 7), which confirms theabsence of any bromine-containing impurities.

The total THM levels (sum of the ratio ofthe concentrations of each THM to its respective

GV) of Bhagirathi WTP in the second half of theyear 2000 and first quarter of the year 2002 wereabove the WHO GV of ≤1. Similarly, total THMlevels of three samples of Haiderpur, Okhla, andWazirabad and two samples of Nangloi of the year2000 and 2002 were above the WHO GV of ≤1;one sample of Okhla WTP in 2003 was above theWHO GV ≤1 (Fig. 8).

Fig. 8 Total THMs (thesum of the ratio of theconcentration of each toits respective WHO GV)

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Conclusion

The water samples were collected during 2000 to2007 on quarterly basis to access the trend of TFPin various water treatment plants. The qualities offinal treated water of all WTPs of Delhi city weremonitored for TFP. Samples were analyzed forindividual species of chloroform, DBCM, BDCM,and bromoform. It was found that 17% samplesof TFP were containing bromoform and rangedfrom below detection level (BDL) to 11 μg L−1.In the year 2007, DBCM levels remain in BDL;chloroform and BDCM were identified in most ofthe samples in all WTPs.

THM levels of final water samples exceeded inthe year 2000 and 2002, and one single sample ofOkhla WTP showed above the WHO GV of ≤1.From 2004, all WTPs did not exceed the WHOGV of ≤1. The TFP is used to determine the worstcase scenario. The TFP should provide worst caseconcentration of THMs. The data (Fig. 8) indicatethat from the second quarter of the year 2003, themaximum THM concentrations of all final treatedwater samples of WTPs were below the WHO GVof ≤1. This study reveals that the finished water insix WTPs at Delhi, from 2004 onwards, was foundto be less vulnerable to the THM formation.

Acknowledgements Authors are grateful to the ActingDirector Dr. T. Chakrabarti, National Environmental En-gineering Research Institute (NEERI) for granting per-mission to publish this work. The authors are thankfulto the Delhi Jal Board for the financial assistance andcooperation in the continuous monitoring of water suppliesat Delhi.

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