dbp levels in chlorinated drinking water: effect of humic substances

DBP LEVELS IN CHLORINATED DRINKING WATER: EFFECT OFHUMIC SUBSTANCES

ANASTASIA D. NIKOLAOU∗, SPYROS K. GOLFINOPOULOS, THEMISTOKLES D.LEKKAS and MARIA N. KOSTOPOULOU

Water and Air Quality Laboratory, Department of Environmental Studies, University of the Aegean,Karadoni 17, Mytilene, Greece

(∗ author for correspondence, e-mail: [email protected])

(Received 12 September 2002; accepted 9 May 2003)

Abstract. Chlorination is the most widely used technique for disinfection of drinking water. Aconsequence of chlorination is the formation of Disinfection By-Products (DBPs). The formationof DBPs in drinking water results from the reaction of chlorine with naturally occurring organicmaterials, principally humic and fulvic acids. This paper focuses on the effect of humic substanceson the formation of twenty-four compounds belonging to different categories of DBPs. This in-vestigation was conducted in two water treatment plants in Greece, Menidi and Galatsi, from July1999 to April 2000. Humic substances were determined by the diethylaminoethyl (DEAE) methodwith subsequent UV measurement. The techniques used for the determination of DBPs were liquid-liquid extraction, gas chromatography and mass spectrometry. The concentrations of DBPs weregenerally low. Total trihalomethanes (TTHMs) ranged from 5.1 to 24.6 µg L−1, and total haloaceticacids (HAAs) concentration ranged from 8.6 to 28.4 µg L−1, while haloaketones (HKs) and chloralhydrate (CH) occurred below 1 µg L−1. The content of humic substances was found to influence theformation of DBPs and especially TTHMs, trichloroacetic acid (TCA), dibromoacetic acid (DBA),CH, 1,1-dichloropropanone (1,1-DCP) and 1,1,1-trichloropropanone (1,1,1-TCP). Seasonal variationof TTHMs and HAAs generally followed that of humic substances content with peaks occurring inautumn and spring. The trends of 1,1-DCP, 1,1,1-TCP and CH formation seemed to be in contrastto TTHMs and HAAs. Trends of formation of individual compounds varied in some cases, probablydue to influence of parameters other than humic substances content. Statistical analysis of the resultsshowed that the concentrations of TTHMs, CH, 1,1-DCP, 1,1,1-TCP, TCA and DBA are stronglyaffected from humic substances content (at 0.01 confidence level). The opposite is true for dichloro-acetic acid (DCA) concentration. Humic substances also vary to a statistically significant degreeduring different months, as well as the concentrations of TTHMs, CH, 1,1-DCP, 1,1,1-TCP, TCAand DCA. The variance of DBA was not statistically significant. Regarding the effect of samplingstation, humic substances content showed no statistically significant difference between the two rawwater sources studied.

Keywords: haloacetic acids, chloral hydrate, drinking water, humic substances, trihalomethanes

1. Introduction

Humic substances content in surface water has been found to be a major factoraffecting the formation of organic by-products during drinking water disinfection.Humic substances include humic and fulvic acids, the concentrations of which vary

Environmental Monitoring and Assessment 93: 301–319, 2004.© 2004 Kluwer Academic Publishers. Printed in the Netherlands.

302 A. D. NIKOLAOU ET AL.

TABLE I

Cancer group classification, reference dose and drinking water equivalent levelfor DBPs

Compound Cancer Group RfD DWEL

(EPA)a (mg kg−1 day−1) (mg L−1)

Chloroform B2 0.01 0.4

Dichlorobromomethane B2 0.02 0.7

Dibromochloromethane C 0.02 0.7

Bromoform B2 0.02 0.7

Dichloroacetonitrile C 0.008 0.3

Dibromoacetonitrile C 0.02 0.8

Chloral hydrate C 0.0002 0.06

a Group B: Probable human carcinogen; Group C: Possible human carcinogenRfD: Reference Dose. An estimate of a daily exposure to the human populationthat is likely to be without appreciable risk of deleterious effects over a lifetimeDWEL: Drinking Water Equivalent Level. A lifetime exposure concentrationprotective of adverse, non-cancer health effects, that assumes all of the exposureto a contaminant is from a drinking water source.

depending on the vegetation near the water source, the concentration of algae inwater and the time of the year (Kavanaugh et al., 1980; Singer, 1994). A numberof studies (Christman et al., 1983; Miller and Uden, 1983; Oliver, 1983; Trehyet al., 1986; Sanchez Zimenez et al., 1993; Summers et al., 1996; Korshin et al.,1997; Huixian et al., 1997; Golfinopoulos et al., 1998) have focused on the reactionof humic and fulvic acids with chlorine and the subsequent yield of DisinfectionBy-Products (DBPs).

DBPs detected in drinking water, belong to the categories of trihalomethanes(THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs),chloropicrin (CP), chloral hydrate (CH), as described in a large number of reports(Rook, 1974; Reckhow and Singer, 1986; Krasner et al., 1989; Nieminski et al.,1993; Lekkas, 1996; LeBel et al., 1997; Williams et al., 1997; Simpson and Hayes,1998; Nikolaou et al., 1999, 2000). These compounds are of great scientific in-terest, because of the adverse health effects they may have on human beings (TableI) (Reckhow and Singer, 1985; Bull and Robinson, 1986; Pereira et al., 1986; Bulland Kopfler, 1991).

The maximum contaminant level (MCL) of 100 µg L−1 for the concentrationof total THMs in drinking water set by USEPA (1979) was later lowered to 80 µgL−1. The sum of concentrations of five HAAs (monochloro-, dichloro-, trichloro-,monobromo- and dibromoacetic acid) has also been regulated by USEPA to 60 µgL−1. Chloropicrin, trichloroacetonitrile, dibromoacetonitrile and dichloroacetoni-trile are also going to be regulated (EPA, 1996, 1998). The European Union has

DBP LEVELS IN CHLORINATED DRINKING WATER: EFFECT OF HUMIC SUBSTANCES 303

also regulated the concentration of total THMs to 150 µg L−1 until 2008 and to100 µg L−1 after 2008 (EEC, 1998).

During the present study, humic substances content in raw water entering twowater treatment plants in Greece was determined in order to observe its effect onindividual substances belonging to different categories of DBPs that were detectedin drinking water after chlorination. The compounds studied are: the THMs chloro-form, dichlorobromomethane, dibromochloromethane, bromoform, the other volat-ile DBPs monochloroacetonitrile (MCAN), trichloroacetonitrile (TCAN), dichloro-acetonitrile (DCAN), chloral hydrate (CH), 1,1-dichloropropanone (1,1-DCP), mo-nobromoacetonitrile (MBAN), chloropicrin (CP), bromochloroacetonitrile(BCAN), 1,1,1-trichloropropanone (1,1,1-TCP), 1,3-dichloropropanone (1,3-DCP)and dibromoacetonitrile (DBAN) and the HAAs monochloroacetic acid (MCA),monobromoacetic acid (MBA), dichloroacetic acid (DCA), bromochloroacetic acid(BCA), trichloroacetic acid (TCA), dibromoacetic acid (DBA), dibromochloro-acetic acid (DBCA) and tribromoacetic acid (TBA).

2. Experimental

2.1. SAMPLING

The water treatment plants studied are located in Athens, Greece and receive waterfrom lakes Mornos, Marathon and Iliki. Their design is conventional and includescoagulation, flocculation, sedimentation and filtration. Water samples were col-lected from three different points (raw water, sedimentation tank, finished waterreservoir) in both water treatment plants. Figures 1 and 2 show the processes withineach unit and the location of sampling and chlorination points.

Samples were collected in 40 mL amber glass bottles with polypropylene screwcaps and TFE-faced septa (Pierce 13075). The vials were carefully filled so thattrapping of air bubbles inside was prevented. Sodium sulfite was used as a pre-servative for trihalomethanes and other volatile DBPs and ammonium chloride forhaloacetic acids (100 mg per liter of sample). 500 mL samples were also collectedfrom raw water for analysis of humic substances. These samples were filtered withWhatman GF/A glass microfibre filters 4.7 cm. All samples were kept in the darkat 4 ◦C until analysis and were analyzed within one week.

2.2. GLASSWARE

Preparation of all glassware used during analysis included washing with detergent,rinsing with tap water, ultrapure water (Millipore: Milli-Ro 5 plus and Milli Q plus185), acetone (Mallinckrodt Chemical Works St. Louis) and placing in an oven at150 ◦C for 2 hr.


Figure 1. Galatsi treatment plant. PS = point of sampling; CL = point of chlorination.

2.3. REAGENTS-STANDARD SOLUTIONS

Methanol purge and trap grade was purchased from Sigma-Aldrich, methyl-tert-butyl ether (MTBE) suprasolv grade, sodium sulfate, copper (II) sulfate pentahy-drate and sulfuric acid concentrated ISO for analysis from Merck. Ultrapure waterwas from Milli-Q water purification system (Millipore: Milli-Ro 5 plus and MilliQ plus 185). Stock solutions were prepared in 10 mL volumetric flasks contain-ing MTBE (Merck, for organic trace analysis) by addition of dichloroacetonitrile,bromochloroacetonitrile, dibromoacetonitrile, 1,1-dichloropropanone, 1,3-dichlo-ropropanone, 1,1,1-trichloropropanone, chloral hydrate and chloropicrin (Chem-service, purity > 99%). The concentrations of the stock solutions were calculatedby flask weight change. For THMs certified commercial mix solutions (Chemser-vice, purity > 99%) of known concentration were used. HAAs and their methylesters as well as commercial mix solutions of HAAs and their methyl esters inMTBE were purchased from Supelco and were also accompanied with certificates


Figure 2. Menidi treatment plant. PS = point of sampling.

of analysis (purity > 99%). From these stock solutions, a solution of DBPs 100mg L−1 in MTBE was prepared, known volumes of which were injected into ul-trapure water (Millipore: Milli-Ro 5 plus and Milli Q plus 185) giving standardsolutions with final concentrations ranging from 0.25 to 100.00 µg L−1 for systemcalibration and quality control.

2.4. SAMPLE PREPARATION

For THMs and other volatile DBPs, a modification of EPA Method 551.1, whichincludes liquid – liquid extraction (LLE) with MTBE was performed (EPA, 1998b).


6 g sodium sulfate anhydrous (Merck) and 2 mL MTBE were added to 35 mL ofDBPs solution or sample in a 40 mL vial. The vial was sealed and shaken by handfor 1 min and left undisturbed for 2 min. 1 µL of the ether phase was then injectedinto the gas chromatograph (GC).

For HAAs, acidic methanol esterification (Cancho et al., 1999) was used. To30 mL of HAAs solution or sample the following reagents were added: surrogatestandard 1 (5 µL solution of 2-bromopropionic acid 60 mg L−1 in MTBE), 3 mlconcentrated sulfuric acid (so that pH < 0.5), 6 g anhydrous sodium sulfate, 3 gcopper (II) sulfate pentahydrate and 2 mL MTBE. The vials were sealed, shaken for2 min, and allowed to stand for 5 min. Then, 900 µL of the extract was transferredinto a 14 mL vial containing 2 mL of a solution of sulfuric acid in methanol (10%).After addition of surrogate standard 2 (1 µL of a solution of 2,3-dibromopropionicacid 60 mg L−1 in MTBE), the vials were placed in a water bath at 50 ◦C for 1hr. Then they were cooled to 4 ◦C for 10 min and 5 mL of a copper (II) sulfatepentahydrate/anhydrous sodium sulfate solution 50 and 100 g L−1 respectively inultrapure water was added. The vials were shaken again for 2 min and allowed tostand for 5 min. 300 µL of the final extract were transferred to a 2 mL vial. 1 µLof this extract was injected into the GC.

Humic substances content was determined according to diethylaminoethyl(DEAE) method (APHA, 1992). 70 gr DEAE (Partially quaternized microgranularform, preswollen, capacity approx. 1.0 meq/dry kg, Sigma) were suspended in1000 mL 0.5 N HCl solution. The solution was stirred gently for 1 hr, and thenrinsed with water in a Buchner funnel until effluent pH was about 4. Afterwards itwas resuspended in 1000 mL 0.5 N NaOH solution, stirred again for 1 hr, and rinsedin a Buchner funnel until pH was about 6. Fines were removed by suspendingthe treated DEAE in a 1000 ml graduated cylinder filled with ultrapure water andleaving undisturbed for 1 hr. The supernatant was discarded and the last step wasrepeated. The remaining DEAE was filtered in a Buchner funnel and stored in arefrigerated glass container to be used in column chromatography described below.

Each sample was prepared for humic substances content measurement as fol-lows: 1 g treated DEAE was dissolved in 10 mL ultrapure water. An amount of thissuspension was poured into a 1 × 20 cm glass column with 0.5 cm silanized glasswool plug to make a 1 cm deep column bed. Then another 0.5 cm glass wool plugwas placed on top. The bed was rinsed with 50 mL 0.01 N KCl solution, adjustedto pH 6 with 0.1 N HCl or NaOH. Sample (250 ml) was passed after it was alsoadjusted to pH 6, with flow 2 ml min−1, and eluted by addition of 3 mL 0.1 NNaOH solution. Eluate was collected after 1 mL had passed, it was acidified with2–3 drops concentrated H3PO4 and purged with nitrogen for 10 min to removeddissolved CO2. Humic substances were measured as UV absorbance at 340 nm(Suffet and MacCarthy, 1989).


TABLE II

Analytical conditions for gas chromatographic – mass spectromet-ric determination of DBPs

Gas Chromatograph conditions

Carrier gas flow: 1.3 mL min−1

Split ratio: 1:25

Oven temperature:

THMs and other volatile 39 ◦C (15 min)

DBPs

HAAs 35 ◦C (9 min)

to 40 ◦C (3 min) at 1 deg min−1

to 148 ◦C at 6 deg min−1

Injector temperature: 175 ◦C

ECD temperature: 300 ◦C

Mass Spectrometer conditions

Solvent delay: 12 min

MS Temperature: 280 ◦C

EMV: 2200

Scan sec−1: 1.9

MS Scan Program: 35–265

2.5. APPARATUS

The determination of DBPs was carried out by use of a HP 5890 Series II GasChromatograph equipped with a 63Ni Electron Capture Detector (ECD). A capil-lary fused silica DB-1 column 30 m × 0.32 mm i.d. × 0.25 µm film thicknesswas used. Injections were made in splitless mode, with helium as carrier gas andnitrogen as makeup gas.

A Hewlett Packard Mass Selective Detector 5971, supported by the HP G1034Csystem software, with a fused silica capillary HP-VOC (60 m × 0.32 mm ×1.8 µm) was used for confirmatory purposes.

The analytical conditions are presented in Table II. The determination of humicsubstances content was carried out by use of a Cary 1E UV-visible spectrophoto-meter with 1-cm quartz cells.

The range of method recoveries for THMs and other volatile DBPs, estimatedat six concentration levels, five replicates at each level, is presented in Table III.The range of recoveries for haloacetic acids, estimated at five concentration levels,


TABLE III

Range of mean recovery (%), relative standard deviation (%, in parenthesis) anddetection limits of THMs and other volatile DBPs at six concentration levels (n =5) with the GC-ECD method

Concentration levels (µg L−1) Detection limit

Trihalomethanes 0.25–10.00 (µg L−1)

Chloroform 86 (13.2)–112 (15.9) 0.17

Dichlorobromomethane 87.6 (9.0)–130 (16.3) 0.32

Dibromochloromethane 88 (9.5)–104 (8.6) 0.21

Bromoform 88 (9.5)–104 (8.6) 0.21

Volatile DBPs 0.5–20.00

Monochloroacetonitrile 60.4 (5.4)–139.0 (4.9) 0.06

Trichloroacetonitrile 97.2 (28.3)–118.2 (8.2) 0.52

Dichloroacetonitrile 62.6 (27.7)–124.3 (3.4) 0.06

Chloral hydrate 86.7 (8.3)–144.5 (1.8) 0.03

1,1-Dichloropropanone 83.7 (5.6)–120 (2.6) 0.06

Monobromoacetonitrile 87.9 (18.7)–131.2 (12.2) 0.30

Chloropicrin 58.7 (3.4)–124.2 (6.8) 0.04

Bromochloroacetonitrile 82.5 (2.1)–143.2 (20.3) 0.13

1,1,1-Trichloropropanone 75.8 (5.6)–111.32 (5.3) 0.15

1,3-Dichloropropanone 88.0 (20.9)–100.7 (13.0) 0.98

Dibromoacetonitrile 92.6 (8.5)–121.2 (13.5) 0.31

seven replicates at each level, is presented in Table IV. Calibration curves of highlinearity were obtained in all cases (R2 0.99).

Recoveries of THMs were good and the same is true for the other volatileDBPs, except for MCAN and CP, where low recoveries were observed. Recoveriesof HAAs were generally acceptable, except for that of MCA. Poor recovery ofesterification method for this compound has been previously reported for acidicmethanol (Cancho et al., 1999) as well as diazomethane (Chen and Weisel, 1998)derivatization agents.

The detection limits were calculated as follows:

DL = t × S

where DL: Detection limit (µg L−1), t: Student’s t value for a 99% confidence leveland a standard deviation estimate with n-1 degrees of freedom (t = 3.747 when n =5), S: Standard deviation of replicate analyses.


TABLE IV

Range of mean recovery, relative standard deviation (in parenthesis) and detec-tion limits of haloacetic acids with the acidic methanol esterification – GC-ECDmethod at five concentration levels (n = 7 replicates)

Compound Concentration Recovery (RSD) Detection

(µg L−1) (%) limit (µg L−1)

MCA 0.75–9 24.90 (1.3)–126.29 (0.8) 0.20

MBA 0.5–6 78.79 (8.3)–123.71 (36.2) 0.05

DCA 0.75–9 89.73 (2.7)–104.80 (8.2) 0.02

BCA 0.5–6 94.71 (3.7)–109.43 (5.0) 0.02

TCA 0.25–3 87.79 (3.4)–121.71 (1.0) 0.01

DBA 0.25–3 96.43 (6.0)–141.14 (6.69) 0.02

BDCA 0.5–6 89.93 (5.6)–126 (10.9) 0.10

DBCA 1.25–15 78.14 (2.9)–135.89 (10.3) 0.20

TBA 2.5–30 89.46 (7.5)–108.97 (4.6) 0.20

TABLE V

Data for water samples from Galatsi treatment plant

Parameter Raw water Finished water

mean max mean max

Color (Pt-Co) 3 4 2 3

Turbidity (NTU) 8.95 48.3 0.29 1.88

Temperature (◦C) 13 18 13 18

pH 7.94 8.31 7.6 7.94

Total organic carbon (mg L−1) 0.91 1.39 0.80 1.13

Residual chlorine (mg L−1) 0 0 0.6 1.26

Bromide ion (mg L−1) 0.017 0.035 0.015 0.053

2.6. STATISTICAL ANALYSIS

Statistical analysis of the results was performed by use of Statgraphics 4.0 and in-cluded Kolmogorov-Smirnov tests for distribution fitting and One-Way Analysis ofVariance (ANOVA) to determine whether the influence of different factors on DBPlevels is statistically significant or not (Zar, 1994). The factors studied were humicsubstances content, month and station. Seasonal variation of humic substances wasalso examined.


TABLE VI

Data for water samples in Menidi treatment plant

Parameter Raw water Finished water

mean max mean max

Color (Pt-Co) 3 4 2 3

Turbidity (NTU) 5.35 47.00 0.36 6.8

Temperature (◦C) 13 16 13 17

pH 8.10 8.39 7.87 8.10

Total organic carbon (mg L−1) 0.94 1.32 0.80 1.35

Residual chlorine (mg L−1) 0 0 0.58 1.0

Bromide ion (mg L−1) 0.01 0.042 0.011 0.029

3. Results and Discussion

The parameters measured during sampling and their values are shown in TablesV and VI. Sampling was carried out each month. During this ten-month study,from July 1999 until April 2000, the compounds most frequently detected in watersamples were chloroform, dichlorobromomethane, dibromochloromethane, CH,1,1-DCP, 1,1,1-TCP, MCA, DCA, TCA, DBA and BCA. Bromoform, DCAN,TCAN, DBAN, CP, MBA, BDCA, DBCA and TBA were rarely detected. Theconcentrations of DBPs were generally low. Total THMs concentrations rangedfrom 5.1 to 24.6 µg L−1 and total HAAs concentrations from 8.56 to 107.38 µgL−1, while HKs and CH occurred at even lower concentrations, below 1 µg L−1.The same DBPs speciation has been reported for chlorinated waters under similarconditions (Krasner et al., 1989; Nieminski et al., 1993; LeBel et al., 1997).

Humic substances showed peak concentrations in October and April in oneraw water source and in December and March in the other source studied. Theirconcentrations were also elevated in September in both sources. The seasonal vari-ation observed is in agreement with several studies, where higher concentrations ofTHMs have been determined in samples collected in the warmer months of the year(Krasner et al., 1989; Fayad, 1993; Li et al., 2001; Nissinen et al., 2002). Chloro-form was the main species of THMs due to the very low bromide concentration(Tables V, VI). It has been reported that in such cases chloroform concentrationcan account for as much as 90% of total THMs concentration (LeBel et al., 1997).

The results of the Kolmogorov-Smirnov tests showed that the concentrationsof DCA, TCA, DBA, CH, 1,1-DCP, 1,1,1-TCP and total THM as well as humicsubstances content follow normal distribution. The opposite is true for the concen-trations of total HAA, MCA, BCA, BDCA and individual THM.

ANOVA was applied for the species following normal distribution. The para-meters studied were humic substances content, month and sampling station. AN-


TABLE VII

Results of analysis of variance for disinfection by-products concentration as afunction of humic substances content

Parameter Degrees of F-ratio F0.05 F0.01 Significance

freedom level

TTHMa 68 4.933 2.04 2.72 0.0000

CHa 42 6.495 2.12 2.89 0.0000

1,1-DCPa 56 20.656 2.04 2.72 0.0000

1,1,1-TCPa 56 17.716 2.04 2.72 0.0000

TCAa 68 2.607 2.04 2.72 0.0039

DBAa 68 3.084 2.04 2.72 0.0009

DCA 68 1.734 2.04 2.72 0.0641

BCAa (log) 66 19.848 2.04 2.72 0.0000

BDCAa (log) 44 4.669 2.12 2.89 0.0002

CHCl3a (log) 67 3.853 2.04 2.72 0.0001

CHCl2Bra (log) 66 9.717 2.04 2.72 0.0000

CHClBr2a (log) 57 16.975 2.04 2.72 0.0000

a Statistically significant difference.

OVA results for DBPs concentrations as a function of humic substances contentare presented in Table VII. Significance level lower than 0.05 denotes statisticallysignificant difference. From Table V it can be seen that the concentrations of totalTHM, CH, 1,1-DCP, 1,1,1-TCP, TCA and DBA are strongly affected from humicsubstances content (at 0.01 confidence level, F > F 0.01), which is in agreementwith the results from many investigations reporting higher DBPs concentrationsin water rich in humic substances or surface water than in water with low humicsubstances content or groundwater (Krasner et al., 1989; Fayad, 1993; Li et al.,2001; Nissinen et al., 2002).

ANOVA results for humic substances content and individual DBPs as a functionof month are presented in Table VIII. Humic substances vary to a statisticallysignificant degree during different months ( F > F 0.01). The same is true forthe concentrations of total THM, CH, 1,1-DCP, 1,1,1-TCP, TCA and DCA. Thevariance of DBA was not statistically significant (significance level > 0.05).

ANOVA results for humic substances content and DBPs concentrations as afunction of sampling station are given in Table IX. Humic substances contentshowed no statistically significant difference between the two raw water sourcesstudied. 1,1-DCP, 1,1,1-TCP and CH did not vary significantly at the differentsampling points, whereas the concentrations of total THM, DCA, TCA and DBAvaried significantly versus sampling station (confidence level 0.01).


TABLE VIII

Results of Analysis of Variance for humic substances and Disinfectionby-products concentrations as a function of month


freedom level

Humic substancesa 68 9.015 2.04 2.72 0.0000

TTHMa 69 5.987 2.04 2.72 0.0000

CHa 42 7.281 2.12 2.89 0.0000

1,1-DCPa 57 85.701 2.04 2.72 0.0000

1,1,1-TCPa 56 38.318 2.04 2.72 0.0000

TCAa 69 4.338 2.04 2.72 0.0002

DBA 69 2.035 2.04 2.72 0.0506

DCAa 69 2.358 2.04 2.72 0.0236

BCAa (log) 67 15.249 2.04 2.72 0.0000

BDCAa (log) 45 3.781 2.12 2.89 0.0046

CHCl3a (log) 68 6.412 2.04 2.72 0.0000

CHCl2Bra (log) 67 5.484 2.04 2.72 0.0000

CHClBr2a (log) 58 3.374 2.04 2.72 0.0036


TABLE IX

Results of Analysis of Variance for humic substances and Disinfectionby-products concentration as a function of sampling station


freedom level

Humic substances 68 0.487 4.00 7.08 0.8154

TTHMa 69 3.131 2.25 3.12 0.0095

CH 69 0.583 2.25 3.12 0.7413

1,1-DCP 57 0.091 2.25 3.12 0.9969

1,1,1-TCP 56 0.504 2.25 3.12 0.8021

TCAa 69 2.828 2.25 3.12 0.0168

DBAa 69 3.055 2.25 3.12 0.0109

DCA 69 3.193 2.25 3.12 0.0084

BCA 67 1.162 2.25 3.12 0.3385

BDCA 45 1.440 2.34 3.29 0.2243

CHCl3a 68 3.075 2.25 3.12 0.0106

CHCl2Bra 67 3.757 2.25 3.12 0.0030

CHClBr2a 58 7.161 2.25 3.12 0.0000



Figure 3. Seasonal variation of humic substances content and total THM concentration at Menidiwater treatment plant, sedimentation tank effluent.

Figure 4. Seasonal variation of humic substances content, DCA and TCA concentrations at Menidiwater treatment plant, finished water reservoir.

For the species showing statistically significant difference during differentmonths or at different stations, Least Significant Difference (LSD) tests were ap-plied, in order to determine the sub-groups of data which belong to a differentpopulation. The LSD test for humic substances versus month showed that in Julyand August humic substances content is significantly lower. From the LSD test itwas proved that CH, 1,1-DCP and 1,1,1-TCP concentrations in February and inApril are higher than during the other months, whereas higher total THM concen-trations are observed in March. The results of LSD tests as regards the samplingstation denote that the concentrations of DCA, TCA and total THMs were lowerin the sedimentation tank effluent and higher in the finished water reservoir atboth treatment plants, without statistically significant difference between plants.On the contrary, the concentration of DBA was significantly lower in Menidi wa-ter treatment plant and higher in Galatsi water treatment plant, without statistic-ally significant difference between sedimentation tank effluents and finished waterreservoirs.


Figure 5. Seasonal variation of humic substances content, DCA and TCA concentrations at Galatsiwater treatment plant, sedimentation tank effluent.

Figure 6. Seasonal variation of humic substances content and CH concentration at Galatsi watertreatment plant, finished water reservoir.

At Menidi water treatment plant, humic substances content is elevated in Septem-ber and shows a peak in October and another one in April (Figures 3, 4). TotalTHMs concentration generally followed the seasonal variation of humic substances,with higher concentrations in autumn (September and October) and spring (March)(Figure 3). 1,1-DCP and 1,1,1-TCP concentrations also showed a peak in April.DCA and TCA concentrations were higher in July, in spite of the low humic sub-stances content during this month, possibly due to high temperature. During theother months, the variation of DCA and TCA concentrations also followed that ofhumic substances content, as presented in Figure 4. The same pattern for humicsubstances and DBPs was observed both in the sedimentation tank effluent and inthe drinking water reservoir.

At Galatsi water treatment plant, sedimentation tank effluent, humic substancescontent shows peaks in December and March. The concentration of DCA seemsto follow this fluctuation during all months except August (Figure 5). The hightemperature in August is probably the reason of elevated DCA concentration dur-


Figure 7. Seasonal variation of humic substances content and total THM concentration at Galatsiwater treatment plant, finished water reservoir.

ing this month. However, it must be noted that TCA was not detected in August.1,1-DCP, 1,1,1-TCP and CH occurred in elevated concentrations in February andApril, showing time fluctuation opposite than that of HAA, denoting that formationof these two categories of DBPs may be competitive. Total THM concentrationpeaked in October and March, whereas in December, when peak in humic sub-stances and HAA concentrations occurred, no THM were formed. At the finishedwater reservoir of Galatsi water treatment plant in December very low THM con-centration was also observed (Figure 6). The other DBPs followed the same patternas in the sedimentation tank effluent, with only exception CH, which, in this case,followed the time fluctuation of humic substances, as shown in Figure 7.

The relationships between the variables were examined by simple correlation(Golfinopoulos et al., 1998). The multiple regression was applied as a mean toevaluate the statistically significant variables of the system. The level of signific-ance (α) for inclusion of a variable was 0.05. The F-criterion based on the sum ofsquares due to regression (SSREG) over the sum of squares for error divided by therespective degrees of freedom (s2

e) was used to eliminate statistically insignificantvariables (Golfinopoulos et al., 1998). In particular, for any variable coefficient bj ,Ho: bj = 0 and Ha: bj �= 0, the F statistics can be formed as:

F = SSREG

s2e

It is evident that large F values would provide evidence for rejection of Ho infavor of Ha, that is, the variable is statistically significant.

BCA, BDCA, chloroform, dichlorobromomethane and dibromochloromethaneconcentrations followed the normal distribution when log-transformed, and showstatistically significant difference with humic substances content at confidence level0.01, as shown in Table VII. The same is true for ANOVA results as regardsmonth (Table VIII). Table IX presents ANOVA results as a function of sampling


station. It can be observed that in this case chloroform, dichlorobromomethane anddibromochloromethane show statistical difference, while BCA and BDCA do not.

The results of LSD tests showed that BCA concentration was significantly higherin August, BDCA in July and chloroform in March. Moreover, chloroform con-centration was higher in the finished water reservoir than in the sedimentation tankeffluent of both plants, while dichlorobromomethane concentration was signific-antly higher in Galatsi water treatment plant than in Menidi water treatment plant,with no statistical difference between finished water reservoirs and sedimentationtanks.

Total HAA concentration and MCA concentration did not follow the normal dis-tribution even when log-transformed. Bromoform, MBA, DBA, TBA, CP, DCAN,TCAN and DBAN were rarely detected in very low number of samples, insufficientfor statistical analysis performance.

4. Conclusions

A number of compounds belonging to different categories of DBPs were detectedin two drinking water treatment plants in Greece. Humic substances content wasalso determined and found to influence DBP formation, especially in the cases oftotal THM, TCA, DBA, CH, 1,1-DCP, 1,1,1-TCP. BCA, BDCA and individualTHM species were also found to be influenced to statistically significant degreefrom humic substances. Seasonal variation of total THM and HAA generally fol-lowed that of humic substances content with peaks occurring in autumn and spring.However the trends of 1,1-DCP, 1,1,1-TCP and CH formation seemed to be in con-trast to THM and HAA. The concentrations of DBPs were higher in finished waterreservoir than in sedimentation tank effluent in both water treatment plants studied.Trends of formation of individual compounds varied in some cases, probably dueto influence of parameters other than humic substances content. For example, inGalatsi water treatment plant in August DCA concentration peaked, while TCAwas not detected. In Menidi water treatment plant in July, peaks in DCA and TCAconcentrations occurred in spite of the low humic substances content during thismonth, probably due to elevated temperature.

The goal of disinfection in water treatment is to achieve maximum protectionagainst bacterial contamination while minimizing the formation of DBPs. Thereare three strategies to minimise DBPs formation:

a. Improving the quality of the raw water by reducing precursors or changing thesource. To remove DBPs precursors from the water prior to their contact withdisinfectant, treatment will be required for systems with a total organic contentin the water that exceeds 2 mg L−1.

b. Use of a disinfectant that does not generate DBPs in drinking water.c. Removing organic contaminants and DBPs after they are formed during the

treatment process.


These general practices can be further divided into other control options. Acombination of all three approaches may minimize organic compounds and/oroptimize pathogen control.

THMs form as a result of reactions between humic substances (humic and fulvicacids) and free chlorine and other halogen residuals. The reactions need severalhours, sometimes resulting in significant concentration increases even after twenty-four hours.

A first step to decrease the levels of organics would be to seek another source ofwater. Humic substances comprise the highest percentage of total organic contentin raw water, and these in turn depend on the natural characteristics of the rawwater sources.

If another source of water is not easy to find, a number of other approaches canbe applied. When the source in question has seasonal variation of quality, off-linestorage can provide control over a specific period of time. Water can be pumpedinto a receiver when its quality is good, and bypassed when it is poor.

Off-line storage might also be used as a safeguard against periodic spills ofindustrial contaminants, since water can be checked in a reservoir and rejectedif the organic levels are dangerous. A dual system, i.e. two distribution systems,is another alternative. The first would be used for highly treated drinking waterand the second with lower quality water could be used for cooling or industrialprocesses. This practice requires high capital investments and is suitable for newlydeveloped areas.

It is inevitable that dealing with the organics problem will require extensivechanges in water treatment, including new analytical technology and new processtechnology.

Acknowledgements

This research was supported by the Athens Water and Sewage Corporation. Theauthors thank Prof. Damia Barcelo, Dr Fransesc Ventura and Mr Philippos Tzou-merkas for their scientific assistance.

References

APHA: 1992, Standard Methods for the Examination of Water and Wastewater (18th Edn), AmericanPublic Health Association, Washington, DC, pp. 5–22–5–23.

Bull, R. J. and Kopfler, F. C.: 1991, Health Effects of Disinfectants and Disinfection By-Products,American Water Works Association Research Foundation, Denver, Colorado.

Bull, R. J. and Robinson, M.: 1986, ‘Carcinogenic Activity of Haloacetonitrile and Haloacetone De-rivatives in the Mouse Skin and Lung’, in Water chlorination: Chemistry, Environmental Impactand Health Effects, Lewis Publishers, USA, Vol. 5, pp. 221–227.

Cancho, B., Ventura, F. and Galceran, M.: 1999, ‘Behavior of halogenated disinfection by-productsin the water treatment plant of Barcelona, Spain’, Bull. Environ. Contam. Toxicol. 63, 610–617.


Chen, W. J. and Weisel, C. P.: 1998, ‘Halogenated DBP concentrations in a distribution system’, J.AWWA 90, 151–163.

Christman, R. F., Norwood, D. L. and Millington, D. S.: 1983, ‘Identity and yields of majorhalogenated products of aquatic fulvic acid chlorination’, Env. Sci. Technol.. 17, 625–628.

EEC: 1998, Council Directive 98/83/EC of 3 November 1998 on the quality of water intended forhuman consumption, Official Journal of the European Communities, L 330/32, 5–12–98

EPA: 1996, ‘Drinking Water Regulations and Health Advisories’http://www.epa.gov/ostwater/Tools/dwstds0.html, http://www.epa.gov/ostwater/Tools/dwstds1.html,http://www.epa.gov/ostwater/Tools/dwstds2.html, http://www.epa.gov/ostwater/Tools/dwstds3.html,http://www.epa.gov/ostwater/Tools/dwstds4.html, http://www.epa.gov/ostwater/Tools/dwstds5.html,http://www.epa.gov/ostwater/Tools/dwstds6.html, http://www.epa.gov/ostwater/Tools/dwstds7.html

EPA: 1998, National Primary Drinking Water Regulations: Disinfectants and DisinfectionBy-Products Notice of Data Availability, Office of Ground Water and Drinking Water,http://www.epa.gov/OGWDW/mdbp/dis.html

EPA: 1998b, ‘EPA Method 551.1. Determination of Chlorinated Disinfection By-Products, Chlor-inated Solvents, and Halogenated Pesticides/Herbicides in Drinking Water by Liquid-LiquidExtraction and Gas Chromatography with Electron Capture Detection’, USEPA, Office of Water,Technical Support Center, 26 W. Martin Luther King Dr., Cincinnati, OH 45268.

Golfinopoulos, S. K., Xylourgidis, N. K., Kostopoulou, M. N. and Lekkas, T. D.: 1998, ‘Use of amultiple regression model for predicting trihalomethane formation’, Wat. Res. 32, 2821–2829.

Huixian, Z., Sheng, Y. X. and Ouyong, X.: 1997, ‘Formation of POX and NPOX with chlorinationof fulvic acid in water: Empirical models’, Wat. Res. 31, 1536–1541.

Kavanaugh, M. C., Trussel, A. R., Cromer, J. and Trussel, R. R.: 1980, ‘An empirical kinetic model ofTrihalomethane formation: applications to meet the proposed THM Standard’, J. AWWA 72(10),578.

Korshin, G. V., Benjamin, M. M. and Sletten, R. S.: 1997, ‘Adsorption of Natural Organic Matter(NOM) on iron oxide: effects on NOM composition and formation of organo-halide compoundsduring chlorination’, Wat. Res. 31, 1643–1650.

Krasner, S. W., McGuire, M. J., Jacangelo, J. G., Patania, N. L., Reagan, K. M. and Aieta, E. M.:1989, ‘The occurrence of disinfection by-products in US drinking water’, J. AWWA 81, 41–53.

LeBel, G. L., Benoit, F. M. and Williams, D. T.: 1997, ‘A one-year survey of halogenated DBPsin the distribution system of treatment plants using three different disinfection processes’,Chemosphere 34, 2301–2317.

Lekkas, T. D.: 1996, Environmental Engineering I: Management of Water Resources, University ofthe Aegean, Department of Environmental Studies, Mytilene, Greece (In Greek).

Miller, J. W. and Uden, P. C.: 1983, ‘Characterization of non-volatile aqueous chlorination productsof humic substances’, Environ. Sci. Technol. 17, 150–157.

Li, S., Zhang, X. J., Liu, W. J., Cao, L. L. and Wang, Z. S.: 2001, ‘Formation and evolution ofhaloacetic acids in drinking water of Beijing city’, J. Environ. Sci. Hth A 36, 475–481.

Nieminski, E. C., Chaudhuri, S. and Lamoreaux, S.-T.: 1993, ‘The occurrence of DBPs in Utahdrinking waters’, J. AWWA 85, 98–105.

Nikolaou, A. D., Golfinopoulos, S. K., Kostopoulou, M. N. and Lekkas, T. D.: 2000, ‘Decompositionof dihaloacetonitriles in water solutions and fortified drinking water samples’ Chemosphere 41,1149–1154.

Nikolaou, A. D., Kostopoulou, M. N. and Lekkas, T. D.: 1999, ‘Organic by-products of drinkingwater chlorination: a review’, Global Nest: Int. J. 1, 143–156.

Oliver, B. G.: 1983, ‘Dihaloacetonitriles in drinking water: algae and fulvic acid as precursors’,Environ. Sci. Technol. 17, 80–83.

Nissinen, T. K., Miettinen, I. T., Martikainen, P. J. and Vartiainen, T.: 2002, ‘Disinfection by-productsin Finnish drinking waters’, Chemosphere 48, 9–20.


Pereira, M. A., Daniel, F. B. and Lin, E. L. C.: 1986, ‘Relationship between Metabolism of Halo-acetonitriles and Chloroform and their Carcinogenic Activity’, in Water Chlorination: Chemistry,Environmental Impact and Health Effects, Lewis Publishers, USA, Vol. 5, pp 229–236.

Reckhow, D. A. and Singer, P. C.: 1986, ‘Mechanisms of Organic Halide Formation duringFulvic Acid Chlorination and Implications with Respect to Preozonation’, in Water Chlorina-tion: Chemistry, Environmental Impact and Health Effects, Vol. 5, Lewis Publishers, USA, pp1229–1257.

Rook, J. J.: 1974, ‘Formation of haloforms during chlorination of natural waters’, Wat. Treat. Exam.23, 234–243.

Sanchez Jimenez, M. C., Pedraza Dominguez, A. and Cachaza Silverio, J. M.: 1993, ‘Reactionkinetics of humic acid with sodium hypochlorite’, Wat. Res. 27, 815–820.

Simpson, K. J. and Hayes, K. P.: 1998, ‘Drinking water disinfection by-products: an Australianperspective’, Wat. Res. 32, 1522–1528.

Singer, P. C.: 1994, ‘Control of disinfection by-products in drinking water’, J. Environ. Engin. 120,727–744.

Suffet, I. H. and MacCarthy, P.: 1989, Aquatic Humic Substances: Influence on Fate and Treatmentof Pollutants, American Chemical Society, Washington, DC, pp 107–114.

Summers, R. S., Hooper, S. M., Shukairy, H. M., Solarik, G. and Owen, D.: 1996, ‘Assessing DBPyield: uniform formation conditions’, J. AWWA 88, 80–93.

Trehy, M. L., Yost, R. A. and Miles, C. L.: 1986, ‘Chlorination by-products of aminoacids in naturalwaters’, Environ Sci. Technol. 20, 1117–1122.

Williams, D. T., Lebel, G. L. and Benoit, F. M.: 1997, ‘Disinfection by-products in Canadian drinkingwater’, Chemosphere 34, 299–316.

Zar, J. H.: 1984, Biostatistical Analysis, Prentice-Hall, Inc, Englewood Cliffs, New Jersey.

dbp levels in chlorinated drinking water: effect of humic substances

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