Drinking Water and Health, Volume 7 Disinfectants and Disinfectant By-Products (1987) / Chapter Skim
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3 CHEMISTRY AND TOXICITY OF DISINFECTION
3 CHEMISTRY AND TOXICITY OF DISINFECTION
Pages 27-79
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From page 27... ...
However, most of the carbon in typical surface waters is found in natural humic materials, which are potential precursors of toxic disinfection by-products (Rook, 1976; Thurman, 19851. Many recent studies discussed in this chapter have addressed disinfection by-products produced from these aquatic humic materials, which consist of complex natural mixtures of humic and fulvic acids plus neutral and basic components produced mainly by decaying vegetation.
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From page 28... ...
a number of studies of the reaction mechanisms and types of by-products formed from chlorination of aquatic humic materials. MODEL COMPOUND STUDIES Mechanisms of chlorination by-product formation have been investigated through the use of isolated humic and fulvic acids, as well as simple compounds that are viewed as models of the complex molecules found in natural humic materials.
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From page 29... ...
Similar results were produced with their other model compounds, suggesting that chloroform is a primary reaction product of chlorination of aquatic humic materials that contain substructures similar to these model compounds. Other by-products produced by their model compounds are shown in Table 3-1.
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From page 30... ...
30 DRINKING WATER AND HEALTH TABLE 3-1 Reaction Products from Model Compounds and Hypochlorous Acid (HOCl~a Products Identified Reactant At 0.5 Cl2/C At 2.0 Cl2/C 1,3 DIHYDROXY BENZENE OH OH 'JC1X(X=1-3) HO OH H Cl,4~'C1 1 ~C1 O O CHC13 CHC13 O O 11 11 HO-C-C=3C- C-OH 1 1 H C1 CC13COOH 3-METHOXY-4 HYDROXY CINNAMIC ACID CH=CHCOOH CCH3 OH CH=CHCOOH LOCH OH r3 CH=CHCOOH ~C12 OCH3 OH CH=CHC 1 OCH3 OH CH=CHC 1 OCCIH3 OH CHC 13 CHC13 CHC12COOH CC13COOH aFrom Norwood et al.
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From page 31... ...
31 it: .
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From page 34... ...
A notable difference was that most products of fulvic acid chlorination contained chlorine, whereas most humic acid samples produced at high pH did not. In both cases, however, the dominant chlorinated products were chloroform and chlorinated aliphatic acids, especially dichloroacetic acid (DCA)
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From page 35... ...
A large number of monobasic and dibasic unchlorinated aliphatic acids, from oxalic up to the C27 monobasic fatty acid, were identified from the humic acid fraction (Table 3-3~. Only a few of the dibasic acids were associated with the fulvic acid fraction, and almost none of the monobasic
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From page 36... ...
(1985) subjected humic acid extracted from a peat soil to aqueous chlorination under degradation-scale conditions (0.38 g humic acid per liter of solution, pH 7.2, 24-hour reaction time, ambient temperature, chlorine-to-carbon ratios of 0.39:1 and 3.35:11.
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From page 37... ...
These materials appear to be European lignitic coal extract rather than soil or aquatic humic acid (Malcolm and MacCarthy, 1986~. Chlorination products included chloroacetonitriles, chloroketones, and chlorobenzenes (Coleman et al., 19841.
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From page 38... ...
-COOH OH TRICHLORACETYL TYPE o C13C-C-CC1=CH-COOH o C13C-C-CC1-C(CH3) -COOH o CL3C-CH-CH2-COOH C1aC-C C1 C=C / \ HOOC COOH OHo 111 C13C-CH-CC12-COOHC13C-C\ COOH C=C / \ C1 COOH OH o C13C-CH-CC12-CH 2-CHC1-COOH C13C-C-C-CC1= CC12-COOH FIGURE 3-3 Chloroform precursors detected from the aqueous chlorination of a soil-derived humic acid at chlorine-to-carbon ratios of 0.39 and 3.35 by de Leer and colleagues (1985)
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From page 39... ...
Even under conditions where chloroform would be expected to predominate, it represents only a small quantity of the TOX produced, and DCA and TCA are produced in nearly identical amounts. The yield of identifiable products from chlorination of fulvic and humic acids isolated from natural surface water is a small fraction of the starting organic material.
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From page 40... ...
Using chlorine-to-carbon mole ratios and TOC values more typical of natural water, Reckhow and Singer (1985) showed that when aquatic fulvic acid (4.1 mg of TOC/liter at pH 7)
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From page 41... ...
Conditions: 3.0 mg TOC from peat fulvic acid/liter, 20 mg chlorine dosage/liter, 100 hours contact time, combined chlorine formed by addition of free chlorine to samples containing excess ammonium chloride. From Fleischacker and Randte (1983)
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From page 42... ...
Unfortunately, even using these sophisticated methods we are unable to identify the majority of products formed in water chlorination. ISOLATED BASES Numerous organic nitrogen compounds are present in natural surface waters (C.
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From page 43... ...
have shown that the amino acids, aspartic acid, tyrosine, and tryptophan, as well as the catabolites of tryptophan,
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From page 44... ...
Although the yields of chloroform from the individual amino acids are generally low, the overall yield of chloroform from proteins is comparable to that of humic acid for solutions containing equivalent amounts of organic carbon. Chloropicrin has been identified in chlorinated surface waters (Duguet et al., 1985; Mallevialle et al., 1983; Sayato et al., 19821.
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From page 45... ...
Since chlorine itself has not been found to be mutagenic, attention has focused on the reaction products formed by the chlorination of compounds already existing in untreated surface water. Besides implicating chlorination of humic and fulvic acids as the source of much, if not most, of the mutagenic activity observed in drinking water samples, Meier et al.
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From page 46... ...
(1985) found enlarged livers and hemoglobin in the urine in male Sprague-Dawley rats fed chlorinated humic acid (1.0 g/liter)
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From page 47... ...
This report was followed by a more detailed study of the reaction conditions required to produce the mutagens and to maintain mutagenic activity (Meter et al., 19831. Certain parallels were noted between mutagenic activity of drinking water samples and the model reaction involving chlorinated humic acids.
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From page 48... ...
of Mutagenic Activity in the Ames Test and SCE Induction in CHO Cells on Treatment of Humic Acid with Chlorine (HO Cl/O Cl) a Mutagenic Activityb Humic Acid Sample TA98 TA 100 339 + 29 (100)
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From page 49... ...
(1983) showed that mutagenic activity of chlorinated humic acid can be prevented or reduced either by
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From page 50... ...
. Epidemiological studies of drinking water typically rely on a dichotomous characterization of the water treatment as chlorinated or nonchlorinated combined with a dichotomous classification of the water supply source as surface water or groundwater.
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From page 51... ...
MASSACHUSETTS Tuthill and Moore (1980) related cancer mortality rates for the 1969 to 1976 period in Massachusetts communities supplied by surface water to chlorination exposure data as measured by average past chlorine dose, recent total THM levels, and recent chlorine dose.
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From page 52... ...
In each population group, rates of lung and rectal cancers were higher in communities supplied by surface water than in communities supplied by groundwater; the risk ratio for colon cancer (1.38) was higher only in the 1975-1978 period.
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From page 53... ...
(1981, 1982) compared cancer and noncancer deaths from 1960 to 1975 in Louisiana parishes selected for similarities in industrialization and approximately equal exposure of the population to surface water and groundwater.
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From page 54... ...
Odds ratios for males were highest, increasing to over 3.0 when the lifetime water use variable was used. The association of lung cancer and surface water was statistically significant only among nonwhite males and only for water source at death.
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From page 55... ...
Cases were hospitalized males and females with primary colon cancer; controls were patients with the closest admission date who matched on age, race, sex, vital status, and hospital and who had no previous history of cancer of any type, mental disorder, or major chronic intestinal disorder. The sources of water exposure were initially classified as unchlorinated groundwater, chlorinated groundwater, or chlorinated surface water, with no consideration of levels of pollutants.
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From page 56... ...
There were 400 living colon cancer cases selected from the Wisconsin Cancer Reporting System; 600 controls came from two sources: a random selection from a statewide listing of motor vehicle operators and cancer cases other than gastrointestinal or genitourinary from the Wisconsin reporting system. Lifetime residential and drinking water source histories, diet, medical history, social class, and other life-style factors were obtained by questionnaire.
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From page 57... ...
However, among nonsmokers, a group generally at low risk for bladder cancer, those whose usual source was of chlorinated surface origin had an odds ratio of 1.4, relative to usual users of nonchlorinated groundwater, and there was a relationship between risk and duration of chlorinated surface water use. Among nonsmokers, the relative risk increased from 1.3 among users of chlorinated surface water for less
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From page 58... ...
have revealed positive associations of bladder cancer risk with level of tap water ingestion and duration of exposure, predominantly among study subjects with long-term residence in communities served by chlorinated surface waters. Groups at Increased Risk While there has been a considerable amount of research on the chemistry of disinfection by-products, the data base is often limited with respect to the toxicological effects of such products.
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From page 59... ...
Many large communities in the United States have been treating their drinking water either with chloramines (AWWA, 1985) or chlorine dioxide (Aieta and Berg, 19861.
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From page 60... ...
The quantity of TOX produced by Monochloramine is only 5% to 50~o of the TOX produced by a similar dose of free chlorine, but the concentration of Monochloramine used in water treatment is generally greater because it is less effective as a disinfectant. Few individual, ether-extractable, and GC/MS-identifiable products are produced in the chloramination of humic materials compared with the large number of such compounds produced by chlorine.
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From page 61... ...
CHLORAMINE ANALYSIS The analysis of chloramines in natural water samples has been of two types. The most widely used methods are oxidant or chlorine residual measurements.
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From page 62... ...
Most organic amines and amino acids, however, react even more rapidly with hypochlorite to form organic N-chloramines (Morris, 1967; Well and Morris, 19491. In water containing both ammonia and organic aminonitrogen compounds, the relative amounts of organic (versus inorganic)
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From page 63... ...
As a result, the breakpoint curve of water containing both ammonia and organic amines is a composite of the individual breakpoint curves of ammonia and every organic amino-nitrogen compound in the water that can react with hypochlorite. Figure 3-6 illustrates this using a recently reported method for the derivatization and analysis of organic and inorganic N-chloramines in dilute aqueous solution (Scully et al., 19841.
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From page 64... ...
Consequently, a water treatment facility that practices marginal chlorination of water containing high concentrations of organic amino-nitrogen compounds runs the risk of overestimating the ability of its systems to maintain adequate disinfection. The implications of this have been demonstrated by Wolfe et al.
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From page 65... ...
Although interference of disinfection by organic nitrogen compounds can be demonstrated in laboratory experiments and these used to implicate interferences in treatment plants, there is still a poor understanding of the specific compounds responsible for interferences and their true significance
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From page 66... ...
This brief section discusses the current state of knowledge on the chemistry of ozone as it pertains to water treatment. USE PATTERNS OF OZONE AND CHLORINE DIOXIDE Concern over by-products of chlorine has caused municipal water authorities to consider alternatives for disinfection and oxidation of drinking water.
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From page 67... ...
In summary, all indicators point to the increased use of ozone in water treatment. How extensive this adoption of ozone and chlorine dioxide technology will be is not yet clear.
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From page 68... ...
1986. A review of chlorine dioxide in drinking water treatment.
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From page 69... ...
1983. Reaction pathways of trihalomethane formation from the halogenation of dihydroxyaromatic model compounds for humic acid.
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From page 70... ...
1985. Chloroform Production from Model Compounds of Aquatic Humic Material.
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From page 71... ...
1985. Identification of intermediates leading to chloroform and C-4 diacids in the chlorination of humic acid.
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From page 72... ...
4. Book 1: Chemistry and Water Treatment.
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From page 73... ...
1982. Reaction products of aquatic humic substances with chlorine.
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From page 74... ...
1982. Determination of mutagenic activity in Salmonella of residual fulvic acids after ozonation.
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From page 75... ...
1984. Nitrogenous organic compounds: Identification and significance in several French water treatment plants.
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From page 76... ...
1983. Formation of mutagens following chlorination of humic acid: A model for mutagen formation during drinking water treatment.
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From page 77... ...
1977. Chlorination reactions of fulvic acids in natural waters.
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From page 78... ...
1983. Wastewater treatment plant disinfection efficiency as a function of chlorine and ammonia content.
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From page 79... ...
1982. Mutagenic activity associated with by-products of drinking water disinfection by chlorine, chlorine dioxide, ozone and UV-irradiation.
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