Environ. Sci. Technol. 1996, 30, 16-24
Effect of Bromide Ion on Haloacetic Acid Speciation Resulting from Chlorination and Chloramination of Aquatic Humic Substances
as products of laboratory chlorinations of commercial humic acid in the presence of bromide ion.
GRETCHEN A. COWMAN AND PHILIP C. SINGER*
The goal of the present study was to investigate HAA speciation during chlorination and chloramination of bromide-containing waters. Health effects studies have suggested that individual HAA species are of varying toxicological significance. It is thus important to understand the factors affecting the distribution of HAAs among individual species in drinking water.
Department of Environmental Sciences and Engineering, CB#7400 Rosenau Hall, University of North Carolina, Chapel Hill, North Carolina 27599-7400
The objective of this study was to investigate the effect of bromide ion on the distribution of haloacetic acid (HAA) species resulting from the chlorination and chloramination of waters containing aquatic humic substances. Aquatic humic substances were extracted from a surface water and a groundwater and were chlorinated and chloraminated under standard conditions at pH 8 and pH 6 in the presence of bromide concentrations ranging from 0 to 25 µM (0-2 mg/L). The treated waters were analyzed for all nine of the HAA species containing bromine and chlorine. Standards for bromodichloroacetic acid and dibromochloroacetic acid were not commercially available but were synthesized for use in this study. Bromochloro-, bromodichloro-, and dibromochloroacetic acid were readily formed and constituted at least 10% of the total HAA concentration in waters containing as little as 1.2 µM (0.1 mg/L) bromide. The mixed bromochloro HAA species were major components of the total HAA concentration at bromide concentrations found in raw drinking waters. Distribution of the HAA species among the mono-, di-, and trihalogenated forms appeared to be independent of bromide concentration.
Introduction Haloacetic acids (HAAs) are chemical byproducts of chlorination and chloramination of drinking water. Dichloroacetic acid and trichloroacetic acid are the most extensively studied of the HAAs, and they have been identified as major halogenated species both in laboratory chlorinations of aquatic humic substances (1-4) and in chlorinated drinking water (5-7). There are a total of nine HAA species containing chlorine and bromine: chloro-, dichloro-, and trichloroacetic acid (MCAA, DCAA, and TCAA); bromo-, dibromo-, and tribromoacetic acid (MBAA, DBAA, and TBAA); and bromochloro-, bromodichloro-, and dibromochloroacetic acid (BrClAA, BrCl2AA, and Br2ClAA). Pourmoghaddas et al. (8) have identified all nine of these species
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The toxicological properties of these compounds are not well understood, but they are of concern to public health because of their suspected carcinogenicity as well as developmental, reproductive, and hepatic toxicity (9-15). Five of the HAAs (MCAA, DCAA, TCAA, MBAA, and DBAA) will be regulated under the U.S. Environmental Protection Agency’s proposed Disinfectants/Disinfection Byproducts Rule.
It is well known that naturally occurring bromide in raw waters is readily incorporated into HAAs in the form of organically bound bromine during water chlorination. A recent nationwide survey of bromide concentrations in U.S. drinking water sources estimated the mean occurrence level of bromide to be 62 µg/L with an overall observed range of BrCl2AA > BrClAA > Br2ClAA > DBAA > TBAA. At the high end of the bromide range studied (>20 µM), speciation is in a nearly opposite order: TBAA > DBAA > Br2ClAA > BrCl2AA > BrClAA >
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FIGURE 3. Distribution of individual HAA species in chlorinated Myrtle Beach (a) and Palm Beach (b) extracts, pH 8.
DCAA, TCAA. These observed patterns of HAA speciation are qualitatively similar to the results reported previously by Pourmoghaddas et al. (8) for the chlorination of commercial humic acid in the presence of bromide ion.
a
a
b
FIGURE 4. Distribution of HAAs into mono-, di-, and trihalogenated species in chlorinated Myrtle Beach (a) and Palm Beach (b) extracts, pH 8.
Distribution of the HAAs into mono-, di-, and trihalogenated species was also analyzed, and this speciation is shown in Figure 4. Species were grouped in this manner because it is likely that each of the monohalogenated species (MCAA and MBAA) are formed through similar chemical pathways and likewise for the dihalogenated species (DCAA, DBAA, and BrClAA) and the trihalogenated species (TCAA, TBAA, BrCl2AA, and Br2ClAA). The two extracts showed strikingly similar distributions. The trihalogenated species constituted the greatest mole fraction of the total HAA concentration (61-67%), the dihalogenated species made up 30-36% of the total, and the monohalogenated species constituted 3-5% of the total. This distribution appeared to be independent of bromide concentration over the range of concentrations studied. Total bromine and chlorine incorporation into the HAAs is shown in Figure 5. Bromine and chlorine incorporation are equivalent at a ratio of Br- to initial applied HOCl of approximately 0.11 mol of Br-/mol of HOCl in Myrtle Beach extract and 0.07 mol of Br-/mol of HOCl in Palm Beach extract. The results suggest that bromine is more reactive than chlorine in substitution and addition reactions that form HAAs. Over the range of bromide concentration studied, the average halogen composition of the HAAs was approximately 2.6 mol of total halogen/mol of total HAAs.
b
FIGURE 5. Bromine and chlorine incorporation into HAAs in chlorinated Myrtle Beach (a) and Palm Beach (b) extracts, pH 8.
FIGURE 6. Effect of bromide ion concentration on chlorine consumption in chlorinated extracts, pH 8.
There appeared to be a linear increase in chlorine consumption with increasing bromide ion concentration, as shown in Figure 6. Bromide ion exerts a chlorine demand through the reaction: HOCl + Br- f HOBr + Cl-. The slopes of both lines in Figure 6 are slightly greater than 1.0; 50-70 µM HOCl is consumed by the 4 mg/L of humic
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FIGURE 8. Distribution of HAAs into mono-, di-, and trihalogenated species in chloraminated Palm Beach extract.
FIGURE 7. Total HAA formation in Myrtle Beach and Palm Beach extracts chlorinated at pH 8 and pH 6.
material (as C), with approximately an additional 1 µmol of HOCl consumed/µmol of bromide. Sweetman et al. (25) have suggested that Br- may be “recycled” through oxidation reactions. HOBr can participate in oxidation reactions that do not involve incorporation of Br into organics, with Br- being a product of such reactions. Br- can then be reoxidized to HOBr by HOCl, and thus 1 mol of Br- can potentially consume more than 1 mol of HOCl. Under the conditions of this study, there appeared to be little recycling of bromide. HAA Formation and Speciation in Extracts Chlorinated at pH 6. Individual HAA species responded differently to variation in the pH of chlorination, but the two extracts again showed similar behavior. The formation of several species, most notably DBAA, BrClAA, BrCl2AA, and Br2ClAA, was enhanced by lowering the pH from 8 to 6. In general, the di- and trihalogenated species containing bromine appeared to be more greatly affected by pH than their chlorinated counterparts, DCAA and TCAA, which increased only slightly at the lower chlorination pH. MCAA formation was decreased by lowering the pH to 6, while MBAA formation appeared to be little affected. Changing the pH of chlorination from 8 to 6 did not appear to significantly affect distribution of the HAAs into mono-, di-, and trihalogenated species or bromine and chlorine incorporation into the HAAs. Total HAA formation in both extracts is compared at pH 8 and pH 6 in Figure 7. HAA Formation and Speciation in Extracts Chloraminated at pH 8. Both quantitative formation and speciation of the HAAs were dramatically different in chloraminated extracts compared to chlorinated extracts. Total micromolar HAA formation was decreased on the order of 9095%. DCAA was the principal HAA species formed from chloramination, but observed concentrations did not exceed 0.07 µM (9 µg/L). Some brominated species were observed from chloramination, principally MBAA, DBAA, and BrClAA. Formation of the trihalogenated species was greatly suppressed by chloramination. TCAA formation was below the detection limit of 0.0018 µM (0.29 µg/L) in all chlo-
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raminated samples. Br2ClAA and TBAA were quantifiable only in samples containing greater than 12.5 µM Br-, but only at concentrations below 0.01 µM (2 µg/L). BrCl2AA was also detected only at concentrations below 0.01 µM (2.3 µg/L). Distribution of the HAAs among the mono-, di-, and trihalogenated species is shown in Figure 8 for chloraminated Palm Beach extract. In contrast to speciation in chlorinated waters, the dihalogenated species were the principal species formed, while trihalogenated HAAs were the minor species. The average halogen content of the HAAs produced from chloramination was approximately 1.7-1.9 mol of total halogen/mole of total HAAs in the range of bromide concentrations studied. This is in contrast to the observed 2.6 mol of total halogen incorporated/mol of total HAAs in chlorinated waters. Bromine incorporation into HAAs increased with increasing bromide concentration; however, the extent of bromine incorporation into the HAAs was less during chloramination compared to chlorination. Analysis of Finished Drinking Water Samples. The results of laboratory chlorinations of humic extracts presented above suggest that the bromochloro HAA species are readily formed during chlorination of bromidecontaining waters. In order to verify the applicability of this finding to water treatment practice, finished waters from several water utilities were collected at the point of entry to the water distribution system and analyzed for the nine HAAs. The results of these analyses are given in Table 1 for finished waters from the Philadelphia (PA) Suburban Water Co. (PSWC), the Metropolitan Water District of Southern California (MWD), and the cities of Houston, TX, and Corpus Christi, TX. These samples include waters with relatively low (PSWC), moderate (Houston), and high (MWD, Corpus Christi) bromide concentrations. Several of the utilities (Houston, MWD, Corpus Christi) add ammonia to their waters after chlorination to control disinfection byproduct formation. In Table 1, ∑HAA5 is the sum of the five HAAs (MCAA, DCAA, TCAA, MBAA, and DBAA) included in the U.S. EPA’s proposed Disinfectants/Disinfection Byproducts Rule, while ∑HAA9 is the sum of all nine HAA species. In the MWD and Corpus Christi finished waters, the three bromochloro species constituted 48% and 52% of the total HAAs on a mole fractional basis, respectively. BrCl2AA constituted 20%
TABLE 1
Haloacetic Acids in Finished Drinking Waters PSWC TOC ) 2.6 mg/L Br- ) 50.6 µg/L (0.63 µM)
Houstona TOC ) 4.9-8.8 mg/L Br- ) 72-134 µg/L (0.90-1.68 µM)
MWD TOC ) 3.3 mg/L Br- ) 220 µg/L (2.75 µM)
Corpus Christi TOC ) 4.7 mg/L Br- ) 412 µg/L (5.16 µM)
HAA
µg/L
mole fraction
µg/L
mole fraction
µg/L
mole fraction
µg/L
mole fraction
MCAA DCAA TCAA MBAA DBAA TBAA BrClAA BrCl2AA Br2ClAA
BDLb
0.00 0.10 0.70 0.00 0.00 0.00 0.00 0.20 0.00
1.29 12.7 6.89 BDL BDL BDL 4.68 5.28 2.60
0.06 0.45 0.19 0.00 0.00 0.00 0.12 0.12 0.05
1.17 7.02 5.07 1.78 9.18 BDL 10.8 12.2 5.37
0.04 0.19 0.11 0.04 0.14 0.00 0.21 0.20 0.07
BDL 5.45 1.41 BDL 8.39 BDL 6.73 8.75 3.52
0.00 0.23 0.05 0.00 0.21 0.00 0.21 0.23 0.08
∑HAA5 ∑HAA9
20.6 27.1
a
2.15 18.4 BDL BDL BDL BDL 6.55 BDL
20.9 33.4
24.2 52.6
Houston, TX, finished drinking water was produced from a blend of two source waters.
of the total HAAs on a mole fractional basis in the finished water from PWSC, which contained only 50.6 µg/L (0.63 µM) Br- in the source water. These results confirm the laboratory findings that the three bromochloro species are significant species formed during the chlorination of bromide-containing waters. It should be noted, however, that the stability of the more highly brominated HAA species has been questioned (23). Additional research is needed to determine the degree to which these species persist in water distribution systems.
Discussion and Conclusions HAA Formation and Speciation in Chlorinated Extracts. The results of the chlorination studies suggest that bromochloro HAA species are readily formed from the chlorination of humic substances in the presence of bromide ion. In the present study, these species constituted at least 10% of the total HAAs in waters containing as little as 1.2 µM Br- (0.1 mg/L). In this region of fairly low bromide concentration, the principal species observed, in order of significance based on quantitative formation, were TCAA, DCAA, BrCl2AA, and BrClAA. At higher bromide concentrations, in the range of 6-15 µM Br-, BrCl2AA was the principal species formed. The presence of the bromochloro species at significant levels relative to other HAA species was confirmed in finished drinking waters. These species are not currently regulated in drinking water, and their health effects and occurrence are not known. The results of this study suggest that these compounds are likely to be present in typical chlorinated drinking waters at significant concentrations. It is likely that characterization of the total HAA concentration by measurement of only MCAA, DCAA, TCAA, MBAA, and DBAA concentrations, as specified in the proposed Disinfectants/Disinfection Byproducts Rule, is an incomplete description of and may appreciably underestimate the overall presence of HAAs in finished drinking waters. This issue may be of particular concern to utilities treating waters with relatively high bromide concentrations (>0.2 mg/L), where the bromochloro species may well constitute more than 50% of the total HAA concentration. HAA speciation is dependent on the ratio of bromide ion to chlorine. Speciation was similar for the two aquatic
15.3 34.3 b
BDL, below detection limits.
extracts studied, and this suggests that the effect of bromide ion on HAA speciation may be independent of the source of natural organic material. The two extracts showed similar speciation patterns despite the fact that Myrtle Beach extract appeared to be approximately two times as reactive as Palm Beach extract in terms of quantitative HAA formation from chlorination. Smooth curves were observed for the patterns of HAA formation as a function of bromide ion concentration. There are several other factors that were held constant in this study that may also influence HAA speciation. These factors include chlorine dose, reaction time, TOC concentration, and reaction temperature. Decreasing the pH of chlorination appeared to have a greater impact on increasing the formation of di- and trihalogenated species containing bromine as compared to species containing only chlorine. This may reflect lesser stability of the species containing bromine in environments of elevated pH or greater substitution reactivity of HOBr relative to HOCl at lower pH. In chlorinated waters, the two extracts showed nearly identical HAA speciation into mono-, di-, and trihalogenated species, both at pH 8 and pH 6. In the absence of bromide, relative formation of TCAA compared to DCAA on a weight basis was approximately 2.4:1. This was under chlorination conditions of 2 mg of chlorine as Cl2:1 mg of TOC. These results are similar to those reported previously by Miller and Uden (26) of a weight ratio of TCAA/DCAA ≈ 2.25 at a chlorine to carbon weight ratio of 2. One might expect a different distribution at a different chlorine to carbon ratio. Miller and Uden (26) showed that relative formation of TCAA and DCAA is dependent on chlorine dose, with the more highly chlorinated species being favored by high chlorine dose. These observations suggest that the formation of di- and trihalogenated HAA species may proceed through common dihalogenated intermediates that can either be oxidized or hydrolyzed to the dihalogenated HAA species or further halogenated to form the trihalogenated HAA species. This idea is similar to the mechanisms of HAA formation that have been proposed by Reckhow and Singer (27). The present study suggests that different sources of natural organic material may behave similarly in this respect, and the finding that the distribution of mono-, di-, and trihalogenated species is independent of Br- concentration suggests that the HAA species containing
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bromine are probably being formed through the same chemical pathways as MCAA, DCAA, and TCAA.
trihalogenated species
Modeling of HAA Speciation in Chlorinated Extracts Based on Fundamental Probability Theory. Based on the idea that the speciation of the HAAs is primarily a function of the ratio of the reactivities of HOBr to HOCl for halogen substitution into natural organic material, model equations were derived from probability theory to describe the distributions of individual HAA species within the groupings of mono-, di-, and trihalogenated species. The following assumptions were made in the development of the equations:
xTCAA )
(1) The two monohalogenated species are formed through the same chemical pathways, the three dihalogenated species are formed through the same pathways, and the four trihalogenated species are formed through the same pathways. (2) The probability of formation of a particular species within a group is a function only of the ratio of reactivities of HOBr to HOCl. (3) The mole fraction of total HAAs present as mono-, di-, or trihalogenated species remains constant over varying bromide concentration. In the derived equations, a factor γ is introduced to account for the difference in reactivity between HOBr and HOCl in reactions that form HAAs. Values for γ were determined empirically. The following equations were derived from probability theory:
monohalogenated species xMCAA )
1 [HOBr] 1+γ [HOCl]
(1)
[HOBr] [HOCl] xMBAA ) [HOBr] 1+γ [HOCl] γ
(2)
xMCAA is the mole fraction of the total monohalogenated species present as MCAA, etc.
dihalogenated species xDCAA )
1 [HOBr] [HOBr] 1 + 2γ + γ2 [HOCl] [HOCl]
(
)
[HOBr] [HOCl] xBrClAA ) [HOBr] [HOBr] 1 + 2γ + γ2 [HOCl] [HOCl]
2
(3)
2γ
(
( ) (
)
[HOBr] 2 [HOCl] xDBAA ) [HOBr] [HOBr] 1 + 2γ + γ2 [HOCl] [HOCl] γ2
)
2
2
(4)
(5)
xDCAA is the mole fraction of the total dihalogenated species present as DCAA, etc.
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1 [HOBr] [HOBr] 1 + 3γ + 3γ2 [HOCl] [HOCl]
(
) ( 2
[HOBr] [HOCl] xBrCl2AA ) [HOBr] [HOBr] 1 + 3γ + 3γ2 [HOCl] [HOCl]
+ γ3
)
[HOBr] [HOCl]
3
(6)
3γ
(
) (
( (
) ) (
2
+ γ3
)
[HOBr] 3 [HOCl] (7)
[HOBr] 2 [HOCl] xBr2ClAA ) [HOBr] [HOBr] 2 [HOBr] 3 1 + 3γ + γ3 + 3γ2 [HOCl] [HOCl] [HOCl] (8) 3γ2
(
)
)
[HOBr] 3 [HOCl] xTBAA ) [HOBr] [HOBr] 2 [HOBr] 1 + 3γ + γ3 + 3γ2 [HOCl] [HOCl] [HOCl] γ3
(
) (
)
3
(9) xTCAA is the mole fraction of the total trihalogenated species present as TCAA, etc. Initial HOBr and HOCl concentrations were used in model calculations, and it was assumed that the formation of HOBr from the reaction of Br- with HOCl is rapid and occurs before reaction of the natural organic material with HOCl. Hence, in applying these equations, the concentration of HOBr was set equal to the initial bromide concentration, and the concentration of HOCl was set equal to the difference between the applied HOCl concentration and the moles of HOBr produced from reaction with bromide. Results of this modeling effort are shown in Figure 9a-c where the lines represent the model equations and the points represent empirical data obtained from Myrtle Beach samples chlorinated at pH 8. The probabilistic model shows the same pattern of HAA speciation as was observed experimentally. The fact that choosing a γ value of 10 fit the data well suggests that under the conditions of these experiments bromine was approximately 10 times more reactive than chlorine in substitution reactions forming HAAs. The model equations underpredict MBAA, DBAA, and TBAA mole fractions in regions of high bromide concentration. The equations also tend to overpredict BrClAA and Br2ClAA mole fractions. One explanation for these apparent discrepancies between experimental observations and model predictions is that the model assumes that the halogenation reactions have proceeded to completion. The experimental measurements, however, were all made after 24 h, at which time a free chlorine residual still persisted for all test solutions. A higher percentage of brominated byproducts would be expected under these conditions compared to the model predictions. The underprediction of MBAA, DBAA, and TBAA mole fractions may also be due in part to the “recycling” of some bromide ion that was suggested by the observation of increased chlorine consumption in waters with high bromide concentrations. Recycling of bromide could increase the effective activity of bromine relative to chlorine.
a
FIGURE 10. Modeling trihalomethane speciation [experimental data from Bird (28)].
b
c
FIGURE 9. Modeling (a) mono-, (b) di-, and (c) trihalogenated HAA speciation in chlorinated Myrtle Beach extract, pH 8.
Such an effect is not presently accounted for in the model equations, although the effect of recycling is not expected to be great in view of the results illustrated in Figure 6. Another factor that was not accounted for in the model equations was TOC concentration. It is expected that if the [HOBr]/[HOCl] ratio remains constant and the halogenation reaction is allowed to proceed to completion, HAA speciation will be independent of TOC concentration. Because this is not typically the case in chlorination practice,
further study of the effect of TOC concentration on HAA speciation is recommended. It was expected that trihalomethane (THM) speciation could also be described by the same equations derived for the trihalogenated HAAs. THM speciation data were obtained from Bird (28) for chlorinations of Aldrich humic acid at 1 mg/L TOC, a chlorine dose of 5 mg/L as Cl2 (70.5 µM), and 0-4 mg/L (0-50 µM) bromide. The model equations derived for the trihalogenated HAAs show the same pattern for THM speciation as observed experimentally by Bird (28) and described THM speciation well for a γ value of 20, as shown in Figure 10. These findings suggest that THM and HAA speciation patterns, and perhaps those of other halogenated disinfection byproducts, resulting from the chlorination of bromide-containing waters can be predicted from fundamental probabilistic considerations. Accordingly, this work along with further study of the effects of chlorine dose, TOC concentration, reaction time, and temperature on HAA speciation may provide a framework for mathematically modeling HAA speciation in chlorinated waters and for predicting their occurrence and speciation in finished drinking water. HAA Formation and Speciation in Chloraminated Extracts. Chloramination is an effective strategy for decreasing HAA formation. In this work, total HAA formation was decreased on the order of 90-95% in chloraminated waters compared to chlorinated waters. Formation of trihalogenated species is greatly suppressed by chloramination, and less bromine incorporation into the HAAs is observed in chloraminated waters compared to chlorinated waters. DCAA formation, however, will continue to be an issue even in chloraminated waters. Formation of HAAs from chloramination may be interpreted as a special case of chlorination with very low chlorine doses, assuming that HAA formation is occurring through the reaction of humic substances with small amounts of free chlorine in equilibrium with monochloramine. Such an explanation appears to agree with the observed predominance of diand monohalogenated HAA species over the trihalogenated forms in chloraminated waters.
Acknowledgments The authors are thankful to Gregory W. Harrington for the collection of the humic substances, to Dr. Avram Gold for the synthesis of bromodichloroacetic acid, to Dr. Yuefeng
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Xie for the synthesis of dibromochloroacetic acid, to Dr. Howard S. Weinberg for assistance in the development of analytical methods, and to Dr. Gary L. Amy for the analysis of bromide ion concentrations in source waters. We are additionally thankful to the following utilities for providing finished water samples: Metropolitan Water District of Southern California, City of Corpus Christi, Philadelphia Suburban Water Co., and City of Houston. This research was supported in part by the American Water Works Association Research Foundation.
Glossary HAAs MCAA DCAA TCAA MBAA DBAA TBAA BrClAA BrCl 2 AA Br 2 ClAA ∑HAA5 ∑HAA9 γ
haloacetic acids chloroacetic acid dichloroacetic acid trichloroacetic acid bromoacetic acid dibromoacetic acid tribromoacetic acid bromochloroacetic acid bromodichloroacetic acid dibromochloroacetic acid sum of the five regulated HAAs (MCAA + DCAA + TCAA + MBAA + DBAA) sum of all nine brominated and chlorinated HAAs ratio of reactivities of HOBr vs HOCl
Literature Cited (1) Johnson, J. D.; Christman, R. F.; Norwood, D. L.; Millington, D. S. Environ. Health Perspt. 1982, 46, 63. (2) Christman, R. F.; Johnson, J. D.; Pfaender, F. K.; Norwood, D. L.; Webb, M. R. In Water Chlorination: Environmental Impact and Health Effects, Vol. 3; Ann Arbor Science Publishers: Ann Arbor, MI, 1980; pp 75-83. (3) Norwood, D. L.; Johnson, J. D.; Christman, R. F.; Millington, D. S. In Water Chlorination: Environmental Impact and Health Effects, Vol. 4, Book 1; Ann Arbor Science Publishers: Ann Arbor, MI, 1983; pp 191-200. (4) Reckhow, D. A.; Singer, P. C. J. Am. Water Works Assoc. 1984, 76 (4), 151. (5) Uden, P. C.; Miller, J. W. J. Am. Water Works Assoc. 1983, 75, 524. (6) Krasner, S. W.; McGuire, M. J.; Jacangelo, J. G.; Patania, N. L.; Reagan, K. M.; Aieta, E. M. J. Am. Water Works Assoc. 1989, 81 (8), 41. (7) Reckhow, D. A.; Singer, P. C. J. Am. Water Works Assoc. 1989, 82 (4), 173.
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(8) Pourmoghaddas, H.; Stevens, A. A.; Kinman, R. N.; Dressman, R. C.; Moore, L. A.; Ireland, J. C. J. Am. Water Works Assoc. 1993, 85 (1), 82. (9) Herren-Freund, S. L.; Pereira, M. A.; Khoury, M. D.; Olson, G. Toxicol. Appl. Pharmacol. 1987, 90, 183. (10) Bull, R. J.; Sanchez, I. M.; Nelson, M. A.; Larson, J. L.; Lansing, A. J. Toxicology 1990, 63, 341. (11) DeAngelo, A. B.; Daniel, F. B.; Stober, J. A.; Olson, G. R. Fundam. Appl. Toxicol. 1991, 16, 337. (12) Mather, G. G.; Exon, J. H.; Koller, L. D. Toxicology 1990, 64, 71. (13) Smith, M. K.; Randall, J. L.; Read, E. J.; Stober, J. A. Teratology 1989, 40, 445. (14) Smith, M. K.; Randall, J. L.; Read, E. J.; Stober, J. A. Teratology 1992, 46, 217. (15) Katz, R.; Tai, C. N.; Diener, R. M.; McConnell, R. F.; Semonick, D. E. Toxicol. Appl. Pharmacol. 1981, 57, 273. (16) Amy, G.; Siddiqui, M.; Zhai, W.; DeBroux, J.; Odem, W. National Survey of Bromide Ion in Drinking Water Sources and Impacts on Disinfection By-Product Formation; American Water Works Association Research Foundation: Denver, CO, 1995 (in press). (17) Thurman, E. M.; Malcolm, R. L. Environ. Sci. Technol. 1981, 15, 463. (18) Singer, P. C.; Harrington, G. W.; Cowman, G. A.; Smith, M. E.; Schechter, D. S.; Harrington, L. J. Proceedings of the 1994 American Water Works Association Annual Conference; American Water Works Association: Denver, CO, 1995 (in press). (19) Standard Methods for the Examination of Water and Wastewater; Clesceri, L. S., Greenberg, A. E., Trussell, R. R., Eds.; APHA, AWWA, and WPCF: Washington, DC, 1989. (20) McGuire, M. J.; Krasner, S. W.; Reagan, K. M.; Aieta, E. M.; Jacangelo, J. G.; Patania, N. L.; Gramith, K. M. Disinfection Byproducts in United States Drinking Waters, Vol. 2; U.S. EPA and Association of Metropolitan Water Agencies: Washington, DC, 1989. (21) Zimmer, H.; Amer, A.; Rahi, M. Anal. Lett. 1990, 23, 735. (22) Xie, Y.; Rajan, R. V.; Reckhow, D. A. Org. Mass Spectrom. 1992, 27, 807. (23) Pourmoghaddas, J. Effect of Bromide on Chlorination Byproducts in Finished Drinking Water. Ph.D. Dissertation, University of Cincinnati, 1992. (24) Minear, R. A.; Bird, J. C. In Water Chlorination: Environmental Impact and Health Effects, Vol. 3; Ann Arbor Science Publishers: Ann Arbor, MI, 1985; pp 151-160. (25) Sweetman, J. A.; Simmons, M. S. Water Res. 1980, 14, 287. (26) Miller, J. W.; Uden, P. C. Environ. Sci. Technol. 1983, 17, 150. (27) Reckhow, D. A.; Singer, P. C. In Water Chlorination: Environmental Impact and Health Effects, Vol. 5; Ann Arbor Science Publishers: Ann Arbor, MI, 1985; pp 1229-1257. (28) Bird, J. C. The Effect of Bromide on Trihalomethane Formation. Masters Thesis, University of Tennessee, Knoxville, Aug 1979.
Received for review November 8, 1994. Revised manuscript received March 22, 1995. Accepted July 27, 1995.X ES9406905 X
Abstract published in Advance ACS Abstracts, October 1, 1995.
