Importance of Bromine-Substituted DBP’s in Drinking Water

Lisa Wulff, Enos Inniss, Tom Clevenger

Water Resources Research Center, University of Missouri-Columbia, Columbia, USA.

DOI: 10.4236/jwarp.2013.58A004                

Abstract

Significant fractions of bromine-substituted disinfection byproducts (DBPs)—particularly trihalomethanes (THMs)— have been observed to form during treatment of water from the Missouri River. THM speciation was also noted to follow a seasonal pattern during a 2.5-year period, during which samples were collected multiple times per month. Although some treatment processes were effective at reducing the chloroform formation potential, no treatment used at this utility significantly reduced the formation of the three bromine-substituted THM species. Using chloramination rather than free chlorination for secondary disinfection, however, was effective at limiting increases in the concentration of all four regulated THM species in the distribution system.

Keywords

Disinfection By-Products; Bromine; Missouri River; Treatment; Chlorination; Chloramination

1. Introduction

Disinfection byproducts have been a contaminant of concern in drinking water since studies first were published on trihalomethane (THM) occurrence and formation during water treatment in the mid-1970s [1-3]. Information concerning the relationship between exposure to these compounds and an increased likelihood of developing certain types of cancers soon followed [4], and THMs became regulated in US drinking water in 1979 at a concentration of 100 parts per billion (ppb) as the sum of all four THM species (TTHM) [5]. In more recent years, this allowable concentration has first been lowered to 80 ppb [6], and the method for determining compliance with this maximum concentration has been modified to better ensure all water system customers will likely be receiving water that meets this standard [7]. Haloacetic acids have also become regulated at 60 ppb as the sum of the concentrations of five particular species (HAA₅) as a part of these regulations.

Although the regulatory strategy in the US and many other countries has only established a limit for TTHM as a group, studies have suggested that individual THM species pose varying degrees and types of health risks. Based on this information, the World Health Organization has suggested guidelines for maximum allowable concentrations of individual THM species [8]; although meeting these guideline values could potentially allow for greater TTHM concentrations than current US regulations, it is an acknowledgement that all THM species do not have the same effect on the human body. Cancer potency factors determined by the US EPA indicate that, at minimum, exposure to bromodichloromethane (BDCM) or dibromochloromethane (DBCM) poses an order of magnitude greater risk to human health than does chloroform; bromoform exposure presents a similar risk to that of chloroform [9]. An estimation of the relative risks that would be posed by concentrations of bromine-substituted HAAs, however, is less straightforward. HAA₅ regulations include only two of the possible brominesubstituted HAA species: monobromoacetic acid (MBAA) and dibromoacetic acid (DBAA). Monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), and trichloroacetic acid (TCAA) are also included in the regulation; the latter two of these species, however, are the only HAA species for which a cancer classification has been assigned by the US EPA [10]. Even if no regulatory changes are made, the incorporation of bromide present in source water into formed DBPs can simply affect mass-based TTHM and HAA₅ values because of the larger mass of the bromide ion relative to the chloride ion.

Studies have shown that reaction of organics with hypobromous acid (HOBr) occurs at a faster rate than reaction with hypochlorous acid (HOCl) [11,12]; rates of bromination have been found to be approximately an order of magnitude faster than chlorination at pH values applicable to most water treatment operations [13,14]. Even faster relative formation rates have been found in studies using model compounds [15]. Therefore, brominesubstituted THMs and HAAs could be formed more quickly than could their chlorine-substituted counterparts. Bromine-substituted THM formation has also been shown to be less sensitive to temperature than chloroform formation [16], perhaps making such compounds more of a year-round concern.

Bromide has also been observed to preferentially be incorporated into halogenated DBPs to a much greater extent than would be predicted by available bromine/ chlorine ratios in the water [12,17,18]. It was initially suggested by the work of Rook et al. [19] that, in water where both are present in excess concentrations, chlorine more often acts as an oxidant while bromine becomes a halogenating agent; subsequent spectroscopic measurements have supported this theory [13]. This apparent faster halogenation observed with bromine atoms over chlorine atoms is therefore the most likely reason for the preferred bromine substitution observed during the formation of halogenated disinfection byproducts. Conventional treatment processes have been found to increase yields of bromine-substituted THM species [20,21]; this presumably occurs primarily because the bromide ion: TOC ratio is increased by removal of TOC but not bromide during treatment.

Although bromine-substituted THMs may not be a significant regulatory concern at all drinking water utilities, they could potentially represent a significant fraction of TTHM for other utilities using source waters that contain both moderate DOC concentrations and sufficient bromide to yield appreciable concentrations of these DBPs. Bromide in surface water is not an issue confined to water bodies in or near coastal areas; concentrations of bromide have been found to be high enough in some major US inland waterways to yield large fractions of bromine-substituted THMs upon disinfection with free chlorine [22]. Use of a large surface water body such as the Missouri River as a water source may then be associated with higher concentrations of bromine-substituted THM species than is typically observed from other water sources in the central US. A better understanding of how concentrations of bromine-substituted THMs may vary over time in this water could assist in decisionmaking processes to keep these and other water systems in compliance with current and future DBP regulations.

2. Methods and Materials

2.1. Selected Water Treatment Plant Study

As part of a more in-depth study of the changes in bromine substitution over time at a drinking water utility treating exclusively Missouri River water, samples were collected from both the treatment process and the distribution system of Boonville, MO. This system serves approximately 10,000 customers in central Missouri and typically treats an average of 5.7 million L/day, although it has a design capacity of approximately 17.4 million L/day. During the study period, plant operations proceeded as normal so that the effects of typical operation could be observed. Because of the distribution system’s large available storage capacity relative to its customers’ usual daily demands, the treatment process usually only needs to be operated for several hours each day; water in an intermediate stage of treatment at the end of the operating day remains in the basin until treatment operations resume the following day.

Table 1 lists the major process units at this facility and locations from which samples were collected as a part of this study. The multiple sedimentation processes employed during treatment at this facility are a result of plant upgrades that resulted in the availability of additional treatment basins; current operating plans involve use of both these older and newer sets of basins to accomplish desired treatment objectives.

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	T. A. Bellar, J. J. Lichtenberg and R. C. Kroner, “The Occurrence of Organohalides in Chlorinated Drinking Waters,” Journal (American Water Works Association), Vol. 66, No. 12, 1974, pp. 703-706.
[2]	J. J. Rook, “Formation of Haloforms during Chlorination of Natural Waters,” Water Treatment and Examination, Vol. 23, 1974, pp. 234-243.
[3]	W. W. Bunn, B. B. Haas, E. R. Deane and R. D. Kleopfer, “Formation of Trihalomethanes by Chlorination of Surface Water,” Environmental Letters, Vol. 10, No. 3, 1975, pp. 205-213. doi:10.1080/00139307509435822
[4]	National Cancer Institute, “Report on the Carcinogenesis Bioassay of Chloroform,” National Cancer Institute: Bethesda, 1976.
[5]	US Environmental Protection Agency, “National Interim Primary Drinking Water Regulations: Control of Trihalomethanes in Drinking Water,” Federal Register, Vol. 44, No. 231, 1979, pp. 68624-68632.
[6]	US Environmental Protection Agency, “National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts,” Federal Register, Vol. 63, No. 241, 1998, pp. 69390-69476.
[7]	US Environmental Protection Agency, “National Primary Drinking Water Regulations: Stage 2 Disinfectants and Disinfection Byproducts Rule,” Federal Register, Vol. 71, No. 2, 2006, pp. 388-493.
[8]	World Health Organization, “Guidelines for Drinking Water Quality,” 3rd Edition, World Health Organization, Geneva, 2008.
[9]	US Environmental Protection Agency, “Drinking Water; National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts,” Federal Register, Vol. 59, No. 145, 1994, pp. 38668-38829.
[10]	R. M. Clark and B. K. Boutin, “Controlling Disinfection By-Products and Microbial Contaminants in Drinking Water,” National Risk Management Research Laboratory, Office of Research and Development, Cincinnati, 2001.
[11]	J. M. Symons, S. W. Krasner, L. A. Simms and M. Sclimenti, “Measurement of THM and Precursor Concentrations Revisited: The Effect of Bromide Ion,” Journal (American Water Works Association), Vol. 85, No. 1, 1993, pp. 51-62.
[12]	C. J. Nokes, E. Fenton and C. J. Randall, “Modeling the Formation of Brominated Trihalomethanes in Chlorinated Drinking Waters,” Water Research, Vol. 33, No. 17, 1999, pp. 3557-3568. doi:10.1016/S0043-1354(99)00081-0
[13]	P. Westerhoff, P. Chao and H. Mash, “Reactivity of Natural Organic Matter with Aqueous Chlorine and Bromine,” Water Research, Vol. 38, No. 6, 2004, pp. 1502-1513. doi:10.1016/j.watres.2003.12.014
[14]	G. Hua, D. A. Reckhow and J. Kim, “Effect of Bromide and Iodide Ions on the Formation and Speciation of Disinfection Byproducts during Chlorination,” Environmental Science & Technology, Vol. 40, No. 9, 2006, pp. 3050-3056. doi:10.1021/es0519278
[15]	J. L. Acero, P. Piriou and U. von Gunten, “Kinetics and Mechanisms of Formation of Bromophenols during Drinking Water Chlorination: Assessment of Taste and Odor Development,” Water Research, Vol. 39, No. 13, 2005, pp. 2979-2993. doi:10.1016/j.watres.2005.04.055
[16]	R. S. Summers, S. M. Hooper, H. M. Shukairy, G. Solarik and D. Owen, “Assessing DBP Yield: Uniform Formation Conditions,” Journal (American Water Works Association), Vol. 88, No. 6, 1996, pp. 80-93.
[17]	H. Pourmoghaddas, A. A. Stevens, R. N. Kinman, R. C. Dressman, L. A. Moore and J. C. Ireland, “Effect of Bromide Ion on Formation of HAAs During Chlorination,” Journal (American Water Works Association), Vol. 85, No. 1, 1993, pp. 82-87.
[18]	B. G. Oliver, “Effect of Temperature, pH, and Bromide Concentration of the Trihalomethane Reaction of Chlorine with Aquatic Humic Material,” In: R. L. Jolley, W. A. Brungs and R. B. Cumming, Eds., Water Chlorination: Environmental Impact and Health Effects, Ann Arbor Science, Inc., Ann Arbor, 1980, pp. 141-149.
[19]	J. J. Rook, A. A. Gras, B. G. van der Heijden and J. de Wee, “Bromide Oxidation and Organic Substitution in Water Treatment,” Journal of Environmental Science and Health, Part A, Vol. 13, No. 2, 1978, pp. 91-116. doi:10.1080/10934527809374796
[20]	Y. C. Soh, R. Roddick and J. van Leeuwen, “The Impact of Alum Coagulation of the Character, Biodegradability, and Disinfection By-Product Formation Potential of Reservoir Natural Organic Matter (NOM) Fractions,” Water Science and Technology, Vol. 28, No. 6, 2008, pp. 1173-1179.
[21]	D. Gang, T. E. Clevenger and S. K. Banerji, “Effects of Alum Coagulation on Speciation and Distribution of Trihalomethanes (THMs) and Haloacetic Acids (HAAs),” Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances & Environmental Engineering, Vol. 40, No. 3, 2005, pp. 521-534. doi:10.1081/ESE-200046555
[22]	R. E. Rathbun, “Speciation of Trihalomethane Mixtures for the Mississippi, Missouri, and Ohio Rivers,” Science of the Total Environment, Vol. 180, No. 2, 1996, pp. 125-135. doi:10.1016/0048-9697(95)04938-X
[23]	US Geological Survey, “Surface-Water Data for the Nation,” 2012. http://waterdata.usgs.gov/nwis/sw
[24]	R. C. Hoehn, C. W. Randall, F. A. Bell and P. T. B. Shaffer, “Trihalomethanes and Viruses in a Water Supply,” Journal of Environmental Engineering Division ASCE, Vol. 103, No. EE5, 1977, pp. 803-814.
[25]	M. D. Arguello, C. D. Chriswell, J. S. Fritz, L. D. Kissinger, K. W. Lee, J. J. Richard and H. J. Svec, “Trihalomethanes in Water: A Report on the Occurrence, Seasonal Variation in Concentrations, and Precursors of Trihalomethanes,” Journal (American Water Works Association), Vol. 71, No. 9, 1979, pp. 504-508.
[26]	J. N. Veenstra and J. L. Schnoor, “Seasonal Variations in Trihalomethane Levels in an Iowa River Water Supply,” Journal (American Water Works Association), Vol. 72, No. 10, 1980, pp. 583-590.
[27]	L. Liang and P. C. Singer, “Factors Influencing the Formation and Relative Distribution of Haloacetic Acids and Trihalomethanes in Drinking Water,” Environmental Science & Technology, Vol. 37, No. 13, 2003, pp. 2920-2928. doi:10.1021/es026230q
[28]	L. Heller-Grossman, J. Manka, B. Limoni-Relis and M. Rebhun, “Formation and Distribution of Haloacetic Acids, THM and TOX in Chlorination of Bromide-Rich Lake Water,” Water Research, Vol. 27, No. 8, 1993, pp. 1323-1331. doi:10.1016/0043-1354(93)90219-8
[29]	S. D. Boyce and J. F. Hornig, “Reaction Pathways of Trihalomethane Formation from the Halogenation of Dihydroxyaromatic Model Compounds for Humic Acid,” Environmental Science & Technology, Vol. 17, No. 4, 1983, pp. 202-211.
[30]	M. J. Farré, J. Reungoat, F. X. Argaud, M. Rattier, J. Keller and W. Gernjak, “Fate of N-Nitrosodimethylamine, Trihalomethane and Haloacetic Acid Precursors in Tertiary Treatment Including Biofiltration,” Water Research, Vol. 45, No. 17, 2011, pp. 5695-5704. doi:10.1021/es60157a014
[31]	J. L. Schnoor, J. L. Nitzschke, R. D. Lucas and J. N. Veenstra, “Trihalomethane Yields as a Function of Precursor Molecular Weight,” Environmental Science & Technology, Vol. 13, No. 9, 1979, pp. 1134-1138.
[32]	P. C. Singer, H. S. Weinberg, K. Brophy, L. Liang, M. Roberts, I. Grisstede, S. Krasner, H. Baribeau, H. Arora and I. Najm, “Relative Dominance of Haloacetic Acids and Trihalomethanes in Treated Drinking Water,” Awwa Research Foundation/American Water Works Association, Denver, 2002.
[33]	T. S. Norman, L. L. Harms and R. W. Looyenga, “The Use of Chloramines to Prevent Trihalomethane Formation,” J. AWWA, Vol. 72, No. 3, 1980, pp. 176-180.
[34]	S. A. Hubbs, D. Amundsen and P. Olthius, “Use of Chlorine Dioxide, Chloramines, and Short-term Free Chlorination as Alternative Disinfectants,” Journal (American Water Works Association), Vol. 73, No. 2, 1981, pp. 97-101.
[35]	G. Hua and D. A. Reckhow, “DBP Formation during Chlorination and Chloramination: Effect of Reaction Time, pH, Dosage and Temperature,” Journal (American Water Works Association), Vol. 100, No. 8, 2008, pp. 82-95. doi:10.1016/j.jhazmat.2008.05.058
[36]	J. Lu, T. Zhang, J. Ma and Z. Chen, “Evaluation of Disinfection By-Products Formation during Chlorination and Chloramination of Dissolved Natural Organic Matter Fractions Isolated from a Filtered River Water,” Journal of Hazardous Materials, Vol. 162, No. 1, 2009, pp. 140-145. doi:10.1016/j.watres.2007.01.032
[37]	G. Hua and D. A. Reckhow, “Comparison of Disinfection Byproduct Formation from Chlorine and Alternative Disinfectants,” Water Research, Vol. 41, No. 8, 2007, pp. 1667-1678.