Environ. Sci. Technol. 2010, 44, 7184–7192
Concentration, Chlorination, and Chemical Analysis of Drinking Water for Disinfection Byproduct Mixtures Health Effects Research: U.S. EPA’s Four Lab Study JONATHAN G. PRESSMAN,† S U S A N D . R I C H A R D S O N , * ,‡ THOMAS F. SPETH,† RICHARD J. MILTNER,† MICHAEL G. NAROTSKY,§ E. SIDNEY HUNTER, III,§ GLENN E. RICE,| LINDA K. TEUSCHLER,| ANTHONY MCDONALD,§ SHAHID PARVEZ,| STUART W. KRASNER,⊥ HOWARD S. WEINBERG,# A. BRUCE MCKAGUE,∇ CHRISTOPHER J. PARRETT,† N A T H A L I E B O D I N , #,O R U S S E L L C H I N N , ⊥ CHIH-FEN T. LEE,⊥ AND JANE ELLEN SIMMONS§ National Risk Management Research Laboratory, U.S. EPA, Cincinnati, Ohio 45268, National Exposure Research Laboratory, U.S. EPA, Athens, Georgia 30605, National Health and Environmental Effects Research Laboratory, U.S. EPA, Research Triangle Park, North Carolina 27711, National Center for Environmental Risk Assessment, U.S. EPA, Cincinnati, Ohio 45268, Metropolitan Water District of Southern California, La Verne, California 91750, Gillings School of Global Public Health, Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina 27599-7431, and CanSyn Chem. Corp., Toronto, Canada M5S 3E5
Received December 27, 2009. Revised manuscript received April 19, 2010. Accepted April 21, 2010.
The U.S. Environmental Protection Agency’s “Four Lab Study” involved participation of researchers from four national Laboratories and Centers of the Office of Research and Development along with collaborators from the water industry and academia. The study evaluated toxicological effects of complex disinfection byproduct (DBP) mixtures, with an emphasis on reproductive and developmental effects that have been associated with DBP exposures in some human epidemiologic studies. This paper describes a new procedure for producing chlorinated drinking water concentrate for animal toxicology experiments, comprehensive identification of >100 DBPs, and * Corresponding author phone: (706) 355-8304; e-mail:
[email protected]. † National Risk Management Research Laboratory. ‡ National Exposure Research Laboratory. § National Health and Environmental Effects Research Laboratory. | National Center for Environmental Risk Assessment. ⊥ Metropolitan Water District of Southern California. # University of North Carolina. ∇ CanSyn Chem. Corp. O Current affiliation: Centre de Recherche Halieutique Me´diterrane´enne et Tropicale, Institut de Recherche et de De´veloppement, Se`te Cedex, France. 7184
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quantification of 75 priority and regulated DBPs. In the research reported herein, complex mixtures of DBPs were produced by concentrating a natural source water with reverse osmosis membranes, followed by addition of bromide and treatment with chlorine. By concentrating natural organic matter in the source water first and disinfecting with chlorine afterward, DBPs (including volatiles and semivolatiles) were formed and maintained in a water matrix suitable for animal studies. DBP levels in the chlorinated concentrate compared well to those from EPA’s Information Collection Rule (ICR) and a nationwide study of priority unregulated DBPs when normalized by total organic carbon (TOC). DBPs were relatively stable over the course of the animal studies (125 days) with multiple chlorination events (every 5-14 days), and a significant portion of total organic halogen was accounted for through a comprehensive identification approach. DBPs quantified included regulated DBPs, priority unregulated DBPs, and additional DBPs targeted by the ICR. Many DBPs are reported for the first time, including previously undetected and unreported haloacids and haloamides. The new concentration procedure not only produced a concentrated drinking water suitable for animal experiments, but also provided a greater TOC concentration factor (136×), enhancing the detection of trace DBPs that are often below detection using conventional approaches.
Introduction Complex mixtures of disinfection byproducts (DBPs) form when natural source water is disinfected with oxidants, such as chlorine. There has been concern over public health consequences of DBPs since chloroform was first discovered in drinking water in 1974 (1) and identified as a carcinogen in 1976 (2). Since then, more than 600 DBPs have been identified in drinking water; despite intense identification efforts, >50% of the total organic halogen (TOX) formed during disinfection remains unidentified (3). Concerns over DBP exposures have increased through the years due to some epidemiologic studies showing associations between consumption of chlorinated water and bladder cancer (3), and adverse reproductive outcomes, including spontaneous abortion and low birth weight at term (4). The estimated potency of DBPs investigated either individually or in defined mixtures does not account for the magnitude of effects reported in the positive epidemiologic studies, suggesting the need for toxicologic evaluation of whole DBP mixtures, including the unidentified DBPs (5, 6). To address this problem, a multidisciplinary team of researchers from four national Laboratories/Centers of the U.S. Environmental Protection Agency’s (EPA’s) Office of Research and Development initiated the research project, “Integrated Disinfection Byproducts Mixtures Research: Toxicological and Chemical Evaluation of Alternative Disinfection Treatment Scenarios” (7), also known as the “Four Lab Study”. A primary objective of the Four Lab Study is to thoroughly assess the reproductive/developmental effects of DBP mixtures through a “whole mixture” approach, integrated with extensive quantitative and qualitative chemical analyses. This objective was impossible with existing methods for preparing DBP concentrate, which, for toxicologic studies, typically involves XAD resin extraction and elution with an organic solvent (5). Principal factors against using XAD resin extraction include (a) the concentrate is produced in an organic solvent and it is difficult to redissolve the organics into a 10.1021/es9039314
2010 American Chemical Society
Published on Web 05/24/2010
water matrix required for in vivo toxicology; (b) the large concentrate volumes needed for a multigenerational rodent bioassay far exceed the amount of water that could be practically concentrated using XAD resins; and (c) some hydrophilic and volatile DBPs are lost during this procedure. In contrast, reverse osmosis (RO) membranes offer the advantage of concentrating large quantities of water more quickly than XAD, while maintaining a water matrix suitable for animal toxicologic studies. RO membranes have been used previously to concentrate natural organic matter (NOM) (8–10). We recently reported the use of RO membranes for concentrating DBPs in finished drinking waters (11, 12); the principal disadvantage of concentrating finished (treated) waters with RO was that volatile DBPs were lost during the membrane-concentration procedure. This paper describes a new method for producing drinking water concentrate by first concentrating NOM with RO membranes, and then chlorinating the NOM concentrate. This method (a) preserves a large proportion of NOM and its original hydrophilic/hydrophobic character, (b) produces DBPs in a concentrated water matrix suitable for toxicologic studies, (c) results in stable, environmentally representative DBP mixtures (when normalized to total organic carbon (TOC)); and (d) enables production of large volumes needed for animal studies. One additional benefit is a greater concentration factor for organics, such that trace DBPs that are typically below detection in conventional methods are detected and identified. Although inorganics are also concentrated, this can be controlled to acceptable levels for toxicity testing. Thus, this method not only benefits toxicologic studies, but also helps identify chemicals too low to be detected in drinking water or other environmental waters.
Materials and Methods Drinking Water Concentration, Sulfate Removal, and Chlorination. Coagulated-settled surface water from a fullscale drinking water treatment plant was concentrated using a continuous-flow process (Figure S1, Supporting Information (SI)). Settled water was pumped to two 19P37-30 Membralox ceramic ultrafiltration (UF) membranes (0.02µm pore size, Pall Corp., Port Washington, NY), which removed microbes and particulates. Ion exchange resin (Ambersep 200H hydrogen-form, Rohm and Haas, Philadelphia, PA) was used to remove calcium, magnesium, and sodium to reduce membrane fouling and osmotic pressure. RO membranes were used for concentration (165× by volume), resulting in a small loss of TOC (∼13%). Two identical RO systems (three Filmtec BW30-4040 in series, Dow, Midland, MI) were used, with a 4 L/min recycle flow rate and a variable speed piston pump to control the concentrate effluent flow rate, which was the controlling parameter for the concentration factor. Concentrate was pumped into 100 gal stainless-steel tanks; barium hydroxide (barium-to-sulfate molar ratio of 0.85:1) was added to precipitate and remove sulfate (Figure S2, SI) because sulfate levels (>3400 mg/L) in the unprecipitated concentrate caused adverse effects (diarrhea) in experimental animals (13). The final sulfate concentration was 3055 mg/L (53% removal) with 0.7 mg/L remaining barium and a small loss of TOC (∼5%). Supernatant was pumped to a 500 gal stainless-steel tank, where the concentrate (1724 L for the entire study) was pH adjusted to 6.8 (with 2 M Na2CO3 to provide neutral pH for animal experiments), filtered (0.45 µm AquaPrep 600, Pall Corp., Port Washington, NY), and stored in 16 30-gal plastic drums lined with 2.0 mil PFA (perfluoroalkoxy) bags (Welch Fluorocarbon, Dover, NH). Water quality parameters were measured and compared to ultrafiltered 1× water (UF1X) (Table S1, SI). Final TOC was 318 mg/L for a concentration factor that was 136 times as great as that of the UF1X.
RO concentrate was held at 4 °C in the dark with minimal headspace until each batch was chlorinated as needed (every 5-14 days) over the course of the animal studies (125 days). Before each chlorination event, concentrate from a single drum was pumped into a 30 gal stainless-steel drum and warmed to room temperature (19.4 ( 0.9 °C). The drum was lined with 2.5 mil Modified-PTFE (polytetrafluoroethylene) (Welch Fluorocarbon, Dover, NH) and covered with floating 2.5 mil Modified-PTFE, sealed to the drum liner with Teflon tape. The cover had two ports for pumping concentrate in/ out, evacuating headspace, and adding potassium bromide and sodium hypochlorite (Figure S3, SI). Potassium bromide was added (to achieve an equivalent concentration in 1× water of 74 µg/L bromide) to replace bromide lost during concentration (only 250 µg/L remained, prior to bromide supplementation, for a 5× membrane concentration factor) and to create a mixture of chlorinated/brominated DBPs representative of waters containing moderate bromide levels. Bromine-containing DBPs were desired because they are more genotoxic and carcinogenic than their chlorinated analogs (14) and have been associated with adverse reproductive effects in humans (4). Chlorine demand studies were conducted to determine the amount of chlorine capable of decaying to zero in 48 h (SI Figure S6), maintaining a relatively stable DBP mixture for animal studies and avoiding exposure of the animals or in vitro assays to chlorine. A chlorine:TOC ratio of 1.3 resulted in zero free chlorine residual at 48 h and a chlorine:bromide ratio of 41. An extra 24 h hold time was added to ensure full consumption of chlorine. Any water not immediately provided to animals was stored at 4 °C in the dark with limited/no headspace. The water delivery system consisted of 6 L Teflon FEP (fluorinated ethylene propylene) (5 mil) bags designed to minimize headspace in polystyrene coolers with ice packs (to keep the concentrate chilled and in the dark) and stainlesssteel tubing connections to specialized drinking valves (15). Chemical analyses of the water concentrate were conducted for each chlorination; concentrate was sampled immediately prior to placement on the animal cages (pre-exposure sample), at various time periods from arbitrarily selected cages (midexposure sample), and when the concentrate was removed from the cages (postexposure sample). Comparison of pre-, mid-, and postexposure samples allowed evaluation of DBP stability and overall animal DBP ingestion. Target Compound Analyses. EPA Methods 552.3 and 551.1 (16, 17) were used to measure nine chloro-bromo haloacetic acids (HAA9), four regulated trihalomethanes (THM4), dichloropropanone and trichloropropanone, dichloro-, bromochloro-, dibromo-, and trichloroacetonitrile, trichloroacetaldehyde (chloral hydrate), and trichloronitromethane (chloropicrin). Eight nitrosamines (Table 1) were measured using a liquid-liquid extraction-gas chromatography (GC)/ high resolution-mass spectrometry (MS) method based on the Ontario Ministry of the Environment Method E3291 (18). The remaining priority unregulated DBPs were quantified (iodo-THMs, other halomethanes, 3,3-dichloropropenoic acid, halonitriles, haloamides, haloketones, haloaldehydes, halonitromethanes, and halofuranones) based on methods published elsewhere (19–22). Methods for measuring TOC, TOX, and inorganics (e.g., bromide, bromate, chlorite, chlorate), coliforms, and heterotrophic bacteria are described elsewhere (11). Broad-Screen Analyses. Chlorinated concentrate samples (0.5 L) were extracted using a published XAD resin process (21). Half of the 1.0-mL extracts were derivatized with diazomethane. Comprehensive GC/MS analyses were performed on a high-resolution magnetic-sector mass spectrometer (Autospec, Waters, Inc., Milford, MA) equipped with an Agilent model 6890 gas chromatograph. Additional details VOL. 44, NO. 19, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. DBPs and Other Chemicals Identified or Measured in Chlorinated Water Concentrate (Pre-Exposure Samples)a percentile concentration (µg/L) compound
regulated trihalomethanes chloroform bromodichloromethane dibromochloromethane bromoform unregulated halomethanes dichloroiodomethane chlorodiiodomethane bromochloroiodomethane bromodiiodomethane dibromoiodomethane iodoform carbon tetrachlorideb regulated haloacids chloroacetic acid bromoacetic acid dichloroacetic acid dibromoacetic acid trichloroacetic acid unregulated haloacids bromochloroacetic acid bromodichloroacetic acid dibromochloroacetic acid tribromoacetic acid 2,2-dichloropropanoic acid 3,3-dichloropropanoic acid 3,3-dichloropropenoic acid cis-bromochloropropenoic acid trans-bromochloropropenoic acid trichloropropenoic acid 2-chloro-3-methylbutanoic acid 2,2-dichloro-4-oxopentanoic acid cis-chlorobutenedioic acid trans-chlorobutenedioic acid cis-bromobutenedioic acid trans-bromobutenedioic acid cis-dichlorobutenedioic acid trans-dichlorobutenedioic acid cis-bromochlorobutenedioic acid trans-bromochlorobutenedioic acid trans-2,3-dibromobutenedioic acid cis-2-chloro-3-methylbutenedioic acid trans-2-chloro-3-methylbutenedioic acid halonitriles chloroacetonitrile bromoacetonitrile dichloroacetonitrile bromochloroacetonitrile dibromoacetonitrile trichloroacetonitrile bromodichloroacetonitrile tribromoacetonitrile bromopropanenitrile haloketones chloropropanone 1,1-dichloropropanone 1,3-dichloropropanone 1,1-dibromopropanone 1,1,1-trichloropropanone 1,1,3-trichloropropanone 1-bromo-1,1-dichloropropanone 1,1,1-tribromopropanone 1,1,3-tribromopropanone 1,1,1,3-tetrachloropropanone 1,1,3,3-tetrachloropropanone 1,1,3,3-tetrabromopropanone pentachloropropanone 7186
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90
1× equivalent (µg/L)
relative amounts (broad screen analysis)
7109 3279 701 59
8188 3789 1126 98
52 24 5 0.39
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