Analysis of Bulk Sodium Hypochlorite Feedstock for the Presence of HAAs and Other DBPs [Project #4412]

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1 Analysis of Bulk Sodium Hypochlorite Feedstock for the Presence of HAAs and Other DBPs [Project #4412] ORDER NUMBER: 4412 DATE AVAILABLE: April 2013 PRINCIPAL INVESTIGATORS: Gary L. Emmert, Paul S. Simone Jr., Yin Yee Choo, Christina M. Henson, Aaron W. Brown, Thomas E. Watts III, William E. Stephens III, Jill P. Williamson, and Patricia L. Ranaivo INTRODUCTION: Chlorination is the most widely used water disinfectant process in the United States; about two-thirds of water utilities use chlorine gas and the other third uses bulk hypochlorite solutions 1. In recent years, there have been homeland security concerns that have driven many water utilities to move away from the use of chlorine gas and toward the use of alternatives to gaseous chlorine. One of the simplest alternatives is transitioning to bulk hypochlorite solutions. Snyder et al. 1 report a shift toward the use of bulk hypochlorite solutions, whether it is through traditional mechanisms, through on-site generation (OSG), or through calcium hypochlorite. About 8% of water utilities use OSG of hypochlorite, and about 8% use calcium hypochlorite as an emergency back-up disinfectant. Water chlorination is a safe and economical water disinfectant and it is unlikely that its use will be diminished in the near future. It is well known that disinfection by-products (DBPs) are found in drinking water distribution systems 2,3,4. The majority of studies focus on formation in the distribution system. Some DBPs originally thought to have formed in the distribution system actually form in bulk hypochlorite solutions. Chief among these are the oxyhalide species, particularly chlorate ion, bromate ion, and perchlorate ion 5. Recommendations have been established for the purchase, storage, handling, and use of bulk hypochlorite solutions. These are very important guidelines to help water utilities minimize the formation of oxyhalides 1,5. They provide a framework upon which to build a detailed, chemically sound program for purchasing, handling, storage, and use of bulk hypochlorite solutions. 1 Snyder, S.A., B.D. Stanford, A.N. Pisarenko, G. Gordon, M Asami Hypochlorite An Assessment of Factors that Influence the Formation of Perchlorate and Other Contaminants. AWWA and WRF 2 Krasner, S.W The formation and control of emerging disinfection by-products of health concern. Phil. Trans. R. Soc. A 367, Richardson, S.D., T.A. Ternes Water Analysis: Emerging Contaminants and Current Issues. Anal. Chem. 83, Richardson, S.D., C. Postigo Drinking Water Disinfection By-products. The Handbook of Environmental Chemistry. pp 1-45 DOI: /698_2011_125 5 Stanford, B.D., A.N. Pisarenko, S.A. Snyder, G. Gordon Perchlorate, bromate, and chlorate in hypochlorite solutions: Guidelines for utilities. J. AWWA. 103(6), 1 13

2 In contrast, organic DBPs are thought to be the product of the reaction of chlorine with natural organic matter, such as humic materials, derived from decayed plant materials present in the raw source water. The two most common classes of organic DBPs include the trihalomethanes (THMs), and the haloacetic acids (HAAs) 6. The regulated THMs include four chemical species: chloroform (CHCl 3 ), bromodichloromethane (CHBrCl 2 ), dibromochloromethane (CHBr 2 Cl), and bromoform (CHBr 3 ). The maximum contaminant level (MCL) 7 for the total concentration of these four THMs (Total THMs) is regulated and should not exceed mg L -1 in the United States 6. Similarly, there are five regulated HAAs that include monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), monobromoacetic acid (MBAA), and dibromoacetic acid (DBAA). These five HAAs species are generally referred to as HAA5 and when grouped with four additional species (bromochloroacetic acid (BCAA), tribromoacetic acid (TBAA), bromodichloroacetic acid (BDCAA), and dibromochloroacetic acid (DBCAA) are called HAA9. The total concentration of HAA5 is regulated in the United States and is generally referred to as Total HAA5. The MCL for Total HAA5 is mg L Most models of THMs and HAAs formation assume that formation occurs following chlorination and occurs in the distribution system. Much less is known about the presence of organic DBPs, such as THMs and HAAs, in bulk hypochlorite solutions. Is it possible that hypochlorite solutions contain significant concentrations of THMs and HAAs? The focus of this project was to explore this question. The answer to this question appears to be yes, at least for HAAs. Significant concentrations of three HAAs (MCAA, DCAA, and TCAA) have been detected in hypochlorite solutions. Screening measurements also demonstrated that THMs were not detected. These HAAs species may be formed during the production process, during storage, during application, or in a combination of all these times 8. Whatever the source of these three HAAs, there is a need to conduct an analytical survey of hypochlorite solutions to evaluate the potential presence (or absence) of these species. Additionally, there has been much attention focused on the presence of hexavalent chromium in public drinking water 9. Hexavalent chromium is currently regulated as total chromium with an MCL of 0.1 mg L -1 and includes both Chromium (III) and Chromium (VI). Recent work has demonstrated its widespread presence on public drinking water. The bulk hypochlorite solutions collected in this project were also subjected to screening for hexavalent chromium. 6 USEPA National Primary Drinking Water Regulations: Stage 2 Disinfectants and Disinfection Byproducts Rule: Final Rule. Fed. Reg.71, , (January 4, 2006). 7 Conventionally, units such as these are written as mg/l. However in this book, the convention mg L - 1 is used to avoid confusion when combinations of concentration units are used relating µg L -1 HAAs / mg L -1 FAC. 8 Emmert, G. Henson, C.M., Brown A.W., Simone, P.S Investigating the Presence of HAAs and THMs in Sodium Hypochlorite Feedstocks. Proceedings of WQTC EWG (Environmental Working Group) Re: Hexavalent Chromium EWG Response to Reviewer Post-Meeting Comments. August 30, 2011

3 RESEARCH OBJECTIVES: Preliminary analyses by the authors 7 indicated the presence of HAAs in bulk hypochlorite solutions from four geographically diverse regions of the country. The results indicated that the presence of HAAs in bulk hypochlorite solutions could potentially be a significant source of HAAs in finished water. Based on these preliminary findings 7, the project goal was to: Evaluate how widespread the presence of HAAs in bulk hypochlorite solution is by conducting a survey of water utilities that use hypochlorite solutions, either in bulk or generated on-site. Specifically, their purchasing (or generating), handling, and storage practices will be explored. Collect bulk hypochlorite solutions from participating utilities and subject them to detailed chemical analysis aimed at relating the HAAs concentrations to the FAC concentrations of the bulk hypochlorite solution. Identify potential carbon sources for HAAs and THMs production by evaluating the handling and use of bulk hypochlorite solutions by the utility. Estimate the concentrations of TOC necessary to form the concentrations of HAAs observed in the bulk hypochlorite solutions. Develop empirical models estimating the contribution of HAAs found in bulk hypochlorite solutions to the concentrations of HAAs found in finished drinking water. Identify any trends in the data collected with respect to temperature variation and hypochlorite ion concentration and how this relates to the quality of the bulk hypochlorite solutions and its contribution toward HAAs in drinking water. Consider the implication of recommendations made to minimize oxyhalide species and how they might affect the presence of HAAs in bulk hypochlorite solutions. RESEARCH APPROACH: A survey was conducted with water utilities that use bulk hypochlorite solutions for water chlorination. The survey was carried out in two parts. Initially, a questionnaire was completed by the water utility that collected information about the utilities practices related to purchasing, storage, handling, and use of bulk hypochlorite solution. Finally, samples of bulk hypochlorite solution were collected from each of these utilities and the bulk hypochlorite solution sample was subjected to analysis for total chlorine, THMs, HAAs, and hexavalent chromium. The results of the study are summarized with trends related to chemistry of processes that may be occurring seasonally. Initial estimates of the contribution of DBPs species found in bulk hypochlorite solutions to the concentrations of DBPs observed in finished drinking water were suggested. Several apparent trends were observed that may have seasonal implications for manufacturers and users of bulk hypochlorite solution. There were three chlorinated HAAs species (MCAA, DCAA, and TCAA) detected in significant concentrations in all of the utilities surveyed. Hypochlorite solution from three sites contained DBAA, but no other HAAs species were detected. None of the hypochlorite solutions contained significant concentrations of the four THMs species or

4 hexavalent chromium. Using the results from these studies, the HAA3/FAC ratio was calculated so that estimates of the contribution of the HAAs from the hypochlorite solution could be made. The bulk hypochlorite solution could be a significant source of HAAs in finished drinking water, but was not likely a significant source of THMs or hexavalent chromium. Additional experiments were designed to evaluate the percent contribution of the HAAs found in the bulk hypochlorite solution to the concentration of HAAs found in the finished drinking water. A carefully conceived experimental design was implemented to quantitatively establish the percent contribution of the HAAs concentrations in bulk hypochlorite solution to the finished drinking water HAAs concentrations. Three empirical models were proposed for estimating the percent contribution of the hypochlorite solution HAAs to the concentration of HAAs in finished water. The three empirical models are the Dose-Dilution Model, the Kinetic Model, and the Kinetic- Observed Model. The results of applying the models in nine different geographically varied utilities are presented. REPORT OVERVIEW: The Final Report is divided into five chapters. Chapter 1 is an overview of oxyhalide species in bulk hypochlorite solutions, recommendations for minimizing these oxyhalide species, and how these recommendations might relate to organic DBP formation. Chapter 2 describes the three empirical models and analytical methods that are used to determine the percent contribution of HAAs in bulk hypochlorite solutions to the concentrations of HAAs in drinking water. Chapter 3 describes a survey conducted of water utilities that use bulk hypochlorite solution. The results of the chemical analysis for total chlorine, THMs, HAAs, and hexavalent chromium in bulk hypochlorite solutions are presented. Trends of HAAs concentrations are detailed. Chapter 4 outlines the application of three empirical models in nine geographically separated water utilities for the prediction of the percent contribution of HAAs in bulk hypochlorite solutions to the HAAs concentrations in finished drinking water. Chapter 5 summarizes the conclusions and evaluates the recommendations of Snyder et al. 1 for the purchase, transport, storage, and handling of bulk hypochlorite solutions in terms of how they might affect the concentrations of HAAs measured in bulk hypochlorite solutions. Finally, recommendations are made for further research. CONCLUSIONS: A total of 30 individual bulk hypochlorite solutions collected from 24 utilities were analyzed for total chlorine, THMs, HAAs, and hexavalent chromium. All of the bulk hypochlorite solutions contained concentrations of HAAs that could potentially contribute to the MCL through dilution. With doses typically ranging between 1 to 4 mg/l FAC, the contribution of HAAs from the delivered bulk hypochlorite solution on average ranged from 4.1 to 16.4 µg/l of HAA5 (6.8 to 27.3 % contribution to the MCL). The average contribution of HAAs from on-site generated hypochlorite to the drinking water system ranged from 2.2 to 8.8 µg/l HAA5. Conversely, none of the bulk hypochlorite solutions contained THMs or hexavalent chromium, and thus did not

5 contribute to concentrations of THMs or hexavalent chromium in drinking water or the MCL. Apparent temperature effects that would occur seasonally were observed. The warmer months appeared to exhibit higher HAAs/FAC ratios, meaning that more HAAs would be contributed during the summer months. This data is preliminary. This chemistry needs to be studied more closely under carefully controlled laboratory conditions. The HAAs must arise from one or multiple carbon sources, apparently during the manufacturing process for bulk hypochlorite solutions. This chemistry also needs to be further explored. The three empirical models (Dose-Dilution, Kinetic, and Kinetic Observed) were used to determine the percent contribution of HAAs from the bulk hypochlorite solutions to the concentration of HAAs in the finished drinking water. The contribution of Total HAA3 from the bulk hypochlorite solutions to the First Tap using the Dose-Dilution model was 47 ± 34 %, ranging from 11 to 109 %; Kinetic model averaged 38 ± 20 % (ranging 8 to 84 %); and the Kinetic Observed averaged 29 ± 15 (ranging 7 to 46 %). These models suggest as much as a third to one-half of HAAs observed in finished water could arise from the bulk hypochlorite solutions. The HAAs concentrations in the bulk hypochlorite solutions identify the presence of a TOC source that arises during manufacturing or delivery. The minimum TOC content present during manufacturing can be calculated stoichiometrically from the HAAs concentrations. The average minimum concentration of TOC in the delivered bulk hypochlorite solution was 92 ± 50 mg/l. The on-site generated hypochlorite solutions had average minimum TOC concentrations of 3.5 ± 0.8 mg/l. RECOMMENDATIONS: The recommendations made in Snyder et al. 1 are very important recommendations to minimize the decomposition of hypochlorite ion and the subsequent formation of chlorate ion and perchlorate ion. The formation chemistry of chlorate ion and perchlorate ion are well understood and both species are regulated just as THMs and HAAs. Thus, any recommendations made by this report must also be in harmony with the chlorate and perchlorate ion recommendations 1. Fortunately, this study demonstrates that the chlorate and perchlorate ion recommendations should have little adverse effect on the presence of HAAs in bulk hypochlorite solutions. In other words, the results of this research suggest that HAA concentrations in the bulk hypochlorite solutions will not increase significantly when following the recommendations to minimize chlorate and perchlorate ion formation. The recommendations of this report are for the utilities that use bulk hypochlorite solutions should continue following the recommendations to minimize chlorate and perchlorate ion formation. Specifically, the recommendations are to: (1) dilute the bulk hypochlorite solution upon arrival at the plant; (2) store the bulk hypochlorite solution at lower temperatures; (3) control the ph of stored bulk hypochlorite solutions; (4) control the removal of transition metals by using filtered bulk hypochlorite solutions; (5) use fresh bulk hypochlorite solutions when possible; and (6) use high purity salts with on-

6 site, hypochlorite ion solution generation. These practices appear not to increase the contributions of HAAs from bulk hypochlorite solutions, but have a large impact on minimizing chlorate and perchlorate ion from bulk hypochlorite solution. RESEARCH PARTNER: American Water Works Association

Keywords Haloacetic acids, Water analysis, 2-D ion chromatography, ICS-3000

Keywords Haloacetic acids, Water analysis, 2-D ion chromatography, ICS-3000 Evaluation of Various Anion-Exchange Chemistries for the Analysis of Haloacetic Acids in Drinking Water Using -D Matrix Elimination Ion Chromatography and Suppressed Conductivity Detection White Paper