United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati, OH 45268 Research and Development EPA/600/S2-91/036 Sept. 1991 ^ EPA Project Summary Effect of Bromide on Chlorination Byproducts in Finished Drinking Water Hossein Pburmoghaddas Whenever natural water or humic sub- stances are chlorinated, significant con- centrations of trihalomethanes (THMs) and haloacetic acids (HAAs) are pro- duced. Bromide concentration In raw water is a significant factor in the forma- tion of chlorinatlon byproducts in fin- ished drinking water. To investigate the role of bromide ion concentration on formation and speciation of non-THM chlorinatlon organic byproducts, a two- block, full-factorial matrix was designed to statistically evaluate the influence of various parameters that are relevant to drinking water treatment. The first block used a high chlorine dose and the sec- ond block used a low dose. The factorial design Incorporated one factor (bromide [Br"]) at four levels and two factors (time, pH) at three levels for each block. Over 1,600 experimental observations of the chlorination organic byproducts moni- tored in this study were evaluated. The study determined the range of concentration of nine HAAs, four THMs, and three dihaloacetonitrlles (DHANs) produced under different experimental conditions. The percent of total organic halogen (TOX) attributed to HAAs, THMs, and DHANs, was determined for each as a group as well as for individual THMs and HAAs. Almost all of the independent variables were positively correlated with formation of HAAs, THMs, DHANs, and TOX. Br*, in chlorinated humlcacid solu- tion, was shown to shift the distribution of THMs, HAAs, and DHANs to more bromlnated species. As with THMs In the presence of bromide, both brominated species and species containing bromine (Br) and chlorine (Cl) (bromochloroacetic acid [BCAA]), dichlorobromoacetlc acid [DCBAA], dibromochloroacetlc acid [DBCAA]) were formed forthe haloacetic acids. The resu Its of this study show that the percentage of TOX, made up of total THMs plus total HAAs, significantly in- creased With increasing pHand bromide concentration. These observations sug- gested that a higher concentration of bromide and a higher pH caused the formation of mainly bromlnated THMs and HAAs, which can be Identified and quantified by the current method. The study of the three main groups of chlori- nation byproducts indicated that THMs are the largest class of chlorination byproducts detected on a weight basis. The HAAs were found to be the second largest portion of the TOX in drinking water at high pH. This Project Summary was developed by EPA's Risk-Reduction-Engineering Laboratory, Cincinnati, OH, to announce key findings of the research project that Is fully documented In a separate report of the same title (see Project Report ordering Information at back). Introduction To control chlorination byproducts other than THMs in drinking water/more informa- tion is required to understand the factors influencing their formation. One such factor is the presence of certain inorganic chemi- cal species in the source water. For ex- ample, the effect bromide has on THM formation and THM speciation principally dependson concentration of that ion. Hence, the presence or absence of other organic byproducts of chlorination may also depend on the bromide ion concentration in the Printed on Recycled Paper ------- water. Bromide may actually substitute for Cl, producing Br-containing homologs of the more familiar chlorine species. Since bromide serves as a precursor in someof the brominated organic byproducts and probably affects the formation of some of the nonhalogenated byproducts, it is im- portant to understand its effect upon the formation of these byproducts. The pro- posed research was aimed at predicting the non-THM chlorination byproducts and their spociation based on the concentration of bromide ion in water. A predictive model for the organic byproducts would allow ma- nipulation of water quality at the watertreat- ment plant and allow for more ready compli- ance with proposed standards. Bromide can entersource waters through natural or anthropogenic processes. Natu- ral mechanisms include geologic sources and saltwater intrusion of aquifers. Bromide may also appear as a trace impurity in CI2 used for water disinfection. Of equal consequence are sources of bromide that relate directly to human activi- ties. This category includes methyl bromide and ethylene dibromide. Methyl bromide is widely used in agricultural applications to fumigate crops and soil. Once in the soil, methyl bromide breaks down into inorganic forms that are subsequently leached out Into natural waters via agricultural run-off. Ethylene dibromide is a common additive to leaded gasoline. Methyl bromide, a deg- radation product, is converted to inorganic forms before its transport to natural waters. Anothersource of bromide sometimes found in urban run-off is rock salt used to deice roads. Other bromine-containing com- pounds can enter water through sewage and industrial effluents. Bromide is present in sea water at a concentration of 65 mg/L. Once bromide is present in source water, there are no known economical treatment techniques available for removing it. The current list of byproducts targeted for regu- lation contains brominated and mixed bro- mine-chlorine species of THMs and HANs. These are known to form in bromide-con- taining waters when chlorinated. It was expected that analogous mixed halo- and bromoacetic acids might also form.Totestthis hypothesis, phenol, which gives a high yield of trichloroacetic acid (TCAA) as a percentage of TOX, has been chlorinated in the presence of bromide ion under typical formation potential reaction conditions. Given the qualification that sev- eral of the haloacetic acid standards were not available and that some reference mass spectra were not available, interpretation of the data indicate that DCBAA, DBCAA, BCAA, and tribromochloroacetic acid (TBAA) are all formed. The same array of products has since been seen when humic acids are chlorinated under similar condi- tions. The data indicate that the monobromoacetic acid (MBAA) and mixed haloacetic acids probably merit regulatory consideration for consistency with THM and DHAN precedents. The objectives of this research were to: 1. Investigate the effect of bromide ion concentration on the formation and speciation of certain chlorination byproducts other than THMs. 2. Identify the formation of haloacetic acids containing Br and Cl under dif- ferent bromide-ion concentrations and quantify them. 3. Evaluate the relationship of these or- ganic Byproducts with TOX. 4. Determine some of the conditions re- quired to control the formation of non- THM chlorination organic byproducts resulting from the disinfection process with bromide present. Procedure In this experiment, Super-Q water con- taining commercial HA (Fluka)* was used as the principal model system. The study was performed in two blocks of samples. Forthe first block, a high chlorine dose of 25 mg/L was used. Forthe second block, a low CI2 dose of 11.5 mg/L was used. The inde- pendent variables were pH, bromide, and reaction time. The three levels of pH used were 5,7, and 9.4. The pH range of 7 to 9.4 is typical of treated waters at softening and coagulation plants before chlorination. The fourbromide levels studied were 0,0.5,1.5, and 4.5 mg/L as Br". The three reaction times were 6,48, and 168 hr. All of the tests were conducted at 25°C. A two-block, full-factorial design was used to accomplish this study. The use of a full- factorial design allowed for.the effects of each variable to be evaluated with accuracy and precision. The factorial design further allowed for detection of the main and inter- action effects of the variables. The factorial design incorporated one factor (Br") at four levels and two factors (time, pH) at three levels for each block. A computer program (SAS) was used for statistical analysis. The Harvard Graphics software package was used for plotting the formation curves, and Lotus 1,2,3 was used for the calculations. 'Mention of trade names or commercial products does not constitute endorsement or recommendation for Experiments were conducted to deter- mine the percent recoveries of the HAAs using the TOX method. Two concentra- tions, high and low, and triplicate samples were used. Results and Discussion Br" in chlorinated HA solution has been shown to shift the distribution of HAAs to more brominated (DBAA, TBAA) and mixed halogenated (BCAA, DCBAA, DBCAA) spe- cies. Although TCAA and DCAA are the princi- pal halogenated organics other than THMs in the absence of bromide ion, these com- pounds decrease rapidly in a manner simi- lar to trichloromethane (TCM) with the in- cremental addition of bromide ion. This study also revealed that for the HAAs, the bromi- nated and mixed species would" I5e~the" dominant components in the presence of a high bromide ion concentration. The analysis-of-variance (ANOVA) tests, run to compare the effects of high and low CI2doses, showed no significant differences in the relative concentration of individual HAAs (except for the mixed halogenated acetic acids BCAA, DCBAA and DBCAA). The concentration of each of these three byproducts was significantly less atthe lower chlorine dose. All tests were conducted at 0.05 level of significance. There were significant interactions among the various parameters that influenced byproduct concentrations. Thefull report was submitted in fulfillment of Work Assignment No. 01-2W130, T&E Contract No. 68-03-4038, by the University of Cincinnati under sponsorship of the U.S. Environmental Protection Agency. •fru.S. GOVERNMENT PRINTING OFFICE: 1991 - 548-028/40058 ------- ------- Hosseln Poumoghaddas was with the University of Cincinnati, Cincinnati, OH 45221. Ronald C. Pressman is the EPA Project Monitor (see below). The complete report, entitled "Effect of Bromide on Chtorination Byproducts in Finished Drinking Water," (Order No. PB91-217919; Cost: $23.00, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Monitor can be contacted at: Risk Reduction Engineering Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 Official Business Penalty for Private Use $300 EPA/600/S2-91/036 ------- |