Wat. Res. Vol. 35, No. 4, pp. 891–900, 2001 # 2001 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0043-1354/01/$ - see front matter PII: S0043-1354(00)00334-1 WATER QUALITY FACTORS AFFECTING BROMATE REDUCTION IN BIOLOGICALLY ACTIVE CARBON FILTERS MARY JO KIRISITS 1 *, VERNON L. SNOEYINK 1M , HATICE INAN 2 , JOANNE C. CHEE-SANFORD 3 , LUTGARDE RASKIN 1M and JESS C. BROWN 1 1 University of Illinois at Urbana-Champaign, 3230 Newmark Civil Engineering Laboratory, Department of Civil and Environmental Engineering, 205 North Mathews Avenue, Urbana, IL 61801, USA; 2 Department of Environmental Engineering, Gebze Institute of Technology, P.O. Box 141, 41400 Gebze/ Kocaeli, Turkey and 3 Department of Animal Sciences, 454 Animal Sciences Laboratory, University of Illinois at Urbana-Champaign, 1207 West Gregory, Urbana, IL 61801, USA (First received 1 February 2000; accepted in revised form 1 June 2000) Abstract}Biological removal of the ozonation by-product, bromate, was demonstrated in biologically active carbon (BAC) filters. For example, with a 20-min EBCT, pH 7.5, and influent dissolved oxygen (DO) and nitrate concentrations 2.1 and 5.1 mg/l, respectively, 40% bromate removal was obtained with a 20 mg/l influent bromate concentration. In this study, DO, nitrate and sulfate concentrations, pH, and type of source water were evaluated for their effect on bromate removal in a BAC filter. Bromate removal decreased as the influent concentrations of DO and nitrate increased, but bromate removal was observed in the presence of measurable effluent concentrations of DO and nitrate. In contrast, bromate removal was not sensitive to the influent sulfate concentration, with only a slight reduction in bromate removal as the influent sulfate concentration was increased from 11.1 to 102.7 mg/l. Bromate reduction was better at lower pH values (6.8 and 7.2) than at higher pH values (7.5 and 8.2), suggesting that it may be possible to reduce bromate formation during ozonation and increase biological bromate reduction through pH control. Biological bromate removal in Lake Michigan water was very poor as compared to that in tapwater from a groundwater source. Bromate removal improved when sufficient organic electron donor was added to remove the nitrate and DO present in the Lake Michigan water, indicating that the poor biodegradability of the natural organic matter may have been limiting bromate removal in that water. Biological bromate removal was demonstrated to be a sustainable process under a variety of water quality conditions, and bromate removal can be improved by controlling key water quality parameters. # 2001 Elsevier Science Ltd. All rights reserved Key words}bromate, disinfection by-product, reduction, granular activated carbon, biologically active carbon Abbreviations}BAC, biologically active carbon, BrO  3 , bromate, CUW, Champaign-Urbana water, DBP, disinfection by-product, DO, dissolved oxygen, DOC, dissolved organic carbon, EBCT, empty bed contact time, EPA, Environmental Protection Agency, GAC, granular activated carbon, LOD, limit of detection, LMW, Lake Michigan water, NH 3 , ammonia, NO 3  , nitrate, NOM, natural organic matter NOMENCLATURE m micro INTRODUCTION Ozone has been applied in drinking water treatment as a disinfectant, to oxidize taste and odor com- pounds and organic micropollutants, and to increase the biodegradability of natural organic matter (NOM) present in natural water. While the benefits of ozonation are numerous, the production of disinfection by-products (DBPs) must also be con- sidered. After ozonation of water that contained bromide, Richardson et al. (1999) observed the formation of dibromoacetonitrile and twenty unha- logenated DBPs previously unreported as ozonation by-products. von Gunten and Hoigne´ (1994) deter- mined that both molecular ozone and hydroxyl radicals can contribute to the oxidation of bromide to bromate (BrO 3  ). A survey of nine full-scale drinking water treatment plants and one pilot-scale plant using ozone showed bromate formation in the range of 52–19 mg/l (Lefebvre et al., 1995). Bromate is an especially important ozonation by-product since it has been shown to cause renal cell tumors in rats *Author to whom all correspondence should be addressed. Present address: Department of Civil Engineering, Northwestern University, Technological Institute A330, 2145 Sheridan Road, Evanston, IL 60208-3109. Tel.: 1-847-467-5710; fax: 1-847-491-4011 891