EMPIRICALLY AND THEORETICALLY-BASED MODELS FOR PREDICTING BROMINATED OZONATED BY-PRODUCTS

During water treatment, ozonation of waters containing bromide ion pro duces both organic and inorganic disinfection byproducts. Bromide ion concentrations in U.S. waters range from 0.01 to 2 mg/L (Krasner, 1989 ). Bromoform and dibromoacetic acid (DBAA) are the major organic bypro ducts and bromate ion is the major inorganic byproduct derived from oz onation. Bromoform is a known carcinogen and the existence of bromate ion in water supplies also is of public health concern (Lykins, 1986). Bromate ion causes renal failure and hearing loss in laboratory anima ls and in human beings (Kruithof, 1992). The provisional guideline for bromate ion as proposed by the World Health Organization is 25 mug/L and may be exceeded in water treatment processes using ozone. Also dra ft drinking water regulations in the U.S. will specify a maximum conta minant level (MCL) of 10 mug/L for bromate ion and a best available tr eatment (BAT) of pH adjustment. Hypobromous acid (HOBr) reacts with or ganic precursors, measured as dissolved organic carbon (DOC), to produ ce bromoform, DBAA and total organic bromine (TOBr), indicative of var ious organo-bromine byproducts. Empirical models are defined for predi ction of bromoform, bromate ion, dissolved ozone and TOBr formation as a function of seven experimental variables; DOC, pH, transferred ozon e dose, bromide ion concentration, ozonation temperature, reaction (in cubation) temperature, and reaction time. Rate equations obtained from the different reactions involved in the formation of bromate ion have been solved analytically, and the results have been compared with emp irical models obtained by multiple regression analysis of experimental data.