Empirically and Theoretically-Based Models for Predicting Brominated Ozonated by-Products

During water treatment ozonation of waters containing bromide ion produces 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 byproducts and bromate ion is the major inorganic byproduct derived from ozonation. 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 animals and in human beings (Kruithof 1992). The provisional guideline for bromate ion as proposed by the World Health Organization is 25 pg/L and may be exceeded in water treatment processes using ozone. Also draft drinking water regulations in the U.S. will specify a maximum contaminant level (MCL) of 10 μg/L for bromate ion and a best available treatment (BAT) of pH adjustment. Hypobromous acid (HOBr) reacts with organic precursors measured as dissolved organic carbon (DOC) to produce bromoform DBAA and total organic bromine (TOBr) indicative of various organo-bromine byproducts. Empirical models are defined for prediction of bromoform bromate ion dissolved ozone and TOBr formation as a function of seven experimental variables; DOC pH transferred ozone dose bromide ion concentration ozonation temperature reaction (incubation) 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 empirical models obtained by multiple regression analysis of experimental data.