EMPIRICAL MODELING OF BROMATE FORMATION DURING OZONATION OF BROMIDE-CONTAINING WATERS

Empirical bromate formation models were developed from observed batch ozonation data to simulate the effects of important water quality char acteristics and treatment processes on bromate formation. Data generat ed from true batch ozonation studies with an orthogonal matrix design, served as the base for development of empirical models for bromate fo rmation. The variables examined include pH, initial bromide concentrat ion, alkalinity, ozone dose, ammonia and dissolved organic carbon leve l. This array of variables was selected to evaluate the effects bf imp ortant water quality characteristics and treatment processes on the fo rmation of bromate ion during water ozonation. Limited temperature var iation data were also generated. Isolation and fractionation of natura l organic matter (NOM) by ultrafiltration and reverse osmosis membrane techniques allowed assessment of source water variations and the role of molecular size on bromate formation. Multiple linear regression of logarithmic transformations was used to generate the models. Results obtained from the empirical models indicate that bromate formation is favored at high pH, initial bromide concentration, alkalinity and high ozone dose. On the other hand, increasing DOC and ammonia concentrati on decreased bromate formation. The models also indicated that NOM iso lated from different water sources have a strong influence on bromate formation upon ozonation of model solutions composed of different memb rane isolates. Both internal and external validation of the models dem onstrated that the bromate models predicted bromate formation well. Fi nally, the models indicated that acid addition (pH depression) strateg ies can be used to control bromate formation. Copyright (C) 1996 Elsev ier Science Ltd.