AWWA JAW54591

A pilot-scale study, based on a fractional factorial experimental design, was performed to evaluate the indirect impact of preozonation (0-1.5 mg/L) and/or the addition of powdered activated carbon (PAC) (0-20 mg/L), and the direct impact of intermediate ozone (O3) dose (1.2-3.0 mg/L), pH (6.0-7.5), and hydraulic residence time (HRT--12-18 min) on bromate (BrO3-) formation. Under the conditions of this study, neither preozonation nor PAC addition had a significant impact on BrO3- formation observed at the outlet of the pilot contactor. The most influential parameter was pH, followed by intermediate O3 dose. A cross-effect (interaction between pH and intermediate O3 dose) was also statistically significant. Consequently, the impact of pH depression on BrO3- formation was shown to be O3-dose-dependent. During these experiments, the BrO3- standard of 10 ug/L was achieved with O3 doses of < 1.6 mg/L and a pH of < 6.3. These conditions were consistent with 2-log (but not 3-log) inactivation of Cryptosporidium. Includes 24 references, tables, figures.