Pilot-Scale and Full-Scale Evaluation of the Chlorine-Ammonia Process for Bromate Control During Ozonation

An innovative approach to minimize bromate formation using sequential chlorine and ammonia (Cl2-NH3 process) was developed at pilot scale and validated in a full-scale drinking water facility. Pilot-scale results showed the Cl2-NH3 process minimized bromate formation by 65–95% compared to 40–70% using ammonia only. A 90-day full-scale evaluation confirmed the Cl2-NH3 process could prevent bromate concentrations from exceeding 10 μg/L. Full-scale implementation of the Cl2-NH3 process allowed an increase in ozone exposure level from 3.0 mg-min/L to 8.6 mg-min/L at 15.1°C. The increased exposure level is important as drinking water utilities strive to meet more stringent drinking water regulations such as Cryptosporidium inactivation.