Prevention of nitrification using chlorite ion: Results of a demonstration project in Glendale, Calif.

The city of Glendale, Calif., has experienced nitrification episodes in many of its distribution system reservoirs. The objective of this study was to evaluate nitrification prevention by feeding sodium chlorite to an isolated area of the Glendale distribution system that included three large reservoirs. Results from phases 1 and 3 of the study showed that nitrification was prevented from occurring in 968 reservoir over eight months. (Numbers that precede “reservoir” or “tank” indicate elevation.) For two other reservoirs, nitrification was initially controlled with chlorite ion but reestablished itself after two months. At the end of phase 2, breakpoint chlorination was practiced on 1290 reservoir and 1666 tank. All ammonia‐oxidizing bacteria in these two reservoirs were inactivated in the system before the reintroduction of chlorite. From the beginning of phase 3 until completion two and a half months later, no nitrification occurred in 1290 reservoir and 1666 tank. The results from this study demonstrated that chlorite effectively prevented the reestablishment of nitrification when it was used in reservoirs and a distribution system that was not already undergoing severe nitrification.