Demonstration testing of nitrification control using chlorite in Irvine, Calif

Irvine Ranch Water District in Irvine, Calif., has experienced significant, frequent nitrification occurrences in its large, 181 sq-mi chloraminated distribution system. A demonstration-scale study investigated chlorite ion effectiveness for nitrification prevention in a reservoir consisting of two cells with identical configurations, which enabled comparison of a chlorite-treated cell (test cell; 0.3 and 0.6 mg/L) and an untreated cell (control cell; no chlorite). During the six-month study, severe nitrification (nitrite of 0.150 mg/L as N) occurred in the control cell. The test cell had less than half the nitrite concentration, with nitrite that did appear attributed to water carried over from the nitrified water in the reservoir transmission pipeline or to later onset of nitrification (based on timing and magnitude). Combined with historical and post-study results, this study provides additional evidence that chlorite is effective in minimizing nitrification.