洛杉矶水电局（LADWP）从南加州大都会水区（MWD）的一家批发供应商处购买了部分水。1985年，他们将消毒剂从氯改为氯胺后，分配系统中出现了不明原因的消毒剂残留量减少。MWD举办的研讨会有助于指出生物硝化作用，或氨氧化为亚硝酸盐和硝酸盐，可能是原因之一。根据这一假设，启动了一个取样程序，以确定是否发生了硝化作用，以及在何处发生了硝化作用。确定硝化作用后，讨论了从分配系统中消除硝化作用的几种方案。氯化以保持分配系统中的游离残留物被认为是处理该问题的最佳方法。客户意识、运营限制以及其他影响是，并将继续是主要的水质问题。

The Los Angeles Department of Water and Power (LADWP) purchases some of its water from a wholesale supplier in the Southern California area, the Metropolitan Water District (MWD). After their change of disinfectant from chlorine to chloramine, in 1985, unexplained disinfectant residual decreases in the distribution system occurred. Seminars conducted by MWD helped point out that biological nitrification, or oxidation of ammonia to nitrite and nitrate, could be responsible. Acting on that assumption, a sampling program was initiated to identify if and where nitrification was occurring. After nitrification was identified, several options were discussed to eliminate it from the distribution system. Chlorination to maintain a free residual in the distribution system was considered the best method for dealing with the problem. Customer awareness, operational constraints, among other impacts were, and continue to be, major water quality concerns.