加利福尼亚州大都会水区已将其消毒过程从游离氯改为组合氯（氯胺），以降低三卤甲烷（THM）水平。这一变化将允许成员机构遵守美国环境保护局（USEPA）THM法规。这是美国所有公用事业公司消毒过程中最大的一次转变。在决定使用氯胺时考虑了一些问题。这些问题包括:氯和氯胺化学；消毒能力；味道和气味；对未覆盖水库和游泳池的影响；分配系统管道中氯胺残留物的有效性；氯胺对健康的影响；对大都会成员机构的影响；技术可行性和成本。包括30个参考文献、表格和图表。

The Metropolitan Water District of California has converted its disinfection process from free chlorine to combined chlorine (chloramines) to reduce trihalomethane (THM) levels. This change will allow member agencies to comply with the United States Environmental Protection Agency (USEPA) THM regulation. This involved the largest changeover in disinfection processes for any utility in the United States. A number of issues were considered in deciding to use chloramines. These issues included: chlorine and chloramine chemistry; disinfection capability; tastes and odors; effects on uncovered reservoirs and swimming pools; effectiveness of chloramine residuals in distribution system piping; health effects of chloramines; implications for Metropolitan member agencies; technological feasibility, and costs. Includes 30 references, tables, figures.