本文分析了76-88家公用事业公司九年来的总三卤甲烷（TTHM）和卤乙酸（HAA5）数据 1997年至2005年在密苏里州。虽然这些结果表明 自2001年以来，许多植物的TTHM和HAA5浓度显著降低 仍在违反最高污染物水平。月份 这些消毒副产物在样本中的最大浓度各不相同 对于大多数公用事业公司来说，每年都是如此。 小型系统 继续有更高的TTHM和HAA5浓度，并有更大的困难 实现法规遵从性。TTHM和HAA5中的大多数似乎是 在处理厂内形成，尽管两者都显著增加 在分配系统中可以观察到浓度。一氯胺在医疗中的应用 分配系统与显著降低的TTHM和HAA5相关 大系统中的浓度，但不适用于小系统。更高的原材料和成品总量 有机碳浓度均与显著较高的TTHM和HAA5相关 浓度。观察到符合强化凝血要求 对于大型系统（>10k）比小型系统（<10k）更好。对于小型系统， 符合强化混凝要求的公用事业公司具有较低的TTHM和 HAA5浓度高于公用事业公司，但没有出现类似的趋势 对大型系统进行观察。包括14个参考文献、表格和图表。

This paper presents an analysis of nine years of Total Trihalomethane (TTHM) and haloacetic acids (HAA5) data for 76-88 utilities in the state of Missouri for the years 1997-2005. Although these results show that since 2001, TTHM and HAA5 concentrations have decreased significantly, many plants are still in violation of the maximum contaminant levels. The month in which the maximum concentration of these disinfection byproducts occurred in the samples varied widely throughout the year, and from year to year, for most utilities. Small systems continue to have greater TTHM and HAA5 concentrations, and to have greater difficulty in achieving regulatory compliance. A majority of both TTHM and HAA5 appear to be formed within the treatment plant, even though significant increases in both concentrations are observed in distribution systems. Use of monochloramine in distribution systems was correlated with significantly lower TTHM and HAA5 concentrations in large systems, but not for small systems. Higher raw and finished total organic carbon concentration both correlated with significantly higher TTHM and HAA5 concentrations. Compliance with the enhanced coagulation requirements was observed to be better for large systems (>10k) than for small systems (<10k). For small systems, the utilities in compliance with enhanced coagulation requirements had lower TTHM and HAA5 concentrations than the utilities out of compliance, though a similar trend was not observed for large systems. Includes 14 references, table, figures.