配水系统中的微生物质量反映了原水特性、处理工艺配置和配水系统内的物理条件。通过案例研究，作者讨论了与氯需求有关的各种生物膜问题；原水pH值的季节性波动；冷水温度（降低消毒效果）；改进处理方法，以优化消毒副产物形成的减少；消毒应用点的变化；使用颗粒活性炭过滤器（这可能为特殊微生物种群提供优势）或生物活性炭； 以及消毒剂替代品（二氧化氯、高锰酸钾和臭氧）。减少处理屏障冗余或试图控制消毒副产物的形成，可能会对配水系统的水质产生不利影响。配水系统中的不良水质最终可能导致管段生物膜定植、味觉和气味投诉以及大肠菌群的增加。其他案例研究被用来说明这个问题。

Microbial quality in the distribution system is a reflection of raw source water characteristics, treatment process configurations, and the physical conditions within the distribution system. Using case studies, the author discusses various biofilm problems that relate to chlorine demand; seasonal fluctuations in raw water pH; cold water temperatures (which decreases disinfection effects); treatment modifications to optimize reductions in disinfection byproduct formation; changes in the point of application of disinfection; the use of granular activated carbon filters (which may provide opportunities for specialized microbial populations to become predominant) or biological activated carbon; and disinfectant alternatives (chlorine dioxide, potassium permanganate, and ozone). Adverse effects on water quality in the distribution system may accrue from reduction in treatment barrier redundancies or attempts to control the formation of disinfection byproducts. Adverse water quality in the distribution system may eventually lead to biofilm colonization of pipe sections, taste and odor complaints and increased coliform occurrences. Additional case studies are used to illustrate this problem.