美国环境保护署（US Environmental Protection Agency）可能会实施处理法规，例如强制过滤消毒所有地下水，以防止微生物病原体、贾第鞭毛虫和病毒，这些都与越来越多的水传播疾病暴发有关。一些水系统可能会根据系统原水质量的性质或替代处理技术，寻求与所需处理法规的差异。为了开发方差分析方法，对过滤、消毒和水库蓄水的性能进行了审查。特别关注目标生物体、贾第虫和病毒的去除和灭活效率。 本文中描述的三种方差分析基于与标准处理方法相比，估计特定系统中目标生物体的去除和失活百分比。包括55个参考文献、表格和图表。

The US Environmental Protection Agency may impose treatment regulations, such as mandatory filtration-disinfection of all groundwaters to safeguard against the microbial pathogens, Giardia and viruses, that are being linked to increasing numbers of outbreaks of waterborne disease. Some water systems may seek variances from the required treatment regulations, either on the basis of the nature of the system's raw water quality or on the basis of an alternative treatment technique. In order to develop the methodology for the variance analyses, the performance capabilities of filtration, disinfection, and reservoir storage are reviewed. Particular attention is focused on the removal and inactivation efficiencies for the target organisms, Giardia and viruses. The three variance analyses described in this article are based on estimating the percent of removal and inactivation of target organisms in a particular system in comparison with standard treatment methods. Includes 55 references, tables, figures.