1981年11月，科罗拉多州高地供水和卫生区发生了一次水传播贾第虫病暴发。虽然爆发疫情的直接原因是泵故障导致氯接触时间缩短，但电厂存在许多设计和运行缺陷。缺乏化学预处理、反冲洗程序不当、原水在过滤器中的应用不当，以及未能监测工厂状况，都是疫情爆发的原因。浑浊度和细菌学记录没有显示任何问题，证实了多屏障技术的正确设计、安装和操作在预防水传播贾第虫病暴发中的关键作用。多屏障技术包括化学添加，用于混凝、沉淀和过滤，然后进行消毒。包括13个参考文献、图表。

In November 1981, a waterborne giardiasis outbreak occurred at the Highlands Water and Sanitation District in Colorado. Although the immediate cause of the outbreak was reduced chlorine contact time because of a pump failure, numerous design and operational deficiencies existed at the plant. Lack of chemical pretreatment, improper backwashing procedures, poor application of raw water to the filter, and failure to monitor plant conditions all contributed to the outbreak. Turbidity and bacteriological records did not indicate any problems, confirming the crucial role of proper design, installation, and operation of the multibarrier technique in preventing waterborne giardiasis outbreaks. The multibarrier technique includes chemical addition for coagulation-flocculation, sedimentation, and filtration followed by disinfection. Includes 13 references, figures.