作为美国环保局小型系统技术倡议下的一个示范项目，在加利福尼亚州弗里斯通市安装了一个预制双级过滤系统，该社区约有70人。事实证明，对于这个小型水系统，过滤系统是一个符合成本效益的选择，该系统有着长期的微生物污染和沸水订单历史。对月平均浊度为4.25-23 ntu的水源水进行双级过滤，始终产生浊度浓度远低于0的水。 5台大。使用先进的遥测设备，将关键操作数据传输到他的办公室。在工厂现场，操作员能够成功操作和维护设备，平均每月工作13小时（包括旅行时间和州规定的每周现场访问）。Freestone双级过滤系统的总成本为7.56美元/1000加仑（3.8立方米），比该场地类似规模的混凝过滤系统的估计成本低42%。 将该系统的所有权转让给索诺玛县是该项目成功的关键因素。包括10个参考文献、表格和图表。

A prefabricated dual-stage filtration system was installed as a demonstration project under the USEPA Small System Technology Initiative at Freestone, California, a community of approximately 70 people. The filtration system proved to be a cost-effective compliance option for this small water system, which had a long history of microbiological contamination and boil-water orders. Dual-stage filtration of a source water that averaged monthly turbidities of 4.25-23 ntu consistently produced water with turbidity concentrations well below 0.5 ntu. Using an advanced telemetry device that relayed key operating data to his office 13 mi. from the plant site, the operator was able to successfully operate and maintain the equipment working an average of 13 hours/month (including travel time and state-mandated weekly site visits). The overall cost for the dual-stage filtration system at Freestone was $7.56/1,000 gal (3.8 m3), 42 percent less than the estimated cost for a similarly sized coagulation-filtration system for this site. Transferring ownership of the system to Sonoma County was a key factor in the success of this project. Includes 10 references, tables, figures.