在常规处理的饮用水过滤设施中，大约3%到8%的处理水可能会因反冲洗介质过滤器而流失。过去，反洗废水通常会返回到处理过程的前端，并与正在处理的原水混合，或根据国家污染物排放消除系统（NPDES）许可证排放到地表水（见图1）。对贾第虫和隐孢子虫等原生动物以及回收反冲洗水产生的其他污染物的潜在浓度效应引起了监管机构和水务公司的关注。回收反冲洗水会增加处理过程中污染物的浓度，从而增加原生动物进入分配系统的风险。 采用中空纤维微滤膜在三个不同水质和处理工艺的地点进行了膜过滤处理反洗废水的中试试验。通过对贾第虫囊肿和隐孢子虫卵囊进行挑战性研究，证实了膜过程的物理去除能力。在膜中试系统运行期间，监测水质和运行参数，以评估工艺装置的性能。其中最重要的是能够在所用的操作条件下提供一致的微生物和颗粒去除。研究了利用膜过滤技术回收反冲洗水的可行性。

Approximately three to eight percent of water treated in conventionally treated potable water filtration facilities can be lost from backwashing the media filters to waste. In the past, backwash wastewater was typically returned to the front of the treatment process and blended with the raw water being treated, or discharged to a surface water under a National Pollution Discharge Elimination System (NPDES) permit (see Figure No. 1). The potential concentration effects for protozoans such as Giardia and Cryptosporidium, and other contaminants from recycling backwash water has raised concern among regulatory agencies and water utilities. Recycling backwash water can increase the concentration of contaminants within the treatment process and thereby increase the risk of protozoans entering the distribution system. Pilot testing membrane filtration to treat the backwash wastewater was conducted at three locations with different water quality and treatment processes using hollow fiber microfiltration membranes. The physical removal capabilities of the membrane process was confirmed by performing a challenge study with Giardia cysts and Cryptosporidium oocysts. During the operation of the membrane pilot system, water quality and operational parameters were monitored to evaluate the performance of the process unit. The most important of these is the ability to provide consistent microbial and particle removals under the operating conditions used. The feasibility of using membrane filtration to recover backwash water was then developed.