Drinking water plants that filter water before sending it to their consumers must periodically clean their filters to remove the particulates that have been captured over time. Water is pumped backwards through the filter to remove these particulates through a process known as "filter backwashing." The resultant filter backwash water may contain significant levels of microbes. Many systems recycle spent filter backwash water back into their treatment plants. This recycling, when performed improperly, may increase the risk of waterborne pathogens entering treated water. Recycle practices have been identified as possible causes for three of the more recent Cryptosporidium outbreaks.

The Filter Backwash Recycling Rule requires public water systems to review their backwash water recycling practices to make sure they do not compromise microbial control. Recycled filter backwash water, sludge thickener supernatant, and liquids from dewatering processes must be returned a system’s filtration process. The Rule specifies the location within the system to which water must be returned, record keeping and reporting requirements.

To read more about this rule, visit the EPA webpage: http://www.epa.gov/OGWDW/mdbp/fbrr_qrg.pdf