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As populations expand around the United States, especially in water stressed areas,quality raw water sources for drinking water supplies are dwindling. This puts majorstresses on drinking water suppliers and their ability to meet their respective systemdemands. Furthermore, there is a continued push towards wastewater reuse to augmenttraditional potable water demands as much as possible. With that stated, there is onesource of water that has not been fully utilized as a drinking water source, and that sourceis already at nearly all of our drinking water facilities: filter backwash water.Traditional WTPs often produce approximately 2 to 5% of its raw water flow inwastewater. Typically, this wastewater is disposed of through an NPDES permit aftersome solids separation or directed immediately to a sanitary sewer. Some WTP facilitiesdo return this water to the head of the conventional WTP for retreatment and productwater, but again, 2 to 5% of this flow would again be wasted. Possibly even moreimportantly, as many traditional WTPs are realizing a transition to MF/UF membranesystems, the wastewater from these facilities often ranges from 5 to 8% of the feed flow.This translates into a potential of an additional 50 to 100% wastewater flow at thesemembrane facilities as compared to conventional treatment.As such, the ability to produce safe and reliable drinking water from this wastewater isfeasible and cost effective with the utilization of some advanced technologies. Takingadvantage of this source is a method by which an existing treatment plant can expand itsproduction capacity by up to 5% without requiring additional withdrawal capacity fromits source water.The City of Lancaster, Pennsylvania is currently constructing two UF membrane facilities, 12 and24 mgd. At the 12 mgd facility, a number of factors presented themselves, many ofwhich are experienced at a number of other drinking water facilities, that resulted in thedesign of a secondary membrane system followed by ultraviolet disinfection prior toimmediate feed to the finished water clearwell. This facility will comply with allLTESWTR requirements for Cryptosporidium removal as well as all other drinking waterregulations. With membrane and ultraviolet technology, filter backwash water can beused as an alternative source of water supply and produce quality drinking water forsystem distribution. Includes table.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 5 File Size: 1 file , 320 KB