AWWA WQTC64100

As populations expand around the United States, especially in water stressed areas, quality raw water sources for drinking water supplies are dwindling. This puts major stresses on drinking water suppliers and their ability to meet their respective system demands. Furthermore, there is a continued push towards wastewater reuse to augment traditional potable water demands as much as possible. With that stated, there is one source of water that has not been fully utilized as a drinking water source, and that source is 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 in wastewater. Typically, this wastewater is disposed of through an NPDES permit after some solids separation or directed immediately to a sanitary sewer. Some WTP facilities do return this water to the head of the conventional WTP for retreatment and product water, but again, 2 to 5% of this flow would again be wasted. Possibly even more importantly, as many traditional WTPs are realizing a transition to MF/UF membrane systems, 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 these membrane facilities as compared to conventional treatment. As such, the ability to produce safe and reliable drinking water from this wastewater is feasible and cost effective with the utilization of some advanced technologies. Taking advantage of this source is a method by which an existing treatment plant can expand its production capacity by up to 5% without requiring additional withdrawal capacity from its source water. The City of Lancaster, Pennsylvania is currently constructing two UF membrane facilities, 12 and 24 mgd. At the 12 mgd facility, a number of factors presented themselves, many of which are experienced at a number of other drinking water facilities, that resulted in the design of a secondary membrane system followed by ultraviolet disinfection prior to immediate feed to the finished water clearwell. This facility will comply with all LTESWTR requirements for Cryptosporidium removal as well as all other drinking water regulations. With membrane and ultraviolet technology, filter backwash water can be used as an alternative source of water supply and produce quality drinking water for system distribution. Includes table.