AWWA MTC64601

The Cities of Albany and Millersburg, Oregon operate a Joint Water Treatment Plant which went on-line in November 2005, using immersed membranes to treat water from the Santiam River at a capacity of 16.5 mgd. The City of Albany operates a conventional plant treating water from a canal diversion off the same source. The first round of quarterly disinfection byproduct (DBP) sampling conducted after the new plant went on-line showed elevated levels of haloacetic acids. In response to the DBP results, the Cities evaluated the use of in-line addition (no flocculation or settling provided) of a nominal dose (5 mg/L) of aluminum chlorohydrate (ACH) as a means of reducing DBP precursors ahead of the free chlorine disinfection process employed at the new plant. Full-scale testing of ACH addition was combined with bench-scale simulated distribution system (SDS) DBP testing of plant finished water to document the reduction of DBPs through the ACH addition. Testing confirmed that a 5 mg/L dose of ACH could significantly reduce HAA concentration under SDS conditions, and that monitoring raw water turbidity and chlorine demand through the plant are excellent indicators of when the coagulant dose needs to be adjusted due to changes in source water quality. Coagulant testing was performed in conjunction with performance testing of the membrane filtration system, whereby one cell of the system was operated for several 30-day test periods under controlled conditions to simulate future plant capacity requirements. The membrane system performance testing showed minimal impact on membrane fouling rates due to the ACH addition. Includes tables, figures.