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The Guadalupe Blanco River Authority (GBRA) began operation of the Western CanyonRegional Water Treatment Plant (WCRWTP), located in central Texas, in 2006. The facilityutilizes a coagulation / microfiltration membrane process to treat reservoir water. The overarchinggoal of the project was to deliver finished water with free chlorine residual to help ensurecompatibility with the existing disinfection practices of wholesale customers. Coagulation wasrequired to remove organics in order to reduce disinfection byproducts.Ferric sulfate was initially used as a coagulant. The membrane process experienced shorter thananticipated runs between chemical cleanings during the initial startup period and subsequentoperations. The membranes also did not return to the expected filtration performance aftercleaning. The clean in place (CIP) chemical waste had to be hauled by truck to a nearby facility,causing unplanned significant costs. The membrane manufacturer (Pall Corporation), GBRA and Malcolm Pirnie began acollaborative effort to identify measures to correct the operational challenges. Polyaluminumchloride (PACl) was considered as an alternative to ferric sulfate. PACl coagulants from severalmanufacturers were evaluated. Bench scale testing was performed, and then a rigorous pilottesting protocol was developed. A close dialogue with the Texas Commission on EnvironmentalQuality (TCEQ) was required to obtain prompt approval of the pilot testing program. Onceapproved, pilot testing was performed utilizing an on-site membrane pilot system. The resultsrevealed a preferred PACl candidate compared to ferric sulfate.Numerous operational and design aspects were considered and used to prepare the WCRWTP forthe changeover. The changeover was conducted in July 2007. To date,GBRA has experienced successful operation using PACl as a coagulant, as indicated by rate oftrans-membrane pressure development and flux recovery after cleaning.This paper presents the methodologies used to plan for and implement thecoagulant changeover, and the consequences including residuals management, overall cost impacts,and lessons learned. Includes table, figures.

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Edition: Vol. - No. Published: 11/01/2009 Number of Pages: 10File Size: 1 file , 1.4 MB