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Forsyth County, Georgia contracted with CH2M HILL to expand the Forsyth CountyWater Treatment Plant (WTP) to a rated capacity of 28 million gallon per day (mgd). The new process trains included rapidmix, clarification (plate settlers), membranes, and disinfection with sodium hypochlorite. The ZeeWeed Ultrafiltration System, manufactured by Zenon Membrane Solutions, ofGE Water effluent to thepilot membrane unit. However, once operations began, it was quickly determined thatthe polymer used by the plant was incompatible with the membranes. This was remediedby changing approaches and renting a Meurer Research, Inc. (MRI) Pilot Plate Clarifierto provide clarified water to the membrane pilot unit and to more accurately simulate theproposed process trains. The MRI clarifier was operated with alum as a coagulant and without the use ofpolymers. However, challenges still remained, including: controlling the dissolved aluminumconcentration in the clarifier effluent to prevent additional membrane fouling; a lack of operational flexibility with the raw water pumpstation and, therefore, a lack of control of the raw water flow rate to the plant; significant peaks and lows of water demand based on outdoor wateringrestrictions under Georgia Level 2 drought watering restrictions; and, cycling between operating at or near capacity and thenshutting off during the low demand periods. During periods when the plant was shut off,there was no raw water to operate the clarifier or membrane pilot units, thus creating poor clarifier performance and yielding incompletemembrane performance data. This paper discusses the challenges encountered throughout the process, including thepolymer incompatibility, dissolved aluminum concentrations, plant on-off cycle, andother challenges such as air-entrained rising floc in the clarifier and mechanicalequipment malfunctions. The paper also describes the solutions to these challenges andthe overall pilot process design. Includes reference, tables, figures.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 31File Size: 1 file , 1.1 MB