NF Design and Operation at 98% Recovery – Two Years of Operation and CIP Results

In 2008, the City of Signal Hill developed Well No. 9 to increase reliability and redundancy to their existing water supply. The well had elevated levels of color at 50-60 color units and required treatment. The treatment project included the design and construction of the well pump and nanofiltration (NF) membrane treatment facility. Production goals for the facility focus on reduction of color and high recovery. The plant has an objective of producing treated water with color below 5 color units without significant reduction of the calcium and alkalinity in the water. The plant has a design flow of 1200 GPM, with future expansion capabilities of up to 1800 GPM. The treatment facility is designed to achieve a recovery of 98%. The design included two parallel NF trains with three stages in a 16:5:3 pressure vessels configuration. To meet both the color and recovery objectives, the system was designed with a unique hybrid configuration membrane system, with Hydranautics HydraCoRe50-LD membranes in the first two stages and Hydranautics ESNA1-LF membranes in the third stage. The higher rejection ESNA membranes in the third stage increase the overall recovery of 98% without scaling. The unique approach at Signal Hill showcases an innovative approach of membrane configurations and system controls that water suppliers can capitalize on membrane treatment while maintaining a high recovery to conserve local resources. This paper will describe the key considerations of the hybrid membrane configuration to achieve both color removal while maintaining high recovery without membrane scaling as well as more than two years of operational data. After more than a year and half of operation the system indicated a cleaning would be required. Data regarding the assessment of the fouling and the recommended cleaning regime and its effectiveness will also be presented.

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