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The City of Sherman, Texas, currently operates a 10-million gallon per day (mgd) watertreatment plant (WTP) to treat brackish water from Lake Texoma. The plant usesconventional treatment (flocculation/sedimentation/filtration) followed by electrodialysisreversal (EDR) to remove dissolved solids. As a result of upcoming regulations and growingwater demands, the City of Sherman is expanding its Lake Texoma Surface WTP by 5 mgdof finished water capacity. Microfiltration/ultrafiltration (MF/UF) followed by reverseosmosis (RO) demineralization was selected as the best apparent technology to meet theCity's operational and water quality goals.Treatment challenges include salinity reduction, turbidity control, total organic carbon (TOC)reduction, elimination of objectionable tastes and odors, and pathogen removal and/orinactivation from the surface water supply sources. Furthermore, the membrane-treatedproduct water will be blended and must be compatible with water from the existing supplyand treatment facilities.A pilot study was conducted to evaluate the ability of the planned treatment to meet theCity's water quality objectives. As mentioned, planned treatment includes dual-membraneprocesses, MF/UF for suspended solids and pathogen removal, followed by RO for dissolvedsolids and TOC reduction. MF/UF pilots from three vendors (Ionics Norit X-flow, PallMicroza, and Zenon ZeeWeed) were followed by two Osmonics RO pilot units. The MF/UFvendors were required to recycle their backwash to achieve an overall system recovery of 99percent. The product water from the MF/UF units was combined and fed to the two separateRO units so that the performance of membranes with varying characteristics could becompared. A scale inhibitor was used in both RO units. RO performance was compared tomanufacturer's projections. Includes tables.

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Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 18File Size: 1 file , 330 KB