Evaluation of Slow Sand Filtration for Reducing Costs of Desalination by Reverse Osmosis

For desalination of surface waters, this study evaluates slowsand (SS) filtration as pretreatment to reverse osmosis (RO). In 2000, Reclamation’s Phoenix Area Office in the appraisal study Alternatives for Using Central Arizona Project Water in the Northwest Tucson Area estimated the costs of three water treatment filtration processes: SS filtration, ?conventional treatment? (coagulation, flocculation, settling, and rapid-sand filtration), and low-pressure membrane treatment (microfiltration (MF) or ultrafiltration (UF)). In 2001 and 2002, Reclamation’s Science and Technology Program co-sponsored a 5-month pilot test using SS filtration to treat Colorado River Water delivered by the Central Arizona Project. Because of SS filtration’s low-cost, and the 2001-2002 successful pilot test results with SS filtration as pretreatment to RO, Reclamation is conducting further pilot testing in 2006-20017 to evaluate SS filtration as one of several alternatives to integrate with existing water treatment processes at the Yuma Desalting Plant (YDP). This paper includes performance results from the 2001-2002 and 2006-2007 pilot tests.

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