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Slowsand Filtration for Reducing Costs of Desalting Surface Waters

Project ID: 5840
Principal Investigator: Chuck Moody
Research Topic: Desalination and Water Treatment
Priority Area Assignments: 2011 (Advanced Water Treatment), 2012 (Advanced Water Treatment)
Funded Fiscal Years: 2011 and 2012
Keywords: None

Research Question

For desalting surface waters, this study evaluates slowsand filtration (SSF) and reverse osmosis (RO) (SSF-RO) to achieve breakthrough cost savings of 20-30 percent compared to conventional water treatment (CT) and RO and microfiltration (MF) and RO. Using the Bureau of Reclamation's (Reclamation) Water Quality Improvement Center (WQIC), the study addresses the question: Does SSF effectively remove particulates from water so that RO desalting equipment can operate with little or no fouling?

Need and Benefit

Any communities that treat or are considering treating (with or without desalting) Colorado River water (CRW) benefit from the evaluation of the low-cost SSF and SSF-RO treatments in these tests on CRW in Yuma.

Communities who treat other water supplies also benefit from this field evaluation of low-cost SSF.

Desalting offers "drought-proof" water supplies to communities with brackish waters or seawater. By reducing the cost of desalting surface waters (including seawater), SSF-RO expands the use of desalting for providing drought-proof water supplies.

Two recent Reclamation studies (Alternatives for Using Central Arizona Project Water in the Northwest Tucson Area [2000] and the Science and Technology Program sponsored Pilot Investigation of Slowsand Filtration and Reverse Osmosis Treatment of Central Arizona Project Water [2002]) have produced exciting results.

These studies estimate that for the subject locality, SSF costs 75 percent less than CT or MF water treatment. For pretreatment filtration to RO desalting equipment, the studies estimated that with SSF, SSF-RO can reduce total desalting costs (including concentrate disposal by a low-volume Central Arizona Salinity Interceptor [CASI] through Yuma) by a breakthrough 20 percent compared to CT-RO and MF-RO. A short-term, 5-month pilot test in 2001 and 2002 demonstrated that SSF effectively removes particulates that foul RO desalting equipment. In addition, SSF provides chemical-free filtration and thereby avoids the problematic fouling and scaling of RO membrane equipment from iron and aluminum salts and organic polymer additives used in CT-RO.

Because of SSF's low cost and the 2001-02 successful pilot test results with SSF as pretreatment to RO, Reclamation is considering SSF for the Yuma Desalting Plant (YDP), where CH2M HILL estimates that, if effective on YDP feedwater, SSF can reduce YDP desalting costs by 30 percent.

Contributing Partners

None

Research Products

Not Reviewed

The following documents were not reviewed. Statements made in these documents are those of the authors. The findings have not been verified.

EVALUATION OF SLOWSAND FILTRATION FOR REDUCING COSTS OF DESALINATION BY REVERSE OSMOSIS - Poster presented at AMTA 2007 (final, PDF, 1.3MB)
By Chuck Moody, Mike Norris, Eric Holler and Charles McCaughey
Publication completed on April 26, 2012

For desalination of surface waters, this study evaluates slowsand (SS) filtration as a low-cost pretreatment to reverse osmosis. During 12 months of pilot tests at Reclamation's Water Quality Improvement Center, SS filtration produced water with average values of 0.17 to 0.22 Nephelometric Turbidity Units (NTU) and 3.1 to 4.5 silt density index (SDI) for two surface water supplies: Colorado River water and Yuma Desalting Plant brackish source water, a 90-percent reduction in both measurements.
Keywords: slowsand filtration, slow sand filtration, reverse osmosis, roughing filter

EVALUATION OF SLOWSAND FILTRATION FOR REDUCING COSTS OF DESALINATION BY REVERSE OSMOSIS - Paper presented at AMTA 2007 (final, PDF, 316KB)
By Chuck Moody, Mike Norris, Eric Holler and Charles McCaughey
Publication completed on April 26, 2012

For desalination of surface waters, this study evaluates slowsand (SS) filtration as a low-cost pretreatment to reverse osmosis. During 12 months of pilot tests at Reclamation's Water Quality Improvement Center, SS filtration produced water with average values of 0.17 to 0.22 Nephelometric Turbidity Units (NTU) and 3.1 to 4.5 silt density index (SDI) for two surface water supplies: Colorado River water and Yuma Desalting Plant brackish source water, a 90-percent reduction in both measurements.
Keywords: slowsand filtration, slow sand filtration, reverse osmosis, roughing filter

This information was last updated on November 26, 2014
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