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AWWA WQTC65867
- Water Quality Performance Comparison of Reverse Osmosis to Dual-Pass Nanofiltration for Seawater Desalination
- Conference Proceeding by American Water Works Association, 11/01/2007
- Publisher: AWWA
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The Long Beach Water Department (LBWD), similar to many Southern Californiautilities, has been facing the issue of decreased potable water supplies. Becauseof its location, the City of Long Beach is ideally situated to take advantage ofdesalinated seawater as a source of drinking water and is interested inincorporating desalinated seawater into its potable water portfolio. However,before seawater desalination can become a reality, additional advances areneeded to further reduce the cost of desalination. LBWD is currently exploring thefeasibility of using nanofiltration membranes (NF) in a dual-pass configuration toevaluate the possibility of achieving additional cost reduction as well as meetingall water quality objectives. Although NF membranes have been previously tested with seawater, theapplication focused on using NF as pretreatment for the reverse osmosismembrane stage rather than using these membranes to produce potable water.In recent years, however, significant developments of NF membranes have beenmade, resulting in products that can achieve high TDS rejections (e 90%) atlower applied pressures. These advances allow a two-step, permeate-staged NFtreatment process capable of producing potable water with lower overall appliedpressure, and potentially lowering operating energy. To date, this concept doesnot appear to have been tested, as evidenced by the lack of literature in thisarea.To provide clear and quantifiable answers to water quality questions related tothe traditional SWRO versus dual-pass nanofiltration process (NF2), LBWD hasformulated an aggressive research program and constructed a 300,000 gallonsper day permeate "Prototype" research facility using full-scale equipment. Thispaper presents LBWD's preliminary evaluation of source water quality and itsremoval throughout the various processes and initial water comparison of SWROand against dual-pass nanofiltration. Includes 13 references, tables, figures.
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