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Because of the uncertainty of water resources in the western U.S., the Long Beach WaterDepartment (LBWD) is considering seawater desalination as a possible source to augment itsexisting water supplies. An AwwaRF-funded project is examining dual-staged nanofiltration(NF2) for seawater desalination as an alternative to traditional reverse osmosis (RO) membranetreatment. The primary goal of this research is to determine whether this desalination system canreduce the operational cost for desalination, as compared to more traditional methods, bylowering operating pressures while producing potable water.A secondary objective was to evaluate the effects of blending desalinated seawater intoLBWD's existing water supplies made up of treated groundwater (GW) and purchased surfacewater (SW). The existing finished water varies in composition during the year, with 100 percentof GW in summer, and 100 percent of SW in winter, the latter being provided either as StateProject water (SPW) or Colorado River water (CRW). Based on these conditions, the objective is todetermine the percentage of desalinated water (DW) that can be blended while considering theissues of DBP formation, disinfectant residual, and corrosivity.The paper presents water quality characteristics for the various waters to be blended. Thecharacteristics for DW vary depending on the permeate salinity and pH targets. The two pHsconsidered represent one that is similar to the existing pH condition of the water in thedistribution system (8.0), and one that is required if additional boron rejection is required (withan interstage pH adjustment to pH 9.8). Includes 4 references, tables, figures.

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Edition: Vol. - No. Published: 06/17/2005 Number of Pages: 12File Size: 1 file , 1000 KB