ELECTRODIALYSIS REVERSAL (EDR) FOR THE REMOVAL OF FLUORIDE AND ARSENIC FROM DRINKING WATER

摘要

Fort Irwin National Training Center (Ft Irwin) is located in the Mojave Desert in the StateCalifornia and serves as a major combat training center for the United States military. Ft Irwincurrently uses a groundwater supply that exceeds the maximum contaminant levels (MCL) forfluoride and arsenic. Water demands average between 2.0 and 2.5 million gallons per day (mgd)and range from 0.8 mgd to 5.3 mgd, depending on troop rotation and season.Ft Irwin currently operates two separate water distribution systems. Potable water for drinking isproduced by treating the groundwater with reverse osmosis (RO) and distributing it through theRO distribution system. Chlorinated groundwater that has not been treated with RO is distributedthrough the domestic water (DO) distribution system for other uses. However, the CaliforniaDepartment of Public Health (CDPH) has determined that the water delivered via the DOdistribution system must meet all applicable drinking water standards. To meet theserequirements, Ft Irwin will construct a new water treatment plant, the Irwin Water Works, whichwill produce up to 6.0 mgd of potable water, as well as combine the two existing distributionsystems to provide a single potable water system.Due to high silica concentrations, the existing RO treatment process operates at a low recoveryrate. Pilot testing was performed to select a more efficient treatment process. This resulted in theselection of electrodialysis reversal (EDR) as the main treatment process for the new Irwin WaterWorks. The EDR process was shown to effectively meet treatment goals while providing arecovery rate greater than 90 percent. The overall plant recovery rate will be further increased togreater than 99 percent by providing additional treatment of the EDR concentrate. The finalresiduals will be discharged to on-site drying beds, resulting in a zero liquid discharge facility.EDR is a membrane process that utilizes electricity to drive the separation of ions from thesource water stream. EDR utilizes a stack of alternating anion and cation exchange membraneswith electrodes, one operating as an anode and one operating as a cathode, located at oppositeends of the stack. The alternating anion/cation exchange membrane configuration results inalternating dilute and concentrate streams.The new EDR system will allow Ft Irwin to produce potable water that meets all applicabledrinking water standards and meet all water demands. In conjunction with the waste streamtreatment process, the Irwin Water Works will produce water with a recovery of greater than 99percent, while discharging no liquid waste. This new treatment facility will allow Ft Irwin tomeet its goals of producing high quality drinking water while conserving their limited resourcesto provide a reliable water source for the base and its personnel for many years to come.