(299i) Flexible Desalination Systems for Variable Salinity Sources

Many water sources are less desirable as a potable water source because they vary in quality over time, such as in tidal reaches on coastal rivers. In other situations water needs to be treated intermittently so that either water from several sources is treated at a common treatment location or equipment is moved to the source of contaminated water such as in centralized produced water treatment and small scale industrial waste treatment. Irrigation return flows vary with the amount of precipitation and irrigation and fertilization schedule. Over a longer scale of time, communities that use ground water may find the salinity increase due to seawater intrusion or declining aquifer levels. In all of these scenarios the treatment process and equipment needs to be adaptable to a wider range of source water qualities.The Variable Salinity Desalination (VSD) project was designed to evaluate modifications to the Expeditionary Unit Water Purifier- Generation 1-A (EUWP), designed to treat any source up to 60,000 mg/L total dissolved solids, 100 NTU turbidity, and temperatures, at between 45-60 percent recovery, to allow higher water recovery operation when treating brackish water. The system was modified with a bypass around the pressure exchanger to attain 75% water recovery to convert the system from a one stage design to two stages. Operability, ease of transition between designs, power requirements, and water quality were evaluated using a brackish groundwater feed source. Performance was compared to operation in the original configuration at three other sites with a wide range of salinity. Power use and water quality were as would be expected for the higher recovery. Options for building in design flexibility and cost impacts are discussed.