Efficient Desalination By Reverse Osmosis PDF Download

Desalination can produce freshwater from seawater and brackish water, alleviating the critical issue of freshwater shortages. There are multiple desalination technologies, but membrane-based technologies are used most frequently because of their low cost, low energy comsumption, compactness, and short installation period. Among the membrane-based desalination technologies, reverse osmosis (RO) is most prevalent because of its ability to treat many types of feed water, ease of maintenance, and production of high-quality water. However, compared to some membrane technologies, RO suffers from high energy comsumption, inadequate water recovery, and membrane fouling. As an alternative to RO systems, nanofiltration (NF) membranes have been developed for desalinating moderately or slightly saline water sources such as brackish groundwater. NF has a lower ion rejection rate than RO, but is more energy efficient because of this and is able to operate at higher flux and lower pressures. Despite these known advantages and disadvantages, it has been difficult to directly compare the performances of RO and NF technologies because RO has a higher ion rejection rate while NF has a higher energy efficiency. This impedes the selection of optimal desalination systems for given conditions. To solve this problem, the present study uses the criteria minimized specific energy consumption and acceptable product water quality to compare the performances of RO, NF, and a hybrid NF/RO system in the treatment of brackish groundwater. Using resources at the Brackish Groundwater National Desalination Research Facility (BGNDRF), optimum operating conditions were obtained for all three systems by varying the parameters of feed flow rate, feed concentration, and system recovery. To prevent membrane fouling, appropriate pretreatment methods were applied in all experiments. Results showed that, based on the calculated specific energy consumption and World Health Organization standards for potable water, NF, hybrid NF/RO, and RO systems were best for desalinating low, moderate, and high salinity feed waters, respectively.