(224s) Comparison Between the Performance of RO and NF Desalination Systems in Pilot Scale

Water scarcity is a major global concern: because of factors such as population growth, inappropriate use of water resources, and climate change, clean freshwater resources are strictly limited. However, seawater and brackish waters are abundant. Therefore, desalination processes are used to produce freshwater from seawater and brackish water, helping to overcome the critical issue of freshwater shortages. The most commonly used desalination processes are membrane technologies, which are dominant because of their low cost, low energy consumption, compactness, and short installation period. There are several different types of membrane technology, but reverse osmosis (RO) systems are the most frequently used: about half of the world’s 16,000 desalination plants use RO systems. The appeal of RO systems comes from their ability to treat many types of feed water, their ease of maintenance, and the high-quality water they produce. However, compared to some other membrane technologies, RO still suffers from high energy consumption, inadequate water recovery, and membrane fouling. As an alternative to RO systems, nanofiltration (NF) membranes have been developed to efficiently desalinate water sources that have less salt content than seawater, such as brackish inland groundwater. NF is more energy efficient than RO systems, and is also able to operate at higher flux and lower pressures. However, direct comparison between the performances of RO and NF technologies has been a challenge, since RO has a higher ion rejection rate while NF has a higher energy efficiency. The goal of the present study was to compare the performance of full pilot-scale RO and NF systems in the treatment of brackish groundwater. Using the resources of the Brackish Groundwater National Desalination Research Facility, optimum operating conditions were obtained for RO and NF systems by varying the parameters of temperature, pH, feed concentration, and inlet pressure. Furthermore, appropriate pretreatment methods were applied to prevent fouling on the membranes of both systems. Under the same operating conditions, it was clearly seen that the two systems treated brackish groundwater differently; however, by investigating the rejection of divalent ions, it was observed that the behaviors of the two systems were reasonably similar to each other.