Energy saving methodology for the SWRO desalination process: control of operating temperature and pressure

This study proposes a new operation methodology for energy saving in the Fujairah seawater reverse osmosis (SWRO) plant, as the optimum feed pressure is determined at the controlled operating temperature. To this end, two functional models were developed by genetic programming (GP) using two-year operational data. The data revealed that the required feed pressure for the plant operation was potentially overestimated. Based on the developed models, simulation of a three-step sequential control was carried out to reduce and optimize the required feed pressure. The simulation results first indicate that the temperature control significantly reduces the required feed pressure at a reasonably high temperature. Second, as the permeate water flow rate (PFR) is determined by the optimized feed pressure instead of the permeate pressure actually used to maintain a steady PFR in Fujairah, the required feed pressure could be substantially reduced. As a result, the proposed methodology can potentially reduce the required feed pressure, by approximately 10 bar, under

Two functional models for the permeate flow rate and salt passage ratio were developed using genetic programming based on the twoyear operational data of the Fujairah SWRO plant, currently the largest desalination plant in the world, a hybrid system consisting of SWRO and MSF. The results of this study show that the hybrid desalination plant has a significant economic potential because utilization of the thermal energy extracted from the MSF process (i.e., the operating temperature control by mixing feed seawater with the high temperature water produced by the MSF process) can improve the efficiency of the SWRO process. Moreover, it was shown that applying the nonisobaric feed pressure control to the plant can reduce the required feed pressure for the entire process. Thus, the application results of the proposed methodology show substantial energy savings in terms of reducing the required feed pressure, approximately 10 bar under the identical performances of both PFR and permeate water TDS in the Fujairah SWRO process. These results further imply that optimized operation and management (O&M) plans are critically important in enhancing the efficiency of the desalination process in the sense of energy and, eventually, cost savings.