Performance evaluation of two RO membrane configurations in a MSF/RO hybrid system

Abstract Although integration between multistage flash distillation (MSF) and reverse osmosis (RO) in hybrid desalination systems has been long discussed in the literature, and has been shown to be technically and economically superior to nonintegrated MSF and RO systems, no serious attempts have yet been made to adopt or implement such an approach in the design or construction of new desalination plants. This, perhaps to some extent, may be attributed to the real need first for some tangible experience on an acceptable scale and to the lack of experimental data on the performance of RO membranes in MSF/RO hybrid systems. Hence, this paper attempts to fill in this gap by presenting: operational experience using reasonably-sized RO production plants, a large body of experimental data on RO membrane performance in a simple MSF/RO hybrid model, and an overall evaluation of the performance of the RO membranes operating under the given conditions. The work represents the second phase of an experimental investigation of MSF/RO hybrid systems. In this phase the performances of two types of RO membranes operating in a simple easy-to-implement MSF/RO hybrid model were measured and evaluated. The experiments were carried out at the Doha Desalination Research Plant (DRP) using two RO units linked with the nearby MSF unit A-1 of the Doha East Distillation Plant via one common feed water header and pretreatment unt. The common feed water system, however, does not prevent either of the two RO units from being operated independently from each other. The RO units are of the spiral-wound and the hollow-fiber twin seawater RO membrane configurations, each of 300 m 3 /d nominal production capacity. Descriptions of the MSF/pretreatment/RO experimental model, measurements of performance data, analytical procedures, and discussions of the results obtained are presented. The results indicate that the two tested types of membranes behave in a very similar fashion, both qualitatively and quantitatively. RO product water recovery under hybrid operation is significantly higher than under isolated surface seawater operation. Up to a 43% increase in the RO product water recovery was realized when data under hybrid operation were compared with those under isolated surface seawater operation and similar feed pressures. The average change in RO product water recovery was almost linearly related to the change in feed water temperature at an average rate of 2.2% 1° C change in feed water temperature.