Theoretical study on feed water designs to reverse osmosis pressure vessel

Scale fouling and power consumption are one of the most important parameters in reverse osmosis (RO) desalination. To reduce scale problems in RO, single or central feeds to the pressure vessel were suggested instead of using end feed. In this paper Reverse Osmosis System Analysis (ROSA) software was used to simulate the differences between single, central and end feed designs. The effect of feed Silt Density Index (SDI) and number of the RO elements in the pressure vessel were investigated here. Feed SDIs 5, 3, and 1 were considered in this paper. To study the effect of the numbers of RO elements, 6 RO and 8 RO elements per pressure vessel were simulated. The simulation results showed that the power consumption in the end feed design was lower than in the single and central feed designs. The simulation results showed that Langelier Silt Index (LSI) and Stiff & Davis Stability Index (SDSI) were lower in the single than central feed design which in turn was lower than in the end feed design. These results indicated that although the power consumption in the single and central feed designs was higher than in the end feed design; the former designs were more efficient in rescuing the RO scale problems.