Most comnerclal seawater
reverse osmosis plants deslgned to date are driven using a feed pressure In the range of 800-1000 psig (5500-6900 kPa). Membranes rated at 1200 psig (8300 kPa) are now available and it is reasonable to expect membranes capable of even higher pressure operatton \n the near future. Operation at these higher pressures can result In a more economic process design.
In this paper, design improvements based on these hlgher pressures are studled and their effects on new plant capital and operating cost for Middle East site condltlons are evaluated.
SUMMARY
Seawater reverse osmosis system costs can be reduced slgnlflcantly by operation at the high conversions now made possible by the high pressure capabllltles of aramtd hollow fine fiber (HFF) membranes. The osmotic pressure associated with the concentrate stream of the seawater reverse osmosis desalination process usually llmlts the system conversion that can be achieved. Consequently, reverse osmosis permeators deslgned for hlgher feed stream hydraulic pressures can be operated at higher conversion. Higher conversion operation results In a lower capital cost for the desalination system and also a lower operating cost because the quantlty of source water that must be processed Is decreased. Nost seawater reverse osmosis membranes offered in the market place today have a maxlmum rated feed pressure of 800 to 1000 psig. However, aramid hollow flne fiber membranes are avallable with a feed pressure ratlng of 1200 pslg and seawater plants in operation today are already demonstratlng membrane capabjlltles of 1150 to 1200 pslg operation and 50 percent conversion. Process economics show that the end user will Incur lower costs at higher membrane feed pressures. It is highly probable that seawater reverse osmosis devices capable of 1300 to 1500 pslg operation wtll appear in the near future as a result of this advantage.