AWWA ACE65280

This powerpoint presentation outlines issues and options for using reverse osmosis (RO) as the preferred technology for seawater desalination. Various desalination processes are compared in terms of energy kWh/kgal, method of operation, recovery (%), and capital costs. Advantages and disadvantages of seawater RO are listed, along with a schematic of a typical seawater RO process. The basics of RO principles are diagrammed, along with the minimum energy required for seawater reverse osmosis (SWRO), factors affecting energy loss within a RO system, effects of recovery, optimum recovery for energy consumption, RO membrane resistance, and system configuration. Two issues are outlined and include: standard seawater elements used throughout, even when salinity is lower; high pressure is maintained throughout the vessel, although OP is high only in latter half; can use combination of elements - high flux (slightly lower rejection) followed by standard; and, use of brackish water elements in first half, seawater elements in second half. A comparison of various RO system configurations with respect to energy consumption, and feed and brine flows is provided, along with other factors such as flux, fouling, pumps, and energy recovery. An AwwaRF research project titled "Desalination Facility Design and Operation For Maximum Energy Efficiency" is underway that involves evaluation of several desalination facilities operation and design issues to identify means of improving energy efficiency.