Sea Water Desalination

Technical Profile

The objective of this process is conversion of seawater for potable water use. Seawater reverse osmosis (SWRO) to remove TDS followed by disinfection is the technology of choice. Often filtration, RO and disinfection are packaged together in a turn-key product.

RO membranes are protected by filtration to remove suspended particles. Multimedia filtration is described under Secondary Solids Separation and cartridge filtration is described under Fine Particle Removal.

RO represents the finest level of filtration and demineralization of all membrane processes. Membranes act as a barrier to all dissolved solids and all but low molecular weight organics. RO typically removes 90 to 99% of dissolved minerals. Recovery ranges from 60 to 85% depending on influent concentration and effluent specifications.

Seawater desalination differs from conventional RO in the level of TDS removed. Seawater generally contains up to 35000 mg/l TDS while conventional RO feed is around 6000 mg/l. It takes approximately 1 psig to treat 100 mg/l TDS on RO equipment (i.e., 350 psig for initial permeate production from seawater). To insure a good flow of water and adequate recovery, SWRO units typically run around 1000 psig (70 barg) while conventional RO runs between 150 and 250 psig (10 to 17 barg). The additional strength of construction materials causes the cost of SWRO to be significantly higher than conventional RO.

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Hydrocarbon Processing Industry