how the plant works (continued)
pretreatment
Before the RO process, seawater entering the desalination plant flows through screens that remove debris, then goes through a traditional treatment process called coagulation and flocculation. In this process, chemicals are added to the seawater to make algae, organic materials and particles clump together so they can be removed more easily in the sand filtration stage.
After sand filtration, the salty water goes through diatomaceous earth filters to remove silt and fine particles. Cartridge filters just before the RO membranes serve as a backstop, removing any particles that may be remaining after the diatomaceous earth filters.
reverse osmosis
Next is the RO process. High pressure forces the pretreated water through semi-permeable membranes to separate the freshwater, leaving twice-as-salty seawater and other minerals behind.
The size of each RO membrane pore is about .001 microns, which is about 1/100,000th the diameter of a human hair.