Sirkar's recently patented system can deliver about 80 liters of drinking water per 100 liters of seawater, he says. A comparable reverse-osmosis system—which relies on pressure to force seawater through a salt-filtering membrane—would reclaim 41 liters from that same amount of saltwater, according to Sirkar.
Membrane distillation's advantages include its ability to produce drinking water with very low salinity. In addition, seawater can be distilled at a range of temperatures—from 30 to 100 degrees Celsius—reducing the amount of heat typically needed for desalination, an energy savings, Sirkar says. Prolonged use may decrease a typical membrane's efficiency, but Sirkar says his system adds an ultrathin layer of a highly porous silicone–fluoropolymer coating to extend membrane lifetime. Fluoropolymer—a polymer that contains fluorine atoms—has a high resistance to the solvents, acids and bases found in ocean water. As for the environmental impact of desalination, Sirkar says dumping concentrated brine back into the sea creates a "minimal" disturbance to sea life. He adds, "Seawater is a very large volume with enough turbulence to dilute [the brine] very quickly."
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