N.J. researchers devise means to extract twice as much potable water from seawater
May 7, 2012By Taunya English
As fresh water becomes scarcer around the world, researchers in New Jersey are working on new ways to remove salt from seawater.
Chemical engineer Kamalesh Sirkar leads the team at the New Jersey Institute of Technology.
He says, for decades, a technique called reverse osmosis has been the state-of-the-art method for removing salt from large volumes of water. That process uses pressurized water.
The New Jersey investigators, however, wanted to get more usable water from briny source water.
"If we can heat it up a little bit -- not too much -- we can get pure water out of it very efficiently, very effectively," Sirkar said.
The New Jersey Institute of Technology device can use solar heat, steam or other readily available heat sources.
The reverse osmosis system can reclaim 41 liters of potable water from 100 liters of brine or seawater, Sirkar said. NJIT's membrane distillation system can cull about 80 liters of water from the same 100 liters of brine, he said.
To describe his device, Sirkar says to imagine an empty picture frame strung with a web of thousands of strings.
"Each one of these strings are actually hollow tubes. [It is as if] your hair had a hole all the way through the length of the hair, and the wall of those hollowed tubes have a very, very particular type of pores in it," Sirkar said.
Water vapor from the heated salt water passes through the pores into the tubes, then cold water -- running through the tubes -- condenses and collects the nearly pure water.
While vapor is able to pass through the tiny holes in the tubing, still-salty water stays out because the mesh is made from a waterproof material, similar to Gortex.
"If water falls on a Gortex jacket it just falls off, like it falls on the feather of a bird," Sirkar said.
There's a critical need for fresh water in developing countries, but Sirkar envisions uses for his desalination device in this country too, especially is the Southwest United States.
"Or even in Jersey, for example," Sirkar said. "Where seawater is intruding into the wells of coastal communities, so the well water in southern Jersey coastal communities is getting contaminated with salt."
The researchers are testing their approach on different kinds of salty water. They recently won a patent for the device, but Sirkar says commercialization is still years away.