Oasys Water Inc., a company built around research from Yale, has announced it has landed $10 million in venture funds to see if its novel desalination technique, which exploits fundamental chemistry and waste heat, can go commercial.
The company's EO "forward osmosis" process can desalinate water for about half the cost of standard reverse osmosis desalination, it says.
In reverse osmosis, water is filtered and then shoved through a membrane at high pressures. Building up the pressure consumes vast amounts of energy. (The water also gets heated.) Some estimates put desalination at $650 to $1,000 or more per acre foot when water agencies often sell water for $200 an acre foot. Put another way, a 25 million gallon a day reverse osmosis plant for seawater can cost $100 million.
The EO process is essentially a forward osmosis process. Salt water comes to the membrane under its own energy. On the other side is a solution mixed with ammonia salts that contains a higher salt concentration than seawater. Since water will flow naturally to a higher salt concentrations, the water passes through the membrane without external energy or pressure. Most of the sea salt stays behind. (The same thing happens to your cells when you eat soy sauce laden food.)
Then the magic of chemistry begins. The water with ammonia salts is heated to evaporate the ammonia. It takes less energy to do that than to heat the water until it turns into steam. (Other compaines are using the steam/distillation method.) The salts are subsequently recovered and used again.
"We are leaving the water as is and turning the salt into gases" said CTO and Co-Founder Rob McGinnis.
To further cut prices, Oasys uses waste heat to evaporate the salt. (We're big on waste heat here; see Will Waste Heat Be Bigger Than Solar? and Tapping Americas Secret Power Source).
"There is a thermodynamic minimum for removing salt form water. You can't beat that," he said. "But you can decide what kind of heat to use."
Despite the costs, demand is rising. Water agencies in California, Israel, China, Australia and other areas that are facing water scarcity have already begun to approve or are considering major desalination plants. It's even worse in emerging areas of the world. An estimated 2.4 billion of the world's 6.8 billion people now live in highly water-stressed areas, according to the World Health Organization.
Startups and others, naturally, have flocked to the field to reduce the cost. Last year, Energy Recovery, had one of the biggest – and only – green IPOs. It makes a system that captures pressure from the waste streams coming out of a reverse osmosis system to pressurize incoming water. The company is working on projects around the globe.
Some of the new startups will be bought by large conglomerates like General Electric. Others will fade away. But in the meantime, it will be like a Cambrian period, with all sorts of ideas emerging.
Porifera, a spin-out from Lawrence Livermore Labs, has developed a membrane from carbon nanotubes (see Startup Cuts Water Purification Costs With Carbon Nanotubes). Water flows through the tubes, but particles get stuck. It can be gravity-driven. New Mexico State has a process that can desalinate water at 45 to 50 degrees Celsius, about half the conventional temperature. Secretive Quos, a Khosla Ventures company, has a graphite electrode that can purify seawater (see A Guide to the Water World). Then there is also Stonybrook Purification and NanoH20.