An Israeli company called Emefcy has developed a process that promises to decrease the energy drain of wastewater treatment. This week, Energy Technology Ventures—a joint venture between GE, NRG Energy, and ConocoPhillips—invested in the company, marking the venture’s first-ever investment in a non-U.S. company.
Conventional wastewater treatment consumes 2 percent of global power capacity, some 80,000 megawatts, at a cost of $40 billion per year.
Using conventional microbial fuel-cell technology and its own proprietary engineering, Emefcy harvests energy from wastewater, generating enough to power the entire treatment process. In the treatment of particularly carbon-rich industrial wastewater, the company says, the process produces excess electricity that can be fed back into the grid at a profit.
In microbial fuel cells, naturally occurring microorganisms oxidize wastewater. An anode and cathode, placed a critical distance apart in the water, create an electrical circuit from the electrons gained from this oxidation.
Ely Cohen, Emefcy’s vice president of marketing, says the company’s process reduces the total cost of wastewater treatment by 30 to 40 percent by eliminating spending on energy, and also reduces the amount of sludge that must be trucked away afterward by up to 80 percent.
Traditional wastewater treatment involves forcing air through the water to aerate it. This is also important to the activity of the microbial cells. Emefcy exposes more wastewater to air but without the energy-intensive process of pumping air through water. Instead, the wastewater flows through a “biogenic reactor” made of tubes 1.7 meters in diameter and four meters high. Inside the tubes, water and air flow alongside each other separated by a membrane.
“The reactor is split into two areas,” says Emefcy CEO Eytan Levy. “In one area there is a lot of wastewater but there is no air. In the other area there is air but no wastewater. These two areas are separated by a membrane wall and both areas are connected to an electrically-conductive surface on which the bacteria grows.”
The electrons produced by the bacteria flow towards the oxygen in the air through nanowires made of naturally-occurring hair-like projections found on the surface of the microbes. “Under these reactor conditions the bacteria develop the ability to convert these pili to become electrically conductive and it behaves just like a metallic wire,” says Levy.
The electrodes used are made of a coated plastic, which makes them cheaper, and easier to maintain.
Each stack can process 10 cubic meters of wastewater a day, and has a planned lifespan of 15 years. Stacks can be added on a modular basis, avoiding the need for a large up-front investment in infrastructure. Emefcy hope to begin industrial production this month, with first sales targeted for early 2012.
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