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Power from the Sewer: One Person’s Wastewater is Another’s Electricity

Wastewater treatment plants are often among the biggest users of electricity, sending power down the drain. Engineers at GE, however, have hit on a solution that could remove waste from the equation – literally and figuratively. “What if you can have it all,” says Tom Stanley, chief technology officer at GE Water & Process Technologies. “We can help turn wastewater treatment plants from energy consumers into energy producers.”

Stanley says that part of the solution was finding new ways to reduce the plants’ energy consumption. One clear target was aeration, a process that brings oxygen into the sludge collected from water to help bacteria break down the organic matter that’s in it. Today, the average water treatment facility uses as much as 60 percent of its energy on aeration.

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Top GIF and above: Rather than just pumping oxygen into the water, the reactor is sending the gas through bundles of hollow fibers to grow a biofilm. GIF credits: GE Power

Stanley’s solution revolves around a technology called membrane aerated biofilm reactor (MABR) that uses oxygen to grow bacteria that neutralize organic pollutants in the water. The reactor sends the gas through bundles of hollow fibers that grow the bacteria in a biofilm on their surfaces. The fibers deliver the oxygen much more efficiently than just pumping it in the water. The design, called ZeeLung, is so effective that a plant can cut the energy needed for wastewater aeration four-fold.

The technology is also easy to install. “A great thing about using a MABR is that you don’t have to shut down a facility to achieve this upgrade,” Stanley says. “You can retrofit within the plant’s existing footprint by inserting a MABR into the existing biology tank, enabling higher throughput and improved nutrient removal.”

But there’s more. Plants can start using the biofilm to produce energy. The GE design feeds it into an anaerobic digester where another set of bacteria turns it into biogas. The water treatment plant can use the biogas to fuel a gas engine to generate electricity or send it to other users through a pipeline. “Both options are efficient, effective and cost-conscious ways to run a wastewater treatment plant,” Stanley says.

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Workers are installing a MABR reactor . Image credit: GE Power & Water

Everyone can benefit. Stanley says that in the U.S. alone, wastewater treatment plants use enough energy to power 2 million homes. Demand will likely grow, following population increase and more stringent regulations. “At the end of the day, the EPA is not coming to a plant asking them to reduce energy,” he says. “But municipalities need to meet effluent quality specs, as well as a budget. With the advances in technology, they can now expand capacity, meet regulatory demands and reduce the energy bill by employing technology investments with a good return.”

The technology could be even a bigger deal in developing countries, where electricity as well as clean water are often scarce. Says Stanley: “For cities in emerging markets that currently have no wastewater plant in place, they have an opportunity to do it right from step one and build a self-sufficient, independent, cost-effective wastewater treatment plant that doesn’t require access to the grid for electricity.”

 

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