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It takes water to create energy and energy to treat water. But wastewater treatment plants are also often one of the biggest users of electric power, sending electricity down the drain.
Engineers at GE, however, have hit on solutions that could solve both problems in one fell swoop. “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 equation is finding new ways to reduce their energy consumption. One area ravenous for power inside wastewater treatment plants is aeration, a process that brings oxygen into the sludge and helps bacteria break down the organic matter.
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Top GIF and above: Rather than just pumping it in the water, the reactor is sending oxygen through bundles of hollow fibers to grow a biofilm. GIF credits: GE Power & Water
Today, the average water treatment facility spends as much as much 60 percent its energy on aeration, a clear target for savings.
Stanley’s solution revolves around a technology called membrane aerated biofilm reactor (MABR). Rather than just pumping it in the water, the reactor is sending oxygen through bundles of hollow fibers to grow a biofilm. The fibers transfer it more efficiently to the biofilm and help it neutralize the wastewater pollutants.
The design is so effective that a plant can reduce energy needed for wastewater treatment aeration four-fold. “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.”
Once you have addressed energy consumption, you can also start using the solids caught inside the plant to produce energy. The GE design feeds them into an anaerobic digester where another set of bacteria turns them into biogas.
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Workers are installing a MABR reactor . Image credit: GE Power & Water
The water treatment plant then uses the biogas to fuel a power-generating gas engine or sends it to other users through a pipeline. “Both options are efficient, effective and cost-conscious ways to run a wastewater treatment plant,” Stanley says.
All countries can benefit from the solution, regardless of their GDP. Stanley says that in the U.S. alone, for example, wastewater treatment plants use enough energy to power 2 million homes. The demand will likely grow by 20 percent, 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.”
