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WSU Researchers Are Using Microbes To Clean & Produce Energy From Wastewater

This discovery could lead to less dependence on the energy-intensive systems that currently treat wastewater.

By BuzzwordPublished 3 years ago 3 min read
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Researchers at Washington State University have produced a sustainable wastewater treatment system that uses electron-producing microbial communities to clean out water.

This discovery could lead to less dependence on the energy-intensive systems that move and treat wastewater, which accounts for up to 2% of total electrical energy consumption in the US.

The project is led by Abdelrhman Mohamed, postdoctoral research associate, and Haluk Beyenal, Paul Hohenschuh Distinguished Professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering. The researchers have been reporting their findings to the journal, Bioelectrochemistry.

"These are difficult systems to build," said Beyenal. "I think everything is so easy when I write the proposal, but this takes a lot of time and a lot of new discovery. There is nothing like this on the market."

For processing wastewater treatment, aeration is an energy intensive and essential procedure to remove unwanted contaminants. Pumps work continuously to mix air with water and add oxygen to the bacteria to oxidize organic matter and pollutants. The researchers found using a unique microbial fuel cell system they developed as a substitute for external aeration is more effective.

"If we cut the energy use even by a small percentage in the U.S., that is billions of dollars in annual costs," said Mohamed. "Energy costs are one part but that also means reducing environmental emissions, too."

Microbial fuel cells work by allowing microbes to convert chemical energy into electricity in a way that resembles a battery. The microbes don't generate very much electricity, so they have to be used in low-power applications, particularly in remote areas where batteries are currently used.

For wastewater treatment, the microbial fuel cell can replace the role that aeration and oxygen originally fill — accepting electrons that bacteria generate as a product of their metabolic work.

"We tried to think about it in two steps," said Mohamed. "We lower the energy costs because you don't have to aerate and add oxygen, but the second part is we generate a little power that we can use for some useful applications in the wastewater treatment plant itself."

"It's like we're double dipping," added Beyenal. "We use the electrodes and then the electron acceptor to promote microbial growth. On the other hand, we gain a little bit of electricity for the pump and to aerate. With this approach it is more powerful and can treat the wastewater faster."

Fuel cells have been experimentally used in wastewater treatment systems under certain conditions, but often fail under real and different conditions.

"The microbial fuel cells lack internal regulation controlling the potential of anodes and cathodes, and thus cell potential," said Mohamed. "This can cause system failure."

In the system that the WSU team has developed, the researchers have integrated an additional electrode that provides greater control of their fuel cell system. This system is switchable. It can either function as a microbial fuel cell itself, consuming no energy while slowly disposing of waste, or it can be switched to a fuel cell that consumes less energy than ventilation and cleans more intensively. Mohamed invented an inexpensive portable electronic device that can control the electrodes.

The researchers were able to operate their system for a whole year in the laboratory and on a pilot scale at an experimental wastewater treatment plant in Moscow, Idaho. Owner and operator of the pilot plant, is Professor Erik R. Coats of the University of Idaho Environmental Engineering, who is one of the collaborators involved with the project. The system removed waste at similar rates compared to aeration.

The system could potentially be used independently from a power grid, and many researchers believe it could be used for small-scale sewage treatment plants, such as cleaning cattle farms.

"Over time, we have made a lot of progress," said Mohamed, "There are still challenges that we need to overcome to see this as a real application, but it's exciting to see the field moving significantly over a period of time."

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