Research Team Develops A System That Uses Wastewater To Make Electricity, While Cleaning It Up Too

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A professor from Washington University in St. Louis is on a quest to explain that the way people look at wastewater as full of “waste” is just ‘a matter of perspective.’ Professor Zhen He shares, “Why is it waste? It’s organic materials.” And moreover, he says that this so-called ‘waste material’ can actually provide energy in multiple ways.

Plus, he also points out that that it’s not just the organic waste that’s worth something, but the actually water in wastewater.

Professor He’s lab has managed to create one system that actually uses both these sources, by filtering wastewater while creating electricity at the same time. His bench-scale trials were published in the May copy of the journal Environment Science: Water Research & Technology and was even featured on the cover.


Professor He explains that waste materials are actually full of organic materials, and more importantly, they are considered food to bacteria.

He writes, “Bacteria love them and can convert them into things we can use. Biogas is the primary source of energy we can recover from wastewater; the other is bioelectricity.”

His work has gained traction, and even Egyptian researchers that are working with him are hoping to use similar technological platforms in the desalination of water.

While ways to capitalize on bacteria to create energy from wastewater already exist, many times, these methods work at the ‘expense of the water.’ What this means is that it can be filtered and used in other ways, not for drinking, but as “gray water” uses like toilet flushing and irrigation.

What Professor He’s lab did was to take the two processes of filtration and energy production and put them together by adding a filtration system ‘into the anode electrode of a microbial electrochemical system.’

How the system works is that it’s set up ‘like a typical microbial fuel cell, a bacterial battery that uses electrochemically active bacteria as a catalyst where a traditional fuel cell would use platinum.’ In this system, the bacteria attach to the electrode, so when the wastewater gets pumped into the anode, the bacteria go on to “eat” the so-called organic materials in order to release electrons, therefore making electricity.

Notably, in order to filter the same water actually requires a different system altogether. But Professor He’s lab managed to combine all the systems, creating a penetrable anode that works as a filter.

The anode is described as ‘a dynamic membrane, made of conductive, carbon cloth.’ When used together, the membrane and bacteria manage to filter out 80% to 90% of organic materials. The result is water that’s considered close enough to be discharged into nature, or when treated even further, for other non-potable water uses.

The team used a mixed culture of bacteria that all had one common or shared feature, which was that the bacteria needed to be able to survive or live in a zero-oxygen environment.

Professor He said, “If there was oxygen, bacteria would just dump electrons to the oxygen not the electrode. If you cannot respire with the electrode, you’ll perish.”


Moreover, in order to find the right bacteria, Professor He said he ‘defers to nature.’ He shares, “It’s not 100 percent natural, but we select those that can survive in this condition. It’s more like ‘engineered selection’,” as the bacteria that did not ‘survive and respire with the electrode’ was chosen to be used in the system.

While the amount of electricity that was made was not nearly enough to power a city, the idea is that it’s enough aid to offset the significant amount of energy that’s normally used in most U.S. water treatment plants.

According to Professor He, “in the U.S, about 3% to 5% of electricity is used for water and wastewater activity.” He also shares from what he’s observed in the usage of local municipal plants, he trusts that the system he has created can lessen the amount of energy consumption substantially. “Wastewater is a resource in the wrong location,” he adds.

He goes on to say, “Typically, the process consumes about 0.5 KWH of electricity per cubic meter.” And based on the original bench scale experiments, he says “We can reduce it by half, or more of that.”

Although Professor He explains that the system’s primary goal is not electricity production, but rather it’s wastewater treatment and nutrient recovery.

He explains, “Bacteria can convert those organic materials into things we can use. We can recover nutrients like nitrogen or phosphorus for fertilizer. We can use it to feed plants. It’s only when we don’t use it, then it becomes waste.”

 

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