Starving Bacteria Could Mean Energy Neutral Wastewater Treatment

Increasingly, sewage is being seen less as waste and more as a potential source of energy.

In one primary indicator of this growing trend, a team of biochemists and microbiologists from Belgium’s Ghent University are collaborating on a pilot project with DC Water. It is trying to make the microorganisms used to treat wastewater more efficient.

“If we want sewage treatment to be truly self-sustaining, the trick will be to find an efficient way to separate the organic matter form the wastewater — that way the wastewater can be recycled, and the organic matter can be used to generate bioenergy,” New Atlas reported. “Currently, the overall principle of most sewage treatment plants revolved around optimizing the way microorganisms such as bacteria, fungi, and protozoans feed on the organic contaminants in wastewater.”

According to New Atlas, the project is focused on improving the contact stabilization step, a process in which two aeration tanks are used to make microorganisms as active as possible before they are introduced to a batch of effluent needing treatment. Currently, the sewage treatment process recovers about 20 to 30 percent of organic matter.

“Our approach is unique because we have developed a high-rate variation of the so-called contact-stabilization process,” Dr. Francis Meerburg, a researcher on the project, said.

The team has found some success to date by manipulating the microorganisms’ diet. Their methodology can reportedly recover more than 55 percent of the organic matter from sewage, generating enough power to treat sewage without added electricity.

“We periodically starve the bacteria, in a kind of ‘fasting regimen’,” Professor Nico Boon explained. “Afterwards, wastewater is briefly brought into contact with the starved bacteria which are gluttonous and gobble up the organic matter without ingesting all of it. This enables us to harvest the undigested materials for the production of energy and high-quality products.”

The process is being implemented as part of a full-scale DC Water treatment installation. Soon, researchers will evaluate how the process can achieve more efficient wastewater treatment on this large scale, and how much it can save the public on energy costs.

“For comparison: in our region of six million people (in Flanders), the energy usage of our sewage treatment municipality, Aquafin, corresponds to the residential electricity use of more than 690,000 people (more than 10 percent of the population),” Siegfried Vlaeminck said. “This gives an idea on the energy saving potential and impact, if all sewage treatment could be energy neutral.”