Generating Power from Sewage Treatment Plants

Traditionally, treating wastewater and other refuse is a very energy-intensive process, which requires numerous components in order to function. The process is extremely complex, and features numerous species of bacteria, each of which has its special environmental requirements. But now, experts propose a new species of bugs that could help treat water more efficiently, while at the same time producing energy, rather than consuming it. The bacteria was discovered by scientists at the Delft University of Technology, in the Netherlands, who were led by expert Gijs Kuenen, NewScientist reports.

The standard clean-up process starts with numerous bacterial cultures being organized in an activated sludge, which is used to digest solid wastes. The result is methane gas, which is derived directly from the organic matter the microorganisms consume. Following this stage, all that remains is ammonium and phosphates-filled liquid wastes, which then need to be further processed. They are introduced into special chambers, where the ammonium inside the wastes is converted into nitrates by bacteria. The wastes are again passed in other chambers, where the nitrate is again converted, this time into nitrogen gas, in the presence of methanol.

The DU team managed to find a solution to treating wastewater that could see the need for the energy-intensive, bacteria-reliant stages disappear. Their secret weapon is an uncommon type of bacteria, which is apparently able to consume ammonia without having to be fed oxygen artificially. The result is producing nitrogen gas directly, and an added bonus of using anammox bacteria is the production of methane. Kuenen explains that the gas can then be easily harvested, and stored for later use. According to his calculations, this process would generate up to 24 watt-hours of electricity per person per day.

“This is about trying to make waste water treatment plants completely sustainable, in the sense that they could even produce energy, which is not the case in present treatment facilities,” the expert adds. “The anammox story shows how fundamental discoveries by microbiologists can revolutionize waste water treatment,” says University of Vienna in Austria microbiologist Michael Wagner. He goes on to say that anammox bacteria were only discovered about 20 years ago, and that they are already beginning to have important applications.