Anammox bacteria can be persuaded to generate electricity from wastewater, if they are grown on electrodes in the absence of nitrite. The finding is the result of new research carried out by microbiologists at Radboud University, in collaboration with colleagues from the US and Saudi Arabia, published in Nature Communications. It’s the final piece of the puzzle in a long scientific investigation by lead researcher Mike Jetten into “impossible reactions”.
Anammox bacteria are known all over the world for their ability to turn ammonium into nitrogen without using any oxygen. For a long time, scientists considered this an impossible reaction. The anammox bacteria that can do this were discovered 25 years ago, and they’re actually quite common in canals, oceans and on sea floors.
Anammox bacteria are now used all over the world in water purification systems to remove hazardous ammonium from wastewater. Because this method requires so much less oxygen, it’s very energy efficient and therefore more sustainable than standard methods of water purification.
Electricity from wastewater
Another possible interesting use of this bacteria has also emerged. “When one substance is turned into another, bacteria can release electrons, and you can then use those to produce electricity. So our question was: can we persuade anammox bacteria to generate electricity from wastewater?” says Mike Jetten, Professor of Ecological Microbiology at Radboud University.
The answer was yes. Ordinarily, when ammonium is broken down, electrons are released which are then used by the bacteria to break down nitrite. By gradually reducing the quantity of nitrite, the researchers forced the anammox bacteria to dispose of the electrons from ammonium in some other way. “Using special metal electrodes, we were able to capture the released electrons in a mini-reactor, and then run them through electrical wiring. And sure enough, eventually the electricity metre surged,” says Jetten.