A type of bacteria accidentally discovered during a water research project could significantly reduce the amount of electricity consumed for nitrogen removal during wastewater treatment.

The discovery during the EPSRC-funded Healthy Drinking Water project has upended a century of conventional thinking. The microorganisms –‘comammox’ (complete ammonia oxidising) bacteria – can completely turn ammonia into nitrates. Traditionally, this vital step in removing nitrogen from wastewater has involved using two different microorganisms in a two-step approach: ammonia is oxidised into nitrites that are then oxidised into nitrates, which are turned into nitrogen gas and flared off harmlessly.

Wastewater treatment is a huge consumer of electricity, accounting for two to three per cent of all power usage in western countries, and no less than 30 per cent of its energy bill results from the need to remove nitrogen. Most of the sector’s efforts to reduce its energy use have focused on the two-microorganism approach.

The discovery of Comammox was made in a drinking water system in the US by scientists working on the Healthy Drinking Water project, led by the University of Glasgow in collaboration with the University of Michigan. Team leader, Dr Ameet Pinto, said that the discovery took the scientists completely by surprise. He said: “The discovery of a single microorganism capable of full nitrification will have a significant impact on our understanding of the nitrogen cycle and on efforts to manage nitrogen pollution. The potential is there for the wastewater treatment sector to exploit this breakthrough. That would be an important step towards informing the development of robust approaches in terms of cutting costs and reducing carbon emissions associated with generating the huge amounts of electricity that the sector uses.”