Some microbes grow little electricity-conducting wires, which act as a kind of snorkel, allowing the bacteria to penetrate deeper into sediment, where they can use this electrochemical process to survive where there is no oxygen. The electroactive bacteria can purify water up to ten times faster than conventional methods. “The result is clean water, with zero energy cost and no residual pollution,” says Abraham Esteve-Núñez, researcher in environmental biotechnology at IMDEA AGUA and iMETland project coordinator. the system doesn’t require any external source of energy . Here is the exact description of the method: The wastewater from the nearby town is collected in a septic tank. From there, it flows through this biofilter, where it turns into clean water that can be used for irrigation , up to 25,000 litres per day. That’s enough to cover the needs of a small community. The Spanish experimental plant is run by the Centre for New Water Technologies (CENTA). Similar projects are tested in Mexico, Argentina and Denmark.