Electrogenic bacteria exist in sludge, the by-product of wastewater treatment, which contains rich organic nutrients and diverse microbes that feed on them. While studying wastewater as a potential energy generator, the scientists realized that these clever microbes could do even more: They can purify water. To this end, Qian devised a method to inoculate MFCs with bacteria-filled sludge collected from a local water reclamation plant. The bacteria attached to the MFC anode, coating it with a biofilm that converts organic waste into carbon dioxide, producing electrical current while also reducing organic matter in the water. “We can consider this microbial fuel cell a multifunctional device,” Qian says. “It produces energy and also treats wastewater. We hope to develop this technology and scale it up for broader use