Engineers say they've developed microbial fuel cells that can produce up to 50 times more electricity directly from wastewater as previous efforts.
The Oregon State University researchers say this could eventually change the way that wastewater is treated all over the world, replacing the widely used 'activated sludge' process that has been in use for almost a century.
The new approach would produce significant amounts of electricity while effectively cleaning the wastewater.
"If this technology works on a commercial scale the way we believe it will, the treatment of wastewater could be a huge energy producer, not a huge energy cost," says associate professor Hong Liu.
"This could have an impact around the world, save a great deal of money, provide better water treatment and promote energy sustainability."
Using reduced anode-cathode spacing, evolved microbes and new separator materials, the technology can now produce more than two kilowatts per cubic meter of liquid reactor volume, says the team.
The system also works better than an alternative approach based on anaerobic digestion and lacks the associated environmental drawbacks, such as the production of unwanted hydrogen sulfide or methane.
With the new system, bacteria oxidize the organic matter and, in the process, produce electrons that run from the anode to the cathode within the fuel cell, creating an electrical current. Almost any type of organic waste material can be used to produce electricity, says the team, from wastewater to grass straw.
The next step is a pilot study, but the team reckons that the capital construction costs should eventually be comparable to that of the activated sludge systems currently in use - and even less when future sales of excess electricity are factored in.