A self-powered waste water treatment plant using microbes has just passed its biggest test, bringing household-level water recycling a step closer. Personal water treatment plants could soon be recycling our waste water and producing energy on the side.

Boston-based Cambrian Innovation have began field tests of what’s known as a microbial fuel cell at the Naval Surface Warfare Center in Maryland. Called BioVolt, in one day it can convert 2250 litres of sewage into enough clean water for at least 15 people. Not only that, it generates the electricity to power itself – plus a bit left over.

Conventional treatment plants guzzle energy, consuming 1.5 kilowatt-hours for every kilogram of pollutants removed. In the US, this amounts to 3 per cent of the total energy demand. If the plants could be self-powered, recycling our own waste water could become as commonplace as putting a solar panel on a roof.

Existing treatment plants use bacteria to metabolise the organic material in waste water. At the end of the process, the microbes can make up a third by weight of the leftovers to be disposed of. Before being put in landfill, this “microbe cake” itself needs to be heat-sterilised and chemically treated, which uses a lot of energy.

The idea Brhind microbial fuel cells is that the biochemistry involved in metabolising the contaminants can yield electricity to help power the process. But fuel cells of this kind have been very difficult to scale up outside the lab. But once scaled up, the Cambrian system will be processing more than 20,000 litres per day. Microbial fuel cells may do for renewable water what solar and wind did for renewable energy

Others are working on the same problem. The mix of organisms used by BioVolt, for instance, liberate some electrons as they respire, effectively turning the whole set-up into a battery. This has the added benefit of slowing bacterial growth, so that at the end of the process you have electricity and no microbe cake.

Cambrian CEO Matt Silver sees a future in which different kinds of microbial fuel cells treat different kinds of waste, perhaps recovering useful by-products. Another of the firm’s designs, EcoVolt, generates methane as it cleans up waste water produced by a Californian brewery. It has also cut the brewery’s energy use by 15 per cent and its water use by 40 per cent. (adapted from an article by Sally Adee, New Scientist)

You look around and sometimes despair of when you think of thr future of our over-crowded, over-heated planet. But then you look at what scientists are doing and faith is restored. Science is not respected among a section of the population, but it is science, and really clever science, that will see us through. Scientists are Epicureans, bringing us practical solutions to seemingly dreadful problems. We should honour them.