New Technology Turns Sewage Plants into Power Plants

Whilst it may not be a thought that often crosses your mind, sewage plants and the water treatment service as a whole uses a lot of energy whilst performing a vital service. For years scientists have been searching for ways to turn these plants, into a net energy creator, not a net energy user. Two options have always been favoured; using a microbial fuel cell within which bacteria consumes the organic matter to produce an electric current; and, a system of reverse electro-dialysis where positive and negative ions are separated by a series of membranes creating a potential difference and therefore a resulting electrical current.

A group of scientists has had success with the revolutionary idea of bringing those two schools of thought together, and claim that they can turn waste treatment stations into power plants for the entire water grid.

Professor Bruce Logan of the Pennsylvania State University in the US was in charge of the team that developed the technology. He said that, “there were a lot of people looking at fuel cells and a completely different group looking at reverse electro-dialysis. We brought the technologies together.” He believes that the technology could provide the power to “take care of the whole water system: the treating and pumping of water, which currently requires substantial amounts of power.”

The two methods for producing electricity from waste water treatment are flawed. Microbial fuel cells are inefficient and the specialised membranes in electro-dialysis are expensive. Logan said that, “by combining the two technologies, we overcame the limitations of the fuel cell and synergistically generated energy for the reverse electrodialysis system.”

The system enables the plants to produce 0.9 kilowatt-hours kWh) of electricity per kilogram of organic waste processed. Not much, but an improvement from the 1.2kWh per kilogram that the treatment used to consume.

Logan believes that switching sewage plants from energy user to energy generators will be especially useful in developing countries.  “There are 2 billion people in the world who need sanitation, including 1 billion who need access to clean water," he said. "If you go into a country and give them a waste treatment system - the World Bank and others have done this - they do not keep it going, as it needs power and maintenance. It is a drain on the community. But if you can also provide electricity for lighting, or charging mobile phones, that's a game-changer.”

By. James Burgess of Oilprice.com