Salmonella bacteria, earlier today

Electricity from urine biotech solution also found to kill pathogens

Researchers at the University of the West of England in Bristol have discovered that the technology they have developed which has already been proven to generate electricity through the process of cleaning organic waste, such as urine, also kills bacteria harmful to humans.

The special process that the research team has developed, in which wastewater flows through a series of cells filled with electroactive microbes, can also be used to attack and destroy a pathogen – the potentially deadly Salmonella.

It is envisaged that the microbial fuel cell (MFC) technology could one day be used in the developing world in areas lacking sanitation and installed in homes to help clean waste before it flows into the municipal sewerage network, reducing the burden on water companies to treat effluent.

Research team leader Professor Ioannis Ieropoulos, director of the Bristol BioEnergy Centre based in the Bristol Robotics Laboratory at UWE Bristol, said it was necessary to establish that the technology could tackle pathogens in order for it to be considered for use in the developing world.

“We were really excited with the results,” he said. It shows we have a stable biological system in which we can treat waste, generate electricity and stop harmful organisms making it through to the sewerage network.”

It had already been established that the MFC technology created by Dr Ieropoulos’ team could successfully clean organic waste, including urine, to the extent that it could be safely released into the environment. Through the same process, electricity is generated – enough to charge a mobile phone or power lighting in earlier trials.

In the unique system, being developed with funding from the Bill & Melinda Gates Foundation, the organic content of the urine is consumed by microbes inside the fuel cells, breaking it down and creating energy.

For the pathogen experiment, Salmonella enteritidis was added to urine flowing through the system, then checked at the end of the process to identify if bacteria numbers had been reduced. Results revealed pathogen numbers had dropped significantly – beyond the minimum requirements used by the sanitation sector.

Other pathogens, including viruses, are now being tested and there are plans for experiments which will establish if the MFC system can eliminate pathogens completely.

John Greenman, Emeritus Professor of Microbiology, said: “The wonderful outcome in this study was that tests showed a reduction in the number of pathogens beyond the minimum expectations in the sanitation world.

“We have reduced the number of pathogenic organisms significantly, but we haven’t shown we can bring them down to zero – we will continue the work to test if we can completely eliminate them.”

Professor Ieropoulos said his system could be beneficial to the wastewater industry because MFC systems fitted in homes could result in wastewater being cleaner when it reaches the sewerage system: “Water companies are under pressure to improve treatment and produce cleaner and cleaner water at the end of the process. This means costs are rising, energy consumption levels are high and chemicals that are not good for the environment are being used.”

In previous urine-focused research work done by the team, a miniature fuel cell that costs less than £2 was created which could generate electricity from a single visit to the toilet and was able to recharge a smartphone. 600ml of urine provided three hours of phone calls for every six hours of charge time.

The team also produced the first completely self-sufficient wearable wireless transmitter powered by urine and the energy of human steps. The pair of custom-made socks were embedded with miniaturised microbial fuel cells that use urine as a source of energy and the system requires no additional source of energy as the urine circulates through the fuel cells solely with the help of the footsteps of the system’s wearer. The device successfully sent a signal to a PC.

Further research work is ongoing looking into microbial fuel cells that can use urine for fuel to generate electricity.

Other novel research into the beneficial uses for urine include the Belgian team that invented a solar-powered machine that turns urine into potable water and fertiliser. The scientists from the University of Ghent demonstrated their technology at a music festival in the city of Ghent, where it successfully recovered 1,000 litres of water from the urine of the festival goers. This water was subsequently used by a local brewery to make beer.

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