Wastewater treatment is vital to remove pathogens, but is typically incredibly energy intensive – responsible for around 3 per cent of energy use in the UK, equivalent to 13 billion kilowatt hours.
The researchers managed to cut the energy used in the purification process by using microbial electrolysis cells that use electromagnetic microorganisms to break down organic pollutants in waste water, producing clean water and hydrogen gas.
The ability to produce hydrogen gas is valuable in itself, as it can be sold to chemical and plastics industry or used in hydrogen fuel cells for energy storage or electric vehicles.
Although the research sounds promising, it hasn’t yet been developed on an industrial scale, as the anode materials – which are used in the reaction to breakdown the organic pollutants – are made of graphite or carbon and cost several hundred pounds per square metre. They also only produce low rates of hydrogen.
However, the research team has been refining the technique by looking at alternative anode materials and processing methods and have successfully identified recycled carbon-fibre mats as an alternative anode, which only cost £2 per square metre – significantly cheaper than existing anode materials.
After testing the carbon-fibre mats on both synthetic wastewater and real wastewater, researchers found that the bacteria developed on the recycled carbon-fibre anode, which had better temperature tolerance and produced more hydrogen than previously used materials.
They then decided to pilot their techniques at Severn Trent’s Minworth waste treatment site, where they successfully processed up to 100 litres of wastewater per day, removing 51 per cent of organic pollutants and up to 100 per cent of suspended solids from the water, whilst also producing 18 times more hydrogen (at 100 per cent purity) than the graphite material.
Dr Stuart Coles, research team leader from the University of Warwick, said: “We are really excited about this technology. By taking waste from the automotive and aerospace sectors, we have developed a circular solution to a longstanding problem. Instead of just treating the wastewater, we are now able to extract value from it in the form of hydrogen at a lower cost than ever before.
“The next phase of this work is look at optimising the design of the microbial electrolysis cells and further reduce the level of pollutants in the water. This in turn should help produce even more hydrogen!”
Bob Stear, chief engineer at Severn Trent, added: “This technology has the potential to create a more circular wastewater treatment process which will be essential to delivering on our long-term sustainability goals and net zero plans. We’re currently scoping scaling up the technology at our test-bed plant in Redditch.”