Clean energy from dirty water: new technology combines wastewater treatment with hydrogen production

Posted: Thursday 21st February 2013

A new technology that harnesses the power of bacteria could transform wastewater from an expensive problem to a sustainable source of hydrogen and valuable chemicals. These ‘bioelectrochemical systems’ are described in a new report from Science for Environment Policy published on 7 February 2013.

Electrically-active microorganisms in bioelectrochemical systems can remove contaminants from wastewater while, at the same time, producing valuable commodities, such as hydrogen or caustic soda. Pilot studies have indicated that energy captured by the systems as hydrogen can greatly offset, or even surpass, the energy needed to initiate the process.

Providing an introductory guide to the technology, the report ‘Bioelectrochemical systems: Wastewater treatment, bioenergy and valuable chemicals delivered by bacteria’ is free to download from:

http://ec.europa.eu/science-environment-policy

Wastewater treatment can be an expensive and difficult process, requiring large amounts of energy. However, in bioelectrochemical systems, microorganisms break down the contaminants of wastewater, a process that releases electrons. This creates a current and generates electricity.

In a further process, these electrons, if deprived of oxygen, can produce hydrogen gas from protons, an important environmentally-friendly fuel source. Bioelectrochemical systems can also be set up to produce other valuable products, such as caustic soda.

The technology is yet to be used on a wide-scale basis, but pilot studies on domestic and industrial wastewater have shown promising results. A bioelectrochemical pilot scheme in the UK, mainly treating domestic wastewater, used hydrogen capture to recover 70% of the initial energy used and, with planned improvements, researchers predict that the scheme could become ‘energy positive’, i.e. produce more energy than is required to run the wastewater treatment.

In a similar system piloted on winery wastewater, the energy content of hydrogen and methane gas captured exceeded that of the initial electrical input.

Other than energy efficiency and cost reduction, the report indicates that there are other advantages of bioelectrochemical systems. Unlike conventional wastewater treatments, they produce almost no sludge by-product, remain active at low temperatures and do not require new facilities to be built, as existing infrastructure can be modified to incorporate the systems.

However, some barriers to commercialisation remain, such as high capital costs. The scientific studies summarised by the report suggest that these could be offset by focusing on the recovery of resources, such as hydrogen or caustic soda, as the main asset of the systems, as these have a high economic value.

Despite these challenges, researchers are optimistic that commercial installations could be available in two to five years’ time.




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