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Wastewater-treatment system could also produce electricity

Researchers in Scotland are hoping a new low-cost wastewater-treatment system for the developing world could also produce electricity.

A multi-disciplinary team led by Glasgow University has received £1m from the EPSRC to create a bacteria-based system for treating waste in areas on the outskirts of cities that have poor or no sewage facilities.

Scientists will bio-engineer bacteria to break down large amounts of solid waste using anaerobic digestion (without oxygen) in a reactor based on existing technology used by distilleries and pharmaceutical companies.

They hope to be able to capture the gas from the process to generate electricity. Because the system would not produce other waste products, they also hope it could improve wastewater treatment in the developed world.

An estimated one billion people worldwide live in peri-urban zones that only have open sewers and pit latrines rather than water-based sewage systems, principal investigator Dr Gavin Collins told The Engineer.

‘We can use anaerobic digestion where we can pump high volumes of high-solid wastewater in to achieve a much more efficient system and at the same time not pump energy into the system because it doesn’t need air.

‘The obvious alternatives are based on aerobic digestion like those used in developed countries. But these are unsustainable approaches where we don’t recoup any energy or useful products. Instead we put a lot of energy in and it costs a lot of money.

‘Conventional techniques also result in the production of huge volumes of excess sludge and new waste, which we also want to avoid.’

The project involves researchers from Brighton, Cranfield, Newcastle, Sheffield and Ulster universities and is expected to take four years to produce a prototype system.

Existing anaerobic systems are typically used to treat industrial wastewater with a low solid content. These expanded granular sludge bed (EGSB) reactors rely on the bacteria staying in the tank but high-solid waste would push them out.

‘Our hypothesis is that we can eco-engineer the bacteria so that they will stay in the system despite the fact that we’ll be pumping high-solid waste water through,’ said Collins.

Part of the challenge will be designing a system that will be socially and culturally acceptable, as well as practical, for populations in the developing world, he added.

The team has yet to work out how it will capture the gas from the system and needs to determine on what scale it can be feasibly and acceptably done in developing countries. It also has the challenge of getting the waste to the digesters.

If it can successfully build a high-rate solid-waste system, there might also be an opportunity to employ the technology in the developed world to treat the sludge produced by aerobic digestion.

‘We could radically increase the rate at which we treat sewage sludge in the UK, which is growing every year as we roll out more wastewater-treatment plants and is the biggest problem the water industry has in this country,’ said Collins.

Readers' comments (5)

  • Am I missing something?
    I think the article needs to go into a bit more detail to explain in which particular field the original work will be done that requires 4 years and £1million worth of research.
    The author seems to confuse concepts of sludge treatment and attached growth wet stream treatments. If it is sludge (i.e. pit latrine concentrate and the like, as seems to be more strongly implied) how will the research “improve wastewater treatment in the developed world"?
    UK public health engineers have supplied huge numbers of sewage and sludge treatment solutions all round the world since the days of Bazalgette. Our own water industry is operating digesters in vast numbers, adding new solids, capturing gas and burning it to supply internal and external demand for heat and power, many designed and delivered by my own company as the world leader in wet infrastructure. We already have knowledge and understanding of a vast array of problems and their solutions.

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  • The principal investigator, Dr Gavin Collins is an environmental microbiologist affiliated to Glasgow University's School of Engineering.

    The partners are:
    - Cranfield University (Prof Simon Parsons: water chemistry and treatment),
    - University of Sheffield (Prof Catherine Biggs: environmental biotechnology),
    - Institute of Development Studies, University of Sussex (Dr Lyla Mehta: sociology),
    - University of Ulster (Dr David Raffo: product design),
    - University of Newcastle (Dr Jaime Amezaga and Dr Charlotte Paterson: environmental policy and planning).

    As well as treating waste water with high amounts of solid waste, Collins hopes the process will be applicable to the waste products of existing waste water treatments used in developed countries. If these products can be treated more quickly then the whole wastewater treatment process will be improved.

  • the treated waste will still require dewatering to reduce disposal costs, and that will inevitably throw up a nutrient and BOD rich waste stream and some form of biological oxidation will still be required

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  • Such systems were built more than 25 years ago in East Germany to treat the sewage of Berlin. The energy inherent in the sewage was used to operate the plant.

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  • The idea is very good. However, the researchers are probably unaware of the scenario in the developing world, which is being targeted. For example, majority of the people have no proper facilities for latrine and they go in the fields. How do you tap such source for collection and further processing. Most of such researches are funded in the name of developing world but end up helping further the developed world. May be the researchers can throw some light on this. Thanks.

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  • I've yet to see a waste to energy extraction system which harnesses AD methane to dual fuel engine generator [with CHP feed], followed by sludge to centrifuge to dewater, then pass to boiler, feeding turbine generator and CHP and producing reduced volume of ash for disposal.
    Obviously NIMBY action would resist the installation but couldn't the CHP feed a commercial estate? [as practised by Scottish & Southern] I'm surprised a joint venture with a water co has not been mooted/trialed in recent years, despite the numerous historic examples of elements of the above process.

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