Pressure cooking green power for the future

19.01.2011

Work is about to start on a plant to convert sludge remaining after sewage treatment into green electricity.

It will power Northumbrian Water’s main treatment works on Tyneside in a major move towards environmental sustainability.

The scheme at Howdon Sewage Treatment works will compliment Northumbrian Water’s other advanced digestion plant recently installed at its largest works at Bran Sands on Teesside.

This change of process at Northumbrian Water’s second biggest five acre treatment works at Howdon, North Tyneside, is a £34million investment.

Work will start on site on 28 January, 2011 and the plant will be fully operational by summer 2012.

It will use the emerging new technology of ‘thermal hydrolysis advanced digestion’ and keeps Northumbrian Water at the forefront of the water industry.

More than 500,000 tonnes of sludge - from the treatment of domestic sewage and industrial effluent from a population equivalent of 1,000,000 people – will be reduced to about 60,000 tonnes and will generate four mega watts of green electricity.

Sludge will be loaded into pressurised reactors and heated at 165 degrees centigrade at 6Bar.

This stage of the process can be loosely compared to domestic pressure cookers, found in most people’s kitchens.

The sludge is then depressurised and cooled before being fed into large concrete digesters for the bacterial process to start.

Methane given off by the bugs digesting the waste will then be collected in 11-metre diameter biogas storage bags before being used to fuel gas engines to create enough renewable electricity to power most of the entire Howdon treatment works.
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Any waste heat will also be captured and utilised efficiently within the advanced digestion process itself.

The digested sludge ‘cake’ remaining after the process will be a Class A biosolid - a safe and low odour product containing no detectable levels of pathogens, such as E-coli, and will be used as a valuable agricultural fertiliser.

The new process will significantly reduce the company’s carbon footprint as well as improving efficiency and the work will also include additional odour control measures on the site.

Northumbrian Water’s Technical Director, Dr Colin Price, said: “Development of this sustainable process to re-use and recover valuable resources from sludge and create renewable energy puts both Howdon and Bran Sands in the national spotlight as centres of environmental excellence.”

The new Advanced Digestion process at Howdon will treat sludge from Tyneside and north of the river Tyne.

Sludge from sewage treatment from south of the River Tyne and in the Tees Valley will continue to be treated by the advanced digestion facility at Northumbrian Water’s Bran Sands site at Tees Dock.

The current sludge treatment facility at Howdon, which utilises lime stabilisation, will be decommissioned and will remain available as a strategic contingency.

The £34 million contract to design, construct, install and commission the new Howdon plant has been awarded to Galliford Try Infrastructure Services and Imtech Process, companies that have a proven track record in delivering advanced digestion plants in the UK.

For further information contact Alistair Baker 0191-301-6851 or 07711-793493.

Illustration caption: Northumbrian Water’s existing advanced digestion plant at Bran Sands on Teesside - the plant at Howdon will be a similar design.

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