Northumbrian Water developing waste digestion plant

WORK has begun on a Tyneside plant which will convert waste products into green electricity.

Bran Sands on Teesside
Bran Sands on Teesside

WORK has begun on a Tyneside plant which will convert waste products into green electricity. Northumbrian Water is developing the advanced digestion plant at its Howdon sewage treatment works in North Tyneside.

It plans to process sludge remaining after sewage treatment to generate electricity to power the site in a major move towards environmental sustainability.

The firm already has a similar plant at its largest works at Bran Sands on Teesside.

This change of process at Northumbrian Water’s five-acre treatment works at Howdon is a £34m investment.

Work started on site at the end of January and the plant is due to be fully operational by summer next year.

It will use the emerging 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 one million people – will be reduced to about 60,000 tonnes and will generate four megawatts 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 people’s kitchens.

The sludge is then de-pressurised 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 11m-diameter biogas storage bags before being used to fuel gas engines to create enough renewable electricity to power most of the Howdon treatment works.

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.

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 reuse and recover valuable resources from sludge and create renewable energy puts 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 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 £34m 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.

The same process could also be used to turn food scraps in household rubbish and farm waste products into green energy.

Northumbrian Water’s project comes as the Office of Fair Trading (OFT) announced it will carry out a study looking at whether the market for treating organic waste is working effectively to deliver the best outcomes for customers.

The OFT says there are new opportunities to use advanced technologies such as digestion for producing clean energy from this waste.

The study, supported by water industry watchdog Ofwat, will examine whether there are appropriate incentives in place for the efficient use of these technologies and whether barriers are getting in the way.


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