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Sustainable sewage treatment impresses award judges


image depicting The South West Water team receiving their Cornwall Sustainability Award
The South West Water team receiving their Cornwall Sustainability Award
The unglamorous world of sewage treatment enjoyed a rare moment in the spotlight at this year's Cornwall Sustainability Awards.

South West Water's team at Hayle Sewage Treatment Works, near St Erth in Cornwall, won the resource management category for their environmental achievements.

One of the by-products of the sewage treatment process is biogas, produced during the anaerobic digestion process, which can be burned to provide heat and power.

Historically, the biogas created at Hayle has had high levels of hydrogen sulphide gas, which damages combined heat and power (CHP) engines. This year, the team fitted a gas scrubbing unit to reduce the amount of hydrogen sulphide in the biogas to prolong the life of the engines and upgraded the computer systems controlling the CHP process.

As a result, the three CHP engines on site now generate enough electricity to power the entire anaerobic digestion process and any surplus is exported to the National Grid. Between April 2012 and September 2013, the site generated a total of 454 MWh of electricity.

Another by-product of the treatment process is the aptly named 'sludge' - which when treated to produce a nutrient-rich organic matter called biosolids can be recycled on agricultural land as fertiliser.

In order to make biosolids suitable for local crops, sludge is treated with quicklime to destroy potential pathogens - but quicklime can be stinky, expensive and raise soil pH above the optimum level after repeated applications.

Instead, this summer the biosolids from the site have been recycled at a licensed and approved land restoration area in the china clay waste tips near St Austell.

As well as transforming a derelict wasteland to a green landscape, the team saved an estimated 1.8 tonnes of carbon dioxide by reducing the amount of quicklime quarried and transported.

And the good news for customers is that all this has been achieved without the nasty smells commonly associated with sewage treatment - over the summer there were only two odour complaints compared to 35 during the same period in 2011.

Operations Manager Mike Galligan said: "We were delighted to be recognised for the improvements we have made at Hayle Sewage Treatment Works.

"It just goes to show that even sewage can play its part in producing renewable energy and improving the local environment for everyone."

It's the second award in a row for the West team, who last year won the Low Carbon Business Award for energy use at Par Sewage Treatment Works at the same event.

Notes to editors

  • South West Water provides water and sewerage services to over 1.6 million people across Devon, Cornwall and parts of Somerset and Dorset
  • South West Water operates over 630 sewage treatment works and 29 water treatment works
  • South West Water maintains 14,800km of public sewers and 15,101km of water mains
  • We supply our customers with around 349 mega litres (79 million gallons) of drinking water every day
  • On average, half a billion litres of sewage arrives at South West Water's treatment works every day.
  • In 2014 South West Water will submit its business plan for the years ahead to the UK water industry regulator Ofwat. We are inviting customers to find out more and tell us what they think our priorities should be at www.southwestwater.co.uk/waterfuture

Published: 10 December 2012

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