Leeds boosts sludge recycling

Yorkshire Water and Marie Roberts

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Leeds boosts sludge recycling
Design drawing of Knostrop WwTW showing new sludge treatment works in beige

Knostrop waste water treatment works (WwTW) has been treating sewage from domestic properties and industry in Leeds for approximately 100 years. It serves the whole of the city, treating waste water from 1.1 million customers and returning it back to the watercourse. Now Yorkshire Water is investing £72 million in a state-of the-art sludge treatment and anaerobic digestion (AD) facility at the works.

Sludge at the works is currently incinerated or transferred offsite for further treatment. Yorkshire Water is committed to lowering its dependence on incineration, in favour of more sustainable alternatives. The new facility on Knowsthorpe Lane will replace the existing sludge and bio-solid incinerator built in 1993 and enable the more efficient and effective treatment of sewage, combined with the additional benefit of renewable power production from the waste water effluent.

Nevil Muncaster, Director of Asset Management, said: “This is the single biggest investment of our current investment period (2015-2020) and will not only provide increased treatment capacity for our sludges but will also deliver significant operational cost savings, enabling us to keep customer bills as low as possible.”

Black & Veatch and civil engineering partner Clugston Construction are working together to construct the £72 million bio-energy facility.

Planned for completion in 2019, the new Knostrop facility will be capable of processing 131 tonnes of dry sludge a day. The new AD facility will break down the sludge in four digesters, eventually generating enough renewable energy to power 8,000 homes or over half the site’s energy needs. This method of treatment lowers YW’s dependence on incinerators.

In October 2014, a 123-metre-high wind turbine was constructed at Knostrop. This structure, which cost around £3.5 million, is already a major source of power for the site.

As Knostrop WwTW’s project manager, Fiona Sugden, explains: “The micro-organisms involved in the AD process give off methane which we can capture and turn into electricity. This will then be used to power the site which, along with our wind turbine, will provide 65 per cent of the site’s energy needs.”

The sludge is further treated using lime so that it is safe to use as a fertiliser on farmland and fields in the surrounding area.

The technology has been tried and tested by other water companies as well as at a number of other Yorkshire Water sites, such as Blackburn Meadows in Sheffield.

Benefits

•    15 per cent reduction in carbon emissions across the company

•    Provide 55 per cent of the site’s energy needs

•    Contribute towards achieving 94 per cent recycling of the region’s sludge by 2020

 

Nevil Muncaster explained: “Knostrop is designated as a strategic waste site so by increasing the future sludge and bio-solid treatment capacity of the works the project will support also growth in the Leeds sub-regions.”

The project is the latest step in Yorkshire Water’s commitment to investing in renewable energy to benefit the environment and keep customers’ bills low. The company intends to generate approximately 18 per cent of its energy needs by 2020.

The project also supports Leeds City Council’s ambition for the Lower Aire Valley to become a hub for green energy and industry.

www.yorkshirewater.com