Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | ocTober 2014 | 27 The most efficient and cost-effective solution was to use an electric submersible pump on each digester A nglian Water's Pyewipe water recycling centre in Grimsby not only processes 400m3 of sludge every day from the sewage works on site, but also processes an additional 600m3 of sludge and 100 tonnes of cake each day from other sites on the Anglian Water network. The site has used thermal dryers to process the sludge for many years, using heat to dewater the sludge and kill bacteria to enable the waste to be recycled as pellets for use as fertiliser. The process was reliable and effec- tive but it was also very energy inef- ficient. Explains treatment optimiser at Anglian Water John Jennings: "The site has its own Combined Heat & Power (CHP) plants which are pow- ered using methane from the sludge digestion during processing. However, despite energy efficiency measures like this, the thermal drying process was using huge amounts of energy which had both cost and sustainability impli- cations for Anglian Water. "As a result, the decision was made to convert the sludge dewatering process to a heat, pasteurisation & hydrolysis (HPH) advanced digestion process, which would not only gener- ate energy efficiencies but would also reduce the operational requirements on site, streamlining our operations and helping us to reduce costs." Pumps & pumping systems Managing a technology transition A hot topic Sludge treatment at Pyewipe is fed by three digesters where the sludge had to be maintained at 3% dry solids for the thermal drying process. The sludge was also maintained at a constant Project focus ● Pyewipe plant moved from thermal dewatering to advanced digestion for sludge treatment ● existing pumps could not cope with the change in sludge temperature and viscosity ● Temporary pumps kept the site running during the transition Chris GrAhAm sales direcTor, sykes PumPs ● reducing operating costs and improving the sustainability of water and waste water treatment assets is a key focus for Anglian Water and this project achieves both of those important goals. ● The move from thermal drying to hPh will reduce energy consumption at Pyewipe as the new engines will provide all the power for the site requirements. ● hPh also reduces the amount of cake produced which will be used as a fertilizer which will contribute to the overall operational savings. • Drivers • Challenges ● managing the change- over from one process to another is always challenging because the waste stream cannot be put on hold while the infrastructure is updated. ● Careful planning and ensuring those plans were implemented to business critical dead- lines was pivotal to the success of the asset im- provement scheme. The inability of the pumps to maintain the required sludge at the increased level of solids content could have pushed that timeline off course.

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