International environmental engineer MWH has been appointed lead consultant on a new waste water sludge treatment plant being installed at the Bran Sands site, near Middlesbrough.
Work has begun on the £28m plant which is being constructed for Northumbrian Water (NWL). It will use thermal hydrolysis advanced digestion, and is due to be fully operational in June 2009.
Dave Young, programme manager at MWH’s Newcastle upon Tyne office said: ‘The raw sludge, which is treated using the current plant, is dried and pelletised using giant thermal driers. The new plant will use a completely different sludge treatment process, which provides NWL with many advantages.
‘This means a significant reduction in gas and electricity currently used, with a consequent reduction in carbon emissions, and will also produce 5MW of electricity in the process.’
In the new process, the sludge water content will be reduced before being loaded into giant steam ‘pressure cookers’ at 165oC, then cooled and fed into new digesters. The methane given off by the digestion process will then be collected in 11m diameter biogas storage bags before being used to fuel 5MW gas engines which could generate enough renewable electricity to power about half of the entire 21 hectare treatment works site at Bran Sands.
The digested sludge cake remaining after the process will be an enhanced, treated product, with low odour, that will be used as an agricultural fertiliser.