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Northumbrian Water has added four new centrifuges and a complete spare rotating assembly’s at a new energy-from-sludge facility serving its Bran Sands sewage treatment works in Teesside.

The project was a part of the overall £33-million scheme which uses anaerobic digestion to treat sludge from the wastewater treatment works, generating biogas which is used onsite in the CHP unit.

The centrifuges – Hiller Decapress model DP76–402 VAHY units – and spare assembly were supplied by MSE Hiller, via JN Bentleys

The Northumbrian Water project used CAMBI thermal hydrolysis process (THP), using heat and pressure to break down cell walls increasing enzyme hydrolysis and therefore digestion rates. This is said to lead to halve volume of sludge produced and significantly increase biogas quantity.

The new plant generates some 4.7 MWe from biogas which is used to power the treatment process. This has reportedly reduced the plant's reliance on natural gas to less than 10% of its former figures, aiding the path to become self-sufficient for energy.

Two of the new centrifuges are used to pre thicken sludge prior to the THP plant providing a controlled discharge of cake at 18 % dry solids at flow rates of up to 100 m3/hr each, explains MSE Hiller.

The HMR5000 control system and hydraulic scroll drive enables the machine to counter for variances in feed dry solids and continuously optimises machine performance, the supplier added.

Post THP the digested sludge is dewatered at flowrates of 35 to 70 m3/hr using two of the Hiller DP76-402VAHY centrifuges to a cake of over 30% dry solids. It can then be disposed off site as a Class A bio solid with no detectable pathogens and as a valuable agricultural fertiliser.