Thames Water is to employ a Biothelys thermal hydrolysis plant, from Veolia Water Solutions & Technologies, at its Oxford sewage treatment works (STW). The unit is scheduled to be in operation by March 2014.

The Oxford plant will treat a throughput of 25,000 tonnes of dry solids per year. This will be composed of a mixture of primary and secondary sludges produced, both at the Oxford works itself together with those imported from outlying works.

The treated sludge produced by the thermal hydrolysis process will be fed to the downstream anaerobic digesters at a much higher dry solids concentration (typically 10 – 12%) compared with only 5-6% for untreated sludge.  This will, in effect, double the existing digester throughput.

The use of thermal hydrolysis at Oxford will also substantially increase the amount of biogas produced by the existing AD plant.  This biogas will then be used to generate “green” electricity via a combined heat and power (CHP) plant.

In addition, due to the higher destruction of volatile matter, there will be less sludge left at the end of the process for final disposal.

Veolia’s contract for the Biothelys thermal hydrolysis plant at Oxford was awarded by Kier Infrastructure and Overseas Ltd – main contractor for the overall scheme.

The scheme also comprises refurbishment of the existing anaerobic digestion plant and new sludge storage and handling facilities.

The contract award follows Yorkshire Water's recent adoption of the Biothelys technology at its Esholt STW.