The first commercial-scale plant, to convert sewage sludge to oil, using the ENERSLUDGE(TM) technology, has recently been constructed at the Subiaco Wastewater Treatment Plant (WWTP) in Perth, Western Australia. The plant, designed to process up to 25 dry tonnes per day (tpd) of mixed raw primary and thickened excess activated sludge, comprises numerous unit operations which allows the facility to operate in four distinct modes, namely as a chemical stabilisation plant, an LPG-fired dryer, an autogenous sludge dryer and ultimately as a sludge conversion plant. As of June 1999, the plant is operable in the first three modes of operation. Commissioning of Mode 4, namely sludge conversion to commence in August 1999 and initial results provide confidence in the technology, with the major problems being mechanical in nature. Operating results have indicated sludge quality has a major impact on plant performance. To improve operability, a strainpress has been installed to remove much of the hair and fibre present in the sludge. The plant can now successfully process sludge with between 20 and 50% by weight of thickened excess activated sludge.
