Mott MacDonald has won a contract from SUE Vodokanal of St Petersburg â St Petersburgâs water and wastewater utility â to supervise the provision of wastewater sludge incineration facilities for its northern wastewater treatment. The new facilities â which will reduce the quantities of sludge currently going into landfill sites â are also being designed to generate electricity and supply district heating by utilising waste heat. Under the EUR 41 million first stage of the âdesign-buildâ? contract, two fluidised bed incinerators will be developed, each capable of incinerating 61 tonnes of sludge and dry solids per day. The majority of the ash in the incinerator flue gas will be removed by electrostatic precipitators. Chemicals will then be injected into the flue gas streams to react with substances such as sulphur and mercury to produce solids, which together with the remainder of the ash will be removed by bag filters so that the flue gas released into the atmosphere complies with the latest European Union directive. The incineration process wonât require additional fuel as the existing sludge thickening and dewatering process will be upgraded so that the dry solids content of the sludge entering the incinerators is not less than 25% weight for weight. The hot flue gases will be used to raise steam so that the waste heat from the incinerators can be utilised to generate up to 3 MW of electricity and to provide heat for an existing district heating system. The project will be completed and commissioned in October 2006.
