Operating experience with the first plant commissioned in England is described with particular reference to the changes in operating conditions and costs which have occurred. In the year ending 31st March, 1970 the operating costs, including transport of presscake and ash, were ₤2.8 per tonne sludge dry solids but in that ending March 1982 they were ₤73.

The factors, in addition to inflation, which were responsible for this are discussed. Reference is also made to plant reliability and maintenance aspects and to the improvements which have been made.

Investigations of ways of reducing costs, notably by tipping half the presscake in conjunction with the ash produced by burning the rest of the presscake, are described. Trials using waste derived fuel as a substitute for oil are referred to as is the use of polyelectrolytes for sludge conditioning instead of lime and copperas.

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