Side-Stream Treatment of Raw-Sludge Liquors using Activated Sludge: Pilot Investigations and Full-Scale Design Rationale

The end of sludge disposal at sea in 1998 will lead to increased volumes of sludge requiring treatment and disposal. Accordingly, there will be further quantities of high-strength liquors arising from sludge thickening and dewatering processes, and additional treatment capacity will therefore be required at treatment works.
This paper describes a three-year project to develop a dedicated side-stream treatment process for the treatment of raw-sludge liquors at Knostrop sewage-treatment works (Leeds) based on the activated-sludge process. Large pilot-scale trials are described which assisted in the construction of simple process design models for full-scale design. Together with additional pilot-scale aeration testing and modelling, a cost model for a full-scale plant was developed, allowing the lowest whole-life cost plant, based on 'net present cost'analysis, to be specified.