Technical Bulletin No. 0491: An Examination of Secondard Clarifier Design and Performance in the Pulp and Paper Industry

This technical bulletin was prepared to determine the validity of reports that some parameters associated with the design and operation of existing secondary clarifiers might significantly influence activated sludge effluent quality. It drew on 39 years of performance data in the National Council's treatment plant database and reflected the performance of twenty-one activated sludge systems. Effluent quality for suspended solids and BODS was presented in detail. However, this bulletin focuses on the conditions under which activated sludge was separated from a liquid and thickened in a secondary clarifier.