The performance of a pilot-scale series of ten ponds treating municipal sewage in northeast Brazil

The performance of a pilot-scale long series of ten ponds was evaluated in terms of the removal of BOD5, COD, suspended solids and faecal coliforms with data from two experiments with total mean hydraulic retention times of 19 and 28.5d. Overall removals were very good and in both experiments the final effluent of the series complied with the recommended FC count of less than 1000 per 100ml for unrestricted irrigation, and unfiltered BOD5 concentrations were less than 20 mg/l. The long series of ponds was concluded to be a land-saving alternative compared to other pond configurations previously studied at EXTRABES. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.