AWWA JAW48139

Tighter regulations governing stream discharge of coagulation sludge from the primary sedimentation process prompted the University of Iowa Water Treatment Plant to consider sludge-handling options. This pilot study was undertaken in order to investigate differences in the mechanical dewatering of sludges formed by using either alum or ferric sulfate coagulants. Dewatering of the coagulation sludge was evaluated for two reasons: the low solids content of the sludge would be easier to handle if the sludge was dewatered; and, the costs associated with sludge handling would be reduced. The approach used various volumes of wasted lime sludge produced from the plant's softening process as a filtering aid. The results of the study are discussed. Includes 14 references, table, figures.