Dewatering characteristics of algae-containing alum sludge

Abstract

The presence of algae in source waters not only causes problems in the water treatment process, but also complicates the treatment and disposal of sludge. This has become a major concern in Taiwan because of the increasing eutrophication of water sources. The purpose of this study was to determine the effects of algae during aging process on the characteristics of potable water treatment residuals and investigate their conditioning in order to provide water treatment plants with guidelines for treating algae-containing sludge. In this study, we measured the bound water content and CST to evaluate the influence of algae and their exudates on sludge conditioning. The change in zeta potential was monitored during sludge aging. During the aging process up to 5 days, the surface charge of sludge became more negative and the dewaterability was enhanced by algal exudates. Microphotographs of the algae-containing sludge suggest that algae and their exudates cause the bio-flocculation phenomenon. (C) 1999 Elsevier Science B.V. All rights reserved.