Abstract
High viscous substances were extracted from activated sludge with 2 N and 0.1 N NaOH solution, and their floc-forming abilities were examined. Both alkaline extracts flocculated kaolin and Escherichia coli suspensions at below pH 3, but not near pH 7 which is a flocculating range for activated sludge. The substance extracted from E. coli with 2 N NaOH did not flocculate kaolin suspension in any pH range. The substance extracted from activated sludge was insoluble in strong acidity range and it was assumed that there was a correlation between acid insolubility and flocculation.
