IMPORTANCE OF FLOC STRUCTURE IN CONDITIONING AND DEWATERING

In this study, the basic structure ofactivated sludge flocs is described and the changes in settling and dewatering caused by changes in wastewater characteristics, solids handling procedures and digestion will be detailed. The role of biopolymer and cations, especially iron, in determining floc structure will be explained. This information will explain why sludges differ and how aerobic and anaerobic digestion can alter sludge properties and increase the demand for conditioning chemicals. It will be shown that the release of biopolymer into solution leads to increased polymer conditioning demand. The amount of conditioning chemical required is directly related to the solution colloidal protein content. Anaerobic digestion results the reduction of iron in flocs and the release of large quantities of protein into solution and as a result, conditioning demand is high. Conditioning using iron results in coagulation of solution proteins and produces stronger and less compressible flocs that have different dewatering properties than polymer conditioned sludges.