Reactions: Chemical Conditioning

Abstract

Sewage sludges possess several characteristics which directly inhibit the rate and performance (degree of clarification, thickening and dewatering) achieved by any solid-liquid separation process. The presence of colloidal particles increases the water binding, the specific resistance and the compressibility of the sludges; therefore, colloids adversely affect all processes of sedimentation and dewatering. Most sewage sludges exhibit a net negative charge. This charge makes the particles tend to repulse each other and thus resist agglomeration into larger particles. A large percentage of the sludge solids have a portion of bound water firmly attached to the particles. The retention of this water can result in a high water content respectively low in cake solids after solid-liquid separation. The objective of sludge conditioning is to alter any of the properties outlined above so as to increase the ease with which water can be removed from the sludge.