Influence of Surface Charge and Exopolysaccharides on the Conditioning Characteristics of Sewage Sludge

Mechanical cell disintegration is a new procedure in the process of sewage sludge treatment. The objective is to improve and accelerate the digestion of sewage sludge and to decrease the amount of sludge to be disposed. Cell disintegration on the other hand has a strong influence on the conditioning and dewatering characteristics. Especially the polymer emand of sludge increases significantly. A correlation between the polymer demand and the surface charge of the sludge particles as well as a correlation between the surface charge and the amount of exopolysaccharides (EPS) were pointed out. The amount of EPS is basically responsible for the polymer demand. Intracellular polysaccharides are released by means of mechanical disintegration and therefore the surface charge of the sludge increases. During the anaerobic digestion the EPS could hardly be degraded so the increased polymer demand of the disintegrated sludges is caused by non-degraded polysaccharides. Applying dual polymer conditioning the polymer demand of the sludge could be reduced.