Effects of suspended solid and polyelectrolyte on settling and rheological properties of municipal activated sludge

Studying sludge rheology is an important factor for the management and disposal of produced sludge in a wastewater treatment plant. In this paper, the rheological characteristics of fresh and conditioned municipal sludge at different total solid contents (ranging from 1.8 to 3.7 g/l) were investigated. The selected conditioning agent was cationic polyacrylamide high molecular weight (CPAM-80). It was found that all samples behaved as shear thinning and limiting viscosity increased with increasing total solid concentration which followed Bingham model. In addition, settling index was increased by 50% with increasing solid content by 50%. The use of conditioning agent improved settling properties and the increased concentration of this agent reduced yield stress and limiting viscosity.