Conditioning of Anaerobically Digested Sludge

Abstract

Synthetic organic polyelectrolytes can be used to condition sludges to enhance their dewaterability. When conditioning biological sludges, the charge on the polymer has a significant impact on the effectiveness of the polymer as a conditioner. The objectives of this investigation were to determine the most effective type of polymer product for conditioning anaerobically digested sludge prior to dewatering, and to investigate how the chemical characteristics of the polymer influence the way it interacts with the sludge particles. Capillary suction time and particle electrophoretic mobility measurements were employed to achieve this objective. The results indicate that cationic polymers with molecular weights in excess of 106 appear to be required for effective conditioning. However, effective sludge conditioning can be achieved with either high or low charge density cationic polymers and that dosing to achieve charge neutralization of the sludge particles is not a prerequisite for effective sludge conditioning.