Efficient dewatering of polymer-rich aerobic granular sludge with cationic polymer containing hydrocarbons

Abstract

This study compared the dewatering properties of aerobic granular and activated sludge from full-scale wastewater treatment plants, and determined how polymer dose and type affect granular sludge dewatering efficiency. At the same dose, granular sludge filtration cake had about 4% lower humidity than activated sludge cake. Aerobic stabilization improved only activated sludge dewatering. The granular sludge reactor had over 1.5 times more extracellular polymeric substances (1.8 times more alginate) per reactor volume than the activated sludge reactor, but the high polymer content did not decrease granular sludge dewatering. Granular sludge dewatered best with FLOPAM EM 840MEB, due to its composition (n-alkanes, isoalkanes, cyclic/aromatic hydrocarbons). With this polymer, sludge cake moisture was lowest (84.7 ± 0.4%) at 1.6 g polymer/kg MLSS. With all tested polymers, the lowest dose (0.2 g/kg MLSS) ensured low cake humidities; this dose was far lower than typical doses for activated sludge dewatering. Upgrading from activated to granular sludge technology significantly facilitates excess sludge management.