Effect of chemical coagulants on the sedimentation properties of activated sludge

摘要

Bulking sludge and foam formation on the surface of activated sludge reactors constitute significant problems in biological wastewater treatment systems. The improvement of the sedimentation properties of the sludge can be achieved using chemical oxidants or coagulants. In this study, coagulants--polyaluminum chloride, polyaluminum chloride + iron (II) chloride, sodium aluminate, iron (II) chloride, iron (III) chloride and iron (III) sulfate--were used to improve the sedimentation performance of activated sludge. The experimental assays were conducted in batch systems. The results showed varied effects of improvement of the activated sludge sedimentation properties, depending on the type and amount of the applied coagulant. The efficient use of coagulants aims to improve settleability, to decrease the sludge volume index, and to intensify the sedimentation velocity and to decrease the concentration of total suspended solids in treated wastewater. The most effective coagulant in the advancement of sedimentation-activated sludge was sodium aluminate.