Effects of potassium permanganate conditioning on dewatering and rheological behavior of pulping activated sludge: mechanism and feasibility

Abstract

The difficulties in sludge dewatering are associated with the high organic content, colloidal materials in sludge solids and the high hydrophilicity of extracellular polymeric substances (EPS). Based on the principle of advanced oxidation processes, waste pulping activated sludge was subjected to potassium permanganate (KMnO 4 ) oxidation pretreatment and then the influence and mechanism on sludge dewatering were comprehensively investigated in the present study. At lower KMnO 4 dosage, changes of the physicochemical and rheological characteristics were that: (1) as the sludge disintegration degree increased, the total extractable EPS increased and then the bound water were released; (2) the rheological behavior showed that the yield stress and viscosity decreased while flowability increased and the positive thixotropic behavior weakened; (3) the particle size and microscopic structure were changed insignificantly. These changes resulted in damaging the gel-like environment and making the surface of sludge floc stripped but did not completely induce the floc breakage as a result of KMnO 4 with lower redox potential. Thus, sludge dewaterability was improved with the optimum dosage of 16 g kg −1 dry solid. On the perspective of environmental safety, KMnO 4 conditioning on sludge dewatering is feasible.