Abstract
•Sludge was micro-disintegrated by KMnO4 oxidation.•Sludge flocs were reconstructed by FeCl3 flocculation after KMnO4 oxidation.•Biochar helped to build a skeleton sludge cake after KMnO4 and FeCl3 treatment.•Using KMnO4/FeCl3/Biochar to enhance sludge dewaterability is promising.
Feasibility of combined sludge conditioning process of micro-disintegration, floc reconstruction and skeleton building with KMnO4/FeCl3/Biochar to enhance sludge dewaterability was investigated. The changes of sludge characteristics were analyzed to unravel the sludge conditioning mechanisms. The optimal conditioner dosages were: KMnO4 of 20g/kg dry sludge (DS), FeCl3 of 138.09g/kg DS and sludge cake biochar of 70% DS. Compared with raw sludge, specific resistance to filtration (SRF) decreased by 99.03%, net sludge solids yield (YN) increased by 24.6 times and the moisture content decreased from 83.38% to 60.63%. Sludge flocs were micro-disintegrated by KMnO4 oxidation, therefore more EPS and bound water were released from the sludge flocs. The more uniform and compact flocs were reconstructed by electrostatic neutralization of FeCl3 flocculation. Sludge cake biochar helps to build an incompressible and permeable sludge cake to further improve the sludge dewaterability. Combined sludge conditioning by adding KMnO4/FeCl3/Biochar to enhance sludge dewaterability is promising.
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