The disintegration of excess sludge enhanced by short-term interaction with potassium ferrate: Characteristics and mechanism

The increasing amount of excess sludge (ES) has become a heavy burden for biological wastewater treatment, and the function of potassium ferrate (PF) in ES treatment as a strong oxidizing reagent has received increasing attention. This study comprehensively investigated the contribution of different dosages of PF on sludge disintegration in a short time interaction with sludge, from the perspective of the rheological properties, adhesion ability, and microbial mortality rate of sludge. The results of electrochemical impedance spectroscopy found that the adhesion ability of sludge could greatly decrease to 6.9–30% of the initial one by PF treatment, and the results of the rotational rheometer revealed that the cross-linked structure of extracellular polymeric substances could be destructed by the oxidation characteristics of PF (ES/PF<15:3), resulting in the transformation of the sludge from gel to sol structure. Moreover, with the increasing dosage of PF (ES/PF<60:1), the microbial mortality rate in sludge could increase rapidly from an initial 17.3 to 50.4%, and as a result of the above reason, large amounts of biomacromolecules and phosphate were released into the liquid phase. These results concluded that PF could preferentially deconstruct the EPS structure in sludge, and then the excess PF could damage the cell membrane, which results in the release of intracellular materials, and eventually, ES was totally disintegrated. This study provided an investigation to understand the function of PF in the sludge disintegration and a reference for the application of PF in a mass reduction of sludge in a short time.