Enhanced Sludge Dewaterability by Efficient Oxidation of α-Mn₂O₃/Peroxymonosulfate: Analysis of the Mechanism and Evaluation of Engineering Application

Sludge dewatering reduces huge volumes of sludge, which can help save costs of subsequent sludge treatment and disposal. Extracellular polymeric substances (EPS) in sludge hinder the efficient removal of sludge water due to their strong hydrophilicity and water-holding capacity. In this study, we prepared a new type of α-Mn₂O₃ by the hydrothermal method and explored the effects of α-Mn₂O₃/peroxymonosulfate (PMS) on the properties of EPS and sludge dewaterability. Results confirmed that centrifuged weight reduction (CWR) increased from 87.5 to 94.7%, while water content (WC) decreased from 78.1 to 70.4%, under optimized additions of α-Mn₂O₃ and PMS, which were 0.12 mmol/g VSS and 0.18 mmol/g VSS, respectively. The mechanism investigations indicated that α-Mn₂O₃/PMS clearly degraded the EPS, destroyed their structure, and weakened their hydrophilicity and water-holding capacity, leading to much reduced intermolecular forces of EPS and the transformation of bound water to free water. Furthermore, we also ascertained the oxidized mechanism of α-Mn₂O₃/PMS on the degradation of EPS, and the pathway for generating reactive oxygen species (ROS) was also uncovered. Remarkably, SO₄^•- and ^•OH were the leading ROS on the degradation of EPS during oxidation with beyond 70% rate of contribution. Importantly, prepared α-Mn₂O₃ was compared with the standard Mn₂O₃ to verify the feasibility of applying it in practical engineering applications. This research has great significance for applying persulfate to enhance sludge dewaterability, which is expected to promote the wide application of manganese oxides (MnO_x)/PMS in sludge reduction and dewatering.