Targeted regulation of digestate dewaterability by the ozone/persulfate oxidation process

Dewatering is the first step in the subsequent treatment and disposal of food waste digestate (FWD). However, FWD is difficult to dewatering. In this study, persulfate was synergistic oxidized by ozone to improve digestate dewaterability. The optimal conditions was at pH = 3, O₃＝40 mg/g TS and PDS＝0.1 g/g TS, under which the reductions in the normalized capillary suction time (NCST) and bound moisture (BM) of the FWD were 89.97% and 65.79%, respectively. Hydrophilic functional groups (oxygen- and nitrogen-containing groups) and hydrophilic protein molecular structures were decomposed by the reactive species of sulfate radical (SO₄·^-) and hydroxyl radicals (·OH) generated in the ozone-persulfate oxidation process, disrupting the binding between EPS and water molecules. The contributions of SO₄·^- and ·OH to digestate dewaterability were 42.51% and 28.55%. In addition, the introduction of H⁺ reduced electrostatic repulsion and contributed to the condensation of digestate flocs. The environmental implication assessment and economic analysis suggested that the O₃/PDS oxidation process was cost-effective and has a low environmental implication when applied to the FWD dewaterability improvement process. These results can serve as a reference for the management of FWD and further improvement of FWD treatment and disposal efficiency.