Enhanced Sludge Dewaterability and Pathogen Inactivation by Synergistic Effects of Zero-Valent Iron and Ozonation

In this study, the efficiency of the combined zerovalent iron (ZVI) and ozone (O3) treatment at a pH of 2 (acid-ZVI-O3) for simultaneous improvement of sludge dewaterability and pathogen inactivation was investigated. The results showed that the ozone treatment alone deteriorated sludge dewaterability, while the introduction of acid-ZVI into the ozone treatment could significantly enhance the sludge dewaterability. At the optimal conditions with 30 mg O3 g–1 of total solid (TS) and 63 mg ZVI g–1 of TS at a pH of 2, the capillary suction time of conditioned sludge was 1.63 s L g–1 TS, which was much smaller than those of raw sludge (10.45 s L g–1 TS), the single ozonation treated sludge (16.07 s L g–1 TS), and the acid-ZVI-treated sludge (6.98 s L g–1 TS). The acid-ZVI-O3 treatment promoted the generation of hydroxyl radicals and showed synergistic effects in removing key hydrophilic substances which would deteriorate sludge dewaterability, i.e., humic acid-like compounds and soluble microbial byproduct-li...