Microbial iron reduction activating sodium percarbonate for improving the dewaterability of iron-rich sludge

Sludge conditioning is a critical process to improve sludge dewaterability. This research developed a novel iron-rich sludge conditioning method by microbial iron reduction activating sodium percarbonate (MIR/SPC) treatment. The sludge conditioning parameters were optimized. The results showed that the MIR/SPC treatment could significantly improve the sludge dewaterability. The optimal conditions for sludge conditioning are as follows: 5-day anaerobic MIR treatment, pH 3 and 1 g/L of SPC. Under the optimal condition, the CST value of the conditioned sludge was reduced by over two-thirds, and the moisture content of dewatered sludge was decreased to 51.5% in full-scale application. The critical mechanism of MIR-promoted advanced oxidation process (AOP) in sludge conditioning was explored. The facilitation of iron reduction by MIR under microbial-driven reductive condition promoted the generation of hydroxyl radicals. The improved AOP generate more ROSs to attack floc structure of sludge, modify the EPS properties and cell status, strengthen the hydrophobicity and flocculability of sludge, and propel the release of bound water for enhanced dewaterability.