The microwave-enhanced advanced oxidation (MW/H2O2-AOP) treatment of sewage sludge in a continuous-flow 915 MHz microwave system was studied. A higher H2O2 dosage at the same flow rate resulted in better solids disintegration in terms of higher soluble chemical oxygen demand. The highest soluble chemical oxygen demand concentration of 5174 mg/L was obtained at a dosage of 0.005 L/L (0.5 % v/v). A higher soluble chemical oxygen demand was obtained at a higher flow rate with the same H2O2 dosage. A substantial amount of soluble phosphorus (over 60 % of total phosphorus content) was produced for all treatments, regardless of H2O2 dosage. A first-order reaction kinetics of soluble chemical oxygen demand was proposed in this study. Real-time energy consumption corresponding to performance efficacy, which provides a realistic assessment of the process efficiency, was calculated. Energy consumption was found to vary between 0.22–0.29 kWh/L of sludge treated. The results demonstrated that a continuous-flow 915 MHz microwave system resulted in high treatment efficiency in terms of nutrient release, solids disintegration, and low energy consumption, which is suitable for real-time industrial applications.

Phosphorus was recovered from dairy manure via a microwave-enhanced advanced oxidation process (MW/H2O2-AOP) followed by struvite crystallization in a pilot-scale continuous flow operation. Soluble phosphorus in dairy manure increased by over 50% after the MW/H2O2-AOP, and the settleability of suspended solids was greatly improved. More than 50% of clear supernatant was obtained after microwave treatment, and the maximum volume of supernatant was obtained at a hydrogen peroxide dosage of 0.3% and pH 3.5. By adding oxalic acid into the supernatant, about 90% of calcium was removed, while more than 90% of magnesium was retained. As a result, the resulting solution was well suited for struvite crystallization. Nearly 95% of phosphorus in the treated supernatant was removed and recovered as struvite.

A pilot-scale continuous-flow 915-MHz microwave enhanced advanced oxidation (MW/H2O2-AOPMW/H2O2-AOP) treatment system was specifically designed and used for the treatment of sewage sludge. The focus of this study was to examine the interrelationship between chemical changes and physical transformation on the treated sewage sludge, and to perform energy analysis of the treatment system. A higher temperature and/or higher hydrogen peroxide dosage resulted in higher levels of solubilized total phosphate and total Kjeldahl nitrogen, an increase in chemical oxygen demand solubilization and volatile fatty acids production, reduced total suspended solids, and improved sludge dewaterability and settleability. The results demonstrated that this treatment system was well designed and could be used for the treatment of sewage sludge effectively. The scaled-up version of this MW/H2O2-AOPMW/H2O2-AOP treatment system could readily be implemented for real-time application in wastewater treatment plants.