Microwave enhanced advanced oxidation process (MW/H₂O₂-AOP) treatment of sewage sludge at different pH conditions

The primary focus of this study was to investigate the effectiveness of a microwave-enhanced advanced oxidation process (MW/H₂O₂-AOP) for treating sludge from a membrane-enhanced biological phosphorus removal process in neutral, acidic (pH 4) and alkaline (pH 9) conditions. Two different MW systems were utilized; the bench-scale (2450 MHz) and pilot-scale (915 MHz) systems that operate in batch-mode and continuous-flow mode, respectively. The effects of pH on solids disintegration, nutrient release and the physical properties of sludge were examined. The MW/H₂O₂-AOP treatment was very effective; the total suspended solids reduction and chemical oxygen demand solubilization was better for alkaline sets rather than acidic. However, acidic conditions were superior in the release of orthophosphate, particle size distribution, dewatering properties and settling. In the treatment of acidified dairy manure, with the 915 MHz pilot-scale system at temperatures of 90 and 110°C and with a hydrogen peroxide dosage of 0.6% (v/v) per percent of total solids, the MW/H₂O₂AOP yielded a clear supernatant, rich in the nutrients required for struvite (MgNH₄PO₄·6H₂O₂) crystal formation. A total of fifteen salt water experiments were conducted with a salt concentration ranging from 10 to 120 g/L at three different flow rates (6, 7.5 and 9 L/min). The dominant heating mechanism was dipolar polarization and ionic conduction at a high flow rate and high salt concentration, respectively. High concentrations of ions suppressed the dielectric polarization, resulting in lower temperatures. Energy consumption was similar among the sets.Applied Science, Faculty ofCivil Engineering, Department ofGraduat