Optimization of H_2O_2 dosage in microwave-H_2O_2 process for sludge pretreatment with uniform design method

摘要

A microwave-H_2O_2 process for sludge pretreatment exhibited high efficiencies of releasing organics, nitrogen, and phosphorus, but large quantities of H_2O_2 residues were detected. A uniform design method was thus employed in this study to further optimize H_2O_2 dosage by investigating effects of pH and H_2O_2 dosage on the amount of H_2O_2 residue and releases of organics, nitrogen, and phosphorus. A regression model was established with pH and H_2O_2 dosage as the independent variables, and H_2O_2 residue and releases of organics, nitrogen, and phosphorus as the dependent variables. In the optimized microwave-H_2O_2 process, the pH value of the sludge was firstly adjusted to 11.0, then the sludge was heated to 80℃ and H_2O_2 was dosed at a H_2O_2:mixed liquor suspended solids (MLSS) ratio of 0.2, and the sludge was finally heated to 100℃ by microwave irradiation. Compared to the microwave-H_2O_2 process without optimization, the H_2O_2 dosage and the utilization rate of H_2O_2 in the optimized microwave-H_2O_2 process were reduced by 80% and greatly improved by 3.87 times, respectively, when the H_2O_2:MLSS dosage ratio was decreased from 1.0 to 0.2, resulting in nearly the same release rate of soluble chemical oxygen demand in the microwave-H_2O_2 process without optimization at H_2O_2:MLSS ratio of 0.5.