The post treatment of composting leachate with a combination of ozone and persulfate oxidation processes

Abstract

Due to the presence of refractory substances, biological methods are often not sufficient for leachate treatment to meet the standards of treated wastewater. O₃/persulfate oxidation is a kind of AOP, which has been proven to be an appropriate technology for the final treatment of these types of wastes. In this study, the capability of an O₃/persulfate oxidation process to act as a post treatment method for composting leachate was examined at laboratory scale and in batch mode. The effects of some factors, such as the initial pH, oxidant concentration and reaction time, were investigated on the removal of the organic load and the color of the leachate. Based on the results of the experiments, maximum COD removal (87%) was obtained after 210 minutes of ozonation with a 0.79 g h⁻¹ ozone mass flow rate at pH 9, and in the presence of 4500 mg L⁻¹ sodium persulfate. Under such conditions, the maximum removal of color was also 85%. Based on the results of this study, the combination process showed a higher potential for the removal of contaminants compared with ozonation or persulfate processes alone. In this research, the biodegradability (BOD₅/COD) of the leachate improved from 0.13 to 0.61 and the toxicity reduced by more than 80%. SPE-GC-MS analysis revealed that the composting leachate contained various groups of humic substances, most of which could be degraded into compounds with lower molecular weights, using a combined O₃/persulfate process. Therefore, it is a useful method for the degradation of refractory organic materials in contaminated waters.