Managing sulfate ions produced by sulfate radical-advanced oxidation process using sulfate-reducing bacteria for the subsequent biological treatment

Persulfate and sulfate radicals with strong standard oxidation potentials and relatively low cost be used in advanced oxidation processes. The object of this study was to evaluate the performance of a sulfate radical-based advanced oxidation process with surfactant-modified zeolite for treatment of the composting leachate followed by the effect of Surfactant-modified zeolite for the removal of sulfate from leachate in an ASBR biological process. The BOD/COD ratio under the optimal condition of oxidation process was 0.7712. The most contributed factor in this process was temperature. Analysis showed that persulfate causes an increase in sulfate ions during the oxidation process. Surfactant-modified zeolite had a significant effect on decrease of the final sulfate ions concentration produced by persulfate. Therefore, the combination of advanced oxidation process and surfactant-modified zeolite with biological sulfate reduction processes for simultaneous removal of COD and sulfate ions could be recommended. The effect of COD/sulfate ratio on the activity of sulfate-reducing bacteria in the ASBR reactor was discussed. The study showed that applying the process can clearly improve the removal efficiencies of COD and sulfate from the leachate. The optimum condition for ASBR reactor operation was obtained in COD/sulfate ratio of 1.34. These process provides significant efficiencies of 93% and 74% for sulfate ion and COD removal, respectively. On the other hands, the TOC removal efficiency increased from 61% to 76% in row leachate samples without biological treatment by addition of SMZ to SR-AOP.