Pyrite-activated persulfate oxidation and biological denitrification for effluent of biological landfill leachate treatment system

The feasibility of pyrite as catalysts in the persulfate oxidation and electron donor for subsequent bacterial denitrification was investigated. The results demonstrated that pyrite-activated persulfate oxidation could efficiently degrade the organic matter in the effluent of biological landfill leachate treatment system, and COD removal efficiency of about 45% was achieved at the optimum parameters: pH = 6, pyrite dosage = 9.28 mM, dimensionless oxidant dose = 0.25. Among the dissolved organic matter, hydrophobic dissolved organic carbon (HO DOC), humic acids and building blocks were the main components. After the pyrite-activated persulfate oxidation, humic acids and HO DOC were primarily degraded, followed by building blocks, while low molecular weight neutrals were probably the degradation products. In the subsequent biological process, nitrate reduction was satisfactorily accomplished with autotrophic denitrification as the main pathway. When the influent nitrate concentration was about 180 mg L-1, the effluent nitrate concentration was stable below 20 mg L-1 with the nitrogen removal rate of about 108 mg L-1 d-1. To sum up, the pyrite-activated persulfate oxidation and the following biological denitrification was a feasible application in the effluent of biological landfill leachate treatment system.