Background and Aim: High concentrations of organic compounds and ammonia and entry of toxic pollutants lead to a low efficiency of direct biological treatment of landfill leachate. The aim of this study was to determine the efficiency of a repeated fed-batch biological reactor with powdered active carbon (PAC) for landfill leachate treatment.

Methods and Materials: Raw leach ate was pretreated by coagulation and flocculation processes and, then, the ammonia was removed by air stripping at a high pH, before biological treatment. The pretreated leach ate was treated bio-treated in an aeration tank by the repeated fed-batch method. Three cycles of 1×40, 5×8, and 4×10 hours were attempted in the absence and presence of 2 g PAC /L.

Results: Results indicate that the presence of PAC increased the COD removal efficiency significantly. The initial COD effluent was 3900 mg/L. Its values were 169 mg/L and 622 mg/L in the presence and absence of 2 g/L PAC, respectively, for the cycle of 5×8 h.

Conclusion: Based on the results of this study and findings of other investogations in this field, it can be concluded that repeated fed-batch bio-reactor has is quite effective for treatment of pretreated leachate.