Slaughterhouse wastewater treatment by combined anaerobic baffled reactor and anaerobic filter: study of OLR and HRT optimization in ABR/AF reactors

Background: Slaughterhouse wastewater (SWW) is hardly treated due to the large amount of organic matter, nutrients and suspended solids. These materials are naturally decomposed through biological processes, and then environmental pollution, transmission of pathogens and problems become smelled. Conventional purification methods require high investment costs, high energy consumption and expert workforce. Therefore, the efficient and sufficient treatment of SWW with low cost, efficient construction and operation is important. Methods: A combined anaerobic system consisting of three pilot-scale anaerobic baffled reactors (ABRs) in the first stage and three anaerobic filters (AFs) were used to treat SWW. The ABR reactors arranged at three hydraulic retention times (HRTs) of 12, 18 and 24 hours and organic loading rates (OLRs) of 4, 7 and 10 kg/m(3)/d. The OLR applied for ABR reactors, was 0.5 to 1.55 kg COD/m(3)/d. Results: Evaluation of the ABR reactor indicated that this reactor at OLR of 7 and 10 kg COD/m(3)/d and HRT of 18 hours, had removal efficiency of 83.29% and 85.79%, respectively. AF reactor, at OLR of 0.981, 0.576 and 0.561 kg COD/m(3)/d and HRT of 36 hours, had removal efficiency of 79.39%, 74.09% and 63.14%, respectively. Conclusion: The optimum HRT and OLR were 24 hours and 7 kg COD/m(3)/d and 36 hours and 1 kg COD/m(3)/d in ABR and AF reactor, respectively.