Laboratory bench-scale anoxic/aerobic reactors with complete mix and continuous flow conditions were operated with high-strength synthetic wastewater to achieve simultaneous COD and nitrogen removal. High concentrations of organic carbon and nitrogen can be found in slaughterhouse, dairy, and food processing wastewaters, and also in some landfill leachates. Therefore, the goal of this study is to find a simple, efficient, reliable, cost-effective, and general solution for organic carbon and ammonia removal from streams with high influent concentrations of more than 5000 mg/L COD and 250 mg/L NH3-N. The highest COD (97%) and NH3-N (91%) removal efficiencies were obtained with initial COD and ammonia concentrations of 5211 mg/L and 262.8 mg/L NH3-N with volumetric loading rates of 11.26 kg COD/m3 d and 0.57 kg NH3-N/m3 d for COD and ammonia, respectively. Anaerobic oxidation is the main COD removal pathway in a simultaneous anaerobic oxidation/partial nitrification-denitrification (SAO/PND) system, and nitrogen removal significantly occurs via bacterial assimilation and partial nitrification-denitrification pathways. There are several advantages for this proposed SAO/PND system from a practical point of view, such as feasibility of simultaneous COD and nitrogen removal in a single reactor; simple operation; flexibility and practicality of this system as a general solution and cost effectiveness.
Keywords: COD; Highly polluted; SAO/PND; nitrogen; simultaneous removal.