Modelling of integrated anoxic-anaerobic-aerobic treatment for salmon fishery wastewater in an upflow fixed-bed biofilm reactor

Literature has paid scarce attention to the modelling of the integrated anoxic-anaerobic-aerobic process in upflow fixed-bed biofilm reactors used to treat wastewater. The present study developed a model for industrial salmon fishery wastewater treatment in an integrated anoxic-anaerobic-aerobic upflow fixed-bed biofilm reactor. The model successfully predicted the removal efficiency of both Chemical Oxygen Demand (COD) and nitrogen for two recycle ratios at steady state. The simulation study shows that the COD removal efficiency is not affected by any parameter under the studied conditions, while the nitrogen removal efficiency is affected by the hydraulic retention time (HRT) and the inlet COD concentration, where Total Ammonia Nitrogen (TAN) is the most sensitive variable of the anoxic-anaerobic-aerobic system. The conditions that best obtained removal efficiencies above 70% are: recycle rate between 1 and 2; HRT between 1.4 and 2.2 days and inlet COD concentrations lower than 2500 mg CODL^-1. Analysis of the model's sensitivity indicated that the parameters that exert most influence on the model for the system were μ_{max, M}, k_h, μ_{max, H}, ηNO ^-₃, μ_NOB, K^NOB_DO and D_DO.