Economic optimization of hollow fiber membrane contactors for ammonia nitrogen recovery from anaerobic digestion effluents

Abstract

This study presents the optimization and economic analysis of the membrane contactors to recover ammonia nitrogen from anaerobic effluents. The effects of ammonia nitrogen concentrations and alkalinity of the anaerobic effluents on the operating cost and total recovery cost were investigated, and the optimization of wastewater flowrate and pH was carried out.The sensitivity analysis revealed that the wastewater pH was the dominant parameter of the operating cost, followed by the percentage Am-n recovery and wastewater flowrate. The increase of anaerobic effluent’s alkalinity reduced the optimized wastewater pH and flow rate. The total operating recovery cost, including the production cost of solid ammonium sulfate, was found to be in the range of 0.16–0.31 USD/ kg·ammonium sulfate for the Am-n and alkalinity concentrations of 100–700 mg/L and 400–2800 mg/L as CaCO3, respectively, which are much lower than those of the conventional vacuum thermal stripping/acid absorption technique. The total costs, considering the capital investment of the membrane contactor’s unit, were also determined, and found to be 0.242–0.741 USD/kg·ammonium sulfate in the investigated range of anaerobic effluents