Feasibility of Bio–Coagulation Dewatering Followed by Bio–Oxidation Process for Treating Swine Wastewater

Abstract

The unsatisfactory performance of the conventional swine wastewater treatment is drawing increasing attention due to the large amount of refractory chemical oxygen demand (COD), nitrogen, and phosphorus attached to the suspended solids (SS). In this study, for the first time, a novel process based on bio–coagulation dewatering followed by a bio–oxidation (BDBO) system was developed to treat swine wastewater containing high–strength SS, COD, TN, and TP. Firstly, after the bio–coagulation process, the removal efficiencies of SS, COD, NH3–N, and TP reached as high as 99.94%, 98.09%, 61.19%, and 99.92%, respectively. Secondly, the filtrate of the bio–coagulation dewatering process was introduced into the subsequent bio–oxidation process, in which the residual COD and NH3–N were further biodegraded in a sequence batch reactor. In addition, the dewatering performance of the concentrated swine slurry was substantially improved, with the specific resistance to filtration decreasing from 17.0 × 1012 to 0.3 × 1012 m/kg. Moreover, the concentrated swine slurry was pressed and filtered into a semi–dry cake after pilot–scale bio–coagulation dewatering treatment. Finally, the concentrations of COD and NH3–N in the effluent after the BDBO process, ranging between 150–170 mg/L and 75–90 mg/L, met the relevant discharge standard. Compared to traditional treatments, the BDBO system has excellent large–scale potential for improving the treatment efficiency, shortening the operation period, and reducing the processing costs, and is emerging as a cost–effective alternative for the treatment of wastewater containing high concentrations of SS, COD, TN, and TP.