Enhanced removal of dissolved S2− from a river by the pump-and-treat ex-situ process with enriched consortium

S2− is one of the common pollutants in heavily polluted rivers. A pump-and-treat ex-situ process with enriched consortium (PEPEC) was used to remove S2− in this study. The kinetic model of S2− removal was developed, and the inflow ratio of the PEPEC was analyzed according to the results of the kinetic models. The results showed that the S2− removal ratio could reach 97.5% 5 0.5%, when the inflow ratio was controlled at 2% for the PEPEC operation. Meanwhile, the removal efficiency and operation performance were assessed for both the simulating ex-situ and in-situ bench-scale tests. Compared with the in-situ processes, the PEPEC showed a stable operation performance during 120 h of bio-treatment, and the concentrations of S2−, COD, NH3-N and TP in the effluent reached approximately 0.5, 20, 0.5 and 0.5 mg/L, respectively. The time consumption (8 h for one batch) and consortium dosage (3 g for the whole operation) in the PEPEC were significantly less than those in the in-situ processes. The PEPEC presented some potential advantages for the bio-treatment of a heavily polluted river.