Treatment of Catalyst Wastewater in a Three-Phase Flow Airlift Loop Bioreactor

Abstract

A 12-L gas–liquid–solid three-phase flow airlift loop bioreactor, in which micro-organism immobilization replaced the activated sludge, was used for the nitrifying treatment of the original effluent from Catalyst Complex of Qilu Petrochemical Corp. of SINOPEC, Zibo City, Shandong Province, P.R. China. The original wastewater contained a high strength NH4–N of up to 2,437 mg L−1 and solution electrical conductivity (EC) of nearly 22,000 μScm−1 . The influences of temperature, pH value, superficial gas velocity (ug) and hydraulic residence time (HRT) on the reductions of COD and NH4–N were investigated and discussed, respectively. The optimum operation condition was obtained as temperature 30–35°C, pH value 7.0–7.5, ug 10 mm s−1 , and HRT 15 h at the solid hold-up εs up to 50%. Under this optimum operation condition, the average removal efficiencies of COD and NH4 –N were higher than 85 and 99%, respectively, corresponding to the effluent COD, 25 mg L−1 and NH4 –N, 15 mg L−1 , which was in compliance with the national primary discharge standard of P. R. China as COD ≤ 100 mg L−1 and NH4-N ≤ 15 mg L−1 (GB 8978–1996). Additionally, the radial and axial positions in the reactor showed little influence on the local profiles of COD and NH4 –N.