The pilot study for oil refinery wastewater treatment using a gas-liquid-solid three-phase flow airlift loop bioreactor

Aerobic bio-treatment of the refinery wastewater was carried out in a 170 m3 pilot-scale gas-liquid-solid three-phase flow airlift loop bioreactor (ALR) with a low ratio of height to diameter (s), in which biological membrane replaced the activated sludge. The influences of pH value, air flow rate (AFR) and hydraulic residence time (HRT) on COD and ammonia nitrogen (NH4-N) reductions were investigated and discussed. The optimum operation condition was obtained as pH value 7.0-8.0, AFR 3.2 m3 air (m3 liquid h)−1 and HRT 6.5 h. Under the optimum operation condition, the effluent COD and NH4-N were lower than 100 and 15 mg L−1, respectively for more than 40 days, which have achieved the national primary discharge standard of PR China (GB 8978-1996). Furthermore, this pilot-scale airlift loop bioreactor generated only one-third of the sludge waste compared to the traditional activated sludge process.