Laboratory and full-scale performances of integrated anaerobic granule-aerobic biofilm-activated sludge processes for high strength recalcitrant paint wastewater

Sustainable treatment of wastewaters generated from paint production is increasingly posing an environmental concern. Recalcitrant paint wastewaters are mostly treated by energy and cost intensive physicochemical methods like incineration, distillation or advanced oxidation. This paper reported for the first time a case study applying biological treatment processes to properly handle a high-strength recalcitrant paint wastewater with 5-day biochemical oxygen demand (BOD₅)/chemical oxygen demand (COD) less than 0.02. A biological treatment scheme integrating anaerobic granular sludge blanket reactor, aerobic carrier biofilm reactor and aerobic activated sludge bioreactor was proposed and examined. Laboratory and full-scale trials demonstrated satisfactory operation with overall COD removal up to 99%. Besides yielding consistent effluent quality conforming to the discharge limits, the full-scale plant gained considerable savings in operating cost over a 5-year operation. With proper microbial adaptation and cultivation, as well as adequate reactor and process designs, the scheme offers a good feasibility for efficient and cost-effective treatment of the high strength and recalcitrant paint wastewater.