Simultaneous removal of COD and ammonia from high-strength wastewater in a three-phase fluidized bed reactor

A major challenge of Environmental Engineering is the efficient treatment of wastewater containing high concentrations of chemical oxygen demand (COD) and ammonia. This work addresses that challenge by designing, building, operating and developing a three-phase fluidized bed reactor (TFBR). The TFBR is designed to aerobically remove COD as well as ammonia from a 1,500 L/day of high-strength wastewater containing 5,000 mg/L COD and 230 mg/L ammonia in a short hydraulic residence time of 8 h. Experiments with water and air show that the TFBR provides complete fluidization with the designed liquid and gas flow rates. Furthermore, the oxygen transfer is at least an order magnitude higher than that obtained in previous studies. Under the designed condition, it is found that the TFBR removes 91.7% COD and 56.7% ammonia from the high-strength wastewater, and carries the effluent low concentration suspended solids at the same time. The ammonia removal is found to increase to 75% with a higher-than-design influent COD of 6,000 mg/L, which is responsible for more biomass available for ammonia utilization. The corresponding COD removal however decreases to 84.5%. The treatment carried out in this work is the first of its kind, and the developed TFBR is very promising because it offers effective removal of COD and ammonia from heavily polluted wastewaters in shorter residence times with reduced sludge generation.