Optimisation of anaerobic/anoxic/oxic process to improve performance and reduce operating costs

A laboratory-scale anaerobic/anoxic/oxic reactor system was used to treat synthetic brewery wastewater for I year. The objectives were to enhance denitrifying phosphorus removal, improve biological nutrient removal and reduce operating costs. Three operational strategies were tested: (1) controlling nitrate recirculation to stimulate the growth of denitrifying phosphate-accumulating organisms; (2) adjusting the volume ratio of the anaerobiclanoxic/oxic zones to enhance anoxic P uptake; (3) bypassing a part of the influent flow into the anoxic zone to maximise anoxic P uptake and denitrification. The results showed that not only was anoxic P uptake enhanced but also energy consumption for aeration could be reduced when the anoxic effluent NO3--N concentration was controlled between 1 and 3 mg L-1. The optimal volume ratio of the anaerobic/anoxic/aerobic zones in this system was found to be 1:1:2. The optimal bypass flow ratio was 0.32. The results indicated that the optimal strategies could improve treatment performance and reduce operational costs, but there was still a challenge to treat wastewater with low ON ratio. (c) 2006 Society of Chemical Industry.