REMOVAL OF SIMPLE PHENOLICS IN AEROBIC AND DENITRIFYING SEQUENCING BATCH REACTORS

Six sequencing batch reactors were operated in parallel at varying SRT = 5, 10 and 15 d and at fixed HRT = 16 h. Three reactors were operated with 6 h aeration period within the 8 h cycle and were considered fully aerated; reactors 4, 5, 6 operated with a 3 h anoxic cycle within a full 8 h cycle. Feed to all four consecutive runs had orthochlorophenol (OCP) with various combinations of other substrates: Run 1-casein/dextrose and phenol; 2-phenol; 3-no co-substrate; 4-casein/dextrose. The addition of co-substrate had no effect on the OCP removal rate in the fully aerated reactors but enhanced the performance of the anoxic/aerobic reactors. The increase in volumetric reaction rate was proportional to the increase in SRT. The OCP removal rate in the anoxic/aerobic reactors in the aerated portion of the cycle was much higher (33-48 mg l-1 h-1) than in the fully aerobic reactors (15-17 mg l-1 h-1). Denitrification rates were the highest (7.3 mg l-1 h-1) for the anoxic/aerobic reactor with the longest SRT and with both co-substrates added.