Quick Startup and Performance Characteristic Research of the Micro-Aerobic EGSB Reactor Treating Actual Coking Wastewater at 25-30°C

To obtain the rapid startup and stable operation of the micro-aerobic EGSB reactor for simultaneous removal of COD and NH₃-N treating actual coking wastewater at 25-30°C, the EGSB were operated for approximately 5 months (consist of startup stage and stable operation stage) for the researching of the forming of micro-aerobic granules and the simultaneous removal of the COD and NH₃-N at 25-30°C. By controlling the oxygenation rate in the aeration column, different concentrations of dissolved O₂ were generated in the circulating fluid which supplied dissolved O₂ to the granule sludge bed in the EGSB reactor and to generate micro-aerobic environments. The results showed that it took only about 3 months for the successful startup of the micro-aerobic EGSB for the treatment of actual coking wastewater at 25-30°C. About 2 months for the stable operation, the micro-aerobic EGSB reactor treating actual coking wastewater at 25-30°C run well. With 1536-2316mg·L^-1 and 87-373mg·L^-1 influent COD and NH₃-N concentrations, gradually increased influent flow from 0.6L·h^-1 to 1.3L·h^-1 and shortened HRT from 20h to 9.2h, the average removal of COD and NH₃-N could attain 86.7% and 54.7% regardless influent fluctuate with 5.1kgCOD·m^-3.d^-1 COD load and 0.61kgNH₃-N·m^-3.d^-1 NH₃-N load. The supplement dose of the trace oxygen was controlled by the redox potential (ORP), and the ORP at the inlet of the micro-aerobic EGSB reactor should be kept at -5-+5mV. The settled velocity of the granules decreased to 15m.h^-1. But the granules were still hold in the EGSB reactor without any washout. The micro-aerobic EGSB reactor could keep about 38.0gMLSS.L^-1 sludge concentration and 0.65 MLVSS/MLSS. The successful startup and stab- - le operation was accomplished for the micro-aerobic EGSB reactor treating actual coking wastewater at 25-30°C.