Study On The Treatment Of Petrochemical Wastewater Using A/O Integrative Swim-bed Process

Wastewater biological treatment process is one of the most important methods owing to its mild reaction conditions, many kinds of microorganisms, high environmental adaptation ability and no need of chemical agents without secondary pollution. Compared to conventional biological treatment systems, Swimming-bed biofilm reactor (SBBR) is a kind of novel biofilm reactor with many advantages such as high COD removal rates, short start-up time, less land area, stable operation, easy control and so on.In our study, an A/O swim-bed biofilm reactor was designeded by combining swimming-bed biofilm reactor with A/O technology and was used to treat petrochemical wastewater due to the low removal rates of NH3-N.The optimal operating parameters such as recycle ratio, HRT were determined on the condition of suitable PH, dissolve oxygen concentration and reaction temperature. The effect of C/N ratio and influent loading rates on the removal of COD, NH3-N and TN was also studied. At the same time, the mechanism of removal of contaminants was discussed and key points of operation were provided.More than one-year run period showed that better removal effect of NH3-N and TN in treating petrochemical wastewater was obtained. At the optimal parameters of 20.8 h for HRT and 3.0 for recycle ratio, the removal efficiency of COD was over 90%, and above 95% NH3-N removal efficiency and 70% TN removal efficiency were acquired. The denitrifying efficiency increased with increasing C/N ratio in the system, which meant that organic carbon source had an important influence on denitrification and the denitrifying rate was high with enough carbon compounds. The influent loading had little effect on removal of COD and much effect on removal of NH3-N and TN. The removal efficiency decreased greatly when influent loading overloaded the maximum capacity. It was also necessary to control the biofilm thickness and to avoid the occurrence of anaerobic phenomena inside the biofilm. The results showed the reactor exhibited some advantages such as low power consumption, strong shock resistance and stable operation. It would provide experimental foundation for future application of this A/O swim-bed technology in treating petrochemical wastewater.