| Phenolic compounds are toxic pollutants,which are harmful to environment and human beings. The content of volatile phenols of effluent was high from the Refinery Wastewater Stripper Unit of A branch of China Petroleum and Chemical Corporation, which is between 100 mg/L and 250 mg/L. Direct emission would influence both the stable operation of the wastewater biochemical treatment system and the sewage discharging standard. According to the consideration of the novel process of wastewater treatment, a new biochemical technology is used to pretreat the phenolic wastewater. The moving bed biofilm reactor(MBBR) with the function of inner loop was designed for this study. The aim of this study was that the average removal efficiency of phenol could be up to 80%, the domestication method of the phenol-degrading bacteria, and the optimum process parameters and operating conditions were explored, in order to provide design parameters and technical reference for industrial application. The main conclusions were as follows:(1) The design of MBBR. The designed size of the MBBR unit was 500 L/h. It consisted of two biofilm reactors and one settling tank. The carrier elements of polyethylene were used as the packing. The inner loop function can dilute and mix the high concentration of phenolic wastewater, and can strengthen the mass transfer efficiency of the pollutants between the aqueous phase and biologic facies.(2) The set-up and operation of MBBR. The method of static cultivation and dynamic cultivation was used to cultivate the phenol-degrading bacteria. Amount of microorganisms generated in the reactors, the biodegradation of phenol, COD, p H were stable.(3) The study of different operating conditions of MBBR. The effect of hydraulic retention time(HRT)ã€dissolved oxygen(DO) and p H were explored. The optimum HRT was 10 h, the DO should be maintained between 1~3 mg/L,the value of p H should be maintained between 7.0~9.0, which could ensure the phenol-degrading bacteria was in a state of high biological activity.(4) The study of biodegradability of phenolic wastewater. After the pretreatment of phenolic wastewater by the MBBR, the value of BOD5/COD increased from 0.45 to 0.67, the biodegradability of wastewater was improved significantly, it was better for the next step treatment of wastewater; also it proved that the MBBR could biodegrade the phenolic wastewater.(5) The analysis of the continuous operation of MBBR. The flow rate of wastewater maintained 500L/h,the HRT was 10 h, the gas-water ratio maintained 14:1~18:1 to ensure that the DO was enough in reactors, the MBBR unit operated continuously 28 days under the optimum conditions, the removal efficiency of phenol was 87.14%, the removal efficiency of COD was 33.20%, the continuous operation of MBBR was stable, and the biodegradation of pollutants was significant. |
