Treatment Of BPA Wastewater By MAFOP-EGSB-MBR Combined System

As a quite important raw material in chemical engineering, bisphenol A (BPA for short) is in increasing amount released into environment due to its wide application. Considered to be a kind of recalcitrant compounds, BPA could reach a relatively high concentration in vivo via bioaccumulation effect, which greatly threatens not only water quality but also human beings. The researches on technologies of BPA removal are significantly important. Nowadays the trend in development of treatment technology of toxic non-biodegradable wastewater is the application of highly efficient and novel technology as well as the integrated process with multi-unit techniques.In this study, the combined system with micro-aeration fenton oxidation process (MAFOP), expanded granular sludge bed (EGSB) and membrane bioreactor (MBR), which is environmental-friendly method, is developed to treat synthetic bisphenol A wastewater. The main idea and objective of this study is that partial COD could be removed and some toxic organic compounds are converted into biodegradable compounds by micro-aeration fenton oxidation process. Most of COD in the wastewater could be removed effectively in the anaerobic process, which ensures high loading and low cost in the whole treatment system. The quality of effluent could meet discharge standard after the membrane bioreactor. Research results of this paper are of practical value to achieve low investment, low operating cost, strong stability and high quality of effluent for treatment of chemical wastewater. Based on the results of these investigations, the major conclusions are shown as follows.1. The influence of critical operating parameters on the performance of micro-aeration fenton oxidation process treating synthetic BPA wastewater was investigated. The initial pH was 4.5 and the reaction time was 15 min with mass ratio of H2O2 to COD at 2.0 and mole ratio of H2O2 to Fe2+ at 16. Temperature was room temperature and aeration rate was 0.4 L/min. Under the optimum conditions, the overall COD removal amounted to 70.0% and the ratio of BOD to COD increased from 0.02 to above 0.50. The pretreated synthetic wastewater by micro-aeration fenton oxidation process was suitable for biological treatment.2. The domestication of EGSB reactor was finished in 60 days with the COD removal of 80% by adopting a strategy of quick start-up. The results showed that the organic matter after MAFOP can effectively be degraded in EGSB. And the result was stable.3. The effluent of EGSB was treated by MBR reactor, and the removal efficiencies of COD and NH3-H are 94% and 90%, respectively with the effluent COD and NH3-H concentrations of below 60 mg/L and 2 mg/L. Most of organic matters were degraded by microorganism communities in the activated sludge, while membrane unit separation offsets the unstable biological treatment of COD. Membrane cutoff results in the accumulation of the denitrification bacteria, which is favorable for the remove of NH3-H.4.The synthetic BPA wastewater was treated by the procedure of fenton oxidation, EGSB and MBR bioreactor. By pretreating with fenton oxidation for 9.6 h, the wastewater was treated by EGSB and COD decreased from 12500 mg/L to 550 mg/L with removal rate of 84.3%. By the further treatment in MBR bioreactor, COD in the effluent was below 60 mg/L, and the water quality satisfied the Standard of Grade One in Integrated Wastewater Discharge Standard (GB18918-2002). The COD removal rate reached 99% by the combined process. It showed the system was technically feasible for the treatment of chemical wastewater.