Study On Anoxic-oxic MBR Process For High-strength Ammonia Wastewater Treatment

With the development of industry and agriculture, pollution caused by wastewater containing ammonia has been becoming a worsening problem. Compared withthe conventional nitrogen removal processes, MBR has been studied and developed inrecent years. Membrane bioreactor (MBR) is given more and more attention, owing toits effective separation. In the experiment, an anoxic-oxic MBR for high strengthammonia waste water treatment was studied.The experiment has lasted for 210 days. The influent was synthetic waste water.In the beginning, the influent was composed of domestic sewage and additionalammonium sulfate. The ammonia concentration was continuously rising. When itreached high level, the prepositive denitrification was started up and the methanol wasdosed into the influent as external carbon source. During the anoxic-oxic MBRoperation period, the concentration of influent COD_Cr, NH₃-N, TN respectively was167.9¹379.3mg/L, 186.7²94.8mg/L, 222.1³46.1mg/L. The experiment resultshows that turbidity and organics were eliminated effectively by the process. On anaverage, the turbidity removal efficiency is 99.76%, and the COD_Cr removalefficiency is 94.4% with high influent CODCr concentration. In addition, the processalso has potential advantage for NH₃-N and TN removal. The NH₃-N volumetric loadis up to 0.61⁰.84 kgNH₃-N/(m³Â·d), and averagely 99.18% of NH₃-N can be removed.When the recycling rate is 3, the TN removal efficiency can be as high as 72.7%.According to former researches, pH in the MBR was controlled between 7 and 8for achieving short-cut nitrification. From May 11^th to July 9^th , the nitriteaccumulation obviously occurred, but the accumulation phenomenon was not stableand later began to fluctuate. In this paper, the influential factors of nitriteaccumulation were studied, and low DO was considered as the important factor formaintaining short-cut nitrification.Membrane fouling has been companied with the MBR process, and has limitedthe wide application of MBR. In the early operation period, the membrane foulingwas not severe. During the first 192 days, the maximal effluent flow rate was declinedby 10.6%. After 141 days' operation, the membrane specific flux was reduced to86.1% of initial specific flux. In this paper, various influential factors of membranefouling were discussed, especially microorganism's function on membrane fouling.