Study On Two A/O-MBR Process Treating Low C/N Ratio Landfill Leachate

Landfill leachate is generated by garbage and retting of decaying matter. It contains high COD, BOD, nitrogen-containing compounds, inorganic salts, organic halides and other substances. The stench of landfill leachate contains many carcinogens. Once percolating into the ground, it will cause the hypoxia, deterioration of water quality and soil properties polluted, which has an effect on human health and the environment. Currently, the cost-effective treatment of landfill leachate has become an important issue for many researchers to study. Based on the water quality characteristics of high NH4+-N low C/N ratio and the present situation which existing treatment process effluent NH4+-N is non-compliant or can not be stable, the subject proposes a two-stage A/O-MBR treatment process to strengthen the denitrification, for the biological treatment of landfill leachate new technology. The topic focuses on the rules and mechanisms of treating low C/N ratio of wastewater, so as to provide a new process line and research ideas for the efficient biological treatment of landfill leachate and achieving effluent discharge standards. In this study, two-stage A/O-MBR process was adopted to treat the landfill leachate, and an experiment on simulated and actual leachate was made. In the two-stage A/O-MBR process, the process was debugged by simulated wastewater, and the removal effect of COD and NH4+-N was studied under different influent NH4+-N concentration; then the removal effect of COD and NH4+-N was studied using the actual landfill leachate.In the process, the influent COD was 267 mg/L and 589 mg/L.After it, the effluent COD removal rates were 65.2% and 80.7% in two aerobic tank,83.1% and 84.4% in membrane tank. The flat membrane contributed 3.7%?17.9% of COD removal rate, indicating that the flat membrane had retention of COD and strengthened the removal of effluent COD. During the continuous operation of two-stage A/O-MBR Process, the nitrification process was inhibited by the influent of low C/N ratio, which leaded to effluent of high NH4+-N concentration and a sudden drop of nitrification. After added fresh sludge 10 L, reactor sludge concentration (MLSS) was 8400 mg/L. The NH4+-N concentrations of effluent began to decline from the second day. The NH4+-N removal rate gradually increased to 94% and NF4+-N removal effect tended towards stability. It can be drawn, the activity of the sludge can be rapidly improve by adding fresh sludge, which will help NH4+-N removal and nitrification reaction.When the craft were cultured for domestication adding actual landfill leachate of 5% and 10% to the influent, concentration of NH4+-N were 116 mg/L and 238 mg/L. The concentration of NH4+-N significantly reduced in biochemistry region. The removal rates of NH4+-N and TN were 78.9% and 56.1% in the first-stage A/O segment,87.9% and 46.13% in the second-stage A/O segment. The nitrogen removal effect was deepened; the average removal rate of TN was 51.12% in the two A/O-MBR system, and the removal effect of TN was good. Because of the high sludge concentration (MLSS) in flat membrane tank,8082 mg/L, the aerobic zone and anoxic zone which easily leaded the simultaneous nitrification and denitrification (SND) reaction; therefore, traditional nitrification and denitrification and simultaneous nitrification and denitrification (SND) was mainly used to denitrification in this test.Water quality changing theory of the A/O-MBR system along the way was studied, and the causes of the gap between actual and theoretical denitrification efficiency was analyzed. PH, DO, temperature, NH4+-N, COD, NO3--N, NO2--N and TN along variation in the system were studied.in the two-stage A/O-MBR process, the influent was into the anoxic tank of the first A/O. Due to the low influent organic load, most readily biodegradable organic matter is removed by diluting and assimilation and denitrification in the anoxic tank, creating favorable conditions for nitrification in the aerobic tank; the influent C/N is relatively low and lacks organic carbon, resulting in denitrification incompleted in the two-stage anoxic tank and the concentration of NO3--N progressively increasing in the two-stage anoxic and aerobic tank.