| The BOD, COD concentrations are relatively low in many cities sewage in south China and the carbon source is insufficient. When the conventional activated sludge process was used to treatment the low C/N ratio urban sewage, the nitrogen removal efficiency was low because the lack of low carbon. If the effluent excluded Natural water, the eutrophication potential danger existed. If the advanced treatment was added in the conventional activated sludge process, the running costs was high, and the area was large and nitrogen removal was not complete. However the new biological nitrogen removal process was immature and there was many problems on the engineering application. So the high nitrogen removal in the low C/N ratio urban sewage treatment technology became a problem.Aim at situation of the low C/N ratio urban sewage in south China widely and in order to solve the problem of incomplete nitrogen removal in wastewater reuse by MBR, the Integrated Intermittent-aeration Membrane Biological Reactor (IMBR) has been developed. IMBR set of aeration, sedimentation, membrane filtration in one, through the three-phase separator to integrating the reaction zone and membrane separation zone to strengthen nitrogen removal. This structure can achieve the sludge automatic return back to save the sludge return costs. The continuous influent from the reactor top can meet the required denitrification carbon source to improve nitrogen removal and reduce the running costs of adding carbon source. The main results are as follows.(1) The pollutants removal efficiency of IMBR and the operating parameters on the effect of nitrogen removal study showed that the COD, NH4+-N, TN and SS removal effect of IMBR under the conditionâ…¡(2 hours aeration and 2 hours agitation) had better. The effluent quality of IMBR could meet the standard of the reused water quality criterion (GB/T18920-2002). The conditionâ…¡was determined the optimal condition for the three operating conditions. With the hydraulic retention time (HRT) increased from 4h to 8h, the COD, NH4+-N and TN removal significantly improved under the conditionâ…¡. When the HRT was increased to 12h, the COD removal effect declined and ammonia nitrogen and total nitrogen removal increased slightly. So the HRT of 8h had recommended. As the influent COD concentration and C/N ratio increased, the COD, NH4+-N, TN concentrations in the effluent declined, and TN removal effect significantly improved. Through point A on the curve of the DO, ORP and pH, the end of the carbon oxidation process and the start of nitrification had determined. Down to zero with the DO and through point B of ORP, pH curve, could determine the end of nitrification and the start of denitrification. And through the nitrate curve knee (point C) of ORP and the nitrate peak (point C) of pH curve could determine the end of denitrification and the start of anaerobic phosphorus release.(2) The simultaneous nitrification and denitrification (SND) studies of different working conditions in IMBR showed that SND existed in the working conditionâ… (continuous aeration), working conditionâ…¡(aeration 2h, agitation 2h) and working conditionâ…¢(aeration 2h, agitation 1h) under the low dissolved oxygen conditions.In which SND removal effect of the conditionâ…¢had best and the average TN removal rate was 56.38%, maximum TN removal rate reached 76.97% in the aeration phase. The TN removal by SND was 53.96% in the alternating running cycle with the aeration and mixing. With the increase of DO concentration, the nitrification rate increased and SND rate first increased and then decreased under the working condition III. The SND removal effect was best with the DO concentration of 0.5-1.0mg/L. With the C/N ratio increased, the SND removal effect was increased gradually. When the C/N ratio was 9, nitrification became limiting step in denitrification process the removal rate of TN reduced. The SND removal effect was best with the C/N ratio of 7.(3) The scanning electron microscope (SEM) images showed that the activated sludge floc within the system was bulky and dense. The variety of microorganisms was found in IMBR by the observation of microscope and there were growth of a large number of bacteria, fungi, protozoa and few micro metazoans. This provided an effective guarantee to the normal operation of the IMBR system.(4) According to Monod equation, the kinetic models of SND under aerobic conditions of IMBR were achieved. The nitrate saturation constant KD in the kinetic model of SND under condition II (aeration 2h, agitation 2h) and condition III(aeration 2h, agitation 1h) were 1.37mg/L and 1.86mg/L. It was found KD on the conditions of SND was greater than that of denitrification proeess in general model for single-stage activated sludge system. The kinetic constants A, B and KD of the condition III were greater than A, B and KD of the conditionâ…¡. It showed that the nitrification rate and denitrification rate of the condition III were higher than those of the condition II under aerobic conditions. Also it showed that the SND removal effect of the condition III was better than the conditionâ…¡.(5) Energy (enthalpy) balance analysis and evaluation of energy consumption in IMBR proeess showed that power consumption of the condition II and the condition II in the proportion of total energy inputs were 53.38% and 50.52% and higher than the proportion of influent energy. The effluent and sludge were lower proportion of energy. Most of the energy of influent contaminants was transformed into work and heat loss and degradation of pollutants had been thoroughly. Specific energy consumption of two conditions were high and energy efficiency was low because of many reasons, such as low influent concentration of organic pollutants, a smaller experiment scale and oxygen supply and demand imbalance. So it should improve the oxygen supply and demand balance and minimize the amount of excess sludge to improve energy efficiency.
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