Pilot-scale Study On Nitrogen Removal By CIBR Process For Municipal Wastewater

A new type of biological reactor was studied in this paper, continuous-flow integrated biological reactor (CIBR), which combined aeration, agitation and settling stage in one single bioreactor without internal sludge recycling system. According to continuous feeding and intermittent aeration, CIBR was designed to provide a sequence of aerobic, anoxic and anaerobic sections for organism, nitrogen and phosphorus removal. The focus of this paper was the effect of nitrogen removal, the nitrogen transformation and concentration gradient in the reactor, and the variation of DO and pH in a cycle, which could supply some reference for the reactor autocontrolling.There were four different modes set by the distribution of aeration time, agitation time and settling time for the comparation of COD, NH3-N, and TN removal efficiency. Result showed that under the lower COD/TN ratio with 1.9, 3-2-1 mode(3 hour's aeration, 2 hour's agitation and 1 hour's settling) could achieve COD, NH3-N, and TN removal efficiency of 69.38%, 83.6% and 56.83%, respectively, with effluent concentration of 23.64 mg/L, 4.21 mg/L and 12.73 mg/L, respectively, reach the standard rank A of the first class in GB18918-2002.The concentration distribution of ammonia nitrogen and nitrate by space in the reactor was also studied, result showed that better ammonia nitrogen degradation and nitrate increase were obtained at the edge zone of reactor, which benefited from the annular force caused by aerator and stirrer. The average value of DO during aeration stage and agitation stage were 3.76mg/L and 1.22mg/L, respectively, which proved the efficiency of aeration and agitation. The pH value first rose quickly, followed by a small platform, then declined step by step with a little faster rate while COD degradation and nitrification, the decline continued to some time after anoxic phase, after that pH increased slowly to the end of the cycle, there was a small jumping at the end, the ultimate value was a little lower then the initial value. The variation of DO and pH during a cycle could indicate the flexibility of microorganism, the degradation of COD and nitrification, while the later a little lag.Although DO and pH could indicate the reaction to some extent, in order to get the exact characteristic points of nitrification and denitrification, achieve the on-line autocontrolling for all process, it's suggested that ORP be monitored simultaneity.