Operation Characteristics Of The Air-lift External Circulation Vortex Enhancement Nitrogen Removal Bio-reactor And Their Numerical Simulation

In recent years, water contamination and water eutrophication is becoming increasingly serious day by day. The reason was that nitrogen and phosphorus contents in it increase significantly, which can destroy the balance of water eco-environment and decrease the diversity and stability of aquatic organisms and plants. It therefore, is extraordinary necessary to control control the nitrogen pollution before it being discharged into water. And in sum, it has a practical significance which has practical significance on researching a new kind of bioreactor for biodenitrificat which has the feature of high effciency and stable performance to control the water eutrophication.Thus, a kind of independent research and development with independent intellectual property rights of air lift type circular vortex enhanced biological denitrification reactor was born（authorized invention patent no: ZL201410321199.8; Referred to as reactor I）, in comparison with common internal circulation biological nitrogen reactor（reactor II）, performance of reactor I was investigated by using statistical methods, used west 2012 and Fluent 6.3.26 simulation software, to study the operation characteristics of the air-lift external circulation vortex enhancement nitrogen removal bio-reactor（include removal efficiency; stability; microbial community structure; most suitable water quality parameters） and flow characteristics（include the reactor structural characteristics and flow; the content of extracellular polymer change; trajectory parameters）, get the following conclusion:（1） The operation characteristics results show that:a、The removal efficiency of reactor I much higher than reactor II. During start-up period, the average COD, TN and NH₄⁺-N removal rate in reactor I were 82.9%, 61.4% and 82.5%respectively, the average COD, TN and NH₄⁺-N removal rate in reactor II were 82.4%, 56.5%,78.5% respectively; During stable-operation period, reactor I average removal rates of COD, TN and NH₄⁺-N were 89.9%, 76.1% and 98.6% respectively, reactor II average removal rates of COD,TN and NH₄⁺-N were 89.7%, 75.4%, 97.8% respectively; the results of the west 2012 simulation software to simulate and reactor I and II in nitrogen removal efficiency was relatively close to actual operation result.b 、 The stability of the reactor I much higher than reactor II, which used COD, TN and NH₄⁺-N as a specific parameter. During start-up period, the value of CV（COD）, S（COD）, CV（ NH₄⁺-N）,S（ NH₄⁺-N）, CV（TN）, S（TN）in reactor I were 0.77, 0.26, 0.96, 0.95, 0.95 and 0.71 times than those in reactor II, respectively. During stable-operation period, the value of CV（COD）, S（COD）, CV（ NH₄⁺-N）,S（ NH₄⁺-N）, CV（TN）, S（TN） in reactor I were 0.92, 0.87, 0.35, 0.22, 0.96 and 0.82 times than those in reactor II, respectively.c、During stable-operation period, the dominant genera and microbial community diversity in reactor I were higher than that in reactor II. The percents of Proteobacteria 、 Bacteroidetes 、Chloroflexi in reactor I higher than reactor II at phylum level, the percents of Zoogloea 、Tessaracoccus、Nitrosomonas、Nitrospira in reactor I higher than reactor II at genus level the reactor I and reactor II shannon index was 5.1 and 4.9, respectively.d、The most suitable influent water quality parameters in reactor I were: the concentration of NH₄⁺-N were 200 300 mg·L-1, the value of pH were 7.0 8.0. TN concentrations of tolerance were about 300 mg·L-1, TN concentration is too high, the reactor deterioration, effluent water quality became worse.（2）Flow characteristics study show that:a、Set up multistage venturi tube structure inside of the reactor I, through the Fluent 6.3.26 simulation the flow pattern in the reactor I, the result showed that Venturi tube structure capable of efficiently forming a vortex flow field, strengthen the mass transfer process.b、During stable-operation period, the value of Extracellular polymeric substances（EPS） of the sludge in reactor I higher than reactor II. The total value of EPS in Sludge and its protein and polysaccharide content in the EPS were increased,the value of total EPS in reactor I high 43.1mg TOC/g VSS than reactor II.c 、 During stable-operation period, the degradation of COD and the change of NH₄⁺-N concentration gradient in reactor I much faster than that in reactor II. The value of effluent COD low mg·L-1 than that in reactor II, the removal rate in reactor II（kI=-21.95） much lower thanthat in reactor II（k II =-19.66）.Through the study of operating characteristics and flow characteristics of the reactor I,proved reactor I operating performance during the start-up period and stable-operation period,provides datas reference for the engineering application of the reactor I.