Enhancement Of Denitrification Performance And Microbial Community In Two-stage Denitrification Process

Research and development based on the principle of two pieces of denitrifying process design integrated wastewater biological denitrification reactor,continuous slice data show that the water high concentration of nitrate-nitrogen（NO₃^--N）is the total nitrogen（TN）,the main reasons for the excessive by addition polymerization to pitch in the second period of denitrifying pool succinic acid butyl glycol ester（PBS）,improve the C/N in the water body,strengthen the activity of denitrifying bacteria,lower NO₃^--N concentrations in the water,improve the removal rate of TN.Then,to further improve the solid carbon source material,this research will be artificial synthetic carbon source and modified zeolite by freezing-crosslinking method coated to a synthetic material with coagulability polyvinyl alcohol（PVA-SA）-sodium alginate,the preparation of a kind of positively charged solid carbon source material,the physical properties of the carbon source material and release carbon process research,and explore with a positive charge the best carbon source to strengthen denitrification process environmental conditions.Finally,a positively charged solid carbon source was added to the second stage denitrification tank of the integrated wastewater biological denitrification reactor to investigate the effect of the enhanced denitrification process on the denitrifying microbial community structure.The main research results are as follows:（1）The integrated biological denitrification reactor has a certain effect on the removal of nitrogen in wastewater,the COD removal efficiency can reach 95.7%,the TN removal rate is only 57%,and the average effluent NO₃^--N concentration is about 7-7.5mg/L.After adding PBS solid slow-release carbon source in the second stage denitrification tank,the COD removal rate decreased to 91.7%,the effluent TN removal rate significantly increased to 80%,the average effluent NO₃^--N concentration decreased to 3.4 mg·L-1,and the average effluent NO₂^--N concentration also decreased to 0.68 mg·L-1.（2）The densities of positively charged carbon source,PBS,CC,and PS are 1.05,1.33,0.79,and 0.73,respectively,and the density of positively charged carbon source is the closest to that of water.The compression strength range of the positive charge carbon source is greater than 260N,which is better than the other three carbon sources.The positive charge carbon source,CC,and PS have better mass transfer performance for methylene blue solution.The time sequence of carbon release of positive charge carbon source,PBS,CC,and PS accounted for 50%of the total carbon release was CC<PS<PBS<positive charge carbon source and the release amount was high in the first place and low in the second place.PBS and positive charge carbon source had the appropriate maximum carbon release amount,and the carbon release amount was 4.1mg/g and 5.5mg/g,respectively.The COD/DOC value of the positively charged carbon source is closest to the theoretical value of 2.88.The ratio of acetic acid,propionic acid,and butyric acid was stable at（62.93±2.53）%:（25.03±0.57）%:（12.03±1.77）%.The surface morphology of the four-carbon sources is rougher than that of the four-carbon sources,among which the surface of PBS and positively charged carbon sources has a larger total carbon element and distribution area.（3）The effects of temperature,p H,the dosage of carbon source,and hydraulic stirring conditions on the denitrification enhancement of positively charged carbon source materials were investigated.The results showed that the intensity of enhanced denitrification increased first and then decreased with the increase of temperature.In a certain range,with the increase of p H value,the intensity of enhanced denitrification increases gradually.The increase of carbon source dosage is beneficial to the denitrification process,but too high is easy to cause excessive COD of effluent.The intensity of enhanced denitrification increased first and then decreased under the condition of hydraulic agitation,which may be related to the formation of biofilm.The optimum environmental conditions for the process operation are temperature 27℃,p H8,adding the amount of carbon source 4g/L,and hydraulic stirring condition 150r/min.（4）After adding a positive charged solid carbon source,the Chao index increased from642.8 to 801.9,the ACE index increased from 659.7 to 773.2,the Shannon index increased from 4.329 to 6.174,and the Simpson index remained unchanged.High-throughput sequencing results show that Proteobacteria and Bacteroidetes are the dominant phyla,while Thermomonas and Flavobacterium are the dominant phyla,and the addition of solid carbon sources can promote the growth and reproduction of denitrifying bacteria.