Research On Deep Denitrification Treatment Based On PHBV

In view of the fact that the wastewater discharged by many industrial enterprises in China contains a large amount of mixed pollutants such as nitrate nitrogen and nitrite nitrogen,and the characteristics of low C/N,and the traditional carbon source dosing is difficult to respond to the concentration of influent nitrogen,The phenomenon that the total nitrogen in the effluent exceeds the standard or the organic matter exceeds the standard.In this study,the PHBV denitrification packed bed reactor was used to treat metal surface treatment wastewater with low carbon and high nitrogen characteristics.Through the long-term operation of the system,the treatment capacity of the reactor was improved,and the operation effect of the PHBV packed bed reactor at different temperatures and water intake were explored.The stability of the effluent COD when the nitrogen volume load is reduced,and the diversity analysis of the microorganisms in the PHBV denitrification packed bed.Through batch experiment analysis,the influence mechanism of microorganism,pH,temperature and nitrate nitrogen concentration on PHBV denitrification system is obtained.1)The PHBV denitrification packed bed reactor started successfully after 25 days of start-up time,and after about 100 days of operation,when the PHBV denitrification packed bed is 5 h HRT and the nitrogen volume load is 2.16kg/（m³·d）,the effluent is nitrate The nitrogen concentration is stable at about 25mg/L,the removal rate reaches about 92%,the effluent nitrite nitrogen is about 1mg/L,the nitrite nitrogen removal rate reaches about99%,and the denitrification rate reaches 2.018kg/（m³·d）.2)PHBV denitrification packed bed reactor at 25,18,13,8℃,the denitrification rate is 1.88kg/（m³·d）,1.75kg/（m³·d）,1.51kg/（m³·d）),about 1.25kg/（m³·d）.Low temperature has a greater impact on the denitrification effect of PHBV denitrification packed bed.3)When the PHBV denitrification packed bed reactor’s inlet water nitrogen volume load decreases intermittently,the effluent COD shows better stability;compared with the denitrification system with external carbon source,the PHBV denitrification packed bed reactor is in the inlet water nitrogen load When it is reduced,the possibility of excessive carbon source causing the effluent COD to exceed the standard is greatly reduced,reducing the risk of effluent COD exceeding the standard.4)The PHBV denitrification packed bed has good pH buffering capacity.The pH change of the PHBV denitrification packed bed is correlated with the COD concentration of the effluent,and the correlation coefficient R²is 0.9814.5)The PHBV denitrification packed bed will consume the DO carried in the influent water,and the consumption of DO in the influent water is not significantly related to the nitrogen volume load,temperature,and DO of the influent water.PHBV denitrification packed bed is in normal operation stage,PHBV carbon source has a high effective utilization efficiency,and PHBV utilization efficiency is as high as 96%at full load.6)The surface biofilm of PHBV detected that the Proteobacteria was the main flora,accounting for 31.82%of the total flora,the Bacteroides phylum accounted for 27.81%of the total flora,and the Chloroflexus phylum accounted for 19.51%of the total flora;in the classification,the first placeγ-Proteobacteria（Gammaproteobacteria）accounted for28.53%of the total colonies;the second is Anaerolineae（Anaerolineae）,accounting for19.47%of the total community;the third is Bacteroidia,accounting for 18.37%of the total colonies.The first place in the genus classification is Thermomonas,which accounts for19.84%of the total colonies;the second place is PHOS-HE36,which is 17.77%of the total colonies;the third place is It is Acinetobacter,which accounts for 6.05%of the total colony.7)The degradation of PHBV by microorganisms in clean water is relatively low.In the PHBV denitrification system,the release rate of organic matter is controlled by the response of the NO₃^--N concentration in the sewage.8)Temperature has a significant impact on the PHBV-based denitrification system,and the denitrification rate and microbial decomposition of PHBV are greatly affected under low temperature conditions.9)In the environment with low nitrate nitrogen concentration,the denitrification rate increases faster,and with the increase of nitrate nitrogen concentration,when the NO₃^--N concentration increases to 150mg/L,the denitrification rate hardly increases with NO₃^--N The concentration of N increases and increases.A higher concentration of nitrate nitrogen will increase the rate of microbial decomposition of PHBV.When the rate of microbial decomposition of PHBV is too high,more organic matter is released than required for denitrification,and residual COD will appear if the nitrate nitrogen is not consumed.Happening.10)The acidic environment has a more significant impact on the PHBV denitrification system.At the same time,the difference between the pH of the inlet and outlet water is also related to the pH of the inlet water.In addition,pH mainly affects the microbial hydrolysis process,and the microbial hydrolysis will directly determine whether the pH in the biofilm and the amount of carbon source available are suitable for the subsequent denitrification process.