Separation,Purification And Denitrification Of Aerobic Denitrifying Bacteria In Biological Sponge Iron System

Among many denitrification processes,biological denitrification is favored because of its high efficiency,low cost and no secondary pollution.Compared with the ordinary activated sludge process,the biological sponge iron method has a better ability to remove pollutants.The biological sponge iron system not only has the characteristics and advantages of the biological iron process,but also has the advantages of bacteria,which can breed a large number of aerobic denitrifying bacteria with the function of iron oxidation.Aerobic denitrifying bacteria can reduce NO₂^--N and NO₃^--N to nitrogen under aerobic conditions to remove and have been explored by more and more researches.However,there are few researches on aerobic denitrifying bacteria in biological sponge iron system that have both iron oxidation function and aerobic denitrifying performance.In addition,different strains have different requirements and tolerances to environmental factors,so it is extremely necessary to study the influence of various factors on aerobic denitrification process and optimize reaction conditions for large-scale application of aerobic denitrification bacteria to actual wastewater treatment in the future.In this paper,the SBR reactor with sponge iron intervention and good operation of our research group was selected to carry out the separation and screening of aerobic denitrifying bacteria with iron oxidation function,and then an aerobic denitrifying bacteria Z-14 with good growth performance and denitrification characteristics was obtained,and its physiological,biochemical and 16Sr DNA identification was carried out.The effects of p H,concentration of target pollutants,temperature,rotation speed,carbon source and iron dosage state on the growth characteristics and denitrification capacity of aerobic denitrifying bacteria Z-14 were investigated under different nitrogen sources.Finally,response surface methodology was used to optimize p H,temperature and rotational speed.(1)Aerobic denitrifying bacteria were screened and isolated in a well-functioning SBR reactor with the involvement of sponge iron in our research group.After a series of screening processes,including preliminary screening,re-screening and identification of iron oxidation,aerobic denitrifying bacteria Z-14 showed good growth and iron oxidation performance,and Z-14 was selected as the strain used in subsequent experimental research.(2)After preliminary exploration and understanding of the strain Z-14,and the study of its growth characteristics and denitrification characteristics,it was found that its growth state and denitrification performance were good,and the removal rate of TN and NO₃^--N reached58.3%and 91.0%,respectively.The results of 16S r RNA sequencing showed that Z-14 was Delftia Lacustris,belonging to?-Proteobacteria.(3)Taking NO₃^--N and NO₂^--N as the only nitrogen sources,the effects of p H,concentration of target pollutants,temperature,rotation speed,carbon source and iron dosage state on the growth characteristics and denitrification capacity of aerobic denitrifying bacteria Z-14 in the denitrification process were investigated.It was found that the optimal p H of both nitrogen sources was 7.5.The optimal concentration of pollutants was 60mg/L and 40mg/L,respectively,and the TN removal rates reached 59.9%and 56.0%,respectively.When the optimum temperature is 30?and NO₃^--N is used as the nitrogen source,the NO₃^--N removal rate can reach 99.6%.When NO₂^--N was used as nitrogen source,the NO₂^--N removal rate reached 63.2%.100r/min was the optimal rotation speed,and the TN removal rates were62.7%and 61.1%under the two nitrogen sources,respectively.The strain Z-14 had the best growth and denitrification performance when the carbon source was sodium acetate,and the OD600 value reached the maximum of 0.694.When NO₃^--N and NO₂^--N were used as nitrogen sources,the removal rate of TN could reach 67.7%,respectively.68.1%(4)Response surface methodology(RSM)was used to optimize the process with p H,temperature and rotation speed as the influencing factors,and the total nitrogen removal rate as the response value.The optimal process conditions were obtained as follows:initial p H 7.2,temperature 31.0?and rotation speed 97.8r/min,under which the total nitrogen removal rate was 71.9%.