| In this study,samples were collected at different operating periods in the integrated vertical subsurface flow constructed wetland-pond recirculating aquaculture system,and selective straining medium was used to screen the strains that have the capable of nitrogen purification,and a high-efficiency nitrifying bacteria and a high-efficiency denitrification were screened.Then the species identification was studied,and the nitrification characteristics or denitrification characteristics of the corresponding strains were investigated separately.The main research results are as follows:Through the screening of nitrifying bacteria and the determination of the nitrification rate in the samples collected during the different running periods of constructed wetlands,the highest rates of nitrification of the strains in the early stage of the constructed wetland,in the middle of operation and at the end of the operation were 60.61±1.95 mg/(L·d),49.69±1.02 mg/(L·d),and 21.96±1.15 mg/(L·d).The strains were identified by observation of individual morphological characteristics,physiological and biochemical experiments,and 16S rDNA homology analysis.The results showed that the nitrifying bacteria screened at the initial stage of constructed wetland operation was Acinetobacter johnsoni.Both the medium and final nitrifying bacteria are Rheinheimera.The strain with the highest nitrification rate was selected,and the strain characteristics of Acinetobacter johnsonii were screened in the early stage of the constructed wetland operation,and ZX2 was named.The results showed that the ZX2 strain had the strongest nitrification ability at a pH of 7 and a temperature of 30?and a NaNO2 concentration of 0.8 g/L.The nitrification rate reached 68.4 mg/(L·d)and the OD600 value of the bacterial solution was 0.87.Through the screening,speed measurement and strain identification of denitrifying bacteria in the constructed wetland system,the strain with the highest denitrification efficiency in the initial stage of constructed wetland operation was Klebsiella pneumoniae,and the denitrification denitrification rate was 86.2.±1.8%,the denitrifying bacteria screened in the middle and final stages of the constructed wetland were Pseudomonas,but the denitrification denitrification rates were different,85.4±2.5%and 93.1±0.98%,respectively.The strain characteristics of Pseudomonas faecalis with the highest denitrification and denitrification rate were selected at the end of the constructed wetland,and ZF7 was named.The effects of pH,temperature,inoculum and dissolved oxygen on the denitrification of ZF7 were obtained:ZF7 strain was denitrifying at pH 7,temperature 35C°,inoculum 6%,and standing.The strongest,the nitrogen removal rate reached 94.5%,and the bacterial liquid concentration OD600 value can reach 1.00 or more.In this experiment,the physical and chemical indicators during the operation of the integrated vertical subsurface flow constructed wetland were continuously monitored,and the pH range was basically 6.0-8.0,and the temperature range was 19-33 ?.ZF7 strain has a good growth state in the pH and temperature range,the OD600 value can reach above 1.00,the denitrification rate is above 80%,and the nitrification rate of ZX2 strain fluctuates within the range of 50-60 mg/(L·d).It indicates that during the operation of the integrated vertical flow constructed wetland,the fluctuation range of pH and temperature values is suitable for the screening of denitrifying bacteria and nitrifying bacteria to exert their nitrogen purification effect,but the specific effects still need further practical application to test.The aim of this study is to improve the nitrogen treatment efficiency of constructed wetlands by screening,identification,analysis,and application of nitrifying and denitrifying bacteria in specific habitats,in order to provide a certain theoretical basis and technical support for strengthening the nitrogen processing technology of constructed wetlands. |
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