Screening And Identification Of High Ammonia Nitrogen Degradation Bacteria And Study On The Condition Of Ammonia Nitrogen Degradation

In recent years,nitrogen pollutants are one of the main causes of water pollution and eutrophication,so it is very important to strengthen the research of nitrogen removal in wastewater.A large number of studies have shown that photosynthetic bacteria,nitrifying bacteria,Nocardia and Bacillus all have strong degradation ability to ammonia nitrogen in aquaculture water.The purpose of this study was to screen out the dominant strain with high ammonia-nitrogen degradation and to identify the strain from a pig farm wastewater in Guangzhou.The degradation characteristics of ammonia nitrogen in simulated wastewater and aquaculture wastewater were studied to provide excellent indigenous bacteria for ammonia nitrogen degradation in aquaculture wastewater.The main research contents are as follows:(1)From the aquaculture wastewater,two strains of high ammonia nitrogen degrading bacteria were selected and numbered A2 、 C5 respectively.Combined with morphology,physiological and biochemical characteristics,molecular biology identification and in silico(DDH)analyses,the A2 and C5 of the strains were identified as Bacillus tequilensis and B.subtilis subsp.stercoris respectively.(2)Through nine conditions,such as carbon source,carbon-nitrogen ratio and inoculation amount,the single factor test was designed to analyze the ammonia nitrogen degradation characteristics of strain A2 and C5 under different conditions,and to explore the optimum growth conditions.Through the condition optimization,the simulated wastewater with the initial ammonia nitrogen concentration of 848 mg/L 、 488mg/L was A2 and C5,respectively,after 72 h of culture,the degradation rate of ammonia nitrogen was 40.7% and78.1%,respectively,indicating that the strain had high strength ammonia nitrogen tolerance.The ammonia nitrogen degradation effect of strain A2 in aquiculture wastewater is not as stable as C5,but it can maintain high ammonia nitrogen degradation rate in aquiculture wastewater with high initial ammonia nitrogen concentration.The degradation rate of 72 h reached 85.3% at 900 mg/L ammonia nitrogen concentration.(3)Orthogonal design of simulated wastewater,when the A2 was used as the experimental strain,the effects of each factor on the degradation rate of ammonia nitrogen were as follows: temperature > p H > inoculation amount > C/N > carbon source,and the optimum experimental conditions were as follows: temperature 42℃,p H 10,inoculation 8%,C/N 5,the carbon source was sodium acetate;And when the C5 was used as an experimental strain,the effects of different factors on the degradation rate of ammonia nitrogen were as follows: carbon source >p H> rotary speed > inoculation amount >C/N.And the optimal experimental conditions are: the carbon source was starch,p H 9,160 rpm,the inoculation was10%,C/N 20.(4)Orthogonal test on design of aquiculture wastewater,when the A2 was taken as the experimental strain,the effects of each factor on the degradation rate of ammonia nitrogen were as follows: inoculation amount > p H > rotary speed > C/N > carbon source,and the optimal experimental conditions were as follows: inoculation was 5%,p H 7,rotational speed160 rpm,C/N 10,the carbon source was sodium citrate;And when the C5 was taken as the experimental strain,the effects of each factor on the degradation rate of ammonia nitrogen were as follows: C/N > p H > rotary speed > carbon source > inoculation amount,and the optimal experimental conditions were as follows: C/N 20,p H 7,rotational speed 120 rpm,the carbon source was sodium citrate,inoculation was 3%.(5)The results of orthogonal test and orthogonal test show that the strain A2 and C5 have high ammonia nitrogen degradation ability in simulated wastewater.When cultured for 72 h,the degradation rate of ammonia nitrogen was 78.4% and 86.8% for the A2 and C5 of the strain under the optimal conditions;When cultured in aquaculture wastewater for 72 h,the ammonia nitrogen degradation rates of strain A2 and C5 were 95% and 94.7%,respectively,it also shows that the two strains have good application value in wastewater treatment.