Construction Of A Microbial Denitrification Agent

With the development of industry,agriculture and people's living standards,the nitrogen pollution has become a major global environmental problem and aroused widespread concern in the community,which led to the rapid development of biological nitrogen removal technology and many new biological nitrogen removal technology.The emergence of heterotrophic nitrification and aerobic denitrification bacteria makes the nitrification and denitrification process to achieve unity in time and space,and greatly improves the efficiency of nitrogen removal.The emergence of microbial immobilization technology overcomes the difficulty of microbial transport,and the problem of the serious loss.In this study,a total of 3 heterotrophic nitrification and aerobic denitrification bacteria WN1,WN3 and DN02 were isolated from the sludge of a sewage treatment plant of Nanchang city and the sediment of a lake in Nanchang University.The ammonia nitrogen removal rates of theses 3 strains were 68.9%,71.7% and 66.2%,respectively.The experimental results showed that the three strains could be co cultured.The optimum proportion of the three strains was WN1 : WN3 : DN02 = 0.935 : 0.965 : 1.100 with mixture design experiment.In this condition,the ammonia nitrogen removal rate was 90.37%,the maximum concentration of NO₃^--N was 7.58mg/L,and the concentration of NO2--N was always about 0.Further study of the best conditions for nitrogen removing agents,the results show that the best conditions to remaove ammonia nitrogen was the carbon source is sodium succinate,the pH is 7,the temperature is 30?,the rotate speed is 150 rpm,C/N is 12.In this case,the ammonia removal rate reached 91.18%.When the mass fraction of sodium alginate,polyvinyl alcohol and activated carbon is 1%,8% and 2%,respectively,the immobilized pellets has a better performance in stability,ballability and mass transfer.The chemical agents used in the immobilization process may have a certain impact on microbial activity,but after the activity recovery experiment,the nitrogen removal performance of immobilized pellets is similar to the free bacteria.When the dosage of immobilized pellets was 20%,the ammonia removal rate reached 89.78%.The removal rate of ammonia nitrogen of immobilized pellets can reach the maximum within 20 hours and be maintained at around 85% in simulated ammonia nitrogen wastewater which concentration is lower than 500mg/L.When the concentration increases to 1000mg/L,the immobilized pellets need 28 hours to achieve the maximum ammonia removal rate of 81.7%.