Screening And Immobilization Of Heterotrophic Nitrifying Bacteria At Low Temperature

In recent years,nitrogen-containing wastewater treatment is one of the most active research fields in environmental science.However,due to the poor denitrification effect and substandard water quality of sewage treatment plants in northern China in winter,people pay more attention to the denitrification of low-temperature sewage.Compared with autotrophic bacteria,Heterotrophic nitrifying bacteria has a wider range of temperature adaptation,and are more suitable for nitrogen removal in low temperature environment.Because a single strain is not easy to preserve and has poor viability in the new environment,immobilization of the strain can solve these problems.The environmental adaptability of the immobilized bacteria is strong,the bacteria are not easy to lose,the performance of the free microbial system is improved,and the solid-liquid separation is easy.The main content of this paper is to isolate and screen heterotrophic nitrifying bacteria under low temperature,and to immobilize them.First of all,three strains BC-15,SL-14 and MI-4 with good denitrification effect were screened from the activated sludge,biological turntable sludge and aerobic granular sludge in the sewage treatment station.BC-15 was identified as Acetobacter Johnsonii strain,SL-14 as Acetobacter cellular strain,MI-11 as Acetobacter emphasis strain.Secondly,the best ratio of inoculating amount of three strains was 1:1:1,which was the ratio of compounding agents.The most suitable carbon source of the compound bacterium is sodium citrate,and the removal rate of NH4+-N is 84.91%;when the initial concentration of NH4+-N is 50 mg/L,the removal rate can reach 96%,and the microorganism in the compound bacterium can grow normally in the environment of NH4+-N concentration of 400 mg/L,which shows that the bacterium has a certain tolerance to the concentration of ammonia nitrogen.When the pH value is 8,the removal rate of NH4+-N is 80%.The degradation rate of NH4+-N was 65%under 20 g/L and 50%under 30 g/L.The results showed that the bacteria could adapt to the environment of salinity lower than 30 g/L and exert its nitrification ability.Thirdly,the removal rate of NH4+-N was 71.41%by SA diatomite earth method.Study on the factors influencing the preparation of immobilized bacteria,when diatomite 1%,sodium alginate 2%,CaCl2 3%and adsorption material 6 g,the performance of immobilized bacteria was the best.The removal rates of ammonia nitrogen and cod were 72.54%and 95.70%,respectively.The best dosage of immobilized bacteria is 3 g/(100ml),at this time,the removal rate of NH4+-N is 76.1%,and the removal rate of COD is 92%;the immobilized bacteria can degrade NH4+-N below 30 mg/L almost completely,and the removal rate is above 97%;the most suitable pH range of immobilized bacteria is 7-8,and the removal rate of NH4+-N is above 78%in acid and alkaline environment,indicating that the immobilized bacteria can improve the free bacteria The acid and alkali resistance of the agent.Finally,the application of immobilized bacteria in polluted water was studied.The removal rate of ammonia nitrogen,nitrate nitrogen and total nitrogen were 95.86%,43.16%and 43.17%,respectively.