| Urban water consumption has been increasing with the rapid development of urbanization.Improving the efficiency of wastewater treatment and protecting the quality of water environment have become an important subject of urban development.It is a problem to treat sewage at low temperature in the cold northern area of our country.The normal low temperature biological treatment has problems of low microbial activity,low efficiency and high difficulties to reach the standard.Because low temperature has significant effects on sedimentary and adsorption properties of activated sludge,microbial activity in the aeration tank.Therefore,screening microorganism of high efficiency and applying them in the low temperature sewage is one of the fundamental methods to solve this problem.Due to the special environment and climate,There is a unique microbial ecosystem and species resource in polar regions.On the basis of morphological characters,the total of 81 cold-adapted nitrobacteria were isolated from 12 Arctic Ocean sediments by four kinds of screening mediums.Phylogenetic analysis on the basis of 16 S rRNA gene sequences showed that these isolates belonged to 4 phyla,4 classes,8 orders,16 families,22 genera and 30 species,respectively.One isolate having 16 S rRNA gene similarity less than 97% with the closest type strain might be novel species.These isolates could produce many extracellular enzymes,such as protease,urease and β-galactosidase,and they could grow by utilizing many kinds of carbon sources including glucose,mannitol and maltose.Studies on the range of growth temperature and salinity showed that the 18 representative strains were able to survive in 0 to 30 ℃ and 0-90,indicating that these strains could live in a low temperature and high salinity environment.Six strains(R14-ZY-5,CC6-YX-43,NB04-YY-61,CC6-ZY-68,CC6-YY-73 and CC6-YY-74)were screened due to the better growth characters in the screening medium.The nitrifying and denitrifying test showed strain R14-ZY-5 and CC6-YY-74 had better nitrogen removal ability.The key functional enzyme gene(nirS)was cloned from two strains(CC6-ZY-68 and CC6-YY-74).The combined microflora was constructed by strain R14-ZY-5 and CC6-YY-74,and the influences of C/N,temperature and salinity on the degradation were investigated.The results showed that the combined microflora had a good nitrogen removal ability in the range from 8 to 14 of C/N,and the optimum C/N was 11.On this occasion,the removal rate of NH4+-N and NO3--N were 93.41% and 99.96% in 48 h respectively.The combined microflora had a good nitrogen removal ability in the temperature range from 5 ℃ to 20 ℃,and the optimum temperature was 15 ℃.On this circumstances,the removal rates of NH4+-N,NO3--N and COD were 91.70%,99.96% and 87.28% respectively in 48 h.The combined microflora had a good nitrogen removal ability in the salinity range from 15 to 45,and the optimum salinity was 30.On this occasion,the removal rates of NH4+-N,NO3--N and COD were 92.57%,99.96% and 91.35% in 48 h respectively.The research offers new germplasm for the sewage treatment at low temperature,is also helpful to their potential applications in the sewage treatment. |
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