Isolation Of Heterotrophic Nitrification-Aerobic Denitrification Bacteria And Its Application To Restoration Of Water

A large amount of nitrogen-containing compounds are discharged into the water,causing the problem of eutrophication of water to become more and more serious.Biological nitrogen removal is widely used because of its rapid and efficient,but traditional biological nitrogen removal has certain drawbacks,and new biological nitrogen removal needs to be researched and developed.The discovery of heterotrophic nitrification-aerobic denitrification bacteria provides a new idea for biological nitrogen removal.These bacteria have both heterotrophic nitrification and aerobic denitrification,making nitrification and denitrification are achieved at the same time and space.This paper mainly studied the heterotrophic nitrification-aerobic denitrification bacteria isolated and its application in water restoration.Firstly,two heterotrophic nitrification-aerobic denitrification bacteria HY3-2 and SLY2-21 with good nitrogen removal effect were isolated from high-salt aerobic granular sludge system and landfill leachate.Scanning electron microscopy showed that both of them were rod-shaped.And the 16S rDNA sequence analysis of the strain showed that HY3-2 was Klebsiella quasipneumoniae subsp.quasipneumoniae,SLY2-21 was Achromobacter marplatensis,and phylogenetic trees were established.Secondly,the heterotrophic nitrification-aerobic denitrification performance of the two strains were studied.The results showed that:HY3-2 used glycerol as carbon source,C/N 25,temperature 20℃ or 30℃,rotation speed 150rpm,initial pH 7～10,inoculation amount 2%,salinity less than 50g/L,the removal effect of 100mg/L NH4+-N was good,and the removal rate was 90.7%.The sodium citrate was used as carbon source,C/N 25,temperature 30℃,rotation speed 150rpm,initial pH 5～9,inoculation amount 2%,and the aerobic denitrification can be performed when the salinity less than 15g/L,the NO3--N removal rate was over 99%and the TN removal rate was 42.8%.SLY2-21 used sodium citrate as carbon source,C/N 15,temperature 30℃,rotation speed 200rpm,initial pH 7～8,inoculation amount 2%,salinity less than 20g/L.It could carry out better heterotrophic nitrification-aerobic denitrification,and the nitrogen removal efficiency was about 85%.Again,this paper studied the effects of different nitrogen sources on the nitrogen removal performance of the two strains.The results showed that HY3-2 and SLY2-21 of not higher than 1000mg/L of nitrate nitrogen could achieve the removal effect of more than 95%,and the removal rate of SLY2-21 was slower than HY3-2.And the nitrite nitrogen accumulation of HY3-2 was relatively small.Two strains could remove ammonia nitrogen within 1000mg/L and convert ammonia nitrogen directly into nitrogen-containing gas.When ammonia nitrogen was combined with nitrate nitrogen,HY3-2 could promote the degradation of ammonia nitrogen and nitrate nitrogen.When 50 to 200mg/L of ammonia nitrogen was added,ammonia nitrogen was preferentially used by SLY2-21,and then nitrate nitrogen was degraded.HY3-2 could effectively remove 340.53mg/L nitrite nitrogen,and the removal rate was 88.11%within 72h;SLY2-21 lacks nitrite reductase and cannot remove nitrite nitrogen.Finally,the application of the target strains in the ecological restoration of the water was studied.The experiment showed that HY3-2 and SLY2-21 were added to the polluted river in a ratio of 1:1.Within 24 hours,NH4+-N,NO3--N and TN could be removed to the greatest extent,and the removal rates were 95.59%,44.33%and 36.94%,respectively.Later,the removal efficiency decreased to some extent.Overall,the strain has certain application prospects.