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The short-range nitrification-denitrification process refers to the inhibition or elimination of nitrite oxidizing bacteria in the system, so that the conversion of nitrogen is limited to the oxidation ofNH4+ to NO2-, In addition, NO2- is reduced to N2, eliminating the nitrate conversion step and saving the amount of aeration and carbon source addition in the system
.
However, in the high ammonia nitrogen load system, due to the high sensitivity of ammonia-oxidizing bacteria to external environmental conditions, the doubling time is long, and the functional microorganisms are easy to lose, resulting in the instability
of the short-range nitrification unit.
Adding a small amount of carbon source to the system can improve the stability of the system and enhance the accumulation
of nitrite.
However, the microbiological mechanisms involved in this have not been studied in depth
.
Under the guidance of researcher Li Xiangzhen, assistant researcher Cao Qin, member of the biomass energy project team of Chengdu Institute of Biology, Chinese Academy of Sciences, set up and operated two sets of laboratory-scale sequential batch nitrification bioreactors, and one reactor was introduced into synthetic wastewater (CN system) with C/N 0.
6.
The control group was introduced to synthetic wastewater (N system)
with a C/N of 0.
The ammonia nitrogen load of both systems was simultaneously increased from 248 mg N/(L· d) Gradually increased to 1687 mg N/(L· d)
。 The experiments show that the ammonia oxidation efficiency and nitrite accumulation rate of the CN system are higher than those of the N system during the whole operation, and the stability of the CN system is stronger.
Extracellular polymer (EPS) analysis found that the CN system secreted more EPS
.
EPS promotes the polymerization of functional microorganisms and reduces the loss rate
of functional microorganisms.
Through microbial community diversity analysis and community dynamic analysis, it was found that the microbial community of the CN system was more stable
.
Nitrosomonas, the main autotrophic AOB of the CN system, Thauera is The main denitrifying functional microorganisms of the CN system, Paracoccus and Flavobacterium, are CN Heterotrophic nitrifying-aerobic denitrifying bacteria (HN-AD bacteria)
in the system.
HN-AD bacteria play an important role in the system, on the one hand, they can share part of the ammonia nitrogen pressure of AOB; On the other hand, they can metabolize EPS, promoting the enhancement of the spatial stability of the system; Moreover, the competitive effect of HN-AD bacteria and nitrite oxidizing bacteria (NOBs) makes NOBs better eliminated by the system, thereby increasing the nitrite accumulation rate
of the system.
The relevant scientific results of this study "Low C/N promotes stablepartialnitrification by enhancing the cooperation of functional microorganisms in treating high-strength ammonium.
" landfill leachate" was published in
the Journal of Environmental Management.
Original link
