Study On Nitrogen Removal And Heterotrophic Nitrosobacteria

With the rapid development of intensive breeding industry,pollution of livestock and poultry manure is worsening sharply,and becoming an distinct problem in environmental protection.It is urgent to conduct innocent treatment of these manure.Aerobic composting is one of important ways to remove them to high quality organic fertilizer.However,there is severe nitrogen loss in aerobic composting of livestock and poultry manure,which results in serious pollution and reduction of nutrient contents in fertilizer.It has been proved that continuous volatilization of ammonium and denitrification are the main reasons for nitrogen loss,and effects of the former is more obvious.Current methods,such as optimizing composting conditions and using additives, control nitrogen loss macroscopically,under the background of not clarifying microbial mechanisms in aerobic manure composting.Differing from the past,our study started with rules of nitrogen variation in composting,and carried out research on the correlation between quantity change of four groups of nitrogen removal bacteria and nitrogen removal in composting,mainly on function rules and biological characteristics of nitrosobacteria for laying an theoretical foundation for control of nitrogen loss in composting.The main results are showed as follows.(1) The dynamic variations of the quantity of four groups of bacteria,ammonifying bacteria, heterotrophilic nitro-sobacteria,heterotrophilic nitrobacteria and aerobic denitrifying bacteria,and that of contents of organic N,ammonic N and nitrate N are determined for clarifying the relationships between them.The results showed that mesophilic bacteria were the majority in N-transforming bacteria in the process,whose optimum growth temperature is 35℃.After 35℃in the course of temperature rising,the quantity of bacteria decreased with temperature rising; before 35℃in the course of temperature des-cending,it rose with temperature descending. Relationships between the quantity of N-transforming bacteria and the corresp-onding variations of contents of N-transformation were concluded:in the course of temperature rising,the increment amplit-ude of ammonic N was relatively marked as the quantity of ammonifying bacteria, nitrosobacteria and nitrobacteria increase-ed,whi-le it was small when the quantity decreased;in the course of temperature descending,there was no correlation between the quantity of ammonifying bacteria and ammonic N,but there was positive correlation between the quantity of nitrosobacteria and nitrobacteria and nitrate N,and negative correlation between the quantity of denitrifying bacteria and nitrate N.(2)17 strains of dominant heterotrophic nitrosobacteria one were screened,and 3 strains of them,namely,SY35-1,JY35-3 and JY45-2 were determined as high-effective heterotrophic mitrosobacteria.(3) The 3 strains of high-effective heterotrophic nitrosobacteria were studied,and effects of environment conditions to ammonium oxidation activity of are clarified,The conditions involved initial concentration of organic compounds,concentration of ammonium nitrogen,pH,C/N,content of dissolved oxygen and temperature.Related biological characteristics of them,such as ammonification and nitrification,were also discovered.(4) The 3 strains of high-effective heterotrophic nitrosobacteria were identified by classical identification methods.SY35-1 belongs to the genus Corynebacterium,and JY35-3 and JY45-2 belong to Pseudomonas.It has not been reported that the genus Corynebacterium have the capability of heterotrophic nitrosification.