Study On The Way And Mechanism Of N₂O Production In The Aged Refuse Bioreactor Landfill Site

The aged refuse bioreactor can remove contaminants with aged refuse as medium by microbial degradation and adsorption function.Because of its advantages of low cost and stable operation,it has obvious advantages in practical engineering application.However,nitrous oxide?N₂O?will be inevitable produced during the nitrification and de-nitrification process in the process of nitrogen removal.The previous studies showed that ammonia nitrogen load and oxygen concentration were the important factors on influencing the N₂O production in the process of treating leachate by aged refuse bioreactor.However,it had a lack of in-depth study on the mechanism of N₂O under different ammonia nitrogen load and oxygen concentration.In this paper,a simulation device of indoor mineralized bioreactor was established.This paper researched influence on the ammonia load and oxygen concentration on the reactor in the leachate N₂O production?2 h,12 h,24 h,36 h,48 h,72 h,100 h,120 h,144 h?and the way of production?24 h,72 h?by using 15 N isotope labeling techniques.At the same time,this paper researched the effect of ammonia nitrogen loading on the amoA and nosZ gene abundance by RT-PCR molecular biology technique,so that it provided theoretical guidance for the N₂O production capacity,generation and generation mechanism.The results were as follows:?1?In a reaction cycle?144 h?,the early stage of the bio-reactor?24 h?,N₂O was mainly produced by the nitrification process.However,in the late stage of the reaction?72 h?,the de-nitrification process became the main process of N₂O release in the reactor.?2?The increase of ammonia nitrogen load enhanced the production of N₂O in bioreactor,besides increasing the ammonia nitrogen load can increase the nitrification proportion of N₂O in the reactor.Under the 0.8 mg/g ammonia nitrogen load,the peak value of N₂O in the reactor was about 1090 ?g N,higher than 0.2,0.4 mg/g the load of ammonia nitrogen.The correlation analysis showed that NO₃^--N and NO₂^--N were the main factors of N₂O production.?3?With the increasing of oxygen concentration,the amount of N₂O decreased.Under 10% oxygen concentration,aged refuse bioreactor in N₂O production peak was about 1053 ?g N,higher than 20% and 30% oxygen concentration.Besides,the oxygen concentration increased the contribution rate of nitration reaction to N₂O.When the reaction time wass 24 h,the contribution rate of 30% oxygen concentration to N₂O is up to 55.9%,and the proportion of the latter can still reach 39.84%.But,under the 10% and 20% oxygen concentration,the contribution rate of nitrification to N₂O was 28.32% and 32.68%.?4?RT-PCR experimental results showed that under the conditions of the ammonia nitrogen loading,the amoA gene abundance was higher in the early stage of the reaction,but the nosZ gene abundance was higher than that in the early stage,which indicated that the production of N₂O was higher than early stage of the reaction.Under different loading conditions,the amoA,nosZ genes were positively correlated with the increase of the ammonia nitrogen load,which was consistent with the high yield of N₂O under the condition of high ammonia nitrogen loading.