Removal Of High Concentration Ammonia Nitrogen From Landfill Leachate By Mixed Bacteria With Heterotrophic Nitrification-aerobic Denitrification

Landfill leachate is a pollutant produced by landfill in daily life.Landfill leachate contains high concentrations of organic matter and ammonia nitrogen.Among them,high concentration ammonia nitrogen is one of the most significant features,which is a difficult problem in landfill leachate treatment.At present,most of the methods of post-physical and biochemical methods are used to treat high ammonia nitrogen in landfill leachate,which is costly and complicated.In addition,the traditional biological nitrogen removal mainly relies on autotrophic nitrifying bacteria and anoxic denitrifying bacteria.When treating landfill leachate,high concentration of organic matter can inhibit the nitrification of autotrophic nitrifying bacteria,resulting in low nitrogen removal efficiency,and traditional nitrogen microorganisms have weak tolerance to high concentrations of ammonia nitrogen,and it is prone to deactivation when treating landfill leachate,resulting in the entire system not working properly.In this paper,the heterotrophic nitrification-aerobic denitrifying bacteria with strong denitrification performance under high concentration of organic matter and high concentration of ammonia nitrogen were enriched and acclimated from real landfill leachate,and a small test was conducted to investigate the actual treatment effect on landfill leachate.the result shows:?1?In-situ landfill leachate from Chongqing Changsheng bridge Landfill is used as the source of microbial agents,enriching the microbial agents with heterotrophic nitrification-aerobic denitrification and denitrification,and observing the morphology of the microbial agents.The biological micro-screening of the mixed microbial agents was carried out.After two times of separation and purification,two strains of pure bacteria were obtained,which were identified as water producing Alcaligenes and Saccharomyces.In addition,the mixed microbial agents were domesticated for 2-3months,and initially had heterotrophic nitrification-aerobic denitrification characteristics.?2?Under the conditions of laboratory shake flask culture,the nitrogen removal characteristics and nitrogen removal ability of the mixed bacteria were investigated.The single factor optimization experiments of carbon source,pH,temperature,rotation speed and C/N showed that the denitrification effect of the microbial agent was greatly affected by the denitrification conditions,and the optimal nitrogen removal condition was as follows:carbon source was sodium citrate,pH was 7.0-8.0,temperature At 30°C,C/N is 10;in order to optimize and improve the denitrification effect of landfill leachate,a 4-factor 4 level orthogonal experimental scheme of pH,temperature,C/N,and rotational speed was established,and it was found that the growth of the microbial agent was found.The factors that influence the size of the denitrification are:pH>speed>C/N>temperature.Compared with unoptimized and single-factor denitrification results,after multi-factor orthogonal optimization,the removal effect of ammonia nitrogen in the removal of landfill leachate was significantly enhanced.?3?The heterotrophic nitrification performance of the microbial agents were investigated under the optimal pH,temperature,carbon source,rotation speed and C/N conditions with ammonia nitrogen as the sole nitrogen source.The results showed that when the concentration of ammonia nitrogen was 985 mg/L,the OD₆₀₀ value of the cells could reach 2.113 after 96 hours of culture.After the completion of the heterotrophic nitrification process,the ammonia nitrogen removal rate reached 80.7%;When the aerobic denitrification performance was investigated for the sole nitrogen source,the nitrite nitrogen decreased from 408.35 mg/L to 281.79 mg/L after 120 h of culture,and the removal rate reached 31.1%;the total nitrogen was from the initial 385.42 mg/L decreased to 212.99 mg/L and the removal rate was 44.7%.When aerobic denitrification was carried out with nitrate nitrogen as the sole nitrogen source,the total nitrogen removal rate after the reaction for 120 h was 48.3%.?4?The simulated high-ammonia nitrogen wastewater was treated with stable strains.The results showed that the ammonia nitrogen concentration decreased from1880.7 mg/L to 799.3 mg/L during the treatment,and the average of ammonia nitrogen,nitrate nitrogen,TN and COD in 96 h.The removal rates were 61.5%,32.5%,44.5%and 67.7%,respectively.After the denitrification treatment of simulated high ammonia nitrogen wastewater by mixed bacteria,the treatment efficiency of mixed bacteria to high concentration ammonia nitrogen in landfill leachate was investigated.The removal rate of ammonia nitrogen increased gradually after 96 h treatment,and the average removal rates of ammonia nitrogen,nitrate nitrogen,TN and COD still reached 57.5%,28.5%,41.5%and 62.5%,respectively.Finally,high-throughput sequencing was used to analyze the changes of microbial community structure in different stages of landfill leachate treatment.According to the analysis of diversity and microbial abundance,after the enrichment and acclimation,the microbial communities in the mixed microbial agents are abundant.In the process of treating real landfill leachate,the microbial community structure is different.At different stages,the overall richness and diversity of microbial communities are similar,and the abundance of microorganisms and core species in mixed microbial agents are quite different,which indicates that different microorganisms in the microbial agents were role in various stages of nitrogen removal.