| The effective treatment and standard reached discharge of ammonia nitrogen wastewater are important guarantee to reduce water eutrophication.Compared to physical and chemical treatment technology,biological technology has the advantages of low treatment cost,small secondary pollution and simple process on removing nitrogen.However,there is a bottleneck in the application of traditional biological technology for the nitrogen removal of high ammonia nitrogen wastewater,such as chemical industry,landfill leachate and aquaculture wastewater.One of the most important reason is that when the concentration of ammonia nitrogen was over 200 mg/L,a large amount of free ammonia will inhibit the nitrification activity and growth rate of microorganisms,resulting in the decrease of nitogen removal efficiency,biomass and biological activity.Previous studies have shown that the microorganism with the function of heterotrophic nitrification aerobic denitrification（HN-AD）can simultaneously realize the removing of ammonia nitrogen and nitrate nitrogen under the condition of aerobic.In addition,HN-AD functional mixed bacteria has the special metabolic characteristics,which makes it has the adaptation mechanism of multiple stress conditions with the characteristics of fast growth rate,high nitrogen removal efficiency and strong environmental adaptability.It also shows great application potential for the treatment of high ammonia nitrogen wastewater.In order to break through the bottleneck of traditional microorganisms in the application of high ammonia nitrogen wastewater,this paper enriched HN-AD functional mixed bacteria from real high ammonia nitrogen wastewater,studied the optimal culture parameters of mixed bacteria and carries out subculture domestication,and investigated the treatment effect of mixed bacteria on real high ammonia nitrogen wastewater after pilot scale-up.which expect to provide a theoretical basis for the development of new biological technology that aims to remove nitrogen,The results are as follows:1.HN-AD functional mixed strain HY-1 was obtained.Using the surface fecal water of a rural septic tank in Chongqing and the wastewater of a pig farm in Chongqing as bacterial sources,a nitrogen removal and mixed bacterium with tolerance of high ammonia nitrogen was enriched and domesticated,named HY-1.After continuous cultivation and acclimation for 25 days under the condition of 400 mg/L ammonia nitrogen concentration,the ammonia nitrogen removal rate of mixed strain HY-1 can reach more than 98%within 120 hours.In heterotrophic and fully aerobic environment,the mixed strain HY-1 can remove ammonia nitrogen,nitrate nitrogen and nitrite nitrogen simultaneously,and has the function of HN-AD.Through diversity analysis,the changes of abundance of mixed bacterium HY-1 during domestication were studied.The results showed that the bacterial structure was more stable after domestication,and the dominant microorganism was Acinetobacter with a abundance of more than 80%.2.The culture parameters of mixed strain HY-1 were optimized.Considering the ammonia nitrogen removal rate（≥80%）,cell density(OD600≥1.5)and culture cost,the optimization experiments of key factors such as carbon source type,carbon nitrogen ratio,rotating speed and initial ammonia nitrogen concentration were carried out based on the engineering application.The optimum culture conditions of mixed strain HY-1 were determined as follows:carbon source was sodium acetate,carbon nitrogen ratio was 10,rotating speed was 150 rpm,the initial ammonia nitrogen concentration was 400 mg/L.3.The pilot scale-up test of mixed strain HY-1 was carried out.Based on the optimum culture conditions,the amplification medium was designed and the mixed strain HY-1 was domesticated for the second time.The results showed that the ammonia nitrogen removal rate of mixed bacterium HY-1 reached 90%（the initial concentration was 400 mg/L）after 30 days of secondary acclimation,t and the dominant bacterium was Acinetobacter with an average abundance of more than 70%.When the mixed strain HY-1 cultured in conical flask was connected to a 5 L fermentor with 400 mg/L of initial ammonia nitrogen concentration for amplification,the ammonia nitrogen removal rate was 94.1%and the total nitrogen removal rate was 84.9%after 49 hours.After the mixed strain HY-1 was connected to a 1000 L reactor with 400 mg/L of initial ammonia nitrogen concentration for pilot scale-up,uthe ammonia nitrogen removal rate was 99.3%and the total nitrogen removal rate was 70.9%after 42 hours.The changes of bacterial structure during the pilot scale-up of mixed bacterium HY-1 were analyzed.It was found that Acinetobacter was always the dominant bacterium,and the abundance was maintained at more than 70%.4.The treatment effect of mixed bacterium HY-1 on real high ammonia nitrogen wastewater was investigated.The mixed strain HY-1 was used to treat landfill leachate,chemical wastewater and aquaculture wastewater.The results showed that the removal rates of ammonia nitrogen and total nitrogen in landfill leachate（194.0 mg/L of ammonia nitrogen and 268.7 mg/L of total nitrogen）were 93.8%and 81.9%respectively.The removal rates of ammonia nitrogen and total nitrogen in chemical wastewater（573.8 mg/L of ammonia nitrogen and 673.9 mg/L of total nitrogen）were 88.1%and 64.8%respectively.The removal rates of ammonia nitrogen and total nitrogen in aquaculture wastewater（3022.9 mg/L of ammonia nitrogen and 3326.9 mg/L of total nitrogen）were79.2%and 58.1%respectively.The results show that the mixed bacterium HY-1 has strong adaptability and nitrogen removal ability to the real high ammonia nitrogen wastewater,and has great application potential in the treatment of high ammonia nitrogen wastewater. |
