The Effect Of Carbon Source And Ammonia Nitrogen On Anaerobic Flora And Its Mechanism Of Methane Production

The anaerobic biological treatment process has become the first choice for the harmless treatment and resource utilization of organic waste due to the generation of clean energy.It has low operating costs,recyclable energy,low energy consumption,high organic load,and low residual sludge.The advantages of a wide range of applications.However,organic wastewater often contains high concentrations of ammonia nitrogen,which can cause fluctuations in the performance of the anaerobic digestion system and even failure of operation.This research is aimed at improving the efficiency and stability of anaerobic biological treatment system in the treatment of high ammonia nitrogen wastewater.The entry point is the metabolic response of the anaerobic methanogenesis system domesticated by different types of carbon sources and ammonia nitrogen concentration conditions to ammonia nitrogen stress.4 sets of UASBs reactors are used to set up different types of influent carbon sources（acetate,ethanol and acetate）and ammonia nitrogen concentration（0.11 g NH₄⁺-N/L,1 g NH₄⁺-N/L）.After operation,4 different types of anaerobic sludge were domesticated.Four kinds of sludge were tested for different concentrations of ammonia nitrogen stress,and the corresponding sludge’s methanogenic activity and pathways,microbial community structure,ATPase system and potassium（K⁺）transport system response changes under ammonia nitrogen stress were investigated.Anaerobic digestion treatment of high ammonia nitrogen organic wastewater provides theoretical guidance and technical support.The long-term operation results show that,except for the acetate remaining about100 mg C/L～200 mg C/L in the effluent of UASB_Ace-N,the substrates of the remaining three reactors are completely degraded.The average CH₄ yields of UASB_Ace,UASB_Ace-N,UASB_Mix and UASB_Mix-N were 833.1,337.8,753.6 and 527.8 m L/L,respectively.The conductivity of anaerobic sludge acclimated with different carbon sources and ammonia nitrogen concentration is quite different.The long-term acclimation of ethanol as a carbon source will promote the growth of electricity-producing bacteria,thereby increasing the conductivity of sludge;however,high ammonia nitrogen conditions are not conducive to production.The growth of electrical bacteria will reduce the conductivity of the sludge.The results of the ammonia stress test showed that the substrate metabolism and methanogenesis activity of UASB_Ace-N and UASB_Mix-N under 1 g NH₄⁺-N/L ammonia nitrogen were not significantly inhibited,indicating that the anaerobic reactor was operated for a long time under this ammonia nitrogen condition Later,the ammonia nitrogen-tolerant methanogens were domesticated;and UASB_Ace had a significant difference under the conditions of low ammonia nitrogen and medium ammonia nitrogen,which indicated that the acetate substrate anaerobic sludge that had not been domesticated for a long time with medium ammonia nitrogen had a substrate under this ammonia nitrogen concentration.Metabolism and methanogenesis activity will be significantly inhibited.The ethanol oxidation process is less affected by the toxicity of ammonia nitrogen.Long-term domestication under 1 g NH₄⁺-N/L ammonia nitrogen conditions can reduce the total abundance of methanogens by more than 13%,and the dominant genus of methanogens has changed from Methanothrix to Methanosarcina..In the reactor(UASB_Ace-N)where acetate was added as a single organic substrate,the genes encoding the methanogenesis,ATPase system and K⁺transport system were inhibited by 1 g NH₄⁺-N/L ammonia nitrogen.However,in the reactor(UASB_Mix-N)where ethanol and acetate are added as mixed organic substrates,ammonia-resistant co-operating bacteria（ie Geobacter）have been domesticated,and Geobacter has a high relative abundance of encoding ATPase system and K⁺transport system genes.Compared with the control reactor(UASB_Mix),its strong ethanol oxidation capacity and ammonia nitrogen detoxification activity enhanced the subsequent methanogenesis（including acetic acid nutrient methanogenesis）,which increased the maximum methanogenesis rate by 78%.Due to the detection of the bacteria and the Pil A gene with the ability of direct electron transfer between species（DIET）,it is speculated that there may be direct electron transfer between species（DIET）under the condition of ammonia nitrogen stress.