Study On The Efficiency And Mechanism Of Anaerobic Digestion And Denitrification Of Coal-fired Hydrogen Production Wastewater Enhanced By Exogenous Hydroge

Coal-gasification wastewater includes coal gasification washing wastewater and butanol production wastewater.It is difficult to treat because of high concentration of toxic substances such as alcoholic aldehyde and ammonia nitrogen.Biological treatment is the predominant technology of coal-gasification wastewater,but microbial degradation and denitrification are easily restricted by the inhibition of toxic pollutants and the lack of easily degradable carbon source.Therefore,it is urgent to explore an efficient anaerobic treatment technology of coal-gasification wastewater to meet the increasingly strict discharge standards.In this paper,the anaerobic methane production and denitrification of coal-gasification wastewater were enhanced by exogenous hydrogen（EH₂）,which provided a new idea for efficient degradation and resource utilization of wastewater.Firstly,EH₂ coupled GAC was used to enhance the anaerobic methane production of butanol octanol wastewater.The results showed that methane production in EH₂/GAC group is 289.55±17.43 m L CH₄/g COD,which is 1.07,2.04,and 1.98 times of that in GAC,EH₂,and Control groups,respectively.In the EH₂/GAC group,the relative abundance of Geobacter and Methanosaeta increased rapidly to 25.36%and 52.81%,respectively,and the relative abundance of Clostridium was 9.78%.The mechanism may be that GAC promotes the enrichment of Geobacter,while EH₂ enhance the metabolic mechanism of homoacetogenesis in Clostridium and promotes the enrichment of Methanosaeta.EH₂/GAC may promote direct interspecific electron transport（DIET）and increase the anaerobic methanogenesis rate of butanol octanol wastewater.Secondly,this study investigated the effects of different factors on EH₂ enhanced anaerobic degradation of wastewater.The results indicated that the higher the hydrogen partial pressure,the better the organic methane conversion effect of wastewater,and the maximum value was 289.55±17.43 m L/g COD（hydrogen partial pressure is 0.5 atm）.H₂:CO₂=4:1（V:V）was the best reaction ratio.When exploring the factors affecting homoacetogenesis,the results showed that the cumulative acetic acid production of medium temperature condition（38°C）was the highest,which was 1.22 and 1.12 times that of group 28°C and 48°C,respectively.The cumulative acetic acid yield of p H=8group was the highest,reaching 530.24±2.14 mg/g VSS,and the ETS activity of sludge increased by 8.73%,indicating that alkaline condition was beneficial to improve the electron transfer efficiency of anaerobic bacteria and promoted the cooperation between microorganisms in the process of wastewater degradation.In the experimental group with Na HCO₃ concentration of 500 mg/L,the daily acetic acid yield was the highest,and the effluent p H decreased the least,indicating that adding basicity to the anaerobic system can solve the problem of p H decline and promote homoacetogenesis.The acetic acid yield of each group was similar after adding carbon-based materials,indicating that carbon-based materials had no significant effect on homoacetogenesis.Finally,the study realized the efficient and stable operation of isotype acetic acid producing unit by reflux of denitrifying solution.The total nitrogen removal amount of E reactor using anaerobic fermentation solution as carbon source was slightly higher than that of C reactor using sodium acetate as carbon source,which indicated that the fermentation solution had the potential to be denitrifying carbon source.At the end of the experiment,the yield of acetic acid per unit H₂ after reflux was 10.19 times of that without reflux,because reflux of nitrifying solution played an important role in regulating the p H of acid producing unit and solved the problem of inhibition of acetic acid accumulation on the process of homoacetogenesis.Therefore,the addition of EH₂ provided a new idea for anaerobic digestion and denitrification of coal-gasification wastewater.