Study On The Efficiency Of Anaerobic Biological Treatment Of Redox Mediator

The process of organic methane fermentation is completed by acidogenic fermentation bacteria,hydrogen-producing acetic acid bacteria,isotype acetic acid-producing bacteria and methanogenic bacteria.Among all kinds of microbial flora,hydrolytic fermentation bacteria have the most species,and their metabolites are diversified,which leads to the diversification of fermentation types.Redox mediators(ROMs)can accelerate the transfer of electrons between electron donors and electron acceptors by cyclic transformation of their oxidized and reductive states,which affects the fermentation types.In order to avoid the accumulation of propionic acid in anaerobic digestion system and improve the operation efficiency and stability of the reactor,the electronic transfer function and biocatalytic function of oxygen ROMs were used to regulate the fermentation type and increase the degradation rate of propionic acid.Firstly,graphene oxide(GO)and anthraquinone-2,6-disulfonic acid(AQDS)were selected as redox mediators,glucose as substrates,and cultured in constant temperature oscillation at 35 C.The directional regulation of GO and AQDS on fermentation types was studied.The results showed that GO could regulate the fermentation type of granular sludge,and make the fermentation type change from mixed acid fermentation to butyric acid fermentation,and 80 mg/L GO had the strongest effect on promoting mixed acid fermentation to butyric acid fermentation.AQDS and GO can regulate the flocculent sludge fermentation type and make the fermentation type change from butyric acid type to ethanol type.When GO concentration is 80 mg/L and AQDS concentration is 400 mg/L,the effect of promoting butyric acid type fermentation to ethanol type fermentation is the strongest.In order to further reveal the biological mechanism of GO and AQDS directional regulation of fermentation types,the composition of activated sludge mediated by mediators was analyzed by high throughput sequencing technology.The results showed that Clostridium sensu stricto was the dominant acid-producing bacteria in granular sludge mediated by GO,and its relative abundance was 13.6 times that of the blank group.Clostridium sensu stricto is a kind of fermentation bacteria which produces butyric acid and acetic acid by organic fermentation.Clostridium sensu stricto is enriched in activated sludge,which improves the production of butyric acid in the fermentation system,thus promoting the transformation of the system from mixed acid fermentation to butyric acid fermentation.The dominant acid-producing bacteria in flocculent sludge mediated by AQDS and GO were Pseudomonas and Clostridium sensu stricto,respectively.The addition of AQDS promotes the enrichment of Pseudomonas,thereby increasing ethanol production.GO improves ethanol production by enriching Clostridium sensu stricto,and realizes the transformation from butyric acid fermentation to ethanol fermentation.Propionic acid is often accumulated in anaerobic digestion system,and excessive accumulation of propionic acid often leads to "acidification" of anaerobic digestion system.Therefore,this paper continues to investigate the effects of GO and AQDS on the degradation of propionic acid and its biological mechanism.The results show that GO can promote the biodegradation of propionate in anaerobic biological treatment system,and when GO concentration is 80 mg/L,it can promote the anaerobic degradation of propionate most significantly.AQDS did not promote the degradation of propionic acid and inhibited the production of hydrogen,acetic acid and methane.The dominant functional bacteria in activated sludge mediated by GO are Pseudomonas,Acinetobator and other hydrogen-producing acetic acid bacteria.The enrichment of hydrogen-producing acetic acid bacteria makes GO significantly promote the anaerobic degradation of propionic acid.