Effect Of Graphene Oxide On Operational Performance And Microbial Community Structure Of Sequencing Batch Reactor

Graphene oxide(GO)is used in composite materials,flexible lithium-ion batteries,adsorbent materials and other fields due to its rich functional groups on the surface.Its wide application will lead to a large increase in GO-containing wastewater.Municipal wastewater treatment systems are potential receptors for wastewater containing GO,and little is known about the effects of GO's chronic toxicity on this system.In order to more fully understand the impact of GO on the performance of the sewage treatment system and the microbial community,this article first explores the short-term impact of the high concentration GO material leaking into the urban sewage treatment system on the sewage treatment system.Then the effects of increasing GO concentration on the organic matter removal,nitrogen removal effect and microbial community of the sequential batch activated sludge system were investigated.Finally,the long-term existence of low-concentration GO in the stable batch activated sludge system was further explored,the performance of the reactor and the changes of microbial community structure were analyzed in detail,and the microorganisms with different GO concentrations were compared.Differences in community impact.The main findings are as follows:(1)In the short-term impact test,the removal performance of chemical oxygen demand(COD)and total nitrogen(TN)decreased,and the microbial activity became weak.The higher the GO concentration,the more the activated sludge will be affected,which will result in more significant inhibition of the removal of effluent N.GO stimulates the ability of activated sludge to resist environmental changes,and at the same time reduces the metabolic activity of microorganisms.The dehydrogenase activity of activated sludge is more strongly suppressed as the GO concentration increases.Moreover,the activated sludge changes from the compact state of aggregation to loose and messy under the action of GO,which seriously affects the original community shape of the microorganisms.(2)In the experiment of increasing the concentration of GO,the removal performance of COD,ammonia and phosphate decreased.Low concentration of GO(1-10 mg / L)has a greater impact on ammonia and phosphate removal performance.Under each concentration gradient,the removal efficiency has a certain recovery trend.The results of 16 S rRNA gene sequencing show that long-term exposure to GO will significantly change the composition and structure of the activated sludge microbial community.Specifically,as the concentration of GO increases,the richness and uniformity index of the bacteria both decrease.After adding GO,a significant change in the bacterial community structure was observed,and then recovered slightly during the recovery phase without GO addition.In addition,functional bacteria,such as Dechloromonas,Nitrosomonas,Nitrospira,S.aureus,and Staphylococcus aureus transferred significantly,which may be related to changes in nutrient removal performance and EPS production.(3)The effect of low concentration GO on the performance of sewage treatment system and microbial community can provide scientific basis for the treatment of graphene-based nanomaterial pollutants in sewage treatment plants.Long-term addition of low-concentration GO will increase the content of polysaccharides in EPS to adapt to the GO environment,thus slightly affecting the sedimentation performance of activated sludge.The low-concentration GO sewage has a small negative effect on the removal of organic matter in the activated sludge treatment system,but the adsorption capacity of low-concentration GO affects the concentration change of organic matter in the effluent,and maintaining a low level of GO concentration may have a positive effect on the effluent effect.Among the denitrifying functional bacteria,the denitrifying bacteria are generally negatively affected,which has a promoting effect on the genus of bacteria that is beneficial to the removal effect of ammonia nitrogen.The effect of trace GO on the activity of denitrifying bacteria.Phosphorus removal effect has a greater impact,with the increase of time,the removal effect has a tendency to gradually recover.