Research On Substrate Metabolic Mechanism Of Aerobic Granular Sludge And Effect Of Graphene Oxide On The Removal Of Nitrogen And Phosphorus

Aerobic granular sludge is gradually applied in the treatment of industrial wastewater and municipal sewage due to its advantages such as compact structure,good sedimentation performance,abundant biological phase and strong impact resistance.Recently,the nitrogen and phosphorus pollution is increasingly serious,which has forced us to explore an effective method to improve the efficiency of nitrogen and phosphorus removal.In-depth analysis of the metabolic mechanism of nitrogen and phosphorus removal matrix in aerobic granular sludge can provide theoretical support from the microscopic perspective.Furthermore,graphene oxide maretials and its derivatives have been intensively applied in all trades and professions of life,which inevitably affects the activity of functional microorganism in wastewater treatment.In this study,the GO material was used to embed aerobic granular sludge to explore the effect of GO on biological nitrogen and phosphorus removal.The results are showed as follow:(1)The matured aerobic granular sludge cultured with sodium acetate as carbon source was characterized by yellowish-brown regular spherical edges,dense structure and clear outline.The lots of primary and metazoan animals such as filamentous bacteria,campanularia and cladoceles were distributed on the surface and pores of the sludge.Furthermore,at the outside of granule,a lot of fungal filaments,rods,and cocci were interlaced and exited stable three-dimensional mesh skeleton and some filamentous bacteria are cross-linked with each other.On the surface of granular sludge,some short bacillus are mainly distributed.The sludge volume index(SVI)of matured sludge was maintained at about 10 mL/g,with the fine sedimentation performance.(2)The matured sludge with the high activity of the function microorganisms,the average CODcr,nitrogen and phosphorus removal rates were reached 85.34%,98.54% and 94.64%,respectively.(3)The main component of extracellular polymeric substances(EPS)polysaccharide(PS)was basically maintained at 30 mg/g VSS during granulation process,but protein(PN)increased with the gradual maturation of granules.PN content in mature granular sludge could reach about 170mg/g VSS,accounting for about 70% of total EPS.Ortho-P and polyP are the main fraction of intracellular phosphorus and extracellular phosphorus and the intracellular phosphorus accounted for 86.70%.EPS not only acted as a buffer region for material transport in sludge cells and water environment,but also participated in the process of biological phosphorus accumulation.(4)The MiSeq high-throughput sequencing was used to analysized the microbial community structure of aerobic granular sludge,it was showed that there were existed rich microbial populations.Bactaroidetes and Proteobacteria were the dominant bacterial,the abundance were reached 38.93% and 34.29%,respectively.(5)It could be find that sodium acetate could be rapidly absorbed by functional microorganisms in granular sludge at anaerobic stage and stored in the form of PHB and glycogen,which are energy storage materials for each other in the whole reaction cycle.(6)0.06 g/L of Graphene oxide(GO)materials could be well attached to the surface of granular sludge and promoted the bioactivities of ammonium oxidizing bacteria(AOB)and nitrite oxidizing bacteria(NOB)and EPS production.However,the bioactivities of PAOs was inhibited and the production of EPS decreased.