The Study Of The Effect Of Silver Nanoparticles On Anammox Process Efficiency And Microbial Population

In order to clarify the environmental effects of silver nanoparticles,ensure the effective and healthy circulation of urban water environment and water quality safety,and at the same time facilitate the efficient and stable operation and popularization of the anaerobic ammonium oxidation process(Anammox),this experiment explored the effect of silver nanoparticles(Ag NPs)on the Anammox process efficiency and the effect of microbial populations,this experiment uses anaerobic reactor,takes anammox granular sludge as the research object,through three-dimensional fluorescence,scanning electron microscope(SEM),particle size analysis,Scanning Electron Microscopy-X-ray Spectroscopy(SEM-EDX),ICP-MS and other equipment explored the changes of ANAMMOX granular sludge and revealed its differences.And based on metagenomic sequencing technology,the effects of different concentrations of nano-silver on the microbial population structure were investigated.The study found that under short-term exposure,the higher the concentration of silver nanoparticles added,the more obvious the inhibition of anammox process.There was no significant difference in the effect of silver nanoparticles above 1 mg/L on anammox(p>0.05);under long-term exposure,0.5 mg/L and 1.0 mg/L Ag NPs had no strong inhibitory effect on anammox,while 1.5 mg/L Ag NPs had no strong inhibitory effect on anammox.1.5 mg/L L and 2.5 mg/L Ag NPs significantly inhibited the anammox process(p<0.05).The toxicity of Ag~+ is stronger than that of Ag NPs under short-term exposure;under long-term exposure,the system quickly recovers its activity,which may be due to Ag~+ and Cl~-in the system forming Ag Cl precipitation,which makes Ag+ lose its toxicity.ICP-MS results show that the dosage of nano-silver is proportional to the content of silver in the mud and water phases,and most of the silver is adsorbed in the activated sludge.The results of EPS measurement showed that 0.5-1.5 mg/L nano-silver made the microorganisms in the system secrete more EPS to resist the toxicity of Ag NPs,and when 2.5mg/L,the EPS secretion amount was the least.Based on sludge volume ratio(SVI),sludge specific resistance(SRF),and capillary water absorption time(CST),the results showed that the change of Ag NPs concentration had a significant impact on the performance of sludge-water separation.EEM analysis showed that Ag NPs had an effect on microbial metabolism,inhibiting microbial activity and reducing metabolism.Scanning electron microscopy(SEM)results showed that with the increase of Ag NPs concentration,the cells were damaged and the morphology became irregular;Scanning Electron Microscopy-X-ray Spectroscopy(SEM-EDX)analysis showed that the Ag NPs and nanoparticles aggregated and adsorbed on the cell surface.The amount of silver added is proportional.Particle size analysis showed that silver ions did not significantly affect the particle size of granular sludge,while Ag NPs would reduce particle size and increase specific surface area.Based on 16 S r RNA high-throughput sequencing technology,nano-silver was found to change the richness and diversity of the community through diversity index.In the anammox system,the main phyla observed were Chloroflexi,Proteobacteria,Bacteroidetes,Planctomycetes,Acidobacteria.The relative abundance of Planctomycetes was increased by0.5 mg/L of nano-silver,but the relative abundance of Planctomycetes gradually decreased with the increasing concentration of Ag NPs.Ag NPs affects the relative abundance of the genus Candidatus_Kueneniad.Principal coordinates analysis(PCo A)analysis showed that the microbial community structure of the silver ion-added system was similar to that of the blank group,and the microbial community structure of the 0.5 mg/L and 1.5 mg/L Ag NPs system was similar.2.5 mg/L Ag NPs caused great changes in the microbial community in the system.Functional unit PCo A analysis showed that Ag NPs led to changes in the functional units of the microbial community.In the microbial metabolic function analysis of the KEGG database,the relative abundance of the first-level metabolic pathway Amino Acid Biosynthesis module was the highest.Amino acids are the raw materials for protein synthesis.The enzymes involved in the anammox process,cell synthesis and EPS all require protein,so to a certain extent reflect the activity of the system microorganisms.Correlation network analysis showed that Candidatus_Kuenenia was strongly positively correlated with NB1-j bacteria,and its abundance affected the quantity of extracellular polymers secreted by the activated sludge and the sludge dewatering ability to a certain extent.