Effect Of Copper And Zinc Ions On Simultaneous Methanogenesis And Denitrification In Expanded Granular Sludge Bed Reactor And Its Microbial Community

This topic studied the influence of different concentrations of copper and zinc ions in influent on simultaneous methanogenic denitrification and microbial community structure in EGSB reactor.The main research results are as follows:(1)By adding different concentrations of copper ions,zinc ions and their composite ions into the influent of two same EGSB reactors,the influence on the SMD process of EGSB reactor can be seen as follows: Both copper and zinc ions have influence on SMD process of EGSB reactor.When the concentration of copper ions in the influent is greater than or equal to 20mg/L,its toxic effect is obviously enhanced,and its COD removal rate decreases to 43%.When the influent copper ion concentration decreases,the COD removal rate will gradually increase,and when it decreases to 10mg/L,the COD removal rate of the reactor will gradually recover to 67%.When the influent concentration of Cu ion is less than 10mg/L,its effect on denitrification is weak,and the removal rate of nitrate nitrogen remains above 95%.However,when zinc ion concentration is lower than10mg/L,its effect on the EGSB reactor is weak,and its COD removal rate remains above79%.When the concentration of zinc ions in the influent increases to 40mg/L,the COD removal rate drops to 80%.The effect of zinc ions on the SMD process of EGSB reactor is weaker than that of copper ions.When the concentration of zinc ion is less than 5mg/L,the effect of nitrate removal is not significant,and the removal rate is still above 90%.In addition,no matter the order of adding Cu and Zn ions into the influent,the influence of Cu and Zn ions on the SMD process of EGSB reactor is superimposed.(2)Through high-throughput sequencing analysis,it can be seen that: In the copper ion environment at the phylum level,Proteobacteria could be slightly inhibited but the change was small.When the concentration of Cu2+ in the water was 1mg/L,Bacteroidetes became Bacteroidetes and the relative abundance increased from 0.73% to31.44%.The relative abundance of Firmicutes reached the maximum when the influent copper concentration was 1mg/L,37.56%.When zinc ions are contained in the water,the dominant bacteria at the gate level are: The relative abundance of Proteobacteria is37%-70.8%,Firmicutes 15%-33%,Actinobacteria 0.1%-10.8% and Bacteroidetes2%-23.2%.Chloroflexi 0.01%~9.01%;Zinc ions can promote the growth of Bacteroidetes,Chlorobi,Proteobacteria and Spirochaetes.However,Proteobacteria and Bacteroidetes were the main bacteroidetes.(3)Metagenomics analysis showed that: Whether increasing zinc ion or copper ion concentration,the trend of change in denitrifying functional genes(nir C,nir D,nor B and nor M/pmp M)is significantly increased by nor B functional genes,and the gene abundance is in direct proportion to the concentration of metal ions.For znu A/yeb L,znu B/yeb I,znu C/yeb M,zur/yjb K and zup T/ygi E,znu C/yeb M and zup T/ygi E have strong resistance to zinc ions.Although the other three genes can also resist some zinc ions,they are inferior to znu C/yeb M and zup T/ygi E genes.These two genes also have the maximum abundance when the concentration of zinc ions is 1mg/L,and can promote the growth and reproduction of microorganisms containing these two genes.