| Zinc ions and chlortetracycline are relatively common heavy metals and antibiotics in livestock wastewater,the two substances enter the sewage biological treatment system with livestock and poultry manure,due to their own physical and chemical properties,they will cause changes in the life activities of microorganisms in the activated sludge,thus affecting the effect of biological sewage treatment.Therefore,the study of the effects of zinc ions and chlortetracycline on the biological denitrification performance of livestock wastewater and the characteristics of extracellular polymer(EPS)of activated sludge is an important part of improving the biological treatment effect of livestock wastewater.However,in the biological treatment process of livestock wastewater,there are few studies on the effects of different concentrations of zinc ions and chlortetracycline mixtures on biological denitrification performance and activated sludge EPS,and the effects on the structure of microbial communities are rarely reported.Therefore,the experiment used Equ Ray to design three binary mixtures of zinc ions and chlortetracycline with different concentration ratios(Ratio1,Ratio2,Ratio3),to study the effects of zinc ions,chlortetracycline and binary mixtures on the performance of biological denitrification,to analyze the changes in the characteristics of EPS in activated sludge by 3D-EEM,and to study the effects of zinc ions,chlortetracycline and binary mixtures on the structure of microbial communities by using High-throughput sequencing technology.It provides a theoretical basis for in-depth exploration of the effects of zinc ions and chlortetracycline on microorganisms in biological denitrification of livestock wastewater.The main conclusions of the study are as follows:(1)By adding zinc ion and chlortetracycline in different batches,the effects of single zinc ion and chlortetracycline on biological denitrification performance and EPS characteristics were studied.The results show that low concentration of zinc ions can improve nitrification performance and COD removal rate.High concentrations of zinc ions and chlortetracycline have a certain inhibitory effect on nitrification performance,total nitrogen and COD removal,and this inhibition effect gradually increases with the increase of zinc ions and chlortetracycline concentration and prolongation of the action time;The addition of zinc ions and chlortetracycline will show a trend of first rising and then decreasing polysaccharide and protein content,which has different effects on the composition of fluorescent substances in EPS,and chlortetracycline will also change the type of fluorescent peak.(2)The concentration ratio of three zinc ions and chlortetracycline binary mixture was designed by Equ Ray,and the effects of zinc ion and chlortetracycline binary mixture on biological denitrification performance and EPS characteristics were studied at different ratios.The results show that the effects of three binary mixtures of different concentrations on the nitrification performance of the reactor,the removal effect of total nitrogen and COD and the EPS characteristics are different,Ratio1 and Ratio2 have a certain promotion effect on nitrification performance and COD removal,Ratio3 has no effect on nitrification performance and COD removal,but the three ratios have a certain inhibitory effect on nitrification performance,total nitrogen and COD removal under the condition of high concentration of the mixture.And this inhibition gradually increases with the increase of the concentration of the mixture and the prolongation of the action time;The PS and PN content in the activated sludge EPS showed a trend of first rising and then decreasing under the action of zinc ion and chlortetracycline binary mixture.Fluorescent substances in EPS show different trends under the action of binary mixtures of zinc ions and chlortetracycline.Under Ratio1 conditions,it only affected the components of the fluorescence,and did not change the type of fluorescence peaks.Under Ratio2 and Ratio3 conditions,the type and composition of the fluorescence peaks are changed.(3)The effects of zinc ions,chlortetracycline and binary mixtures on microbial community structure were studied by High-throughput sequencing technology.The results show that under the action of zinc ions,chlortetracycline and binary mixtures,the number,microbial richness and diversity of OTU in the reactor can be increased within a certain concentration range,but with the increasing concentration of zinc ions,chlortetracycline and zinc ions and chlortetracycline binary mixtures,the number,microbial richness and diversity of OTU in the reactor will gradually decrease;Moreover,the abundance of Dechloromonas,Nitrospira and Thauera with denitrification function in the single zinc ion and chlortetracycline samples will first increase and then decrease with the increase of zinc ions and chlortetracycline concentrations.The strains with denitrification function in the binary mixture of three ratios of zinc ions and chlortetracycline showed different trends with the change of binary concentration,and the bacteria with denitrification function decreased more and more obviously with the increase of the proportion of chlortetracycline.Figure [43] Table [11] Reference [121]... |
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