Effect Of Tetracycline On The Formation Process Of Aerobic Granular Sludge

In recent years,with the extensive and uncontrolled use of antibiotics,a large number of antibiotics have been detected in various sewages,especially in livestock and poultry aquaculture wastewater and antibiotic production wastewater.The release of unmetabolized antibiotics into the environment will seriously pollute the environment and affect the stability of the ecosystem.Aerobic granular sludge(AGS)has the advantages of excellent sedimentation performance,high biomass retention and strong treating capacity,and is considered to be one of the most promising biological wastewater treatment technologies.Studying the effects of antibiotics on the formation of granular sludge will help promote the application of AGS technology in the field of antibiotic wastewater treatment and further understand the formation mechanism of AGS.In this experiment,SBR was used to treat high concentration ammonia nitrogen wastewater.The addition of tetracycline(TC)to R2 influent water was used to analyze the influence of TC on the sludge characteristics,pollutant removal effect and extracellular polymerization(EPS)characteristics,and the influence of TC on the dynamic changes of microbial community structure and the metabolic function of microbial populations during the granulation process of floc sludge was also analyzed.The addition of TC to the influent accelerated the formation of granular sludge and slightly improved the relative hydrophobicity(RH)and flocculation(FA)of the sludge.Compared with the control group R1,R2 containing 2 mg/L TC in the influent formed granular sludge nearly 10 days earlier than R1.At the maturity of AGS,the average sludge size and sludge volume index(SVI)of R1 and R2 were 419.48,500.57 ?m and 82.69,61.50 m L/g,respectively,and RH and FA were 92.26%,95.32% and 44.68%,48.24%,respectively.The decontamination performance of AGS culture process is better.The addition of TC has little effect on the removal of chemical oxygen demand(COD),ammonia nitrogen(NH4+-N)and phosphate(PO43--P).The average removal rates of COD and NH4+-N by R1 and R2 were 90.14%,92.54% and 96.18%,93.20%,respectively;the concentration of nitrite nitrogen increased gradually,and the phenomenon of nitrite accumulation appeared;the average removal amount of PO43--P in R1 and R2 was 4.22 mg/L and 4.32 mg/L.The removal of TC by R2 is mainly completed by the adsorption process.With the extension of running time,the TC content in EPS increases gradually.The TC content in the tight layer(TB-EPS)is slightly higher than that in the loose layer(LB-EPS).On the 80 th day,the TC contents in T-EPS,TB-EPS and LB-EPS were 0.54 mg/g,0.30 mg/g and 0.24 mg/g.The TC in the influent affects the content and composition of EPS.Compared with the control group,the addition of TC increased the PN content of T-EPS,TB-EPS and LB-EPS,and decreased the PS content of T-EPS,TB-EPS and LB-EPS,but for PO43--P content in T-EPS has little effect.TC affects microbial diversity,microbial population structure and potential metabolic functions during the granulation process of floc sludge.The AGS microbial community cultured by adding TC has higher abundance and diversity;the addition of TC causes the relative abundance of some microorganisms to decrease or even disappear,but new resistant genus will emerge.The addition of TC makes the microbial dominant genus change from Paracoccus,Lactococcus,Thauera and Rhodobacteraceae into Thauera,Anaerolineaceae,Lactococcus,Rhodobacteraceae and Paracoccus;at the same time,the relative abundance of Amino Acid Metabolism and Energy Metabolism of the sludge system is reduced,but the relative abundance of Carbohydrate Metabolism is improved.With the gradual maturity of granular sludge,the relative abundance of nitrifying enzymes showed a downward trend,while the relative abundance of nitrate reductase(NAP)and nitrite reductase(NIR)increased significantly.In comparison,the relative abundance of enzymes associated with nitrification and nitrite reductase(NO-forming),nitrous oxide reductase(N2OR)and nitric oxide reductase(NOR)of R2 is lower than R1.