Study On Antibiotic And Its Resistance Genes Abatement Influencing Factors During Sludge Aerobic Composting

Antibiotics have been widely used in the treatment and prevention of human and livestock diseases since the era of inquiry,making a huge contribution to the treatment of bacterial diseases.But due to the indiscriminate and unregulated use of antibiotics,pathogenic bacteria have developed antibiotic resistance genes(ARGs)through adaptive variation through self evolutionary mechanisms.Antibiotic resistant bacteria(ARBs)harboring ARGs pose a great threat to human and animal health.Municipal sludge is rich in nutrients required by plants such as N,P and K,and moving the sludge into land use so that it can re participate in the ecosystem’s material cycle can reduce sludge disposal costs and effectively use useful nutrients from the sludge in line with the sustainable development strategy.But municipal sludge is also a typical ARGs holding bank.However,sludge contains components such as pathogenic bacteria,heavy metals,antibiotics and ARGs,which,if not handled properly,can easily cause secondary pollution to soil,groundwater and crops during land use,have potential ecological risks,and may undergo food chain enrichment and transmission to cause harm to human health.Therefore,it is critical to study the law of abatement of antibiotics and ARG during sludge composting.Numerous studies have shown that process control of composting has important effects on antibiotic concentrations and the abundance of ARGs.Composting experiments were conducted in a wastewater treatment plant in Nanjing,and the effects of process control on the physicochemical properties,antibiotic concentrations,microbial community structure,args were investigated by temperature gradient(59℃,63℃,67℃)and waste Biological Activated Carbon(BAC)concentration gradient(2% DW /DW,4% DW / DW)set by different kinds of fungicides.The microbial community structure and args were quantified by 16 S RNA gene amplicon high-throughput sequencing followed by high-throughput real-time PCR(HT q PCR),and the differences in microbial community structure were investigated by unconstrained analysis(PCo A,NMDS),while the effects of different factors on antibiotics and args were investigated by constrained ranking analysis.The following conclusions were obtained:(1)The temperature gradients of 4 ℃ were formed among the HT2(high temperature fungicide obtained by screening in a certain college),HT1(common high temperature fungicide),and Control(blank control)groups in the composting experiment with the addition of high temperature fungicide.HT2 ramp period 2 days and HT1 and control ramp periods 3days.Organic matter degradation rate at the end of composting: HT2 > HT1 > Control,nitrogen loss rate: HT2 > HT1 > control,the GI value reached more than 80% in the HT2 group and only about 70% in the HT1 and control groups.The addition of high temperature fungicide increases the maximum temperature of composting and increases the organic matter degradation rate,while also causing the loss of nitrogen,and the effect HT2 is better than HT1.HT2 also reduces the composting cycle and increases the degree of putrefaction of the composted product.(2)The BAC2% and BAC4% warming periods were only 2 days in the add-on discarded BAC compost experiment compared with 3 days in the Control group.The highest temperatures of all three groups were in the range of 62.5-63.5 ℃,but the number of days above 60 ℃: BAC4% > BAC2% > Control.Nitrogen loss: Control > BAC2% > BAC4%.All BAC groups could enter the ripening phase within 20 days and composting cycles: BAC2% >BAC4%.Adding waste BAC cannot improve the maximum temperature of the pile,but it can prolong the duration of the high-temperature period,shorten the composting cycle,and improve the degree of ripening of compost products,which can inhibit the loss of nitrogen.The higher the BAC dosing in a certain range,the higher the TN content and the shorter the composting cycle.(3)By PCo A and NMDS analysis,significant differences(stress < 0.05,P = 0.001)in the levels of OTUs between HT1 and HT2,Control and BAC2% groups were found.Common compost,high-temperature fungicide compost,waste BAC compost were similar in microbial community structure at the phylum level and varied considerably at the genus level.Early during composting,Firmicutes and Actinobacteria predominate.At the end of composting,the common compost was dominated by Firmicutes and Actinobacteria,while Firmicutes,Actinobacteria,Proteobacteria were the dominant phyla in the compost of the BAC group and the high-temperature compost group.At the genus level,the abundances of Geobacillus,,Caldibacillus,Thermobacillus,Tuberibacillus,Chelativorans were significantly(P < 0.001)higher in the HT2 group than in the Control group,and the abundances of Thermobacillus,Paenibacillus,Uncultured Bacillaceae and Pseudoxanthomonas were significantly higher in the BAC2% group than in the Control group.(4)Aerobic compost has good removal effect on ETM(Erythromycin),CFX(Ciprofloxacin),TC(Tetracycline)and cannot remove SDZ(Sulfadiazine)effectively.Administration of hyperthermic fungicides and waste BAC can improve the removal of the above three antibiotics(ETM,CFX,TC)in aerobic composting.And the rule of antibiotic removal in experiments at the pilot level did not follow the first-order kinetic equation.According to RDA analysis,temperature had less effect on the removal of antibiotics,and microbial community structure differences dominated the effect on the removal of antibiotics.The Ornithinococcus,Georgenia,Thermobifida,Thermocrispum and Caldibacillus were strongly negatively correlated with CFX concentration.The Ornithococcus,Thermocrispum,and Thermobifida showed strong negative correlations with TC concentrations.The Geobacillus,Ornithococcus,Thermobifida,Unclassified Micrococcales,Mycobacterium and Thermopolyspora showed strong negative correlations with ETM concentrations.Among them,Thermobifida,Thermococcus,Ornithinococcus.(5)Aerobic composting had better abatement of multiple ARGs.The ARGs contained in municipal sludge ranged from 1.13 × 10 ～3.33 × Between 10 copies / g.The removal rates of Aminoglycoside,Phenol resistance genes,MDR,MGE,and MRG could be improved by HT2,and the removal rates of ARGs in the above-mentioned categories were more than90%.The addition of waste BAC can improve the removal rate of Fluorophenicol and Chloramphenicol,Quinolones,Sulfonamides,Paclitaxel resistance genes and MDR,MGE,Insertion Sequences,and the degradation rate of ARGs in the above-mentioned categories is more than 85%.The microorganism played a major role in the abatement of args at 60 ～70 ℃.The effect of microbial community on ARGs was found to be more significant through RDA analysis than temperature.Georgenia,Thermopolyspora with most ARGs(except taxolβ-lactamase ARGs)of lactamase resistance genes were strongly negatively correlated.Thermocrispum,Thermobifida,Thermobacillus showed strong negative correlations were observed with Paclitaxel,β-lactamase resistance genes.The above results provide a certain theoretical basis for industrial level composting to improve the hypertrophic effects and promote the depletion of antibiotics and args,and provide a theoretical basis for the construction and screening of high-temperature fungicides for composting,and provide a new idea for the resourcealization of waste BACs.