| With the extensive use of antibiotics,its impact on the water,soil environment and human health has been attentive.Sulfa drugs are commonly used for prevention and treatment of bacterial infectious diseases in livestock,most of them was excreted in form of active compound or metabolite,and emissions in the environment without treatment always cause water and soil pollution,then through the leaching into the groundwater,resulting in groundwater pollution,under certain conditions to produce harmful microorganisms which with resistance gene,its potential harm to the environment and human health cannot be ignored.The current research on sulfa antibiotics in groundwater environment,mainly concentrated in the test method,migration and transformation,control and repair technology,repair technology usually use physical and chemical methods,in view of the sulfa antibiotics degradation bacteria research,especially combined with the study ares,the removal method which combine the sulfa antibiotics degradation bacteria with carrier material is not reported.This paper depend on National Water Project,aiming at a higher detection rate of sulfa antibiotics in the northeast of china in groundwater--sulfathiazole(ST),Sulfamethyldiazine(SM),Sulfamethazine(SM2)and Sulfamethoxazole(SMX),on the basis of comprehensive analysis of existing data and research results,collected groundwater samples to analyze the space distribution characteristics of sulfa antibiotics and bacterial community,screening of indigenous degrading bacteria for contaminated groundwater in contaminated sites,enrichment and purification,and explored its degradation effect and regularity,analyzed of influencing factors;selected a material to attached degradation bacteria,analyzed sulfa antibiotics removal efficiency and regularity of the material,and connected with the field of groundwater hydrochemistry characteristic to analyzed of the influencing factors,explored the bacteria attach effect and characteristics of the material.On this basis,carried out the sulfa antibiotics degradation bacteria application experiments,combined with the micro simulation column,removal efficiency and regularity of degradation bacteria and degradation bacteria contained material,and in purpose of providing scientific basis for the removal of sulfa antibiotics in groundwater.Conclusions are as follows:1.The spatial distribution chacracteristics of sulfa antibiotics in groundwater of the study area were dominated by point,in regional groundwater it was generally contained SM,near the second Songhua River and the south side of the site the content was higher,32.36ng/L and 85.33ng/L respectively,SM2 was detected in the west side of the field,the concentration was 133.59ng/L,and SMX was only detected in the sediments of the river,the concentration was 0.92ng/L,the GUS values of four kinds of sulfa antibiotics were greater than 2.8,with high leaching migration.2.The microbial populations in groundwater of the study area is relatively abundant,added sulfa antibiotics in the water sample to study the change of microbial populations,the results showed that DNA content increased to 12.6 ng/μL to 0.28ng/μL,the microbial structure changed obviously,the microbial population in groundwater was more than twice as high as that of the high concentration of sulfa antibiotics,the most abundant bacteria in groundwater with high concentration of sulfa antibiotics belongs to Acinetobacter,and the ratio was 99.7%,while it was about 18.9% in the original groundwater sample,the microbial population structure tends to be single.3.Directional domesticated bred and selected the sulfa degradation bacterium,acquired degradation bacteria Acinetobacter,colony morphology for: round,yellow,smooth edge,diameter 0.1cm.It is gram-negative bacteria,the microscopic observation strains was short rod,with a single length of about 120 nm.The results showed that the bacteria did not produce catalase and nitrous acid,free from pyruvate decarboxylase,can produce urease and hydrogen sulfide,and can ferment glucose and hydrolyze starch.When the concentration of four kinds of sulfa antibiotics was 1.0g/L and as the only carbon source,can completely inhibit the growth of the bacteria4.Under the condition of simulating groundwater low temperature and microenvironment,the degradation experiment of four kinds of sulfonamides as the sole carbon source was carried out,the degrading bacteria Acinetobacer in the first two days was the adaptive phase,on the third day,the growth of the bacteria began to show clear trend and reached the peak on the fifth day,that was logarithmic growth phase,then has a slight decline and into stationary phase.The bacteria can degraded the four kinds of sulfa antibiotics effectively,achieved the balance of degradation on the fourth day,the degradation rate of ST,SM,SM2,SMX was 99.85%,50.14%,42.00%,35.42%,respectively;added glucose and yeast extract as supplementrary carbon and nitrogen source,appropriate amount of Fe3+ can shorten the degradation bacteria cultivation cycle and has a promoting effect on degradation.The results showed that there were some differences in the kinetics of degradation of four sulfa antibiotics by Acinetobacer,and the degradation process was more consistent with the first order of ST,the other three were more consistent with the zero-order kinetics equation.5.From the perspective of natural mineral,resource conversion and synthesis,the volcanic slag,peanut shell and synthetic material were used as the attached material of Acinetobacer,and the adsorption experiment was carried out.Adsorption effect Peanut shell> Synthetic material> Volcanic slag,considering the use of resource conversion and reuse of peanut shells as the degrading bacteria Acinetobacer attached material.Volcanic residue,peanut shell,synthetic materials adsorbed four sulfonamides antibiotic effect,the results showed that: To volcanic slag the adsorption rate of four sulfa antibiotics was 28.36%(ST),27.24%(SM),29.32%(SM2),31.14%(SMX),adsorption equilibrium can be achieved in about 2h;To synthetic material,the adsorption rate was 78.31%(ST),12.77%(SM),31.60%(SM2),21.38%(SMX),adsorption rate reached the maximum within 5min,but it had a problem about desorption;To peanut shell,the adsorption rate of four sulfa antibiotics was 72.81%(ST),46.98%(SM),45.08%(SM2),32.84%(SMX),adsorption equilibrium can be achieved in about 12 h,the effect was superior to the above materials,and the adsorption performance was stable,and the adsorption was more accord with pseudo-second-order equation and Henry linear adsorption model,the effect of iron ion and manganese ion on adsorption was improved and the effect was obvious,therefore,in the remediation of contaminated groundwater,remove sulfa antibiotics before remove iron and manganese ions may achieve better results,in addition,the removal efficiency of iron and manganese ion may be improved as same time as in the removal of sulfa antibiotics;Nitrogen and sulfate salt has obvious inhibitory effect on adsorption;Hardness played a promote role to adsorption.6.Preparated the composite materials of adsorption-degradation,carried the dynamic effects experiments.Though the experiment of immobilization of the bacteria,choose peanut shells as suitable material,when the condition of immobilized bacteria elected: peanut shells 1.5g,inoculum amount of 1.5%,immobilization time was 36 h,the comprehensive removal effect of four sulfa antibiotics was better,the removal rate was 89.69%(ST),78.39%(SM),71.38%(SM2),88.55%(SMX);The removal efficiency of sulfonamides is better than that of single adsorbent when the influent flow rate is 1m L/min.Simulation column has the highest removal rate to ST,for more than 90.00%,and over 80.00% of SM,for SM2 and SMX,removal rate was higher when concentration of antibiotics lower,and when it was 0.05mg/L,the removal rate were 64.25% and 75.03% respectively,and when the concentration was 5mg/L,the removal rate were 31.75% and 39.75%.7.By scanning electron microscope(SEM)and infrared spectrometer(IR)analyzed of action mechanism from the microscopic view,compared the medium adsorb sulfa antibiotics before and after,the pore of medium surface was filled in;In process of peanut shell adsorbed sulfa antibiotics,there may be N-H、-CH3、-CH2-、C=O、C-H and other chemical bonds involved;In process of synthetic materials adsorbed sulfa antibiotics,chemical bonds C=CH2、C-H have changed,but has small changes,it can be seen that the adsorption process of synthetic materials was mainly physical adsorption. |
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