Mechanism And Techniques Of Microbial Purification Of Nitrogen-Sulfonamides In Groundwater

With the rapid development of agriculture,the problem of groundwater nitrogen pollution caused by the application of chemical fertilizer in farmland is widespread.A large number of livestock manure produced by large-scale livestock breeding and antibiotic compound fertilizer are used as fertilizer in farmland.This carries antibiotics into the underground environment of the agricultural operation area,which makes the problem of nitrogen-antibiotic compound in the underground water in the agricultural operation area.In addtion,excrement from livestock,poultry and aquaculture,the discharge of wastewater from pharmaceutical and sewage plants can also cause the problem of nitrogen-antibiotic combination in groundwater.This threatens the ecological environment and human health.Tracking research trends and development trends in the field,this paper studies on mechanism and techniques of microbial purification of nitrogen-sulfonamides in groundwater,so as to provide science basis for groundwater environmental quality control and pollution remediation in national and local agricultural operation areas.The main conclusions are as follows.?1?The nitrogen degrading bacteria and sulfanilamide antibiotic bacteria were were mixed with 1:1 of the number of bacteria.The complex bacteria had good removal effect on nitrogen and sulfanilamide antibiotics.It could grow rapidly between 36h and 84h.The maximum specific growth rate was 0.18h^-1.The composition of community structure of bacteria was as follows.Pseudomonas,Serratia,Morococcus,Methylobacterium,Alistipes,Rothia,which were more than 95%,of which Pseudomonas accounted for the largest proportion of61.81%.In the removal of nitrogen and sulfonamide antibiotics,C/N could not be greater than 8.In the neutral water,the denitrification and sulfonamide antibiotics degradation of degradation bacteria are the best.The removal rate of NNH₄⁺-N increased with the increase of DO concentration.For NO₂^--N,with the increase of DO concentration,the removal rate increased,but the overall trend was not significant.For the removal of NO₃^--N,when concentration was less than 2.0 mg/L,the removal rate did not change significantly.With the increase of DO concentration,the degradation rate of sulfonamide antibiotics changed a little.The bacteria was not suitable for the environment with temperature above 30?.Low concentration of Ca²⁺,Mg²⁺,Fe²⁺,Mn²⁺could promote the degradation of nitrogen and sulfanilamide antibiotics.While high concentration of Ca²⁺,Mg²⁺,Fe²⁺,Mn²⁺could inhibit the degradation of nitrogen and sulfanilamide antibiotics.High concentration of SO₄²could inhibit the degradation of NH₄⁺-N,NO₂^--N and sulfanilamide antibiotics.?2?After adding ST,SM,SM2 and SMX,when the concentration was 0.5mg/L,the nitrogen removal by nitrogen degrading bacteria did not reduce obviously.And the order of influence was SMX>SM2>SM>ST.When NH₄⁺-N,NO₂^--N,NO₃^--N were added,the degradation effect of sulfonamides was enhanced.NH₄⁺-N had the best promotion effect,while NO₂^--N,NO₃^--N had no significant difference.For ST removal,the removal rate was positively correlated with the removal rate of NH₄⁺-N,NO₂^--N,NO₃^--N and dehydrogenase activity.For the removal of SM,SM2and SMX,the removal rate was positively correlated with the removal rate of NH₄⁺-N,the removal rate of NO₂^--N,NO₃^--N and the activity of dehydrogenase.?3?The purification of nitrogen-sulfanilamide antibiotics by complex bacteria mainly included degradation and surface adsorption.Enzyme catalysis is significant,The order of degradation rate of nitrogen and sulfonamidase was intracellular enzyme,extracellular enzyme and perimembrane enzyme.For nitrogen removal,the main enzymes are hydroxylamine oxidase,nitrite reductase,nitrate reductase,all of which are intracellular enzymes.For the degradation of sulfanilamide antibiotics,the role of intracellular enzymes is also the main.In addition,different enzymes correspond to different genes.The OTU numbers of nitrogen degrading bacteria,sulfonamides degrading bacteria and complex bacteria were 811 OTUs,1017 OTUs and 1049OTUs,respectively,while 313 OTUs were shared by the microbial communities of the three samples.The samples of complex bacteria and nitrogen degrading bacteria were the most similar,followed by the samples of complex bacteria and sulfanilamide antibiotic degrading bacteria.The distance between the samples of nitrogen degrading bacteria and sulfanilamide antibiotic degrading bacteria was far,and the similarity was the worst.?4?The sum of crushing rate and wear rate,mud content,hydrochloric acid soluble rate and water absorption rate of the carrier material scoria all conformed to the industrial standard of urban construction of the people's Republic of China?CJ/T299-2008?.The charge zero point of scoria was near pH 5.4.When the pH value of the solution was greater than 5.4,the surface of scoria had a negative charge;when the pH value of the solution was less than 5.4,the surface of scoria had a positive charge.The surface of scoria had honeycomb structure,many large and loose pores.Its chemical properties were stable,and particle size was small,with a large specific surface area.So it could be used as a carrier material to fix microorganisms.It was found that the best immobilization conditions for the removal were 3-5%inoculum,48h fixed time,100 r/min oscillating speed,and 1:15 solid-liquid ratio?g:mL?.The composite material had good removal effect on nitrogen and sulfanilamide antibiotics.?5?In the treatment effect of percolation column on composite water,the effect of nitrogen removal was NH₄⁺-N>NO₂^--N>NO₃^--N,the effect of treatment of sulfonamide antibiotics was ST>SM>SM2>SMX.In the study of simulation on removal of nitrogen-sulfanilamide antibiotics in lithologic media by microbial enhancement.It was found that with the increase of time,the concentrations of nitrogen and sulfonamides increased gradually.The first detected was NO₃^--N.After a certain period of time,the nitrogen and sulfonamides penetrated through the micro column.In the experimental range,the breakthrough time was ST>SM>SM2>SMX>NO₂^--N>NO₃^--N.The results of the removal rate corresponded to the analysis of the reakthrough time,which had a positive correlation with the removal rate.The simulation study of target removal by in situ injection of degradation bacteria was carried out.The injection of degradation bacteria had a great influence on the surrounding of injection well and the direction of groundwater flow.The results showed that most of the target substances were degraded by the injection of degradation bacteria,which had a good effect.When it is applied to other sites,the specific design can be carried out according to the actual conditions of different sites.