The Role Of Intermediates In The Sulfadiazinee Biodegradation

Antibiotics are the world's largest and most widely used drugs,the annual use of antibiotics in Europe up to more than 1400 tons,most of which for animals;the United States each year the amount of antibiotics is about 17,800 tons,about 70% for animal husbandry Aquaculture;global antibiotics with an average annual use of about 100,000 tons to 200,000 tons.In recent years,C hina every year there are thousands of tons of antibiotics are used in livestock and poultry industry and human health,China's drug prescription antibiotics up to 70%,compared with Western countries,China's serious abuse of antibiotics.Sulfadiazine(SD),which is an important antibiotic,is a commonly used antimicrobial agent in clinical treatment,animal husbandry and aquaculture.It is composed of pyrimidine ring and benzene ring.Is a nitrogen,sulfur heterocyclic compounds,is the representative of sulfa drugs,are more difficult biodegradable compounds.It is not biodegradable due to the induction of drug-resistant strains after entering the environment.However,in recent years,a large number of sulfadiazine into the environment every year,may be long-term retention,drug residues on the ecosystem and human health are harmful,the degradation of sulfonates wastewater research increasingly important.At present,most of the urban sewage treatment plants are dominated by activated sludge.Currently,most activated sludge systems for treatment of municipal wastewater are mainly designed for conventional nutrients removals,such as BOD,COD,nitrogen,and phosphorus etc.,but they are ineffective for pharmaceuticals removal.Therefore,the conventional activated sludge systems would be easily broken,once pharmaceuticals,like antibiotic drugs,enter into the systems by the way of municipal wastewater.It is significant to use some effective methods for alleviating the inhibition of antibiotic drugs to microorganism,and accelerating their removal rate.The current study found that wastewater containing sulfonamides can be treated by chemical oxidation process effectively,but can not be degraded completely,which may also generate intermediate products that have adverse impact to the environment.Biodegradation process solely has low efficiency,and more often,lead to low bioactivity.However,use UV photolysis or bio logical photocatalytic method as a pretreatment method can significantly improve the biodegradability of sulfonamides,and accelerate the rate of biodegradation.In this experiment,the degradation of SD was carried out by ultraviolet photolysis.The mixed solution of SD and glucose was used as the C and N sources for microbial growth.It was found that the ability of mitigating SD to inhibit the microbicidal ability was obtained.At the same time,in the process of accelerating the degradation of sulfadiazine by UV method,the generation of intermediates under ultraviolet light irradiation was analyzed.While exploring the photolysis of SD,especially in the process of biodegradation,the intermediate product was used as internal aid electron The degradation experiments and the degree of mineralization were studied by using different photodegradation and photodegradation and photodegradation and simultaneous biodegradation.And found that the two main intermediates on the biodegradation of SD has a certain degree of inhibition or promote the role.The results showed that:(1)With an initial concentration of 20 mg/L by UV light(light intensity set to 0.9 mW/cm2).At the same time as SD itself degrades,there are two important intermediate products,each of which is p-aminobenzene Acid(4-ABS)and diaminopyrimidine(2-AP),and the whole biodegradation process can be found,the trend of the formation of p-aminobenzenesulfonic acid was fluctuating,that is,in the initial trend of growth,late decline The Diaminopyrimidine showed a slow rise in low concentration.In the sulfadiazine(SD)degradation at the same time,its own carrying two kinds of ions N ions and S ions will be separated from.As with the results presumed before the experiment,the N ions are re moved in the form of an ammonium root,and at the same time the S ions are removed in the form of sulfate.(2)After the UV photodegradation of sulfadiazine,the resulting intermediates in the next biodegradation process of sulfadiazine biodegradation played a role in promoting degradation.Through the dialectical analysis experiment,the two intermediates were mixed with the sulfadiazine solution after biodegradation,from the results can be proved before the speculation that one of the main intermediate d iaminopyrimidine in sulfadiazine biodegradation produced inhibition On the other hand,another major intermediate,p-aminobenzenesulfonic acid,has a significant effect in the biodegradation of sulfadiazine.It was also proved that the objective of the UV light product p-aminobenzenesulfonic acid was the main reason for the significant increasein the degradation rate of sulfadiazine in the experiment of biological reaction after ultraviolet light.(3)The biodegradation rate of sulfadiazine can be greatly increased by increasing the number of electrons.The degradation rate of the corresponding sulfadiazine is also the same when the electron equivalent is provided at the same time.Through the measurement and analysis of the ion change during the reaction,it can be seen that the S-ion is not released during the biodegradation of p-aminobenzenesulfonic acid,but it promotes the sulfonamide in the process of biodegradation of sulfadiazine after UV photolysis Pyrimidine desulfurization rate,so that sulfadiazine earlier release of S ions.And the two main intermediates produced by UV irradiation in the biodegradation process played a role in promoting and inhibiting,respectively.There is also a certain electronic competition between the two intermediates.The experimental results also show that the effective electrons play a role in the biodegradation of sulfadiazine,but not with the type of active electrons.In summary,in the biodegradation of sulfadiazine after UV irradiation,the resulting intermediate,diaminopyrimidine,also undergoes biodegradation at the same time,resulting in an electronic competition relationship with sulfadiazine during the process,using the other intermediate Product of p-aminobenzenesulfonic acid provided by the electronic preemptive degradation,which also confirmed the diaminopyrimidine inhibition of sulfadiazine degradation of the reasons.