Research On The Treatment Of Sulfadiazine In Wastewater

Sulfonamide antibiotics are a kind of synthetic antimicrobial agents,which have the advantages of broad antimicrobial spectrum,stable nature and simple use.They are widely used in livestock breeding and human medical treatment.In recent years,sulfonamides have been frequently detected in natural water,livestock and poultry wastewater.The pollution of sulfonamide antibiotics has widely concerned due to the potential threaten to human being and ecological environment caused by sulfonamide antibiotics.In this paper,ozone oxidation method,ultraviolet photolysis method and high efficiency degradation bacteria method were selected to treat sulfadiazine in water.The characteristics and mechanism of sulfadiazine degradation by each method were studied.In this thesis,simulated wastewater containing sulfadiazine was treated by ozonation.The effects of reaction time,pH,ozone concentration,initial concentration of sulfadiazine,reaction temperature,anion(Cl-,NO3-,SO42-)and humic acid concentration on the ozonation of sulfadiazine(SD)were studied.The results showed that the ozonation decreased the SD concentration continuously.Under the conditions of pH was 9.0,ozone gas concentration was 2.5 mg/L,ozone flow rate was 1.25 L/min,initial concentration of sulfadiazine was 10 mg/L,and reaction temperature was 10 ?,the removal efficiency of sulfadiazine was 91.7%in 5 min.The ozonation of SD can be well fitted by pseudo first order kinetic model,and the kobs was 0.49 min'1;the ozonation rate of sulfadiazine increased with the increase of pH;the higher ozone gas concentration was beneficial to the ozonation;the kobs of SD ozonation was negatively correlated with the initial concentration;and SD was negatively correlated with the initial concentration.The ozonation rate increased with the temperature when the temperature is lower than 25 ?,but the further increasing of temperature will decreased the ozonation rate.Anions could inhibit the ozonation reaction(NO3->Cl->SO42-).Humic acid could inhibit the ozonation reaction,and the higher humic acid concentration caused significant inhibition.The removal rate of SD from real wastewater by ozonation was significantly lower than that of simulated wastewater,and the removal rate of sulfadiazine reached 87.6%in 10 min.Five intermediate products of SD ozonation were detected by LC-MS/MS,and the degradation pathways SD were speculated.UV photolysis is another main way to degrade antibiotics efficiently.The effects of reaction time,pH,UV lamp power,initial concentration of SD,reaction temperature,anions(Cl-,NO3-,HCO3-,SO42-)and humic acid concentration on the UV photolysis of sulfadiazine were studied.The results showed that SD was efficiently removed under UV irradiation.Under the conditions of pH was 7.0,UV lamp power was 18 W,wavelength was 254 nm,initial concentration of sulfadiazine was 10 mg/L and reaction temperature was 30 ?,the removal efficiency of SD at 60 min was 99.4%.The UV photolysis of SD can be well fitted by pseudo first order kinetic model,and the kobs was 0.080 min-1;the reaction rate of SD firstly decreased and then increased with the increasing of pH,and the photolysis rate and reaction rate were higher under neutral and alkaline conditions;the higher UV lamp power showed better SD photolysis performance;the higher the initial concentration,the lower the kobs of SD photolysis;the higher the temperature was beneficial to the photolysis;the addition of Cl-,HCO3,SO42-inhibited the UV photolysis of SD,while NO3-would be absorb photons to produce ROS thus promote the photolysis of SD;humic acid would compete with SD for photons,thus inhibit the photolysis of SD.Three photolysis intermediates of SD were detected by using LC-MS/MS,andthe SD degradation pathways were speculated.Two SD-resistant strains(JSD1 and JSD2)were screened from domestic sludge by domestication.Through degradation experiments,the JSD2 showed good SD removal effect.The effects of JSD2 dosage,carbon source,pH and reaction temperature on the degradation of SD were studied.The results showed that increasing the dosage of JSD2 was beneficial to the degradation of sulfadiazine and shortened its growth adaptation period.Without additional carbon source,JSD2 grew slowly and the removal rate of SD was low,and the addition of carbon source was beneficial to the degradation of SD.JSD2 had better degradation effect at pH=7.0,and the lower degradation effect in weak acidity and alkalinity.The growth and activity of JSD2 would be inhibited under weak alkaline conditions.Temperature had a great influence on the degradation of SD by JSD2.High or low temperature would inhibit the degradation reaction,and the optimum temperature was 30 ?.Under the optimum conditions,SD can be completely removed after 53 h of reaction with 10%of the dosage,7.0 g/L of carbon source glucose,pH=7.0 and 30 ?.