Study On Strengthening The Process Of A/O-DMBR For Tetracycline Wastewater Treatment With Magnetic Fly Ash

Tetracycline antibiotics,including tetracycline,chlortetracycline,and oxytetracycline,are widely used in livestock and aquaculture,but it is difficult to be completely absorbed in animals.The unabsorbed antibiotics are discharged to the external environment with animal excrement,and the tetracycline antibiotics are not easy to degrade after entering the environment.At the same time,it can also induce the production of resistant genes and have highly environmental risk.In recent years,the studing of its environmental behavior is a hotspot in the field of water treatment.In this study,the most basic tetracycline in tetracycline antibiotics is selected as the research object.The adsorption method and dynamic membrane bioreactor(A/O-DMBR)are used to treat tetracycline,in which the raw material of the adsorbent is fly ash,and the fly ash is used to prepare the magnetic fly ash adsorbent by coprecipitation approach.The adsorption characteristics of tetracycline on the magnetic fly ash are discussed.The effect of treating tetracycline and dosing magnetic fly ash on the tetracycline wastewater in A/O-DMBR were studied.One kind of highly efficient and low cost adsorbant is exploited to remove tetracycline in the environment,which could provide a laboratory basis for the engineering practice of A/O-DMBR treatment of tetracycline antibiotic wastewater.Magnetic fly ash were characterized using SEM and FTIR,and its surface structure and functional group changes were analyzed.Effects of solution p H,magnetic fly ash dosage and temperature on the adsorption of tetracycline to the magnetic fly were investigated.The adsorption isotherm model,the kinetic model and the thermal model were used to simulate the adsorption process of tetracycline.The results show that compared with fly ash,the surface of structure magnetic fly ash is more porous,and is loaded with a large number of magnetic Fe3O4.The effect of solution p H on the adsorption of tetracycline by magnetic fly ash is significant..When p H=6,the adsorption effect of tetracycline is the best,and with the increase of magnetic fly ash dosage,the removal efficiency of tetracycline increased,the adsorptive quantity of tetracycline by per unit mass o magnetic fly ash decreased.The adsorption effect is best at 35?.The adsorption process of tetracycline fitted the pseudo-second order kinetic equation.The Langmuir equation is found to fit the data better.It suggests that the tetracycline adsorption by magnetic fly ash belongs to the monolager adsorption.The thermodynamics study results suggested that the adsorption process was spontaneous and exothermic,and the adsorption system wascharacterized by entropy reduction.A/O-DMBR was used for the treatment of tetracycline wastewater.The main influencing factors and treatment efficiency of tetracycline treated by A/O-DMBR were studied.The results showed that the best technological conditions of A/O-DMBR treatment for tetracycline were: DO was 2~3 mg·L-1,HRT was 12 h,MLSS was 6~8 g·L-1.Tetracycline has a certain inhibitory effect on the removal of conventional pollutants by A/O-DMBR.Tetracycline concentration increases in 50~200 ?g·L-1,which has little effect on the removal rate of COD,and maintains a higher removal efficiency in the whole process,and its removal rate is about 90%;the concentration of tetracycline increases,the removal rate of TN has a obvious decreasing trend.When the concentration of tetracycline increases to 100 ?g·L-1,the removal rate of TN did not decrease obviously,and the stability was about 70%.The addition of tetracycline make more effect on the removal of TP,the greater the concentration of tetracycline,the lower the removal rate of TP.With the increase of tetracycline concentration,the removal rate of tetracycline in A/O-DMBR system is decreasing.Under the optimum conditions,three aspects of the effect of the magnetic fly ash on the removal of pollutants,the characteristics of the mixed liquid of the sludge and the effect of the membrane fouling on the A/O-DMBR treated tetracycline were discussed by the parallel contrast experiment.The results show that dosing magnetic fly ash can improve the water quality of A/O-DMBR treated tetracycline wastewater.The average removal rate of COD,NH3-N,TN,TP and tetracycline increased by 3.38%,7.52%,6.05%,1.95% and 6.35% respectively.Adding magnetic fly ash can slow the increase of EPS,increase the sludge particle size,reduce the viscosity of the mixture and increase the SOUR,which effectively improve the mixed liquid of sludge.Properties of magnetic fly ash can retard membrane fouling.Membrane fouling is caused by plugging and adsorption of membrane pores and formation of deposit on the surface of membrane.