Study On The Control Effect Of Porous Media On Pathogenic Microorganisms

With the development of social economy and the improvement of people’s living standards,the demand for livestock and poultry products has also increased rapidly.However,the waste water produced in the process of livestock and poultry breeding contains a large number of pathogenic microorganisms.If it is not treated and discharged directly,it will cause serious pollution to soil and water,and also pose a direct or indirect threat to human health.Although the traditional treatment method is effective,it also has the problems of high cost and slow effect.In this study,four kinds of economically available porous media(iron filings,calcined magnesite,limestone,straw biochar)were selected,and Escherichia coli T7 and phage MS2 were selected as the research objects.The inhibition and control ability and removal efficiency of different porous media on microorganisms were compared,and the possible inhibition and control mechanism of porous media on two kinds of microorganisms was analyzed.The main results are as follows(1)The results of adsorption kinetics showed that iron filings,calcined magnesite,limestone and straw biochar could effectively remove Escherichia coli T7 and phage MS2 within 12 h.The adsorption capacity of E.coli T7 was 9.60×10~6 cfu/g for iron filings,9.58×10~6 cfu/g for calcined magnesite,7.60×10~6 cfu/g for straw biochar,6.60×10~6 cfu/g for limestone.The adsorption capacity of phage MS-2 was 1.00×10~7 cfu/g for iron filings,9.10×10~6 cfu/g for calcined magnesite,7.40×10~6cfu/g for straw biochar,7.12×10~6 cfu/g for limestone.The experimental results of adsorption thermodynamics show that the adsorption capacity of porous media increases with the increase of bacterial concentration,but the adsorption capacity of porous media decreases with the increase of bacterial concentration.Through the numerical simulation of porous media adsorption of Escherichia coli T7 and phage MS2,it is found that L-type thermoadsorption model have ideal correlation,which can well describe the adsorption process of porous media on microorganisms.(2)The results of dynamic migration experiment showed that iron filings,calcined magnesite,limestone and straw biochar showed different degrees of resistance and control ability to a single microorganism.The removal rate of Escherichia coli T7 was iron filings>calcined magnesite>limestone>straw biochar,and the removal rate of phage MS2 was iron filings>calcined magnesite>straw biochar>limestone.Iron filings and calcined magnesite have strong resistance and control ability to Escherichia coli T7 and bacteriophage MS2.Further study on the resistance and control ability of iron filings and calcined magnesite to the two kinds of microorganisms showed that there was a competitive relationship between Escherichia coli T7 and bacteriophage MS2.In the process of migration,they also occupied the adsorption sites on the medium surface,The inhibition and control effects of iron filings on the two kinds of microorganisms are obviously weakened;The inhibition and control effect of calcined magnesite on Escherichia coli T7 became weaker,and the inhibition and control effect of calcined magnesite on phage MS2 became stronger.(3)Scanning electron microscope and X-ray diffraction were used to characterize the surface morphology and phase composition of porous media before and after the reaction.The results show that the change of iron filings before and after the reaction is significant,and the resistance control mechanism is mainly electrostatic adsorption and oxidation.The surface morphology of calcined magnesite changed significantly before and after the reaction,and the mechanism of resistance and control included electrostatic adsorption,cell infiltration and oxidation.The surface morphology and phase composition of limestone and biochar had no obvious change before and after the experiment,and the main resistance control mechanism was interception and filtration.This paper has 25 pictures,22 tables and 84 references.