Study On Coupling Effect Of Pore Water Velocity And Ironic Strength On The Transport Of Pathogen In Different Media

In recent years,the contamination of farmland soil and water by pathogens frequently broke out,seriously threatening the safety of agricultural and livestock products and drinking water,and hindering the agricultural recycling of organic waste manure from aquaculture industry.To explore the transport and distribution of pathogens in different media can provide theoretical guidance for preventing and controlling the contamination of groundwater by pathogens,and improve the level of safe utilization of organic manure,and also promote the remediation of microbial soil pollution.In this study,the bioluminescent Escherichia coli strain 652T7 was selected as the model pathogen.Quartz sand and modified quartz sand by surface chemical properties were used as porous medium.The advanced IVIS Spectrum imaging system was used to observe the transport behavior and distribution of E.coli in different media in real time under different pore water velocities(3.55 cm/h,10.56 cm/h,and 21.3 cm/h)and ionic strength(2 m M,20 m M,and 100 m M).The transport behavior and distribution of E.coli under different hydraulic condition and electrostatic force indicated the coupling effect and internal mechanism of hydrodynamic force and solid-liquid interface on the transport of microorganisms.The mechanism can explain the transport of E.coli in different porous media,and provide a theoretical basis for the assessment and forecast of pathogen migration.Results were shown as follows.(1)The increase of pore water velocity could promote the transport of E.coli in quartz sand,humic acid coated quartz sand,and iron oxide coated quartz sand.The enhanced effect of the increasing ionic strength on the transport of E.coli was facilitated in quartz sand and humic acid coated quartz sand,but hindered in iron oxide coated quartz sand.The increase of pore velocity could reduce the total amount of E.coli retained in different media,but increase their uniform distribution in the columns.(2)The increase of ionic strength was unfavorable for the transport of E.coli in quartz sand and humic acid coated quartz sand,but was beneficial to the transport of E.coli in iron oxide coated quartz sand.The effect of ionic strength on the transport of E.coli in quartz sand,humic acid coated quartz sand,and iron oxide coated quartz sand were promoted by the decreasing pore flow velocity.(3)The increase of ionic strength could weaken the dominant electrostatic force between the E.coli and medium,and the dominant electrostatic force was depended on the surface electrical properties of the medium.When the media and E.coli contain the same electrical property,the increase of ionic strength would hinder the transport of E.coli.Otherwise,the increase of ionic strength would promote the transport of the E.coli,when the media and E.coli contain the opposite electrical property.(4)The modification of quartz sand could significantly affect the transport of E.coli in the porous media.The transport of E.coli was significantly promoted in humic acid coated quartz sand and significantly hindered in iron oxide coated quartz sand.And the effect was obvious under low ionic strength and low pore velocity.(5)The change of DLVO attractive force at solid-liquid interface was the internal mechanism which dominated the coupling effect of pore velocity and ionic strength on the transport of E.coli in different media.The promotion of increased pore velocity to the transport of E.coli was enhanced,when the DLVO attractive force increased.