Study On Membrane Pollution Control Mechanism Of Anaerobic Conductive Ceramic Membrane Bioreactor

Recently,Anaerobic Membrane Bioreactor(An MBR)is drawing much attention for its potential to treat wastewater due to its low energy consumption,excellent effluent quality and high resource recovery rate.However,the major problem of An MBR is the rapid decline of the permeate flux over operation time,which restricts its large-scale popularization and application.Applied voltage as a novel method of membrane pollution control is now used in An MBR,but the research on membrane pollution behavior and control mechanism in this system is not clear.Therefore,in this study,the carbon-based conductive ceramic membrane was made and the Anaerobic Electric-Membrane Bioreactor(An EMBR)was built.And then we evaluated the effect of different electric field strength on the performance of An EMBR,in the aspect of membrane pollution control.Lastly,the uncovered thermodynamic mechanism of the conductive membrane and pollutant interface was analyzed by the extended derjaguin-laudau-verwey-overbeek(x DLVO)theoretical model.(1)Carbon-based conductive ceramic membrane preparation and performance analysis.Carbon-based chemicals were introduced to the silicon carbide ceramic membrane surface by means of impregnation carbonization method,and investigating the effect of temperature on the conductive properties of the membrane.Experimental results suggested that the membrane had the excellent electric conductivity at 800?,with the value of 4.0 S cm-1.Compared to the control reactor,there was no significant difference in the filtration performance of the conductive membrane.Further studies have found that the anti-abrasionstrength of the conductive membrane is as high as 793 n N.(2)Anaerobic conductive ceramic membrane bioreactor construction and operation performance analysis with applied voltage.An EMBR had a lower fouling rate and better effluent quality with the cathode potential of-2.0 V.The sludge mixture composition analysis showed that the particle size of the mixture increased by adding the electric field,thereby reducing the risk of membrane clogging.In addition,compared to An MBR,the Extracellular Polymer Substances(EPS)reduced and was modified in a certain degree in An EMBR.The external electric field can effectively cut down the protein and polysaccharide concentrations in EPS,which would promote EPS huminification and increases polarity,and thus slow down membrane contamination.(3)Membrane contamination of EPS(Bovine Serum Albumin(BSA),Sodium Sehyanate(SA)and Humoure acid(HA))under the electric field.The electric field application can effectively extend the membrane blockage cycle of BSA,SA and HA.The fouling behavior of BSA was highly fitting with the filter mass-intermediate model with the cathode potential of-2.0 V.The particle size of BSA increased with the growth of cathode potential,which made a slacker filter cake layer on the membrane surface formed and therefore reducing membrane filtration resistance.With the cathode potential of-1.0 V,the polysaccharide on the contaminated membrane was limited and its fouling behavior coincided with the intermediate-standard pore clogging model,which indicated that membrane contamination mechanism of SA mainly stemmed from the pore blockage.Compared to BSA and SA,the anti-fouling characteristics of HA was more significant.When the cathode potential was-1.0 V,with the increase of absolute value of Zeta potential,the repulsion force between the conductive membrane and HA was added.Besides,the pre-filtration was accord with the intermediate-standard pore clogging model,but the late was mainly manifested as the filter cake-middle pore clogging model.Above it,the electric field can reduce the membrane internal pore clogging to extend its operating cycle.(4)The thermodynamic mechanism of the membrane interface for membrane pollutionunder the electric field.In near-field conditions,the electrostatic action energy base position and height would be altered by adding the external voltage,and thus preventing the contaminants from attaching to the surface.With the cathode potential of-2.0 V,the BSA had a higher energy base height and the maximum energy base distance,but at-1.0 V,the SA was the maximum.In addition,the electric field effectively increased the molecular polarity of BSA,SA and HA,so that the polar rejection force boosted between conductive membrane and pollutant interface.Further research showed that the polarity effect can change suddenly in a short separation distance to alter the interface total action energy,which was consistent with the trend of polarity energy curve.With the cathode potential of-1.0 V,the total interaction force between HA and SA was higher than zero.And when the cathode potential was-2.0 V,the total effect of BSA was above zero.In addition,when the particles are smaller than 100 nm,in the far-field region,the contaminated particles are mainly restricted by Brownian force(FB),and in the near-field region,the pollutants are mainly restricted by electrostatic force(FEL);when the particle size is 100 nm-1000 nm,the membrane contamination in the near-field region depends on the van der Waals force,the polar force,and the electric field repulsion force.When the separation distance is less than 5nm,the electric field force effect is negligible.When the particle size is larger than 1000 nm,the pollutants are mainly affected by the shear force(FL)in the far-field region.The electric field mainly improves the repulsive force of the pollutants by changing the particle size of the pollutants,thereby alleviating membrane pollution.In summary,the electric field can affect the membrane-contaminant interface force by changing the particle size of the pollutants,thereby achieving the purpose of alleviating membrane pollution.