Analysis Of The Law And Mechanism Of The Integrated MIEX-UF Process For Controlling Biological Fouling Of Ultrafiltration Membranes

In recent years,ultrafiltration?UF?has played a vital role in purifying water quality systems.However,in the actual use of UF,the formation of membrane fouling has always been the main reason limiting its development.Since its visualization,TEP?Transparent Exopolymer Particles?has been found to be widely present in natural water bodies,and is difficult to remove by conventional pretreatment processes.At present,more and more attention has been paid to the impact of TEP on membrane fouling,but the effects of TEP on the formation and development of membrane biofouling and the effective control of membrane biofouling by TEP have not been systematically studied.In this project,Pseudomonas aeruginosa was used as a simulated strain.First,the effect of TEP on the formation and development of membrane biofouling was studied.Microscopic interface force measurements show that TEP has a stronger affinity for PVDF membranes and is easier to adhere to than typical irreversible organic pollutants such as sodium alginate?SA?,humic acid?HA?,and bovine serum protein?BSA?On the membrane surface,it has a higher irreversible membrane pollution potential.In addition,the adhesion of TEP to bacteria is only slightly lower than SA,but significantly higher than HA and BSA,which means that when TEP is accumulated on the surface of the ultrafiltration membrane,it will accelerate the irreversible adhesion of bacteria on the membrane surface.The irreversible attachment of bacteria to the membrane is the key to the formation and development of biofouling.Filtration experiments on bacteria,TEP and TEP precursors,three typical biofilm components,further proved that,compared with the other two biofilm components,TEP is more prone to irreversible accumulation on the membrane,and the irreversible pollution resistance generated by TEP accounts for 67%of the total pollution resistance.Fluorescence microscopy also showed that both the preaccumulation of TEP on the membrane and the coexistence of bacteria and TEP in water resulted in the irreversible adhesion of bacteria on the membrane far greater than that without TEP.On the other hand,when exploring the feasibility of TEP growth and utilization by bacteria,it was found that TEP could hardly be utilized by bacteria as a nutrient source to promote its proliferation,and even the presence of a large amount of TEP would inhibit the normal utilization of other carbon sources by bacteria in water.In addition,the presence of Ca²⁺and HA in water,the increase of water temperature,and the enhancement of light will promote the transformation of TEP precursors to TEP in water,leading to the increase of TEP concentration,thus increasing the biological pollution potential of water.On this basis,the feasibility of the integrated MIEX-UF process to control the biological contamination caused by TEP was further studied.The results showed that Magnetic ion exchange?MIEX?could not only effectively remove TEP and TEP precursors,inhibit the transformation of TEP precursors to TEP,but also inhibit the proliferation of bacteria and the production of TEP.Micro interface reaction test results show that MIEX between TEP/bacteria significantly greater than the power of the PVDF membrane with TEP/bacteria,the force between the,this means that when resin TEP and bacteria are deposition to form a filter cake layer on the membrane surface,due to the resin and stronger affinity between TEP/bacteria causing filter cake layer between the membrane surface and the binding force is abate,bacteria and TEP when backwashing more easily with the resin particles from the membrane surface,thus to effectively control the TEP and bacteria in irreversible accumulation and membrane surface adhesion,slows down the biofilm formation and development on the membrane surface at the local level.