Study On Magnetic Effect Synergies With Rhamnolipid To Mitigate MBR Membrane Fouling

Membrane bioreactor（MBR）is a sewage treatment process that combines the traditional activated sludge method with membrane separation technology.It is one of the widely used sewage treatment technologies at present.Membrane fouling is the most important obstacle in the application process of MBR.Biosurfactant rhamnolipids（RLs）have good emulsifying,solubilizing,wetting,dispersing and decontamination capabilities,and have the characteristics of high stability,low toxicity,and easy degradation that chemical surfactants do not have.Membrane fouling mitigation has great potential;the magnetic effect produced by magnetic powder（Fe₃O₄）can improve microbial activity,which has been used in membrane fouling mitigation technology.However,there are few studies on reducing membrane fouling through the combination of RLs and magnetic powders.This experiment explored the changes of RLs and magnetic powders to the characteristics of the sludge mixture through the beaker test,determined the optimal concentration and dosage,and carried out MBR.Continuous process,to explore the effect of RLs and magnetic powder on MBR membrane fouling mitigation effect and sewage treatment efficiency.The main research contents and results of this paper are as follows:（1）Add different concentrations of RLs and magnetic powder to the sludge mixture to conduct a beaker test to study its effect on the sludge mixture SV₃₀,sludge mixture viscosity,sludge specific resistance,dehydrogenase activity and supernatant COD Impact.The experimental results show that RLs and magnetic powder can improve the sedimentation performance and filtration performance of the sludge mixture,reduce the viscosity of the sludge mixture,and at the same time increase the dehydrogenase activity of microorganisms and enhance the degradation efficiency of COD.When the dosing condition was 0.3 g/L RLs（8%）+120 mg/L Fe₃O₄,the various characteristic indexes of the sludge mixture reached the best.（2）The experimental devices of M-MBR（adding RLs and magnetic powder）and C-MBR（without adding chemicals）were built,and the optimal feeding conditions of RLs and magnetic powder were brought into the continuous process experiment.During the operation of the reactor,the effects of RLs and magnetic particles on the physicochemical properties of sludge,membrane fouling rate and MBR performance were investigated.The main inspection indicators include transmembrane pressure difference（TMP）,Solublemicrobialproducts（SMP）,Extracellular Polymeric Substances（EPS）,sludge particle size,Zeta potential and effluent COD.The results showed that under the optimal dosage condition of 0.3 g/L RLs（8%）+120 mg/L Fe₃O₄,the longest running time of MBR reached 17 days,an increase of 70%compared with the blank group,indicating that RLs and magnetic powder can Significantly improve membrane fouling and reduce membrane fouling rate.RLs and magnetic powder can play the role of solubilization and adsorption,reduce the concentration of SMP and LB-EPS in the sludge mixture,and achieve the purpose of alleviating membrane fouling;in addition,RLs can increase the concentration of TB-EPS and strengthen the separation between sludge and flocs.binding ability to alleviate membrane fouling.The addition of RLs and magnetic powder can increase the absolute value of the Zeta potential of the sludge mixture and the sludge particle size,with an average increase of 68.35%and 55.77%,respectively.These changes indicate that the membrane fouling has been alleviated.RLs and magnetic powder can promote the degradation efficiency of the reactor,and the average COD degradation efficiency in M-MBR exceeds 95%,which will not negatively affect the stability of the reactor operation.（3）Analyzing the differences in the sludge mixture of each reactor and the microbial community on the membrane module,it was found that adding RLs and magnetic powder can increase the species abundance of the sludge mixture and have little impact on species diversity;the species on the membrane module Increased diversity and reduced species abundance help alleviate membrane fouling.In addition,no matter in the sludge mixture or on the membrane module,Proteobacteria always accounted for a large proportion,and it was easy to adhere to the membrane surface.It was the main microorganism that caused membrane fouling;RLs and magnetic particles could increase the abundance of Flavobacterium and make it play a role in group quenching.Killing effect,to achieve the purpose of delaying membrane fouling.