Characteristics Of Membrane Fouling During Algae-Laden Water Treatment Using A Hybrid Process Of Enhanced Coagulation And Ultrafiltration

With the increasingly strict standards of drinking water quality and seriously status of water crisis,ultrafiltration?UF?has become one of the most widely used as advanced water treatment technologies due to its high efficiency of solid-liquid separation performance and relatively low energy consumption.In China,the eutrophication of water causes seasonal algal blooms,which is a huge challenge for waterworks.Based on the size separation principle,UF is an efficient and effective technology for algae-laden water.The severe membrane fouling caused by ultrafiltration treatment of algae-laden water constrains the further promotion of the ultrafiltration process.On the other hand,the ultrafiltration membrane itself has a low removal efficiency for algae-derived organic resulting in the inefficient removal of soluble organics.Pre-membrane pretreatment technology can improve the quality of ultrafiltration effluent while alleviating the problem of ultrafiltration membrane fouling.In this paper,the effects of coagulation pretreatment,permanganate pre-oxidation and powdered activated carbon adsorption pretreatment on membrane fouling were investigated in depth.The removal efficiency of organic matter and the Influence of membrane fouling using a hybrid process of permanganate pre-oxidation and powdered activated carbon adsorption were investigated.The water purification efficiency of the ultrafiltration combined process and the mechanism of membrane fouling control were investigated when permanganate pre-oxidation or powdered activated carbon adsorption was used alone,or both together combined with ultrafiltration technology.Ferric chloride?FeCl₃?coagulation pretreatment coagulation can effectively remove algal source pollutants,which may be due to the functions of electric layer,electric neutralization and net-sweeping sweep coagulation after adding coagulant make the algae source organic matter coagulate and flocculate,and then can be partially removed by precipitation;at the same time,the reversible membrane fouling of the ultrafiltration membrane is effectively alleviated.And the organic matter forms loose on the membrane surface.The filter cake layer can be better washed by hydraulic backwashing;the aluminum sulfate?Al₂?SO₄?₃?coagulation pretreatment has a small effect on the removal of algae source organic matter by ultrafiltration.However,the reversible membrane fouling of the ultrafiltration membrane can be effectively alleviated,and the organic cake forms a loose filter cake layer on the surface of the membrane,which can be better washed by hydraulic backwashing;the effct of FeCl₃coagulation pretreatment is better than Al₂?SO₄?₃.The optimum dosage of FeCl₃ was 0.2mmol/L.Co-oxidation enhanced coagulation pretreatment of potassium permanganate?KMnO₄?and ferrous sulfate?FeSO₄?has little effect on the removal of algae-derived organic matter by ultrafiltration;the treatment can effectively reduce the reversible membrane fouling of the ultrafiltration membrane;The use of powdered activated carbon?PAC?alone has no obvious effect on the removal of algae pollutants and the reduction of membrane fouling.Because the organic colloid in the solution will adsorb some organic pollutants,PAC may re-contaminate the ultrafiltration membrane as a newly introduced substance,and the two effects cancel each other out,so using PAC alone cannot effectively alleviate membrane fouling;PAC and FeCl₃ coupling pretreatment can effectively remove algal source pollutants,and effectively reduce the reversible membrane fouling of ultrafiltration membrane.This may be attributed to the interaction between PAC adsorption and FeCl₃ coagulation;the pretreatment of PAC with KMnO₄ and FeSO₄ can effectively remove the algal source pollutants and effectively reduce the reversible membrane fouling of ultrafiltration membrane.This may be because the first addition of PAC can adsorb some organic pollutants,reduce the contact of organic matter with the membrane surface and reduce membrane fouling.Then,adding KMnO₄ and FeSO₄ is beneficial to the oxidation of organic pollutants,adsorption and aggregation deposition to form loose cake layer,then further alleviates the membrane pollution caused by algae.The research content of this subject is helpful to alleviate the membrane pollution in the process of ultrafiltration high algae liquid.It is of great significance for the stable operation of ultrafiltration technology in algae outbreak,but further research of control of relavant membrane pollution is needed.