Identification And Control Of Chemical Reversible/Irreversible Membrane Fouling Behavior In The Ultrafiltration Process Of Pearl River Water

The shortage of water resources and the deterioration of water quality promote the development of water treatment technology.Ultrafiltration has potential advantages in advanced treatment of feed water,but membrane fouling is the bottleneck of its popularization and application.According to whether the pollutant can be eluted by the chemical cleaning agent,it is subdivided into chemically reversible foulants?CRF?and chemically irreversible foulants?CIF?.There are more reports on hydraulic reversible/irreversible fouling in the existing literature,but less reports on CRF/CIF.Based on the above,this paper systematically studies the CRF/CIF pollution behavior and the control effect of different pretreatment combinations in the process of ultrafiltration of Pearl River water:Taking the effluent from different process nodes of the water plant as the ultrafiltration influent,the degree of membrane pollution caused is raw water>sedimentation pond effluent>filter effluent.For membranes of different materials,the degree of PES membrane pollution is lighter than that of PVDF membrane pollution.Through the analysis of the composition of the membrane washing liquid and the infrared characterization of the membrane before and after the pollution,it can be known that the substances that cause the ultrafiltration membrane pollution in the raw water are humus,polysaccharides,and protein substances.The CRF are mainly protein and some humus substances,the CIF are mainly polysaccharides.For the removal of natural organic matter in raw water,the optimal dosage of polyaluminum?PACl?,powdered carbon?PAC?and potassium permanganate?KMn O₄?oxidation pretreatment are 20mg/L,30 mg/L,0.1 mg/L,respectively.For the main components of CRF?humus and protein?,the removal effect of PACl and KMn O₄ is better than PAC.For the main component of CIF?polysaccharide?,the removal effect of the three pretreatments is not good?<40%?,among them,the removal effect of PAC is slightly better than that of PACl and KMn O₄.Different pretreatment combinations can effectively enhance the removal effect of CRF and CIF,which can reach more than 65%,and can further effectively alleviate membrane pollution.Comprehensive consideration,PACl?20mg/L?+PAC?30 mg/L?combined pretreatment has the best removal effect on CRF/CIF and the best improvement effect on membrane flux.In the early stage of filtration,the membrane pore size increased the higher the water concentration,the higher the frequency of pollutants colliding with the membrane,resulting in more serious membrane pollution.In the later stage of membrane pollution,the adhesion efficiency is basically the same because the membrane surface is covered with pollutants,and the degree of membrane pollution does not depend on the membrane pore size and inlet the concentration of water pollutants and the maximum stable flux of membrane under different conditions are basically the same.In addition,ultrafiltration membranes with smaller membrane pore sizes can trap more pollutants and deposit them on the membrane surface,so there are fewer pollutants passing through the membrane.Higher concentrations of pollutants in the incoming water will cause more pollutants accumulated on the membrane surface and more pollutants will be found in the membrane permeate.When the.concentration of Ca²⁺.increased from 0 mmol/L to 5 mmol/L,the membrane fouling increased,and when the concentration of Ca²⁺increased from 5 mmol/L to 10 mmol/L,the membrane fouling decreased.