Municipal Sewage Secondary Effluent Foulants Membrane Fouling Behavior Analysis

Sodium alginate(SA),bovine serum albumin(BSA)and humic acid(HA)as the typical urban wastewater foulants representation,as well the different membrane materials including cellulose acetate(CA)/poly(ether sulfone)(PES)/poly(vinylidene fluoride)(PVDF)as the mainstream commercial ultrafiltration membrane interface were selected in this paper.The microscopic interaction parameters between the ultrafiltration membrane and foulants interfac was explored by molecular modeling(MD)and the extended colloid space theory(XDLVO)theoretical analysis,combined with the mathematical model verification of ultrafiltration membrane fouling behavior,which predicted the secondary effluent of membrane fouling behavior by the theory practical application.The main research work was as follows:1.The good concentration linear equations were established for SA,BSA and HA which contained by secondary effluent three typical representation foulants using resonance light scattering and ultraviolet spectrophotometry method at the aid of dye probes.The characteristics of three representative foulants functional group composition and surface property were further analyzed by the potentiometric titration and zeta potential.The method had the higher recovery rate for actual water samples analysis,and established a more comprehensive analysis for the secondary effluent advantage foulants their distribution.2.The binding energy(ΔE)between the typical foulants and three representative ultrafiltration membrane interfaces were studyed by molecular dynamics techniques as the SA,BSA,HA representated the secondary effluent constituent units,respectively.MD simulation calculation showed that ΔE absolute value between SA and salicylic acid at PVDF membrane was much largest,and the ΔE absolute value of cysteine at PES membrane was the maximum.ΔE absolute value of three foulants at the same membrane surface found that the ΔE absolute value of cysteine and membrane was maximum,followed by that of salicylic acid’s,SA’s was the minimum,which forcasted that the PVDF membrane fouling would be the serious,the CA membrane’s is the weakest,the protein-substance would cause the serious membrane fouling behavior and the fouling trend caused by carboxyl was more critical than that of hydroxyl.3.XDLVO theoretical calculation showed that the absolute value of adhesion free energy(ΔGmlfAD)between CA membrane and single sample including SA,BSA,HA were minimum,and the maximum with PVDF membrane.When more SA accounted for mixture would result in the ΔGmlfAD smaller,the larger of BSA or HA in the mixture;which predicted that the fouling trend between protein-representative characterized the secondary effluent water sample and membranes was the strongest,the polysaccharide-like characterized typical water was the weakest.4.Ultrafiltration membrane fouling experiments verifications showed that the law membrane fouling of three representative foulants HA,BSA,SA contained secondary effluent was consistent with the XDLVO and MD theoretical prediction.MD prediction for BSA was different from the actual membrane fouling behavioral,which may be related to the selected representation foulant of cysteine.UF membrane foulng law of secondary effluent typical representation foulant binary mixture remained good correlation with XDLVO theory.Membrane fouling law of four groups of characteristic advantage secondary effluent foulant distribution was basically matching with MD and XDLVO theory prediction.