The Study On Separation Characteristic Of Ultrafiltration For Turbidity And Humic Acid And Analysis Of Operation Conditions On Membrane Fouling

Urban sewage reuse has been the hotspot of the research. Compareing with otherwastewater tertiary treatment technologies, membrane separation, with low energyconsumption, simple operation, good water quality, stable performance and many otheradvantages, is applied for wastewater reuse. However, the universal application ofmembrane separation is retricted by the membrane fouling. This study is aiming atinvestigating the effect of turbidity and humic acid on hydrophilic modified PVDFhollow fiber membrane pollution and control conditions. This will lay the foundationfor the utilization of the modified ultrafiltration membrane during the wastewaterrecycle process. The conclusions achieved are as followed:(1)Ultrafiltration flux decline is little affected by the turbidity and the flux declineslowly during the filtering process.. This pollution was reversible and could beremoved by hydraulic cleaning. The removal efficiency of turbidity is excellent byultrafiltration and the turbidity in effluent (0NTU) is regardless of the influent, whichmeans almost all turbidity was removed (turbidity removal efficiency is100%).(2) Permeation flux decline of humic acid on membrane is much larger thanturbidity, both reversible and irreversible pollution was observed, in which theirreversible pollution plays a major role. Changing the water environmental conditioncan affect the ultrafiltration fouling by changing the property of humic acid..Humicacid macromolecule was the key factor in membrane fouling. The variation of pH andionic strength in solution could affect the adsorption of humic acid on the membranesurface by changing the charged state of the humic acid molecules. The acidic solution environment and high ionic strength increased of membrane fouling, while the alkalineenvironment mitigated the effect of humic acid on ultrafiltration contamination. Thecomplexation of calcium ion and humic acid molecules play the role in ultrafiltrationcontamination. When calcium ion concentration is low,membrane fouling is worse,and when it is high, membrane fouling is reducing.(3)The simulation of actual operation coexisting both turbidity and humic acidindicated that the operation mode is influential for membrane permeation flux. Thedegree of the membrane flux decline will be reduced by increasing the cleaningfrequency, improving the backwash pressure or using chemical enhanced backwash,which could inhibit the membrane fouling.(4)During the actual operation, selecting the appropriate hydraulic cleaningconditions can delay the membrane fouling, and increasing the backwash flow rate isbetter than the increasing flow of quick wash. Besides, chemical enhanced backwashand hydraulic cleaning can effectively control the transmembrane pressure growth andachieve a outstanding effect of inhibition of membrane fouling. The effluent ofultrafiltration membrane has meet the requires of turbidity and organic matter forwastewater reuse as miscellaneous water in living as the result of the removalefficiency of turbidity and organic matter of secondary effleunt.