Fouling Control in a Submerged Membrane-Bioreactor by the Membrane Surface Modification

摘要

To improve the antifouling characteristics,polypropylene microporous membranes (PPHFMMs) weresurface-modified by the sequential photoinduced graftpolymerization of acrylic acid and acrylamide. The graftingdensity and the grafting chain length, which playedimportant roles in the antifouling characteristics, werecontrolled in the first and the second step, respectively.The ATR/FTIR results clearly indicated the successfulmodification on the membrane surface. The static watercontact angle of the modified membrane reduced obviouslywith the increase of the grafting chain length. Thecontact angle of the acrylic acid modified membraneswas lower than that of the acrylamide modified membranewith similar grafting chain length. The graftingchain length increased with the increase of UV irradiationtime and monomer concentration. The grafting chainlength of poly(acrylic acid) (PAAc) was lower than thatof the polyacrylamide (PAAm) under the same polymerizationconditions. Pure water flux for the modifiedmembranes increased with the increase of grafting chainlength, and had maximums. The antifouling characteristicsof the modified membranes in a submergedmembrane-bioreactor (SMBR) were evaluated. The modifiedmembranes showed better filtration performances inthe SMBR than the unmodified membrane, and theacrylic acid grafted membrane presented better antifoulingcharacteristics than acrylamide modified membranes.The results demonstrated that the surface carboxylcontainingmembranes were better than the surfaceamido-containing membranes. The results of Pearson correlationsdemonstrated that the PAAc modified membraneswith longer grafting chain length had higher fluxrecoveries, while the PAAm modified membranes withlonger grafting chain length had lower flux recoveries.