Surface modification of polypropylene macroporous membrane to improve its antifouling characteristics in a submerged membrane-bioreactor: H(2)O plasma treatment

To improve the antifouling characteristics of polypropylene hollow fiber macroporous membranes in a submerged membrane-bioreactor for wastewater treatment, the membranes were surface modified by H₂O plasma treatment. Structural and morphological changes on the membrane surface were characterized by X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM). The change of surface wettability was monitored by contact angle measurement. The static water contact angle of the modified membrane reduced obviously with the increase of plasma treatment time. The total surface free energy and its dispersive component decreased, while the polar component increased with the increase of treatment time. The relative pure water flux for the modified membranes increased gradually with the increase of plasma treatment time. The tensile strength and the tensile elongation at break for the membranes decreased after plasma treatment. After continuous operation in a submerged membrane-bioreactor for about 68 h, flux recovery after water and caustic cleaning, flux ratio after fouling were improved by 2.0, 3.6 and 22.0%, while reduction of flux was reduced by 1.1% for the 1 min H₂O plasma treated membrane, compared to those of the unmodified membrane.