Preparation and application of patterned membranes for wastewater treatment.

Membrane fouling remains a critical factor limiting the widespread use of membrane processes in water and wastewater treatment. To mitigate membrane fouling, we introduced a patterned morphology on the membrane surface using a lithographic method. A modified immersion precipitation method was developed to relieve the formation of dense layer at the solvent-nonsolvent interface, that is, the opposite side of the patterned surface. Diverse patterned membranes, such as pyramid-, prism-, and embossing-patterned membranes, were prepared and compared with a flat membrane in terms of morphology, permeability, and biofouling. Patterned membrane fidelity was largely dependent on the polymer concentration in cast solution. The patterned surface augmented the water flux in proportion to the roughness factor of the patterned membrane. However, the type of pattern did not affect substantially the mean pore size on the patterned surface. Deposition of microbial cells on the patterned membrane was significantly reduced compared to that on the flat membrane in the membrane bioreactor (MBR) for wastewater treatment. This was attributed to hydraulic resistance of the apex of the patterned surface, which induced local turbulence.