  Oily wastewater is an extensive source of pollution to soil and water, and
its harmless treatment is of great importance for the protection of our aquatic
ecosystems. Membrane filtration is highly desirable for removing oil from oily
water because it has the advantages of energy efficiency, easy processing and
low maintenance cost. However, membrane fouling during filtration leads to
severe flux decline and impedes long-term operation of membranes in practical
wastewater treatment. Membrane fouling includes reversible fouling and
irreversible fouling. The fouling mechanisms have been explored based on
classical fouling models, and on oil droplet behaviors (such as droplet
deposition, accumulation, coalescence and wetting) on the membranes. Membrane
fouling is dominated by droplet-membrane interaction, which is influenced by
the properties of the membrane (e.g., surface chemistry, structure and charge)
and the wastewater (e.g., compositions and concentrations) as well as the
operation conditions. Typical membrane antifouling strategies, such as surface
hydrophilization, zwitterionic polymer coating, photocatalytic decomposition
and electrically enhanced antifouling are reviewed, and their cons and pros for
practical applications are discussed.
