Table 1.

Membrane technologies of oil/water emulsion separation.

Membrane processes	Merits	Demerits	Ref
Microfiltration	• Lowest pressure applied • Colloidal can be removed	• Oil drops pile up on the exterior of the membrane • Produce polarization layer	2,9–11
Ultrafiltration	• Non-detrimental separation, without phase transition	• Concentration polarization • Membrane fouling	6,9,11–14
Nanofiltration	• Can hold divalent ions	• Complex process	6,9,11–13
Reverse Osmosis	• Yield high-level quality treated water • Nearly perfect elimination of all the components found in oily wastewater	• Membrane fouling • Extra chemical and energy cost for membrane clean-up and substitutes • Additional downtime of the apparatus treatment • Demands efficient pretreatment for oil and grease exclusion	6,11–13