Produced water (PW) is oily water co-produced during oil and gas exploration and production.  PW contains dispersed oils and suspended solids.

An estimated 21 billion barrels of PW generated from active oil and gas wells in the US in 2007.  Normally, PW is re-injected in geologically isolated wells or is surface discharged with adverse environmental effects.

Membrane filtration is an option but is affected negatively by fouling and concentration polarization.