Patent ID: 7018539

Claim:
A process for treating oily wastewater generated on a ship, comprising: (a) carrying out a centrifugal separation step, comprising: (i) providing a centrifugal separator; (ii) treating the oily wastewater in the centrifugal separator, thereby dividing the oily wastewater into a light oil-rich phase and a heavy oil-depleted phase; (iii) withdrawing the light oil-rich phase as a concentrate stream; (iv) withdrawing the heavy oil-depleted phase as a water stream; (b) carrying out a membrane separation step, comprising: (i) providing a membrane separation unit containing a membrane having a feed side and a permeate side, the membrane being characterized in that the feed side comprises a dense, non-porous membrane capable of permeating water and rejecting both emulsified oil and dissolved oil under ultrafiltration conditions; (ii) passing the water stream across the feed side; (iii) withdrawing from the feed side a residue stream enriched in oil compared to the water stream; (iv) withdrawing from the permeate side a treated water permeate stream.