Abstract: An oil water separator is disclosed having a vertical, cylindrical tank with a plurality of corrugated, oleophilic plates. A corrugated diffusion baffle is located adjacent an oil-water mixture inlet to remove the larger particulate material from the mixture and to cause coalescing of the larger oil droplets. The flow of the oil-water mixture proceeds generally in a vertical direction and passes between the corrugated plates to cause further coalescing of the oil droplets. A separate oil channel directs the coalesced oil to an upper portion of the tank. The clarified water then passes downwardly to a clean water outlet. A second coalescing unit may be located upstream of the clean water outlet to further coalesce and remove the smaller oil droplets. In this case, a second oil relief channel directs these coalesced oil particles to the upper portion of the tank, from which the oil may be removed.