Abstract: A method of, and apparatus for, separating contaminants from a base liquid and whereby the contaminated base liquid is passed through a pretreatment vessel before being passed to a conventional separator. In one embodiment, the pretreatment vessel is of generally cylindrical form arranged with its axis substantially vertical. Base liquid to be decontaminated is supplied into the mid-height regions of the vessel through a tangential device to cause circulating flows within the vessel. The vessel includes an outlet in its top region for the release of light contaminants, an outlet in its lower region for the release of heavy contaminants and an outlet duct in its mid-region, spaced from the inlet, for releasing partially contaminated liquid from the vessel for release into a conventional separator.

Abstract: A separator for separating contaminants from a base liquid. The separator includes a roof arrangement, part of which extends downwardly and radially inwardly into the liquid in the separator. The roof arrangement is generally in inverted conical form. The decontaminated liquid flows from the separator through a flow modifying member which dampens any circulating flows in the liquid, and flows upwardly out of the separator to a reservoir defined by the inverted conical roof arrangement. The arrangement also includes structure for releasing gases from the volumes beneath the roof arrangement, thereby maintaining the whole of the roof arrangement in contact with the liquid to assist in reducing circulating flow in the liquid on the upper regions of the separator vessel.