Abstract: Apparatus is disclosed for separating sludge, oil and the like from contaminated water having walls separating a tank into first and second compartments. The tank has an inlet for carrying the contaminated water thereto, a first outlet for removing separated oil and the like, a second outlet for removing the treated water and an outlet for removing separated sludge and the like. A plate pack is mounted on an inclined wall within the tank with the pack sloping downwardly from a first to a second end. The improved pack includes side walls, a top and a bottom forming a conduit for carrying the contaminated water from the first to the second end. A plurality of plates is mounted one above the other extending between the side walls to provide a plurality of passageways. The plate pack second end defines a substantially vertical plane when the pack is mounted on the inclined wall.