Oil/Water separation and sand cleaning occurs as intermittent rain and washdown water flows through a series of closely spaced baffle plates. The tight spacing of the baffle plates creates quiescent zones which reduce the distance a given oil droplet must rise to be separated from the main flow. Once in the quiescent zone, there is sufficient time for coalescence of the oil particles. The ever-growing droplets then migrate up the underside of the baffle into the oil riser. The risers prevent the oil droplet from being swept back into the turbulent flow stream and remixing with the incoming water. Additional oil/water separation is achieved through coalescence as a result of the large number of baffle plates, long retention time, and low energy output of the Skim Pile. Free oil is removed from sand due to the agitation and abrasion created as the sand tumbles down the series of baffle plates and is disposed of through the end of the caisson. The Sumperator (Skim Pile) is the final stage of the open drain and/or produced water treatment system and is guaranteed to remove all oil globules greater than 50 microns.
A Skim Pile should be the preferred caisson application where strict adherence to regulations is of concern.