A MOBILE PLANT PROTOTYPE FOR THE RESTORATION OF POLLUTED BEACHES BY WASHING OILY SAND

Abstract

ABSTRACT A research program was undertaken in 1980 with the support of the European Economic Community and the French Ministry of the Environment to develop a technique for treating beaches polluted by an oil spill, after the bulk of the oil has been removed from the surface of the sand by mechanical equipment. Final cleanup is often necessary, especially in the case of recreational beaches, when the oil remaining in the upper layer of sand—frequently in the range of 2 to 3 percent—in unacceptable. There is some controversy regarding the use of dispersants for this purpose. The basic principle of the technique is to wash oil-contaminated sand in transportable equipment which is operated either close to the polluted beach or at a centralized location, the washed sand then being returned to the beach or used for other purposes. The selected equipment and three different cleaning agents were tested in pilot trials carried out on sand polluted with heavy fuel oil. A plant prototype was set up and tested in 1985. It is composed mainly of a horizontally rotating wash drum associated with a screen, a hydrocyclone to separate the sand from the wash-water phase and a vibrating screen for sand dewatering. These three pieces of equipment are mounted on the bed of a semi-trailer along with two transfer pumps. Oil and sand fines are separated from the water, before recycling, in several ground tanks in which a flocculating agent may be added. The operating parameters of the process are discussed on the basis of trials carried out at a throughput of 18 metric tons of sand per hour, giving a washed sand with an average oil content of 0.2 percent in the case of moderate weathering.