Petroleum products from fueling and maintenance facilities are common pollutants in surface and groundwater. Most oil/water separators currently in use are coalescing plate interceptor (CPI) units made up of closely-spaced plastic plates submerged in the waste stream. Microscopic oil droplets coalesce on the surfaces of the plates, then collect and rise to the water surface in the plate chamber. The system works effectively but maintenance is expensive because the fragile plate-and-spacer assemblies must be removed for cleaning and are susceptible to damage. This proposal is to study the possibility of using low-coat glass marbles as a coalescing medium in place of plastic plates. Glass attracts oil as well as plastic does, and the interstices between the marbles will allow water to flow through. Oil will coalesce on the surface of the marbles and rise to the water surface for removal. The marbles may be cleaned of sediment by agitating the filter bed with a water or air hose and pumping off the sediment in suspension. The marbles need not be removed and may be re-used indefinitely, saving considerably on the cost of maintenance.
