Purification Step 1: Gravity Separation Pre-treated run-off is gravity fed or pumped (typically with a positive displacement or diaphragm type pump) to the gravity separator through a submerged inlet pipe. The separation process relies on the fact that light fluids have a lower specific gravity than water and thus float on the water surface.

Purification Step 2: Enhanced Coalescing Media In the residual oil media, fine droplets too small to be separated by gravity alone are accumulated into bigger particles that rise to the surface. This enhanced coalescing media is made of durable, netlike, soft polyurethane foam. The media-cartridge is easy to remove and reinstall once it is rinsed with a garden hose. The separated water exiting the system has a residual contamination of free petroleum content of less than 5 ppm.