The terms “oil interceptor” and “oil water separator” are often used interchangeably. However, these units are very different.
Oil interceptors are designed for use in drain lines where oils, sediment and other liquids are intercepted. They are usually steel, fiberglass or poly boxes, and include a baffle plate (designed to restrain the flow of a fluid), a solids bucket, and a separation area. As the water enters the interceptor, the baffle plate then diffuses the flow, which reduces the turbulence of the incoming water. Depending on the flow of the water, some debris and sludge are stopped by the baffle plate and collected in the solids bucket.
A low flow rate and low turbulence allows the oils to rise to the surface of the water through the interceptor, thus producing water that is relatively oil-free for discharge.
Oil Water Separators
Oil water separators are used in applications where there is a potential for a higher volume of water and oil (industrial wash operations, military installations, etc.), as they have a much more sophisticated design. An oil water separator is a tank containing an inlet compartment, baffles system, sludge chamber, separation chamber, and clean water outlet chamber. When water enters the inlet compartment, the oil separation process begins and solids drop out. The water passes through coalescing media, removing essentially all free and dispersed emulsified oils to an effluent concentration of less than 5 ppm.
Due to this design, oil water separators in North Carolina are associated with enhanced efficiency. In comparison to oil interceptors, significantly smaller units are needed for higher volume applications.