Oil & Grease (O&G)
Oil & Grease in Stormwater FAQs
Oil and grease in the form of motor oil and fuel are commonly found in stormwater runoff. Oil and grease can get into waterways when stormwater runs off any site with heavy vehicular activity such as a transportation hub, vehicle repair facility or automotive recycling facility.
Most types of oil and grease are insoluble in water. However, agitation can create a temporary mixing with water. Fatty material from plant and animal sources are made up of lipids which are polar molecules and partially soluble in water.
Oil and grease in the form of various hydrocarbons found in fuels should be removed from stormwater because they can pose a wide range of human health hazards and environmental damage. In humans, hydrocarbons affect the liver, kidneys and blood, and increase the risk of cancer.[ii] Toxicity varies among different types of oils and greases. Refined oils are generally more toxic than crude oils.[i]
Low levels of oil pollution can reduce aquatic organisms’ ability to reproduce and survive.[iii] Studies indicate that 0.3 – 0.6 mg/L of certain aromatic hydrocarbons can be lethal to aquatic organisms,[iv] while chronic concentrations over 50 µg/L may be harmful to estuarine species.[v] Oils can also create chemical oxygen demand.
Oil and grease and other settleable pollutants such as settleable solids, metals, floatables and trash can be removed by gravity separation. Stormwater flows through a chambered gravity separator gradually settling finer and finer particles. Oil and grease are skimmed from the surface and retained during this process. Clara is a highly effective gravity separator for the removal of oil and grease, settleable solids, metals floatables and trash. Find out more about the Clara gravity separator.