Oil & Grease (O&G)

Chemical symbol/abbreviations:

O&G, FOG (fats, oil, and grease)

Form commonly found in stormwater:

Motor oil, fuel

Related constituents:

Total petroleum hydrocarbon – a measure of only petroleum-based substances, mass measurement on the same scale as O&G.

Total organic carbon – a measure of all organic compounds, unlike O&G in that only the mass of carbon is expressed.

Solubility in water:

Most sources of oil and grease are insoluble in water. However, agitation can create a temporary emulsion with water. Fatty material from plant and animal sources are made up of lipids which are polar molecules and partially soluble in water.

Adverse human impacts:

Toxicity varies among different types of oils and greases.  Refined oils are generally more toxic than crude oils.[i] Various hydrocarbons found in fuels can pose a wide range of human health problems, from affecting the liver, kidneys and blood to increasing the risk of cancer.[ii]

Adverse impacts on the environment:

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.

Stormwater Treatment to Remove Oil & Grease


Oil and grease (O&G) is a measure of a variety of substances including fuels, motor oil, lubricating oil, hydraulic oil, cooking oil, and animal-derived fats.[viii]
The concentration of these substances is typically measured within a body of water. Lakes, river, stormwater runoff, and wastewater are all monitored for oil and grease.
Sources of oil and grease are mainly anthropogenic. Oil and greases need to contained and/or recycled typically to keep them from entering the environment. Domestic cooking oil should be poured into a disposable container and thrown out in the trash. Used motor oil and hydraulic fluids should be disposed of at a local automotive part store or a certified hazardous waste facility.[ix] Spill prevention kits should be used to help to clean up spills that occur at the workplace.

U.S. EPA recommended water quality criteria:

None. EPA recommends water quality criteria for many of the constituents in oil and grease. [vi]

and many state and federal water quality standards prohibit oil in quantities that produce a film or sheen on the water.[vii]


[i] Michael Stenstrom, et al., Ass’n of Bay Area Gov’ts, Oil and Grease in Stormwater 46 (1982), http://www.seas.ucla.edu/stenstro/r/r8.

[ii] See U.S. EPA, List of Contaminants and Their MCLs, http://www.epa.gov/safewater/contaminants/index.html.

[iii] Stenstrom, supra at 51.

[iv] Stenstrom, supra at 52.

[v] Stenstrom, supra at 53.

[vi] U.S. EPA, National Recommended Water Quality Criteria, http://www.epa.gov/waterscience/criteria/wqctable/index.html#U (last visited July 30, 2010).

[vii] See, e.g., Or. Admin. R. 340-041-0007(13) (2010); 314 Mass. Code  Regs. 4.05:(3)(b)(7) (2010); EPA Discharge of Oil Rule 40 C.F.R. § 110 (2010).

[viii] E.S. Babcock & Sons, Inc., Storm Water Contamination – A Slick Problem http://www.babcocklabs.com/pdfs%5CStormWaterContaminationArticleDec2009.pdf (last visited July 30, 2010).

[ix] Stormwater Management Joint Task Force, Fats, Oils & Greases, http://www.cleanwaterways.org/downloads/brochures/FOG_brochure_English.pdf (last visited July 30, 2010).

The StormwateRx Clara® is often used as pretreatment to Aquip for removal of oil and grease. For industries with oil and grease loadings, Clara is often the product of choice, as it has oil storage capacity of up to 650 gallons.

The StormwateRx Aquip® industrial filtration system uses an innovative enhanced sand filtration process to effectively remove soluble and insoluble aluminum and other metals as well as oils, suspended solids, organics and nutrients from industrial stormwater runoff.

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