Fats, Oil and Grease | Activated Sludge Process | Wastewater Treatment Plant

FATS, OIL, AND GREASE

CONCEPTS

Fats, Oil, and Grease, or “FOG,” are a group of organic substances that include hydrocarbons, animal fat and grease, oils, waxes, and various fatty acids. They are typically derived from households, food preparation operations, and restaurant operations. They usually do not degrade well in wastewater treatment plants, but they can be made to float in sedimentation basins and air floatation units for relatively easy removal from the wastewater being treated. The collected materials are solid or semisolid in nature and are usually mixed with other waste solids or sludge's for treatment before disposal.

RELEVANCE

The problem with FOG components is their natural tendency to adhere to the walls of pipes and pump stations, significantly reducing pipe carrying capacity, especially in colder weather, and interfering with the proper operation of pumps and floats in pumping stations. FOG that makes its way into the treatment plant can also disrupt the operation of flow measuring devices, main pump station equipment, and sedimentation operations throughout the plant. Despite the fact that FOG components are organic in nature, they are resistant to the biological treatment most commonly used in wastewater treatment plants due to the short resident times in the various treatment units compared to the long retention times required for biological FOG degradation.

The FOG concentration test consists of an extraction procedure using n-hexane and gravimetry to determine the volume of extracted components. It should be noted that FOG components frequently adhere to sampling and testing equipment, so caution is required to ensure reliable results.