Fats, Oils, and Grease (FOG)

FOG is of two types: (1) of petroleum or mineral origin; (2) of animal or vegetable origin.

FOG of petroleum or mineral origin, called nonpolar FOG, can harm the biological phase of sewage treatment where microbes are used to break down wastes. The King County limit for nonpolar FOG is 100 milligrams per liter of discharged wastewater.

Industries use oil and water separators to pretreat wastewater containing nonpolar FOG. Plans for separators must be approved by the local sewer utility or by King County Industrial Waste (KCIW). Information on plan submittal and installation guidelines is available on this Website in the Oil/Water Separator Fact Sheet (161 KB) prepared by KCIW.

FOG of animal or vegetable origin, called polar FOG, can block sewer lines. King County rules require dischargers to minimize free-floating FOG. Wastewater must not be discharged if someone can see FOG floating on the surface or adhering to sides of storage containers. Dischargers may not add agents to emulsify free-floating polar FOG. King County may require companies discharging polar FOG to complete a FOG control plan. The goal of the FOG control plan is to implement reasonable and technically feasible controls of free floating FOG. The basic components of the FOG control plan should include:

FOG Control Plans: The goal of the FOG control plan is to implement reasonable and technically feasible controls of free floating FOG. The basic components of the FOG control plan should include:

• 1. A written policy articulating management and corporate support for the plan and a commitment to implement planned activities and achieve established goals.
• 2. A description of the facility type and a summary of the products made and/or service provided.
• 3. Quantities of FOG brought into the facility as raw product, amounts contained in products, and quantities discharged to the sewer.
• 4. Schematics of process areas illustrating drains and discharge points connected to the sewer.
• 5. A description of current reduction, recycling, and treatment activities.
• 6. Identification of a full range of potentially feasible reduction opportunities.
• 7. A description of the reduction or control opportunities selected for implementation, process(es) affected, and estimated reductions to be achieved.
• 8. Specific performance goals and implementation schedule.