By Robert A. Hollander, P.E.

What are fats, oils, and grease?

Fats, oils, and grease (FOG) are substances that are discharged to sewer systems from commercial, industrial, and residential properties. Of primary concern are waste products of food preparation, such as from food service establishments (FSEs – restaurants). These substances can interfere with wastewater collection and treatment operations of public and private wastewater utilities if not controlled.

Why is FOG a problem? How can FOG be controlled?

Read on for answers to these questions.

Why is FOG a problem?

FOG consists of various fats, oils, and greases. When fats are discharged from an FSE, it is usually at elevated temperature from dishwashing and other cleaning activities where the fats are in a liquid state. When the fats cool in the wastewater collection system, they harden and collect on the walls of the sewer which can restrict the flow of wastewater. Restricted flow can result in surcharging and potential overflows of this untreated wastewater into buildings, homes, and onto streets, creating a potential health problem for the public.

Oils and grease can pass through wastewater treatment plants or interfere with treatment processes which can result in effluent discharges not meeting water quality requirements.

Therefore, FOG needs to be controlled at the source to prevent these problems.

How is FOG controlled?

Control of FOG discharges are included in several laws and regulations. These are listed below:

• The Federal statutory authority comes from the Federal Water Pollution Control Act Amendments of 1972 (aka the Clean Water Act – CWA).
• The CWA established the National Pollutant Discharge Elimination System (NPDES) Program (CWA Section 402). The NPDES program requires Publicly Owned Treatment Works (POTWs) to obtain permits to discharge treated wastewater to waters of the United States to protect those waters. POTWs are wastewater treatment facilities and their sewage collection systems generally owned by local government agencies and designed to treat domestic wastewater.
• The NPDES program requires POTWs that hold NPDES permits to implement pretreatment programs to prevent pass through of pollutants that cannot be treated or that interfere with the treatment process. These pollutants are generated by commercial or industrial customers and must be reduced or removed before the wastewater is discharged to the POTW.
• To support the NPDES permit requirements, the CWA established the National Pretreatment Program (see Sec 307(b)(1) of the Clean Water Act or Title 33 United States Code, Section 1317) and subsequent implementing regulations (40 Code of Regulations, Section 403).
• The CWA requires Federal, State, local, industry, and the public to establish pretreatment programs to prohibit the introduction of pollutants into treatment works that are difficult to treat or that may interfere with the operation of the treatment works (40 CFR 403.1(a)), potentially resulting in permit violations.
• Regulations at 40 CFR 403.5(b)(3) specifically prohibit “Solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW resulting in Interference”. This latter prohibition includes FOG.

Most U.S. states have obtained primary enforcement authority from the Environmental Protection Agency to issue NPDES permits and have an oversight role of the general pretreatment programs implemented by POTWs. POTWs, in turn, must develop and implement on-the-ground pretreatment programs.

We have described what FOG is and how it can be controlled. Part 2 will discuss what should be included in a good FOG control program.