Recently, EPA presented statistics that cited grease accumulation in sewers as the leading cause of sewer blockages resulting in sanitary sewer overflows (SSOs). Such blockages can be attributed to fats, oils, and grease (FOG) discharged from food preparation and manufacturing facilities, concentrated residential areas, and even single family homes. Municipalities and wastewater system managers have responded to this problem by implementing FOG management programs, often successfully reducing FOG blockages and subsequent SSOs. However, many programs are not as strong as they could be in important areas of education, treatment, and enforcement. These weaknesses may ultimately result in FOG management program failures. Municipalities, governmental agencies, and wastewater system managers should anticipate potential “weak links” while addressing the typical aspects of a FOG management program. Common “weak links” include ambiguous or vague ordinances that do not clearly delineate roles and responsibilities, poorly trained kitchen staff, inappropriate grease interceptor (GI) sizing methods, and weak enforcement of FOG management regulations. By adequately reinforcing “weak links” in the FOG management chain, responsible officials and agencies can create a FOG management program that will save money, time and resources, and protect the health of the public and the environment, by reducing FOG accumulation in the sewer system.
For the past several decades, municipalities and government agencies have recognized the importance of addressing excessive fats, oils, and grease (FOG) discharges into the sanitary sewer system. FOG discharged from food preparation facilities, food manufacturing facilities, and residential areas, if not properly pretreated, enters the wastewater collection system. In the typical sewer environment, FOG can solidify and accumulate in sanitary sewer pipes and lift stations, potentially leading to sanitary sewer overflows (SSOs). Additionally, excessive FOG can cause disruptions to lift stations and wastewater treatment plant (WWTP) operations. To mitigate the expensive and potentially hazardous impacts of FOG, most municipalities and wastewater collection system managers have implemented FOG management programs, with much success. However, these programs are often not as strong as they could be in important areas of education, treatment, and enforcement. These weaknesses may undermine an otherwise successful and comprehensive FOG management program. This paper presents common FOG management options and guidelines, and discusses areas that can easily become “weak links” if not properly addressed in the FOG management program.
Fats, Oils, and Grease
Vegetable oils and animal fats from food and food preparation activities (e.g., frying, grilling) are commonly referred to as FOG, an umbrella term for all edible fats, oils, and grease. FOG can be either liquid (oils) or solid (fats and grease), has a lighter density than water, and is not readily water-soluble. These characteristics allow FOG to float on the surface of water, unless influenced by physical and/or chemical factors that can lead to emulsification or mixing, such as high temperatures, high turbulence, mechanical mixing (i.e., pumping) and cleaning products or additives containing surfactants.
Sources. Any facility that prepares, processes, manufactures, or serves food has the potential to contribute FOG to the wastewater collection system. These include food service establishments (FSEs), such as restaurants, schools, and grocery stores; food manufacturing or processing facilities; concentrated residential areas, such as multi-family/apartment complexes; and even single family homes. Food manufacturing and processing facilities can vary greatly and should be included in the municipal industrial discharger program. Grease interceptor (GI) and FOG management programs for such facilities should be developed on a site by site basis. The remainder of this discussion is focused on more typical FOG contributors, such as FSEs and residential areas.