In the sewage collection and treatment business, grease is a serious problem because of its poor solubility in water and its tendency to separate from the water and adhere to other surfaces.
Fats, oils and grease coat the insides of sewer pipes, causing maintenance problems. This blocks pipes, reducing sewer capacity, which in turn leads to sewage backups into property and sanitary sewer overflows to the environment.
Oil and grease also hamper effective treatment at the wastewater treatment plant. Grease in a warm liquid may not appear harmful. But, as the liquid cools, the grease or fat congeals and causes mats to form on the surface of settling tanks, digesters and the interior of pipes and other surfaces. This can cause a shutdown of wastewater treatment processes.
Problems caused by wastes from restaurants and other grease-producing establishments form the basis for regulations like requiring a grease interceptor to control FOG discharges.