Grease interceptor

A grease trap (also known as grease interceptor, grease recovery device and grease converter) is a plumbing device designed to intercept most greases and solids before they enter a wastewater disposal system. Common wastewater contains small amounts of oils which enter into septic tanks and treatment facilities to form a floating scum layer. This scum layer is very slowly digested and broken down by microorganisms in the anaerobic digestion process. Large amounts of oil from food preparation in restaurants can overwhelm a septic tank or treatment facility, causing release of untreated sewage into the environment. High-viscosity fats and cooking grease such as lard solidify when cooled, and can combine with other disposed solids to block drain pipes.

Grease traps have been used since Victorian days. Nathaniel Whiting obtained the first patent for a grease trap in the late 1800s. These reduce the amount of fats, oils and greases (FOGs) that enter sewers. They are boxes within the drain run that flows between the sinks in a kitchen the sewer system. They only have kitchen waste water flowing through them, and do not serve any other drainage system, such as toilets. They can be made from many different materials, such as stainless steel, plastics, concrete & cast iron. They range from 35 liter capacity to 45,000 liters and greater. They can be located above ground, below ground, inside the kitchen or outside the building.

There are three primary types of devices. The most common are the types specified by ASME (American Society Of Mechanical Engineers), utilizing baffles, or a proprietary inlet diffuser.

Grease trap sizing is based on the size of the 2- or 3-compartment sink, dishwasher, pot sinks, and mop sinks. The cumulative flow rates of these devices, as well as overall grease retention capacity (in pounds or kilograms) are considered. Currently, ASME Standard (ASME A112.14.3) is being adopted by both of the National Model Plumbing Codes that cover most of the US. This standard requires that grease interceptors remove a minimum of 90% of incoming FOGS (fats, oils and greases). It also requires that grease interceptors are third-party tested and certified to 90 days compliance with the standard pumping. This third-party testing must be conducted by a recognized and approved third-party testing laboratory.

The most common passive grease traps are smaller, point-of-use units used under three-compartment sinks or adjacent to dishwashers in the kitchen. There has been little innovation in passive grease trap technology until recently, with the introduction of grease trap liners, which provide increased health, hygiene and safety benefits for end users. They restrict flow and remove 85–90% of the incoming FOG. Food solids along with fats, oils, and grease are trapped and stored in these devices. These units are available in many sizes, are often economical, and some can accommodate substantial flow volume. For some applications, this allows a food business to be created where otherwise an in-ground solution would be cost-prohibitive.

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