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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. However, very large amounts of oil from food production in kitchens and restaurants can overwhelm the septic tank or treatment facility, causing a release of untreated sewage into the environment. Also, high-viscosity fats and cooking greases such as lard solidify when cooled, and can combine with other disposed solids to form blockages in drain pipes. Grease traps have been used since the Victorian days, although Nathaniel Whiting obtained the first patent for a modern-day grease trap in the late 1800s. They are used to reduce the amount of fats, oils and greases (FOGs) that enter the main sewers. Effectively they are boxes within the drain run that flows between the sinks in a kitchen to the sewer system. They only have kitchen waste water flowing through them and are not served by any other drainage system such as toilets. They can be made from a number of different materials; e.g. stainless steel, plastics, concrete & cast iron. They range from 35 liter capacity to 45,000 liters and above capacity. They can be located above ground, below ground, inside the kitchen or outside the building. ==Types== 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 the aforementioned devices, as well as overall grease retention capacity (typically 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 United States. This standard requires that grease interceptors remove a minimum of 90% of the 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 small, point-of-use units used under three-compartment sinks within the kitchen. There has been little innovation in this in kitchen passive grease trap technology until recently, with the introduction of a liner grease trap, which provide significant 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. The second most common type of interceptor is the large in-ground tank, which is usually 500–2000 gallons. These units are constructed of concrete, fiberglass, or steel. By nature of their larger size, they have larger grease and solid storage capacities for high-flow applications such as a restaurant or hospital store. They are commonly called gravity interceptors. Interceptors require a retention time of 30 minutes to allow the fats, oils, grease and food solids to settle in the tank. As more waste water enters the tank the grease free water is pushed out of the tank. The rotting brown grease inside a grease trap or grease interceptor must be pumped out on a schedule. The brown grease is not recycled and goes to landfill. On average 300 to 400 pounds of brown grease goes to landfill annually from each restaurant. A third system type, GRDs (grease recovery devices), remove the grease automatically when trapped. The recovered grease or "yellow grease" is recycled with the waste vegetable oil from the kitchen's deep-fryers. Restaurants do not have to pay for grease trap pumping as do restaurants with conventional grease traps or grease interceptors. Passive grease traps and passive grease interceptors must be emptied and cleaned when 25% full. As the passive devices fill with fats, oils, and grease, they become less productive for grease recovery. A full grease trap does not stop any FOG from entering the sanitary sewer system. The emptied contents or "brown grease" is considered hazardous waste in many jurisdictions. "Brown grease" is generally not recycled and goes to landfill waste. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grease trap」の詳細全文を読む スポンサード リンク
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