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grease trap[′grēs ‚trap]
a chamber for separating and retaining fats and petroleum and other oils from effluent water by cutting the flow rate. The fatty materials in the effluent upset the purification plants (biofilters and filter beds), and when they fall into a reservoir, they cover a large area of water with a thin film that hinders access to oxygen and thus retards the reservoir’s self-purification processes. Further, the fats and similar substances are a valuable raw material, which can be processed for commercial purposes. Grease traps are set up at effluent outfalls of individual buildings (restaurants, factory kitchens, meat combines, canning factories, and other industrial concerns), as well as in public sewers. The time of stay of effluent in a grease trap is 5 seconds to 15 minutes, with a flow speed of up to 10 cm per sec. Depending on the amount of fat held back, the latter is removed by a pump or suction arrangement, with heating to 45°-50°C.