The so-called grease trap is a special pool that separates grease, sundries and moisture from the wastewater discharged from the canteen. There are usually three pools. The first tank is used to separate sundries, the second tank is used to separate grease, and the third tank is waste water without sundries and grease, which can be discharged into the sewage pipeline. From the perspective of social responsibility, the waste grease in restaurants should be treated specially. If there is no grease trap, the discharged grease is likely to give some lawless elements an opportunity to become the source of making "waste oil".