The so-called grease trap is a special equipment to separate grease, sundries and moisture from the wastewater discharged from the canteen. But when you buy it back, it's a finished product, usually stainless steel and carbon steel. Can be buried underground, can also be buried in the ground.

The oil separation tank is a self-built tank with brick concrete structure, and its inner surface needs waterproof and anti-corrosion treatment. Usually underground.