According to the density of oil substances, they are generally smaller than water. They can be divided into floatable oil, dispersed oil, emulsified oil, and dissolved oil based on their presence in water. Among them, floatable oil and dispersed oil have larger particle sizes and can be separated from water by the difference in specific gravity between oil and water. Wastewater flows into the pool from one end and flows through the pool body at a lower flow rate. During the flow process, oil particles with a density lower than water rise to the water surface, and water flows out from the other end of the pool. Install oil collection pipes on the upper part of the pool to collect floating oil and export it outside the pool. Emulsified oil cannot be directly removed by static settling. It needs to be demulsified first and converted into floatable oil before it can be removed. Dissolved oil is in a dissolved state in water and cannot be removed using an oil separator.