The proportion of oil in the waste water is generally smaller than that of water, which is mainly existed in three states: Suspended state: Oil particles are large, oil beads are over 0.1 mm in diameter, floating on the water surface, and easy to separate from water. N petroleum industry, this kind of oil takes up about 60 ~ 80% of the oil content in waste water. Demulsification state: The dispersed particle size of oil is small, and the diameter of oil bead is less than 0.1 mm. This kind of oil accounts for about 10 ~ 15% of the waste water oil content. The solubility of oil in water is minimal, and the soluble oil accounts for 0.2-0.5% of the oil content in waste water.
The purpose of separation is achieved by using the proportion of suspended matter and water in the waste water. The grease trap basin is constructed in the form of flat flow. Oily waste water enters into the oil separation tank with rectangular plane through the distribution flume and flows slowly along the horizontal direction. The oil floating on the water surface in the flow is pushed to the oil separation tank by the grease interceptor or the oil scraper arranged on the surface of the pool. Heavy oil and other impurities deposited in the grease trap accumulate in the sludge hopper at the bottom of the pond and enter into the sludge pipe through the mud pipe. Oil waste water that has been treated by oil separation flows into drainage channels and out of the pool for subsequent treatment to remove emulsified oil and other contaminants.