Oil-containing wastewater mainly comes from petroleum, petrochemical, iron and steel processing, coking, gas stations, machinery and other industrial sectors. Oil pollution substances in waste water, apart from the heavy tar relative density of 1.1 per cent, but rest of the relative density is less than 1.
Oil substances in waste water often exist in three States. (1) the floating oil, oil droplet size greater than 100 μ m, easily separated from the wastewater. (2) the dispersed oil. oil drops between the particle size of 101,100 μ m, Ken floating on the water. (3) oil, oil particle size less than 10 μ m, not easily separated from the wastewater. Due to different industrial oil concentrations in the wastewater sector vary greatly, such as oil refining waste water produced in the process, oil content of about 150 1000mg/L, tar in coking wastewater by about 500 800mg/L, tar content of gas generating station discharge waste water can be up to 2000 3000mg/L.
Therefore, oil-containing waste water treatment should first use of grease, oil or heavy oil recovery, address is 60% 80%, oil content in water is about 100 200mg/L: waste water emulsified oil and dispersed oil more difficult, should prevent or minimize emulsification. One is attention to reduce waste in the production process of the oil in the emulsion: second, is in the process, minimizing upgrade wastewater treatment so as not to increase the number of emulsification. Handling methods typically use flotation and demulsification.