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What Are The Characteristics Of Oily Wastewater And How To Control It?
- Jul 04, 2018 -

What are the characteristics of oily wastewater and how to control it?


Oily wastewater mainly comes from petroleum, petrochemical, steel, coking, gas generating stations, mechanical processing and other industrial sectors. The oil-contaminated substances in the wastewater have a relative density of less than 1 except for the relative density of the heavy tar of 1.1 or more.


Oils are usually present in three states in wastewater. (1) Floating oil, the oil droplet size is larger than 100 μm, and is easily separated from the wastewater. (2) Dispersing oil. The oil droplets have a particle size of between 10 and 100 μm and float in water. (3) Emulsified oil, the oil droplets have a particle size of less than 10 μm and are not easily separated from the wastewater. Because the oil concentration in the wastewater discharged from different industrial sectors varies greatly, such as wastewater generated during the refining process, the oil content is about 150-1000 mg/L, and the tar content in the coking wastewater is about 500-800 mg/L. The tar content can reach 2000-3000mg/L.


Therefore, the treatment of oily wastewater should first use the grease trap to recover the oil or heavy oil. The treatment efficiency is 60% to 80%, and the oil content in the effluent is about 100-200mg/L: the emulsified oil and the dispersed oil in the wastewater are difficult. Treatment should prevent or mitigate emulsification. One of the methods is to reduce the emulsification of the oil in the wastewater during the production process. Second, in the process of treatment, the number of times of pumping wastewater is reduced as much as possible to avoid increasing the degree of emulsification. The treatment method usually uses air flotation and demulsification