Water Quality Characteristics
Oil wastewater mainly comes from the water washing beans before processing, oil washing wastewater, the water for washing the machine and floor in the workshops, domestic sewage etc. Oil wastewater is mainly generated during the refining process of vegetable oil, which has complicated contents, mainly including substances such as saponin, phospholipids, protein, oil and pigments as well as a large amount of pollutants such as SS, vegetable oil, COD and BOD. If it is directly discharged, it will cause severe pollution, it generally does not contain heavy metal or toxic chemical substances, the wastewater has rich protein and oil, and it’s typical high-concentration organic wastewater.

Thought for Treatment
In the plant area, the wastewater enters the pretreatment grille ditch after having the floating objects retained by the drainage pipe network, then it enters the flat streaming grease trap where most floating oil and suspended substances are removed, and then it flows to the regulation tank. Design of the regulation tank should consider the anaerobic zone and the facultative anaerobic zone, which not only have the homogeneity and volume balance effect but also the function of sludge digestion and pretreatment of the wastewater; then, the wastewater is lifted to the flotation tank through the lift pump, where most emulsified oil and suspended substances are removed from the water; after flotation, the water flows into the high-efficiency biological contact aeration basin, where second-stage aerobic biochemical treatment is conducted; the effluent has solid-liquid separation through the sedimentation tank to reach the discharge standard; part of the sludge flows back, part of it is delivered out after concentration and dehydration, and the supernatant flows back to the regulation tank.

Typical Treatment Process
In accordance with the characteristics of the high-concentration organic wastewater, the comprehensive treatment process of oil removal + floatation + biological contact aeration is adopted.