Advances in Treatment of Vegetable Oil Refining Wastes

Vegetable oils are mainly extracted from soybean, sesame, sunflower, corn, canola, and cotton seeds. Their yields, compositions, and physical and chemical properties determine their usefulness in various applications aside from edible uses. Crude oils obtained by pressing of such vegetable seeds are not usually considered to be edible before the removal of various nonglyceride compounds through an operation known as refining. The vegetable oil refinery uses various types of physical and chemical processes to offer a premium quality of oil. The refining processes remove undesirable materials, such as phospholipids, monoacylglycerols, diacylglycerols, free fatty acids, color and pigments, oxidized materials, etc., but may also remove valuable minor components, such as antioxidants and vitamins (carotenes and tocopherols). The major steps involved in chemical refining include degumming, deacidification, deodorization, and neutralization processes. During these processes, a high amount of water is used, and highly polluted effluents are formed. The treatment of vegetable oil refinery wastewaters has been a major problem of environmental concern in developing countries for the last decades due to their complex nature consisting of water and soluble and insoluble substances that contain fats and oil, carbohydrates, phenolic compounds, and suspended solids. Therefore, a suitable wastewater treatment prior to their discharge into the receiving bodies is required. Numerous treatment technologies have been applied to treat oily wastewaters. Coagulation/flocculation, electrocoagulation, reverse osmosis, flocculation/membrane filtration, air flotation, microfiltration, and enzymatic catalysis are the most common ones. However, due to the complex nature and low biodegradability of the oily wastewater, some of these technologies may not be efficient in treating such wastewaters, while others may be of high cost and generally require a pretreatment. As a result, in this chapter, the processes involved in the vegetable oil refining, the environmental impacts of those processes, the characterization of the waste produced during the processes, waste reduction at source, recovery from waste, and treatment technologies are discussed.