Removal of oil and grease from vegetable oil refinery wastewaters by coagulation-flocculation process

Abstract

Due to the various industrial uses of oil and grease, the water pollution by these materials becomes more increasingly a serious problem. It is then a great necessity to find an efficient method leading to the removal of the oil and grease from the polluted waters. Attempts are made in the present work to examine the effectiveness of the coagulation process by using ferric chloride as a coagulant for the treatment of vegetable oil refinery wastewater. Thus, the decrease or the removal of various wastewater characteristics such as the organic matter amount expressed as chemical oxygen demand (COD), the aqueous solution turbidity and the oil and grease, using ferric chloride during coagulation process were investigated. Also, the optimum conditions leading to efficient coagulation were achieved by varying the coagulant dosage and the pH of the aqueous solution and by using jar test experiments. The results revealed that in the range of pH investigated, the optimal operating pH was found to be equal to 5. Further, the highest values for the COD (removal of organic matter), the removal of turbidity, and the removal of the oil and grease, from the wastewater, were found to be, respectively, 96%, 92%, and 99%. Theses values were achieved by the addition of 700 mg/L FeCl 3 ·6H 2 O to the wastewater. Therefore, it can be concluded that the coagulation method that we developed in the present work, is useful for the pre-treatment process for vegetable oil refinery wastewater prior to biological treatment.