Pretreatment of industrial wastewater by natural flotation: application to pollution reduction from vegetable oil refinery wastewaters.

Abstract

The objective of this study is to evaluate the effectiveness of the natural flotation process in reducing pollution with reasonable investment and operating costs of an industrial effluent of refining vegetable oils. Flotation tests were carried out in separating funnels and in drums of 30 l. The results obtained have shown that the volume of sludge produced during flotation is related to the pollutant load of the wastewater studied (process wastewater and acidic wastewater). The sludge volume is respectively 600, 12, and 120 ml/l for heavy, light, and medium loads respectively. Therefore, it is essential to find an effective way to remove oils and greases from polluted waters. Natural flotation eliminates on average 88% of COD for acid wastewater and 50% for process wastewater. However, the reduction of BOD5 showed 28 and 43% respectively for acid wastewater and process wastewater. In addition, the yield of fats and oils, TSS, and turbidity varies around 85%, 45%, and 88% respectively for acidic wastewater, while for process wastewater, elimination yields vary around 58%, 46%, and 46% respectively for the grease and oil parameters, the MES, and the turbidity. Flotation allows the elimination of 10659 Kg/day of greases and oils for process wastewater while it eliminates 5765 Kg/day for acidic wastewater. This reduces the cost of treatment related to chemicals and energy. Reducing pollution of wastewater by natural flotation could therefore help reduce the costs of treating wastewater, and recycling would then be more attractive for this purpose for the company.