Biodiesel wastewater treatment by coagulation-flocculation: Evaluation and optimization of operational parameters

Abstract

In this study the coagulation-flocculation process was evaluated as an alternative for treatment of biodiesel wastewater. The role of two coagulants, Al3+ and Fe3+, as well as its dosage, pH, treatment time, stirring and aeration were evaluated. It was observed that in the treatment using Al3+ the pH of the effluent (9.7) does not need to be adjusted, while for Fe3+ a previous adjustment to pH 5.0 was necessary. On the other hand, a high concentration of Al3+ (243 mg L-1) and a relatively long treatment time (70 min) were required to reach more than 96% of turbidity removal, when compared to the processing using Fe3+ (56 mg L-1 and 53 min), attributed to the formation of different mole fractions of hydrolyzed cationic species. Under the optimized conditions, more than 96% of turbidity, apparent color and suspended solids, and 82% of oil and fats were removed.