Landfill leachate pretreatment by biocoagulation/bioflocculation process using plant-based coagulant (optimization by response surface methodology)

Landfill leachate contains persistent organic pollutants, and therefore, it must be treated before it is released into natural water courses. The present study, reports on investigations about the removal efficiencies of turbidity, chemical oxygen demand (COD) and phenols from leachate using a biocoagulant/bioflocculent (cactus cladode) as well as the volume of generated sludge. The experimental variables (pH and coagulant dosage) were optimized by applying response surface methodology (RSM) equipped with the central composite faced design. An empirical quadratic polynomial model can accurately model the surface response with R-2 values greater than 92% for all the responses. The results of confirmatory experiments correspond to the model predictions, which demonstrate that RSM can achieve good predictions with the least number of required experiments. Results showed that the reduction efficiencies for turbidity, COD and phenols at pH 2 and cactus dosage of 1.48 g L-1 were, respectively, 93.25%, 66.50% and 52.95%, to achieve final values of 8.1 NTU, 2,251.2 and 611.65 mg L-1 for turbidity, COD and phenols, respectively. Generated sludge volume was 200 mL at optimum conditions. Cactus dosage and pH variation have a significant effect on pollution reduction in leachate.