Response surface optimization of oil refinery wastewater treatment process

Abstract

In this paper, a laboratory dissolved air flotation (DAF) process was employed for the removal of chemical oxidation demand (COD), soap oil and grease (SOG), total suspended solids (TSS) and turbidity from oil refinery wastewater (ORW) using polyferric sulfate. The optimization was carried out by response surface methodology Box-Behnken design to evaluate the interactive effects of three main independent process parameters (pH, coagulant dosage and flotation time) on the removal of the COD, SOG, TSS, and turbidity. The quadratic model fitted very well with the experimental data at regression coefficients (R2) of values of 0.9986; 0.9992; 0.9847; 0.9858 for COD, SOG, TSS, and turbidity respectively. Under the optimum conditions of coagulant dose of 48 mgL-1, pH (5) and flotation time (17 min), the maximum removal of COD, SOG, TSS, and turbidity were 86%, 92%, 84% and 85% respectively were obtained. The removal efficiencies showed a high significance of the model correlations at 95% confidence level. This demonstrated that the addition of the polymeric sulfate can enhance the treatability performance of the ORW.