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.
