Modeling and optimization of oil refinery wastewater chemical oxygen demand removal in dissolved air flotation system by response surface methodology

In this present study the dissolved air flotation (DAF) system was investigated for the treatment of Kermanshah Oil Refinery wastewater. The effect of three parameters on flotation efficiency including of flow rate (outflow from the flotation tank), saturation pressure and coagulant dosage on chemical oxygen demand (COD) removal was examined experimentally. All the experiments were done under a certain time (in this case 3 min). After final testing maximum COD removal efficiency was obtained 67.86%. In the next step of study, response surface method (RSM) was applied to model oil refinery wastewater COD removal as a function of flow rate, saturation pressure and coagulant dosage. Coefficient of determination, R2, showed that the RSM model can explain the variation with the accuracy of 0.996, indicating there was strong correlation. Moreover, process optimization were performed to predict the best operating conditions using RSM method, which resulted in the maximum COD removal of the oil refinery wastewater. The maximum COD removal of oil refinery wastewater was estimated by RSM to be 67.87% under the operational conditions of flow rate (3.76 – 3.86 L/min), saturation pressure (4.99 - 5bar) and coagulant dosage (24.16 – 24.79 mg/L).