Study On The Treatment Of Electric Desalting Wastewater From A Refinery In Shandong

In this paper, the electric desalting wastewater was pretreated by coagulation, then the wastewater was treated by Fenton reagent and O3/H2O2 oxidation process respectively, and the two methods were compared to determine the suitable method.In the coagulation experiment, the effects of PAC dosage, pH value, temperature, the type and dosage of PAM on coagulation were studied. The coagulation conditions were optimized through orthogonal test. The results showed that the optimum coagulation conditions: PAC dosage was 200mg/L, cationic PAM dosage was 0.75mg/L, pH value was 8.00 and the temperature was 50℃. Under the optimum coagulation condition, the removal rates of turbidity, color, COD, TOC, and?NH3-N were 96.34%, 62.50%, 33.93%, 32.47% and 28.40% respectively.After coagulation treatment, the electric desalting wastewater was treated by Fenton reagent. The effects of pH value, H2O2 dosage, FeSO4 dosage, reaction time and the adding method of Fenton reagent were studied, and reaction kinetics on treatment of electric desalting wastewater by Fenton reagent was investigated. The result showed that the optimum conditions: the pH=3.00, 50.00mmol/L of H2O2 dosage, 5.00mmol/L of FeSO4 dosage, with 120min reaction time and the Fenton reagent added for five times. Under these optimum conditions, the removal rates of COD, TOC, NH3-N, turbidity and color reached 87.52%, 88.17%, 59.58%, 44.42% and 80.95% respectively. Except the pH value, the efflent quality reached the tertiary discharge standards. The kinetic study showed that the removal of COD by Fenton reagent was in accordance with the first-order kinetic model, and the reaction rate constant was 0.0176min-1.After coagulation treatment, the electric desalting wastewater was treated by O3/H2O2 process. The effects of pH value, ozone flow, reaction time and H2O2 dosage on treatment of electric desalting wastewater were studied. The reaction mechanism and kinetics on treatment of electric desalting wastewater were also discussed. The result showed that the optimum conditions were as follows: pH was 9.00, ozone flow was 4g/h, the reaction time was 90min and H2O2 dosage was 15.00mmol/L. Under the optimum conditions, the removal rates of COD, color, TOC, NH3-N and turbidity were up to 97.85%, 99.05%, 98.10%, 90.51% and 90.13%respectively, the effluent quality reached the primary discharge standards. The reaction mechanism suggested that the removal rate of COD was deceased with the increasing of the radical inhibitors concentration, the removal of COD was mainly owing to hydroxyl free radical produced by O3/H2O2 process. The kinetic study showed that the removal of COD was in accordance with the first-order kinetic model, and the reaction rate constant was 0.0434min-1.Compared the coagulation-Fenton reagent with the coagulation-O3/H2O2, the latter by which the effluent quality reached the primary discharge standards was selected, this provided some basis for the treatment of such wastewater.