Study On Treatment Technology Of High COD Oily Wastewater

The composition of the wastewater from oil tank is complex. It is the refractory organic wastewater with high COD content. The COD value is an important target which reflects the extent of the wastewater that is polluted by the reducible substances, especially by the organic substances. The government imposes stringent stipulations of the COD content in different sewage.In this paper, the sewage which is used in this experiment is from oil tank. Its COD value is between 120000mg/L~1280000mg/L. It is difficult to be biodegraded. For these features, three methods are used to treat the wastewater in this paper: ClO2 (chlorine dioxide) catalytic oxidation, flocculating settling technology and electrolytic method. By the static experiments of the ClO2 catalytic oxidation, the optimum conditions are worked out: oxidation dosage (1%ClO2) is 60ml/L, reaction time is 3 hours; catalyst dosage is 150g/L, and aeration is work properly. In the optimum operation conditions, the COD value of the wastewater decreases to 60800mg/L, and the removing rate is 50.97%.After the ClO2 catalytic oxidation reaction, the wastewater is treated by the flocculating settling technology. When addition of the cationic PAM C5015 increases to 400mg/L with 2 hours'holding time, the COD value is 48640mg/L, the total COD removing rate is 60.77%. In order to further improve the wastewater removal rate, electrolytic method is used to treat the sewage which has been treated by the ClO2 catalytic oxidation reaction. The reaction condition is worked out as follows: the electric currency density is 40mA/cm2, the plate distance is 2cm, the reaction time is 120min.Then the wastewater is disposed with flocculating settling technology. After these processes, the COD is 19840mg/L, and the COD removing rate is 84%.Based on these static experiments, the dynamic experiment system is designed. The reaction time is controlled by regulating the inflow. The optimum conditions of the dynamic experiment are the list: the reaction time of ClO2 catalytic oxidation is 3 hours, the oxidation dosage is 100ml/L, and electrolysis treatment time is 100min. The extracted wastewater is treated by flocculating settling technology. Then the COD value is 28160mg/L, and the COD removing rate is 77.29%.The successful of the dynamic experiment system proves that the combination of several treatment methods is feasible in practice.