ELECTROCHEMICAL RECLAMATION OF WASTEWATER RESULTED FROM PETROLEUM TANKER TRUCK CLEANING

Abstract

Petroleum tanker trucks are integral vehicles for delivering fuel and other petrochemical products from place to place and must be cleaned regularly. Pressure washing with hot or cold water serving to remove oil and filth from the tanker truck container, produces oily waste water with an oil concentration of about 300-500 mg L -1 which, according to environmental standards and regulations worldwide, must be disposed of and treated properly. In the present paper an integrated electrochemical treatment for oily wastewater reclamation is presented comprising a) the electrocoagulation process with sacrificial iron and aluminum electrodes, b) the electrooxidation process with platinized titanium (Ti/Pt) and boron doped diamond (BDD) electrodes and c) the electro-Fenton process with iron electrodes and added hydrogen hydroxide. A simulated oil tanker truck washing wastewater was prepared by mixing heating oil with fresh water and separating the aqueous from the oily phase in a separation funnel. The COD of the obtained oily wastewater was 456 mg L -1 . The effect of crucial parameters on oil removal, such as pH, applied current density, initial oil concentration and electro-processing time was explored. During the electrocoagulation treatment at the current density of 5 mA cm 2 using iron and aluminum electrodes, COD was only partially removed by 8 and 11% respectively. The COD removal could drastically be increased exceeding 80 % by performing the electrocoagulation process after initial addition of the surfactant sodium dodecyle sulfate. The electro-oxidation process with platinized titanium (Ti/Pt) and boron doped diamond (BDD) electrodes at the applied current density of 20 mA/cm 2 reduces COD to 15 and 36 % at 25 0 C and to 28 and >98 % at 60 0 C respectively. Finally the electro-Fenton process with Fe electrodes and supplied H 2O2 in acidic solution at the applied current densities of 5 and 10 mA cm 2 , led to a COD reduction beyond 90% in only a few minutes of electro-processing time.