INVESTIGATING THE CORROSION EFFECT OF HIGH SALINITY OIL FIELD PRODUCED WATER ON METAL ELECTRODES FOR MICROBIAL FUEL CELLS

摘要

Produced water (PW) and oil field wastewater is the largest waste stream in the process of oil production. In some fields the generated PW can be as much as 10-20 times the extracted oil. The characteristic of PW vary considerably from one oilfield to the other, but in general PW contains light polar and aliphatic hydrocarbons, anions like chloride and sulphate, cations like sodium and potassium, production process compounds like corrosion and scale inhibitors, production solids like corrosion and scale products, and dissolved gases like H_2S and CO_2. Disposal of untreated PW to the environment in the past has caused serious soil and water pollution and that's why nowadays disposal of PW is subject to strict standards. If the purpose of PW treatment is to efficiently omit its dissolved hydrocarbon components, some methods like adsorption, chemical oxidation and biological treatment would be useful, among which biological treatment has the advantages of not generating a secondary waste stream, having low cost and being environmental friendly. In this research, Microbial Fuel Cell (MFC) technology has been selected as the biological method for treating a sample of high saline PW from an oilfield in Iran. The corrosion behaviour of some different materials that might be potentially used as the electrode of the MFC, means copper alloys (CuNi70/30 and aluminium brass), stainless steel (AISI 404) and carbon cloth, was investigated. The PW aggressiveness is mainly due to chloride and sulphate contents approaching those of the seawater. Oppositely, the hydrophobic nature of the oil dissolved in PW creates a complex environment, from the corrosion point of view. The monitoring of the free corrosion potential of each material, the determination of the linear polarization resistance and electrochemical impedance spectroscopy tests were performed at different redox-potential of the water (aerated and anaerobic condition). The target of the work is to find the better performing materials for the electrodes to be used in MFCs.