Document Type : Original Article


Department of Environmental Engineering, School of Environment, College of Engineering, University of Tehran, Tehran, Iran


Oil refinery is one of the industrial centers and its wastewater has a lot of environmental pollutants which are a serious threat to the environment and water resources. In this study, an electrocoagulation reactor was used to remove and reduce the amount of Chemical Oxygen Demand (COD) in the wastewater from the API unit of the Shazand Oil Refinery in Arak, which is a gravity separator of water and oil.
Material and methods:
In order to simulate the electrocoagulation process in experimental conditions, a 15 × 14 × 13 cm Plexiglas pilot was designed, in which six 10 × 12 cm aluminum electrodes with a thickness of 2 mm were put as sacrificial electrodes during the process. The distance between the electrodes was 2 cm. The monopolar arrangement was selected for electrodes. At each stage of the experiment, after measuring the pH and COD of the initial wastewater, the volume of 2 L was poured out as an internal sample into the coagulation reactor; after the electrochemical process, the secondary pH and COD were measured to determine the effect of the electrocoagulation process.
Results and discussion:
In this research, the effect of time, pH, and voltage in the electro-flocculation process has been evaluated. The amount of COD, pH, and lead were measured 450 mg/L, 5.5 and 5.27 mg/L in initial wastewater, respectively. To avoid the overlapping effect of time, pH, and voltage during the process, the value of one of the parameters was changed and two other parameters were kept constant and the optimum value was determined. In order to minimize the errors during the testing process, each step has been repeated three times. After performing different stages of the test and collecting and analyzing the results, the optimum time of the test, optimum pH, and optimum voltage were considered as 90 min, 6 and 30 V, respectively. Consequently, the COD decreased from 450 to 193 mg/L and 99.05% of lead was removed. The results of the experiments showed that by increasing the duration of electrolysis, the removal rate also increases. The results of other research also showed that the flow density is directly related to the reaction time, and by increasing the time, more removal rate can be obtained. As the results demonstrate, the removal rate is directly related to the applied voltage, which is due to the more production of aluminum hydroxides in the wastewater, which plays the role of coagulant. In previous studies, the results also indicated an increase in the removal rate of pollutants by increasing the applied voltage. The pH also had an important effect on the results. At low pH values, cationic monomeric species such as Al3+ and Al(OH)2+ were obtained from the dissolution of the aluminum anode. On the other hand, with the excessive increase in the pH of the solution, such compounds as Al(OH)4- were formed, which caused disruption and sluggishness in the removal process.
The results of this study showed that aluminum hydroxides as coagulants, which are produced by the electrochemical dissolution of the sacrificial electrodes, play a major role in the pollutant removal process. The higher their production rates, the more removal will occur. To do this, the optimal parameters for producing them should be optimally set. By increasing the electrolysis time, the amount of aluminum hydroxides also increases. Also, adjusting the pH of the solution at an appropriate range provides optimum conditions for the production and formation of gelatin aluminum hydroxide polymer.


  1. Paykari, M., Karbasian, A., 2004, Water Examinations, Published by Arkan, 5-50.
  2. Attour, A., Touati, M., Tlili, M., Ben Amor, M., Lapicque, F. and Leclerc, J.P., 2014. Influence of Operating Parameters on Phosphate Removal from Water by Electrocoagulation Using Aluminum Electrodes. Separation and Purification Technology. 123, 124-129.
  3. Baird, R.B., Eaton, A.D. and Rice, E.W., 2017. Standard Methods for the Examination of Water and Wastewater, Prepared and published jointly by American public health association, American water works association, Water environment federation, 23rd Edition.
  4. Bazrafshan, E., Alipour, M.R. and Mahvi, A.H., 2015. Textile Wastewater Treatment by Application of Combined Chemical Coagulation, Electrocoagulation, and Adsorption Processes. Desalination and Water Treatment. 57(20), 1-13.
  5. Cherifi, M., Hazourli, S., Pontvianne, S., Lapicque, F. and Leclerc, J.P., 2016. Electrokinetic Removal of Aluminum and Chromium from Industrial Wastewater Electrocoagulation Treatment Sludge. Desalination and Water Treatment. 57(39), 18500-18515.
  6. Cook, M.M., Symonds, E.M., Gerber, B., Hoare, A., Van Vleet,E.S. and Breitbart, M., 2016. Removal of Six Estrogenic Endocrine-Disrupting Compounds (Edcs) from Municipal Wastewater Using Aluminum Electrocoagulation. Water. 8(128), 1-15.
  7. Deghles, A. and Kurt, U., 2016. Treatment of Raw Tannery Wastewater by Electrocoagulation Technique: Optimization of Effective Parameters Using Taguchi Method. Desalination and Water Treatment. 57(32), 14798-14809.
  8. Demirbas, E. and Kobya, M., 2017. Operating Cost and Treatment of Metalworking Fluid Wastewater by Chemical Coagulation and Electrocoagulation Processes. Process Safety and Environmental Protection. 105, 79-90.
  9. Elabbas, S, Ouazzani, N., Mandi, L., Berrekhis, F., Perdicakis, M., Pontvianne, S., Pons, M.N., Lapicque, F. and Leclerc, J.P., 2016. Treatment of Highly Concentrated Tannery Wastewater Using Electrocoagulation: Influence of the Quality of Aluminium Used for the Electrode. Journal of Hazardous Materials. 319, 69-77.
  10. El-Naas, M.H., Surkatti, R. and Al-Zuhair, S., 2016. Petroleum Refinery Wastewater Treatment: A Pilot Scale Study. Journal of Water Process Engineering. 14, 71-76.
  11. Eyvaz, M., 2016. Treatment of Brewery Wastewater with Electrocoagulation: Improving the Process Performance by Using Alternating Pulse Current. International Journal of Electrochemical Science. 11(6), 4988-5008.
  12. Fouad, Y.O., 2014. Separation of Cottonseed Oil from Oil–Water Emulsions Using Electrocoagulation Technique. Alexandria Engineering Journal. 53(1), 199-204.
  13. Gatsios, E., Hahladakis, J.N. and Gidarakos, E., 2015. Optimization of Electrocoagulation (Ec) Process for the Purification of a Real Industrial Wastewater from Toxic Metals. Journal of Environmental Management. 154, 117-127.
  14. Gong, C., Shen, G., Huang, H., He, P., Zhang, Z. and Ma, B., 2017. Removal and Transformation of Polycyclic Aromatic Hydrocarbons During Electrocoagulation Treatment of an Industrial Wastewater. Chemosphere. 168, 58-64.
  15. Gupta, V., Mazumdar, B. and Acharya, N., 2017. COD and Colour Reduction of Sugar Industry Effluent by Electrochemical Treatment. International Journal of Energy Technology and Policy. 13(1-2), 177-187.
  16. Ibrahim, M.M., Jaddo, I.A., 2013, Removal of Some Hydrocarbon Pollutants from Baiji Oil Refinery Wastewater Using Granular Activated Carbon Column, Tikrit Journal of Engineering Sciences, 20(7), 84-95.
  17. Kausley, S.B., Malhotra, C.P. and Pandit, A.B., 2017. Treatment and Reuse of Shale Gas Wastewater: Electrocoagulation System for Enhanced Removal of Organic Contamination and Scale Causing Divalent Cations. Journal of Water Process Engineering. 16, 149-162.
  18. Kobya, M., Gengec, E. and Demirbas, E., 2016. Operating Parameters and Costs Assessments of a Real Dyehouse Wastewater Effluent Treated by a Continuous Electrocoagulation Process. Chemical Engineering and Processing: Process Intensification. 101, 87-100.
  19. Liu, Y.H., Lin, C.Y., Huang, J.H. and Yen, S.C., 2016. Particle Removal Performance and Its Kinetic Behavior During Oxide-CMP Wastewater Treatment by Electrocoagulation. Journal of the Taiwan Institute of Chemical Engineers. 60, 520-524.
  20. Llanos, J., Cotillas, S., Canizares, P. and Rodrigo. M.A., 2017. Electrocoagulation as a Key Technique in the Integrated Urban Water Cycle–a Case Study in the Centre of Spain. Urban Water Journal. 14(6), 650-654.
  21. Lobo, F.L., Wang, H., Huggins, T., Rosenblum, J., Linden, K.G. and Ren, Z.J., 2016. Low-Energy Hydraulic Fracturing Wastewater Treatment Via AC Powered Electrocoagulation with Biochar. Journal of Hazardous Materials. 309, 180-184.
  22. Ma, S.S. and Zhang, Y.G., 2016. Electrolytic Removal of Alizarin Red S by Fe/Al Composite Hydrogel Electrode for Electrocoagulation toward a New Wastewater Treatment. Environmental Science and Pollution Research. 23(22), 22771-22782.
  23. Moussa, D.T., El-Naas, M.H., Nasser, M. and Al-Marri, M.J., 2017. A Comprehensive Review of Electrocoagulation for Water Treatment: Potentials and Challenges. Journal of Environmental Management. 186(1), 24-41.
  24. Naje, A.S., Chelliapan, S., Zakaria, Z. and Abbas, S.A., 2016a. Electrocoagulation Using a Rotated Anode: A Novel Reactor Design for Textile Wastewater Treatment. Journal of Environmental Management. 176, 34-44.
  25. Naje, A.S., Chelliapan,S., Zakaria, Z., Ajeel, M.A., Sopian, K. and Hasan, H.A., 2016b. Electrocoagulation by Solar Energy Feed for Textile Wastewater Treatment Including Mechanism and Hydrogen Production Using a Novel Reactor Design with a Rotating Anode. RSC Advances. 6(12), 10192-10204.
  26. Perez, L.S., Rodriguez, O.M., Reyna, S., Sanchez-Salas, J.L., Lozada, J.D., Quiroz, M.A. and Bandala, E.R., 2016. Oil Refinery Wastewater Treatment Using Coupled Electrocoagulation and Fixed Film Biological Processes. Physics and Chemistry of the Earth, Parts A/B/C. 91, 53-60.
  27. Pinedo-Hernandez, J., Paternina-Uribe, R. and Marrugo-Negrete, J., 2016. Alternative Electrocoagulation for Livestock Wastewater Treatment. Portugaliae Electrochimica Acta. 34(4), 277-285.
  28. Prica, M., Adamovic,S., Dalmacija, B., Rajic, L., Trickovic, J., Rapajic, S. and Becelic-Tomin, M., 2015. The Electrocoagulation/Flotation Study: The Removal of Heavy Metals from the Waste Fountain Solution. Process Safety and Environmental Protection. 94, 262-273.
  29. Teh, C.Y., Budiman, P.M., Pui Yee Shak, K. and Wu, T.Y., 2016. Recent Advancement of Coagulation–Flocculation and Its Application in Wastewater Treatment. Industrial & Engineering Chemistry Research. 55(16), 4363-4389.
  30. Thirugnanasambandham, K., Sivakumar, V. and Shine, K., 2016. Studies on Treatment of Egg Processing Industry Wastewater Using Electrocoagulation Method: Optimization Using Response Surface Methodology. Desalination and Water Treatment. 57( 46), 21721-21729.
  31. Tian, Y., He, W., Zhu, X., Yang, W., Ren, N. and Logan, B.E., 2016. Energy Efficient Electrocoagulation Using an Air-Breathing Cathode to Remove Nutrients from Wastewater. Chemical Engineering Journal. 292, 308-314.
  32. Truttim, P. and Sohsalam, P., 2016. Comparison of Electrocoagulation Using Iron and Aluminium Electrodes for Biogas Production Wastewater Treatment. Journal of Advances in Technology and Engineering Research. 2(2), 35-40.
  33. Ye, S. and Li, N., 2016. Comparison of Electrochemical Treatment of Petroleum Refinery Effluents Using Electrooxidation, Electrocoagulation and Electrophenton Process. International Journal of Electrochemical Science. 11(7), 6173-6182.