Open Access ISSN: 2165-784X Journal of Civil & Environmental Engineering Research Article Volume 11:6, 2021 Abstract In this research the electrocoagulation method was implemented in order to study the treatment of the spent caustic effluent from an olefin plant. To optimize the process parameters, Taguchi method was used, and the optimal conditions were found for pH of 6, current density of 35 mA/cm 2 , and treatment time at 40 minutes. The experimental results show that the final efficiency in case of reducing the amount of COD is around 89% under optimum operating conditions and pH has the most significant impact on the process with contribution factor of 79.10%. According to results of XRD and XRF analysis, the sludge behavior is very similar to that of sodium sulfate that is important for its value chain. The study results showed that the electrocoagulation method could be used a complimentary facility to reduce the amount of COD of Spent Caustic from an Olefin Plant. Keywords: Spent caustic • Electrocoagulation • Ethylene plant • Wastewater treatment Abbreviations: SC: Spent Caustic • COD: Chemical Oxygen Demand • WAO: Wet Air Oxidation • AOP: Advance Oxidation Process • TOC: Total Organic Carbon • EC: Electrocoagulation • BOD: Biological Oxygen Demand • XRD: X-Ray Diffraction • XRF: X-Ray Fluorescence • S/N: Signal to Noise Ratio • SS: Sum of Square • DC: Current Density. Application of Electrocoagulation in Treatment of Spent Caustic from Olefin Plants Honarvar E, Bolhasani A, Karamian S, Hosseini S, and Rashedi R Jam Research and Development Center, Jam Petrochemical Complex, Bushehr, Iran *Address for Correspondence: Ehsan Honarvar, Jam Research and Development Center, Jam Petrochemical Complex, Bushehr, Iran, E-mail: ehsan_honarvar_86@yahoo.com Copyright: © 2021 Honarvar E, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received 13 May, 2021; Accepted 22 June, 2021; Published 30 June, 2021 Introduction Spent caustic is a type of injurious liquid waste byproduct, generated from hydrocarbon washing for elimination of acid gases components from hydrocarbon streams in olefin plants and other petroleum refineries [1]. The US Resource Conservation and Recovery Act classified It as harmfully industrial waste [2]. In this regards, it requires special handling and disposal before being released for conventional treatment with respect to sustainability and water security. To conform to the standards of wastes in the receiving medium, several attempts were developed for spent caustic treatment. One practical treatment method is the use of the wet air oxidation (WAO) reactor [3,4]. In this process, the reaction condition is often up to 300°C and 200 bar which makes this process very expensive while due to the sever operating condition, safety is a major concern [5]. Another commonly industrial process established by some technology providers includes neutralization with acids followed by stripping [6]. This process consumes large amount of acids to quench caustic which in fact are not easy handling due to the polymer agglomeration, occasionally observed in degassing vessel. Furthermore, in olefin plants, composition of the liquid feedstock responsible for altering the pyrolysis reaction and the concentration of the sulfur compounds that consequently could contribute to the disturbance in controlling the chemical oxygen demand (COD) of the effluent from the caustic wash tower [7]. Incineration is another available choice for spent caustic treatment; however, despite being a reliable and efficient operation, the energy requirement remains a big problem in this process [8]. Other techniques were also used including but not limited to the biological treatment, crystallization, chemical oxidation and precipitation [5]. Considering the above, each method has its limitation due to their kinetics, effectiveness, cost, safety and secondary pollution [9,10]. However, interest in electrocoagulation (EC), that is the subject of this study, is growing as a promising alternative as it poses benefits that eliminate the weaknesses of the traditional methods [11]. In this regards, the EC process characterized by in-situ generation of coagulants with no helps of chemical additives which in turns prevents the generation of secondary pollutants. Simple equipment and easy operation, short treatment time and also the ability to remove very fine particles are among the other benefits of the EC technology [12]. Because of these advantages, electrocoagulation has been used for treatment of different types of wastewater from petroleum refineries [13] and other industries [11-15]. Among researchers, Hariz et al. [13] has investigated treatment of refinery spent caustic using the electrocoagulation technique. However, despite to the impressive amount of research on the application of the electrocoagulation for treatment of various types of wastewater, a few researchers have been done on treatment of spent caustic from petrochemical plants. The main objective of the present study, therefore, is to introduce a new approach to increase the efficiency of spent caustic treatment from olefin plant by applying the electrocoagulation technique in series with existing neutralization and stripping facilities. In this regards, the evaluation was performed in one litter laboratory scale reactor while Minitab software and Taguchi method were used to design the experiments for determining the effects of PH, time, current density and distance between the electrodes on efficiency of the electrocoagulation process. The produced sludge was separate from the effluent, and the COD was measured to monitor the effectiveness of spent caustic treatment [16-18]. Research Methodology Samples for spent caustic were collected from the olefin plant in Jam Petrochemical Company that manufactures various products such as ethylene and propylene under the license of Technip. Average analysis of these samples is given in Table 1. As it is shown, this wastewater has a very high COD that makes it difficult to be treated by the biological methods that is usually placed after the initial neutralization and stripping facilities, outside of the olefin plants. The electrocoagulation technique, explained by Ville Kuokkanen [19], was used to treat effluent. In this regards, the experiments were carried in an electrochemical cell with total volume of 1000 ml. In each experiment, 500 ml of spent caustic was treated in the cell. Iron electrodes were chosen because of their lower price than other electrodes such as aluminum while it is also more effective than aluminum in reducing the COD of industrial wastewater [20]. The