Oil and grease removal from thermal power plant effluent using electrocoagulation

Abstract

The fuel oil used in thermal power plants mainly falls into the category of low grade fuel such as Heavy Fuel Oil (HFO). They cannot be readily burnt in engines of thermal power generation and need to be further refined. They are refined at the power plant itself. The outcome of this refining process is wastewater rich in heavy oil particles. This has an enormous impact on the country's environment, thus cannot be readily discharged into the environment. Therefore, this study was mainly focused to investigate a scientifically based and an economically viable solution to removal of the oily wastewater. In this case, application of the novel and emerging technique "Electrocoagulation (EC)" for the treatment of oily wastewater generated in thermal power plants was tried out. This technique has been tested successfully for several wastewater treatment solutions in the world (Appendix). However, it has to be noted that EC method has been applied for only a few applications of oily wastewater treatments. In this study, a laboratory scale EC reactor was made using a glass beaker as shown in Fig: 3.1) and results so obtained would help to design an industrial scale EC reactor. Different operation parameters such as influent pH, current density, initial oil concentration and electrode material were examined. During this examination, effect of one parameter for electrocoagulation was studied keeping the other parameters constant. For example, effect of pH on the electrocoagulation was studied keeping the other parameters such as current density, type of electrode material, and initial concentration of the oily wastewater constant. Further, effect of pH on electrocoagulation was examined by using range of.pl-l from 2 to 12, effect of current density was evaluated by varying 2.33 mA/cm2 to 46.8 mA/cm2, effect of initial concentration of oily wastewater was varied from 66 mg/L to 419 mg/L and effect of type of electrodes material was investigated using C and Al electrodes. In addition, performance of the method was mainly tested in terms of COD removal efficiency. The effect of pH on the performance of the method-was not significant in the range of pH - 4 and pH - 10. However, a sharp decrease of COD removal efficiency was not observed when pH was less than 4 and greater than 10. Optimal current density was found as 4.6mA/cm2 , and it was found that there was a little effect of initial oil concentration. Further, Aluminum was found as the most appropriate electrode for anode and there was no effect of cathode material on the efficiency of the EC method. According to the results, it appears that the Electrocoagulation method could be applied for oily wastewater treatment solution to obtain sustainable result