In this work, the performance of electro-Fenton (EF) and electrocoagulation (EC) methods for safranin removal from wastewater in the presence of solar energy and ultrasonic waves was investigated. Experimental parameters were optimized by the response surface methodology (RSM). Under optimal conditions, the best removal% and chemical oxygen demand (COD) reduction were observed in the order of: sono-electro-Fenton (SEF) > electro-Fenton (EF) > sono-electrocoagulation (SEC) > electrocoagulation (EC) > ultrasonic. The removal% and reduction of COD for the SEF method were 99.9 and 85.7%, respectively. Comparison of electro- Fenton and electrocoagulation processes based on the speed and cost of 1 m3 wastewater treatment showed that EF was six times faster and its cost was one fifth of that of the EC processes. Examination of the ultrasonic waves shows that they have a positive effect on the removal (%) and COD (15% improvement) in all of the processes, although their efficiency alone was very low. Finally, the sono electro-Fenton process was selected based on performance, speed and cost. The combination of the solar electrical power generation system reduced the electrical cost by up to 2.8 times, especially in electrocoagulation techniques.
