In this study, efficiency and cost of the Fenton, electro-Fenton, and biosorption processes for treatment of ariazol brown GR and indigo carmine dye mixture were compared. The Box-Behnken experimental design and response surface methodology (RSM) were used to optimize the process variables such as pH, [ Fe2+], [ H2O2], voltage, biosorbent dose, and time. Finally, the costs of 1 m3 wastewater treatment were calculated in optimal conditions. The operating costs for classical Fenton, electro- Fenton, and biosorption processes were 0.92, 0.48, and 0.13 US$ per 1 m3 wastewater, respectively. The efficiency of the Fenton and electro-Fenton processes for dye removal was similar, but the cost of the electro-Fenton method was half of the Fenton. Furthermore, the electro-Fenton was nine times faster than the Fenton. Efficiency of electro-Fenton was better than the biosorption process even if it is repeated four times with fresh biosorbent (total cost is the same as electro-Fenton). As a general conclusion, the electro-Fenton process is an appropriate choice based on speed and cost in wastewater treatment with respect to Fenton and biosorption processes.
