Optimization of electro-fenton parameters for phenol degradation in portable toilet wastewater: Advancing towards sustainability

Wastewater from portable toilets (WWPT) is characterized by a variety of recalcitrant chemical compounds such as phenols and organics that are difficult to treat by conventional methods. However, WWPT treatment is scarce in literature, especially with a focus on sustainability. In this study, the Electro-Fenton (EF) process was used to remove phenols and organics from WWPT and to analyze the toxicity of the effluent for water reuse purposes. The experimental design used response surface methodology to determine the occurrence of operating parameters such as hydrogen peroxide dose (100, 174, 200 g L⁻¹) and current density (10, 50, 90 A m⁻²). The experiments were performed in a 3 L reactor in batch mode. It was found that the optimum operating conditions were 187 g L⁻¹ and 90 A m⁻², which allowed obtaining an effluent pH of 7.4, TSS removal of 87.6 % (418 mg L⁻¹), chemical oxygen demand of 96.4 % (191.5 mg L⁻¹), biological oxygen demand of 98 % (87 mg L⁻¹), phenols with 98 % (0.15 mg L⁻¹) and germination index of 108.9 %. This showed that treated WWPT can be used for irrigation. In terms of cost, the treatment could be US$ 0.88 L⁻¹. Overall, the EF process is presented as a suitable process to treat WWPT and reduce the pollution load on the environment.