Treatment of cheese whey wastewater by electrochemical oxidation using BDD, Ti/RuO2-TiO2, and Ti/RuO2-IrO2-Pt anodes: ecotoxicological and energetic evaluation

The effectiveness of boron-doped diamond (BDD) and titanium metal-mixed oxides (Ti/MMO: Ti/RuO₂-TiO₂ and Ti/RuO₂-IrO₂-Pt) anodes to treat cheese whey wastewater (CWW) by electrochemical oxidation (EO) was evaluated. The results show that EO with BDD is effective in the removal of organic compounds. Conversely, Ti/MMO anodes exhibit higher removals of nitrogenated compounds. After 8 h of EO treatment at an applied current density of 500 A m^-2, the biodegradability index increased from 0.55 to 0.81 with the BDD anode, while with Ti/MMO only reached 0.64. The acute toxicity of the CWW, before and after treatment, was assessed with the model organism Daphnia magna. The use of BDD showed favorable outcomes, leading to a reduction in ecotoxicity, which changed the CWW classification from "very toxic" to "toxic," very close to the "non-toxic" level. Contrarywise, the use of Ti/MMO anodes led to an escalation of potentially harmful substances in the treated effluent. Still, Ti/MMO anodes provide the most favorable energy consumption when operating at current densities equal to or below 100 A m^-2. While both Ti/RuO₂-TiO₂ and Ti/RuO₂-IrO₂-Pt exhibit similar performance, the effectiveness of Ti/RuO₂-TiO₂ is somewhat lower.