Comparative Evaluation of Anode Materials for Electrochemical Treatment of Anaerobic Digestate: Ammonia, Phosphorus, COD and Turbidity Removal

This study assessed the performance of five anode materials (Fe, stainless steel (SS), Al, Zn, and Ti/RuO2–IrO2) in terms of the removal of ammonia, phosphorus, and turbidity from anaerobic digestate using a single-cell hybrid electrocoagulation (EC)–electrooxidation (EO) system, which enabled the simultaneous evaluation of EC and EO processes under identical conditions. Experiments were conducted at a current density of 25 mA cm−2 and 0.5–1% NaCl. Al anodes showed the highest phosphorus (92%) and turbidity (85%) removal, through electrocoagulation, while ammonia removal remained limited (24%). In contrast, Ti/RuO2–IrO2 anodes achieved high ammonia removal (up to 86% at 1% NaCl) via EO, but lower phosphorus and turbidity removal (≤61%). SS and Fe anodes provided moderate and comparable nutrient removal (≈52% P, 68% turbidity, and 32–37% ammonia), whereas Zn anodes were less effective, with selective removal (70%) in P in1 h but limited ammonia and turbidity removal. Ti/RuO2–IrO2 demonstrated high durability with minimal weight loss. These results highlight the critical role of anode material on the balance between EC and EO pathways, offering practical guidance for selecting electrode material for efficient electrochemical treatment of nutrient-rich effluents.