Iron-Based Electrocoagulation Pretreatment to Enhance Magnesium-Struvite Recovery from Livestock Wastewater Using a Tubular Reactor

Livestock wastewater containing high levels of ammonium, phosphate, COD, and TSS poses serious environmental challenges but offers potential for nutrient recovery via struvite precipitation. This study developed an integrated electrochemical process combining iron-based electrocoagulation (EC-Fe) as pretreatment and magnesium-based electrocoagulation (EC-Mg) as the main treatment. The EC-Fe stage efficiently reduced TSS and competing ions, improving the NH₄⁺:PO₄³⁻ ratio from 37.6:1 to 48:1 under 10 A for 5 min, though with high energy demand. Subsequent EC-Mg treatment at pH 9.5 and 15 A promoted rapid struvite formation, achieving 99.97% phosphate and 67.15% ammonium removal within 20 min. Overall, the integrated system removed 88.48% COD, 99.68% TSS, 87.89% NH₄⁺, and 99.97% PO₄³⁻, yielding 31.5 ± 2.52% struvite recovery in 25 min. Despite effective pollutant removal, high energy consumption and non-stoichiometric NH₄⁺:PO₄³⁻ ratios limit recovery efficiency. Optimization of operating parameters and renewable energy integration are recommended to enhance scalability and sustainability.