Magnesite-Assisted Electrochemical System for Enhanced Nutrient Recovery: Comparative Evaluation in a Wastewater Co-Treatment Scheme

Abstract

Recovering nitrogen (N) and phosphorus (P) from wastewater is crucial for environmental protection and resource sustainability. Chemical precipitation and Mg electrocoagulation, although often studied and applied for N and P recovery as struvite, suffer from inherent drawbacks. The former generates poorly settling sludge and re-releases natural organic matter, while the latter encounters issues such as active anode passivation and complex struvite deposition. We propose and validate a new magnesite-assisted electrochemical system that achieved 100.0% NH₄⁺ and 66.9% PO₄^3– removal in easily recoverable struvite without suffering from anode passivation. The system’s core lies in the in situ utilization of the local low-pH environment established via water electrolysis by the anode-packed magnesite minerals, providing an affordable, passivation-free, and tunable Mg source. Meanwhile, the cathode emerges in a local high-pH atmosphere, serving as the sole site for high-purity and condensed struvite precipitation and collection. On top of technological development, we validate a co-treatment concept for the recovery of struvite from mixed wastewater, demonstrating potential cost savings of 76.9% and a 22.4% reduction in CO₂ emissions. Our work offers a new design for enhanced struvite recovery and outlines a green route for co-managing different waste streams and producing valuable products.