Phosphorus Recovery from Decentralized Wastewater by a Novel Siderite-Calcite Integrated Electrochemical Process: Efficacy, Mechanism, and Optimization

Recovering phosphorus (P) from wastewater presents a dual benefit: reducing eutrophication and supplementing finite phosphate rock resources. This study developed an integrated electrochemical fixed-bed reactor filled with siderite and calcite for enhanced P recovery. During operation, H+ and OH– ions generated via electrochemical water splitting dissolve siderite and calcite in situ while simultaneously establishing an optimal pH environment for phosphorus precipitation. By adjusting the current density and feed flow rate, the recovery process can be effectively controlled. Mechanistic investigations revealed that phosphate removal was primarily achieved through Ca–P and Fe–P precipitation, along with the formation of various Fe–Ca–P complexes. The proposed system combines the advantages of in situ electrochemical acid and alkali generation with the cost-effectiveness of natural mineral materials. It also aligns with the technical requirements of sewage treatment plants, offering a compact process and minimal chemical usage. With its flexibility and controllability, this electrochemical system holds promising potential for on-site treatment and phosphorus recovery in decentralized wastewater treatment applications.