Study on removal of phosphorus as struvite from synthetic wastewater using a pilot-scale electrodialysis system with magnesium anode

Abstract Struvite precipitation may become ineffective in removing phosphorus due to the low concentration of phosphate in the liquid. In this study, electrolysis with a magnesium anode was applied to recovering phosphorus and ammonia as struvite from wastewater. A novel electrodialysis process (ED) with a magnesium anode was developed, and its feasibility to treat synthetic wastewater with low phosphate concentration was demonstrated in a pilot-scale experimental system. To achieve high phosphate removal efficiency in the product stream, the optimal initial pH and flow rate were found to be 8.8 and 200 L h−1, respectively, for the ED system at a constant current of 0.1 A. The pilot-scale ED system achieved 95% phosphate removal efficiency in the feed stream, and the phosphate concentration in the product stream was kept at 30 mg L−1 after 280 min with periodically renewing the low-concentrated phosphorus (10 mg L−1) feed stream. The running cost of the ED system was estimated to be $26.51 kg−1 P for synthetic wastewater with 10 mg L−1 P as substrate, mainly resulting from the cost of the loss of the magnesium anode. The precipitates generated from the product stream were confirmed as struvite by XRD analysis.