Evaluating a Dual Chamber Magnesium Electrolytic Process for Struvite Precipitation from Synthetic Wastewater

Abstract

<b><sc>Abstract.</sc></b> Diminishing phosphorus resources worldwide requires developing new technologies to recover phosphorus (P) from wastewaters. A lab-scale electrolytic reactor with a magnesium anode was investigated to remove NH₄⁺ and PO₄^3- from synthetic wastewater by producing struvite. The effects of mixing speed, pH, and applied current on struvite yield, NH₄⁺, and PO₄^3- removal efficiencies were first evaluated using a factorial design. Then, the two most significant parameters were further optimized using Central Composite Design (CCD) coupled with Response Surface Methodology (RSM). A 5.7-fold increase in struvite yield was achieved by increasing the applied current from 0.1 to 0.5 A. The three regression equations generated by the CCD/RSM design with applied current and mixing speed as the two independent parameters were highly correlated with the response variables (struvite yield, NH₄⁺ and PO₄^3- removal efficiencies). The desirability analysis showed the best operating condition: current, 0.5 A and mixing speed, 414 rpm, for the reactor system, under which the optimal struvite yield and NH₄⁺ and PO₄^3- removal efficiencies were 4.75 g/L, 93.0%, and 58.4%, respectively.