Bench-Scale Demonstration and Thermodynamic Simulations of Electrochemical Nutrient Reduction in Wastewater via Recovery as Struvite

Abstract

Land application of manure can be a sustainable supply chain practice that improves soil quality by recycling important nutrients contained in animal waste. Yet, runoff of phosphorus and nitrogen nutrients contained in the animal waste has contributed to significant watershed eutrophication. Recovery of the dissolved nutrient species as a condensed solid fertilizer product would increase sustainability of the agricultural supply chain, while reducing watershed pollution. This study was conducted to evaluate the recovery of phosphorus (primarily) as struvite using an electrochemical process while varying temperature, applied cathodic potential, turbulence and Ca2+ concentration. High phosphorus recovery with high current efficiency and low specific energy consumption was possible at 20 °C, −1.1 V vs Ag/AgCl at the cathode, and a Reynolds number of 9150 in the absence of Ca2+ when the Mg:N:P ratio was 1.37:1:1. Further, a thermodynamic model of the waste solution indicated an increase in Ca2+ concentration, which impedes struvite recovery, can be negated by increasing dissolved Mg2+ concentration and operating at a pH below NH3 volatilization.