Self-driven electrochemical system for struvite and energy recovery from digested wastewater: Device optimization strategy and long-term operation

Abstract

A self-driven electrochemical system (SDES) was utilized to treat anaerobic digestate wastewater, aiming to achieve wastewater resource utilization and energy generation. The efficiencies of pollutant removal, resource recovery, and energy production were enhanced by adjusting device parameters (anode area, external resistance, and electrode spacing). The high pollutant removal rates and struvite purity were achieved with the magnesium anode area of 15 cm², external resistance of 10 Ω, and electrode spacing of 10 cm. The appropriate anode area (3.0 cm²), external resistance (50 Ω), and electrode spacing (7.5 cm) were prone to achieve high electric energy output. For one cycle, the removal rates of PO₄^3--P and NH₄⁺-N were 95.37% and 39.10%, respectively, with an average output power of 50.98W/m³, and 0.0275g of struvite was recovered(50 ml digested wastewater). For the long-term operation (20 cycles), the average PO₄^3--P and NH₄⁺-N removal rates were 89.3% and 23.4%, the CV (Coefficient of Variation)for PO₄^3--P and NH₄⁺-N were 0.1998 and 0.0504, and the average output power was 8.90 W/m³. The SDES showed satisfactory performance without replacing the magnesium anode. Based on the comprehensive efficiency of pollutant removal, resource recovery, and energy production, a replacement cycle of 20 cycles for magnesium anode was determined. In summary, the SDES for treating the anaerobic digested wastewater was demonstrated with stability and efficiency.

Keywords: Anaerobic digested wastewater; Electricity generation; Phosphate and ammonium recovery; Self-driven electrochemical system; Struvite.