Iron-Added Sediment Microbial Fuel Cells to Suppress Phosphorus Release from Sediment in an Agricultural Drainage

Phosphorus (P) release from sediment caused eutrophication in Kojima Lake, Japan. The efficiency of iron-added sediment microbial fuel cells (SMFCs) in regulating P release from agricultural drainage sediment was investigated in this study. Surface sediment collected from an agricultural drainage canal flowing into Kojima Lake was mixed with iron oxide (Fe2O3) or amorphous iron oxyhydroxide (FeOOH) at 50 mmol kg−1. A 14.6-cm high acrylic pipe was filled with 80 mL of deionized water after 130 g of sediment was placed. A 3 × 3 cm graphite felt was used for the anode in a dual chamber SMFC, while a carbon rod was used for the cathode. Three treatments: No Fe, Fe2O3, and FeOOH, were operated for 408 h under open or closed circuit conditions. Results showed that FeOOH addition lowered P release from sediment regardless of SMFC operational conditions, suggesting that higher P adsorption by FeOOH may mask the effect of SMFCs. Fe2O3 did not reduce total P concentration in the overlying water. In addition, electricity generation was not enhanced by Fe-added SMFCs. Although SMFCs increased sedimentary redox potential, P release was not suppressed by the SMFC operation, indicating that organic P would be released by SMFCs from P-rich sediment.