Wastewater treatment plants remove contaminants prior to discharging treated effluent. Removing nitrogen and phosphorus prevents algae blooms but usually requires expensive chemical and energy input. A prime location to implement resource recovery is the nutrient-rich liquid effluent of anaerobic digestion (sidestream), which is normally returned to the head of the plant. Nitrogen can be removed and energy can be recovered in the sidestream by microbial fuel cells (MFCs), which oxidize organic or inorganic matter to generate electricity. The overall objective of this project was to build and assess the performance and biochemical mechanisms of a microbial fuel cell that both removes ammonium and provides energy. The project is innovative because of its sidestream application and its future combination with struvite precipitation for recovery of nitrogen and phosphorus. Our microbial fuel cell accomplishes biological reactions in three chambers: nitrification in the nitrification chamber, denitrification in the cathodic chamber, and organic decomposition in the anodic chamber. Results from 48 days of operation indicate 69% average COD removal in the anodic chamber and 36% average nitrogen removal in the cathodic chamber. Over that time, an average voltage of 85.2 mV and current of 16.9 uA were recorded, resulting in a current density of 26.2 mA/m2 of anode surface area and power densities of 2.23 mW/m2 of anode surface area and 4.80 mW/m3 reactor volume. The results indicate that electrons, which were donated during organic decomposition in the anodic chamber, are being accepted by the denitrification reaction in the cathodic chamber. Because the end-goal of our research is to demonstrate the microbial fuel cell technology in combination with struvite precipitation at a Water Resource Recovery Facility, the research will continue with collaboration with county engineers at the pilot scale at a testbed facility being constructed in Hillsborough County (Tampa, FL).

Microbial fuel cells integrate energy production with nutrient management in municipal wastewater plant sidestreams

253rd National Meeting (2017)

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