The challenge of nutrients recovery by terracotta Microbial Fuel Cells

Terracotta has been studied as a low-cost material to fabricate porous air-water separators, in air-cathode microbial fuel cells (MFCs). Maximizing the air-water interface with such structures could facilitate the scaling up of MFCs for treating wastewater, while recovering nutrients. The tests were repeated with two different wastewaters: swine manure and synthetic wastewater. Over 180 MFCs operation days, consistent amounts of the main macro and micronutrients (C, N, P, K, Fe, Mn, Ca and Mg) were removed from the wastewaters. The electro-osmotic forces generated by the MFCs and the high cathodic pH values (9-11) were the predominant factors leading to salts precipitation on both cathodes and terracotta membrane. Water evaporation from the air-water interface also contributed to elements precipitation, but to a lesser extent. This study aims at the terracotta MFCs in view of recovering nutrients from wastewaters towards a future use in agriculture as bio-fertilizers or soil conditioner enriched of macro and micro nutrients.