Microbial recycling cells: First steps into a new type of microbial electrochemical technologies, aimed at recovering nutrients from wastewater

The aim of this work were to study terracotta-based porous air-water separators (4mm thickness) in microbial recycling cells (MRCs) fed with cow manure (CM), swine manure (SM) and dairy wastewater (DW). Over 125 days, besides the removal of 60-90% of soluble-COD, considerable fractions of the main macronutrients (C, N, P, K, Fe, Mn, Ca, Mg) were removed from the wastewater and deposited on the terracotta separators as both inorganic salts and biomass deposits. Water evaporation at air-water interface as well as the high cathodic pH (10-12), induced by oxygen reduction to OH-, were the predominant factors leading to precipitation. The separators were saturated of up to 10 g per kg of terracotta of the main macronutrients, with negligible concentrations of the main inorganic contaminants. These materials could be directly reused as nutrients-enriched solid conditioners for agricultural soils.