Microbial electrochemical ammonia recovery from anaerobic digester centrate and subsequent application to fertilize Arabidopsis thaliana

Although ammonia recovery from wastewater can be environmentally friendly and energy efficient compared to the conventional Haber-Bosch process, there is a lack of research on the reuse of the recovered ammonia to exhibit a complete picture of resource recovery. In this study, a microbial electrochemical system (MES) was used to recover ammonia from a mixture of anaerobic digester (AD) centrate and food wastewater at a volume ratio of 3:1. More than 60% of ammonia nitrogen was recovered with energy consumption of 2.7 kWh kg⁻¹ N. The catholyte of the MES, which contained the recovered ammonia, was used to prepare fertilizers to support the growth of a model plant Arabidopsis thaliana. It was observed that A. thaliana grown on the MES generated fertilizer amended with extra potassium, phosphorus, and trace elements showed comparable sizes and an even lower death rate (0%) than the control group (24%) that was added with a commercial fertilizer. RNA-Seq analyses were used to examine A. thaliana genetic responses to the MES generated fertilizers or the commercial counterpart. The comparative study offered metabolic insights into A. thaliana physiologies subject to the recovered nitrogen fertilizers. The results of this study have demonstrated the potential application of using the recovered ammonia from AD centrate as a nitrogen source in fertilizer and identified the necessity of supplementing other nutrient elements.