Microbial fuel cell coupled ecological floating bed for enhancing bioelectricity generation and nitrogen removal

An ecological floating bed-microbial fuel cell (EFB-MFC) coupled system was constructed in this study. With windmill grass, goldfish algae, water hyacinth and water spinach chosen as the cathodic floating bed plants, performance with regard to electricity generation and nitrogen removal was investigated. For electricity generation, introducing plants into an MFC reduced the internal resistance of the system by 21.23%-67.66% and increased the average voltage by 26.26%-62.63% compared to the system with no plants. In addition, the coupled system improved the removal efficiency of NH4+-N and TN by 2.54%-16.40% and 2.91%-16.86%, respectively. The water spinach system achieved the best performance for electricity generation and nitrogen removal. However, the extra NH4+-N released by rotten roots of windmill grass impaired the nitrogen removal. Radial oxygen loss and root exudates played significant roles in enhancing electricity generation and nitrogen removal. Moreover, electricity generation can stimulate the activity of enzymes related to nitrogen removal and drive the migration of NH4+-N thereby enhancing nitrogen removal. This study also first revealed that an EFB-MFC showed greater capability than a nonplanted group for protecting enzyme activity related to nitrogen removal from excessive high water temperature (over 30 degrees C). (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the performance of an ecological floating bed-microbial fuel cell (EFB-MFC) coupled system for electricity generation and nitrogen removal. Results showed that introducing plants into the MFC system reduced resistance and increased voltage, while also improving NH4+-N and TN removal efficiency. Water spinach system showed the best performance, but rotten roots of windmill grass released extra NH4+-N which impaired nitrogen removal. Radial oxygen loss and root exudates played significant roles in enhancing electricity generation and nitrogen removal. Electrical stimulation of enzyme activity related to nitrogen removal and migration of NH4+-N contributed to enhancing nitrogen removal.