Two-stage hybrid constructed wetland-microbial fuel cells for swine wastewater treatment and bioenergy generation

A newly emerged alum sludge-based hybrid constructed wetland-microbial fuel cells (CW-MFCs), i.e. vertical upflow CW coupled MFC as 1st stage and horizontal subsurface flow CW coupled MFC as 2nd stage (VFCW-MFC + HSSFCW-MFC), was firstly developed for swine wastewater treatment and electricity generation. Swine wastewater and multi-set air-cathodes were applied to investigate the pollutants removal behavior and the power production. Six-month trial suggested that the overall removal efficiency of SS, COD, NH4+-N, NO3--N, TN, TP and PO43--P was 76 +/- 12.4, 72 +/- 7.4, 59 +/- 28.3, 69 +/- 25.6, 47 +/- 19.7, 85 +/- 9.5 and 88 +/- 8.7%, respectively. The two stages hybrid system (VFCW-MFC + HSSFCW-MFC) continuously generated electrical power with average voltages of 0.44 +/- 0.09 and 0.34 +/- 0.09 V, and power densities of 33.3 +/- 13.81 and 9.0 +/- 2.5 mW/m(3) in 1st and 2nd stage, respectively. The average net energy recovery (NER) of 1st stage and 2nd stage is in turn 0.91 +/- 0.16 and 2.76 +/- 0.70 Wh/kg.COD. It indicates that the hybrid CW-MFCs has higher removal efficiency than single stage CW-MFC, while 1st stage plays the major role both in pollutants removal and power generation. (C) 2020 Elsevier Ltd. All rights reserved.