Wastewater treatment and electricity generation by using an up-flow constructed wetland-microbial fuel cell (UFCW-MFC)

Abstract

An up-flow constructed wetland integrated with microbial fuel cell (UFCW-MFC) has demonstrated its feasibility and effectiveness in simultaneous wastewater treatment and electricity generation. Two laboratory-scale UFCW-MFC reactors employed carbon felt (Reactor 1) and activated carbon (Reactor 2), respectively as electrode material. Both reactors were studied and fed with different concentration of synthetic wastewater in order to examine the performance of UFCW-MFC in wastewater treatment and electricity generation under different operating conditions. UFCW-MFC reactors achieved excellent COD reduction up to 99 %, while the removal efficiency of NH4+ achieved 93 % and 96 % for reactor 1 and reactor 2, respectively. NO3- removal was relatively low in this study due to the aerobic region in the upper bed of UFCW-MFC inhibited denitrification. Maximum voltage output, power density and CE were 500.7 mV, 220.5 mW/m3 and 13.4 %, respectively in reactor 2, which was relatively larger than reactor 1, which obtained 232.9 mV, 3.21 mW/m2 and 1.21 %, respectively. Therefore, electrode material plays a significant role in power outputs in UFCW-MFC as reactor 2 (activated carbon) has demonstrated a more efficient performance in electricity generation than reactor 1 (carbon felt). Besides, voltage output and power density were increased 22.6 % and 32.7 %, respectively when the organic loading rate was increased. Thus, higher organic loading rate has improved the performance of UFCW-MFC in terms of voltage output and power density. Moreover, gram staining analysis has shown that gram negative bacteria exist in cathodic region of UFCW-MFC, which included cocci and bacilli.