Microbial community assessment of microbial fuel cell implemented in constructed Wetlands runnning on urban wastewater.. MFC-Wetland

Horizontal subsurface flow constructed wetlands (HSSF CW) are engineered systems used for wastewater treatment that show marked redox gradients in depth that can be exploited to produce energy via microbial fuel cells (MFC) implementation. This work aimed at determining the amount of energy that can be harvested by implementing MFC in HSSF CW during the treatment of real domestic wastewater. To this aim, six MFC were implemented in a pilot plant based on two HSSF CW, one fed with primary settled wastewater (settler line) and the other fed with the effluent of a hydrolytic up-flow sludge blanket (HUSB) reactor (HUSB line). Water quality parameters and power production were monitored from February to July 2013. Microbial samples were analysed at the end of the study period. Maximum current and power densities were obtained in the HUSB line and were that of 219 mA/m2 and 36 mW/m2. Results also suggest that power production pattern along the day is highly related to water level variation within the wetlands. Moreover, microbial analyses revealed a high relative abundance (13-15%) of one OTU closely similar to Geobacter. The OTUs associated to Geobacter were especially enriched in the anodes from closed circuit MFC implemented in the HUSB line. Main conclusion of the present work is that of constructed wetlands receiving the effluent of a HUSB reactor is the best configuration to maximize power production with MFC.