Microbial Electrochemical Technologies for Wastewater Treatment: Principles and Evolution from Microbial Fuel Cells to Bioelectrochemical-Based Constructed Wetlands

Abstract

28Also, the adoption of those principles for the development of MET set-ups for simultaneous 29 wastewater treatment and power generation, and the challenges that the technology face. 30Ultimately, the most recent developments in set-ups that merges MET with constructed wetlands 31 are presented and discussed.

Microbial Electrochemically Assisted Treatment Wetlands: Current Flow Density as a Performance Indicator in Real-Scale Systems in Mediterranean and Northern European Locations

“…The results suggest a similar performance of the METlands regardless of the different water levels (see Supplementary Figure 1 ) or influent concentrations, due to the adaptability of the microbial community to different oxygen availabilities without impact on the efficiency for removing organic pollutants. COD removal efficiency was similar to the ones previously reported using METlands at the mesocosm scale ( Aguirre-Sierra et al, 2016 ; Ramírez-Vargas et al, 2018 ).…”

“…In the case of systems at IMDEA, CE was between 8.8 and 53% (with OLR between 2.0 and 16.4 g of COD m –2 day –1 ), whereas in the Ørby systems, the CE values ranged from 0.8 to 2.5% (with OLR between 41.9 and 45.6 g of COD m –2 day –1 ). The CE values are within the reported ranges of the merging of TWs and other MET-based systems ( Doherty et al, 2015a ; Ramírez-Vargas et al, 2018 ).…”

“…TWs operating under water-saturated conditions are anaerobic along almost their entire depth profile with anoxic/aerobic conditions only occurring in the uppermost section of the system at the water–air interface ( Aguirre et al, 2005 ). These conditions generate a natural redox profile that matches the gradient of ions and electrons reported in other microbial electrochemical technologies (MET) such as microbial fuel cells (MFC) and combined TW–MFC systems ( Yadav et al, 2012 ; Doherty et al, 2015a ; Ramírez-Vargas et al, 2018 ; Kabutey et al, 2019 ; Srivastava et al, 2020 ). Applications of TW–MFCs at laboratory scale have expanded from treating conventional pollutants ( Oon et al, 2016 ) and nutrients ( Wang et al, 2016 ), to more persistent compounds such as oil ( Yang et al, 2016 ), pharmaceuticals, or heavy metals ( Nitisoravut and Regmi, 2017 ).…”

“…In the case of the Ørby systems, the J values varied from 36.96 to 125.96 mA m –2 for the fully saturated system (Ørby 1) and between 45.84 and 123.01 mA m –2 for the partially saturated system (Ørby 2). Even though the system was not designed to harvest energy, the registered J values were comparable and even surpassed the current densities reported for TW–MET-based systems designed for simultaneous wastewater treatment and energy harvesting ( Corbella et al, 2017 ; Ramírez-Vargas et al, 2018 ).…”

“…In the last decade, a combination of TWs with electrobioremediation strategies has been developed aiming at the intensification of TWs ( Wang et al, 2020 ). Electrobioremediation relies on the metabolic activity of electroactive bacteria (EAB) capable of exchanging electrons from metabolism with electroconductive materials ( Aguirre-Sierra et al, 2016 ; Ramírez-Vargas et al, 2018 ). EAB have been identified in different environments including natural aquatic sediments, aerobic/anaerobic sludge from wastewater treatment facilities, and also in wastewater ( Aguirre-Sierra et al, 2016 ; Ramírez-Vargas et al, 2020 ).…”