Citation: Tamta, P.; Rani, N.; Mittal, Y.; Yadav, A.K. Evaluating the Potential of Multi-Anodes in Constructed Wetlands Coupled with Microbial Fuel Cells for Treating Wastewater and Bioelectricity Generation under High Organic Loads. Energies 2023, 16, 784. https://doi.org/10.3390/ en16020784 Academic Editors: Booki Min and Md Tabish Noori Received: 30 October 2022 Revised: 10 December 2022 Accepted: 29 December 2022 Published: 10 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Evaluating the Potential of Multi-Anodes in Constructed Wetlands Coupled with Microbial Fuel Cells for Treating Wastewater and Bioelectricity Generation under High Organic Loads Prashansa Tamta 1 , Neetu Rani 1, *, Yamini Mittal 2,3 and Asheesh Kumar Yadav 2,3,4, * 1 University School of Environment Management, Guru Gobind Singh Indraprastha University, Dwarka 110078, New Delhi, India 2 CSIR—Institute of Minerals and Materials Technology, Bhubaneswar 751013, Odisha, India 3 Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India 4 Department of Chemical and Environmental Technology, Rey Juan Carlos University, 28933 Mostoles, Spain * Correspondence: neetu_rani@ipu.ac.in (N.R.); asheesh.yadav@gmail.com (A.K.Y.) Abstract: Multiple anodes can significantly enhance the treatment potential of constructed wetlands coupled with a microbial fuel cell (CW-MFC) system, which has not yet been explored. Thus, the present study evaluates the potential of multi-anodes and single cathode-based CW-MFC at significantly higher organic loading rates for treatment performance and bioelectricity generation. For this purpose, two identical but different materials, i.e., graphite granules (GG) and granular activated charcoal (GAC), were used to set up multiple anodes and single cathode-based CW-MFCs. The graphite granules (GG)-based system is named CW-MFC (GG), and the granular activated charcoal (GAC) based system is named as CW-MFC (GAC). These systems were evaluated for chemical oxygen demand (COD), NH 4 + -N removal efficiency, and electrical output at relatively higher organic loading rates of 890.11 g COD/m 3 -d and 1781.32 g COD/m 3 -d. At an OLR of 890.11 g COD/m 3 -d, the treatment efficiency was found to be 24.8% more in CW-MFC (GAC) than CW-MFC (GG), whereas it was 22.73% more for CW-MFC (GAC) when OLR was increased to 1781.32 g COD/m 3 -d. Whereas, NH 4 + -N removal efficiency was more in CW-MFC (GG) i.e., 56.29 ± 7% and 56.09 ± 3.9%, compared to CW-MFC (GAC) of 36.59 ± 3.8% and 50.59 ± 7% at OLR of 890.11 g COD/m 3 -d and 1781.32 g COD/m 3 -d, respectively. A maximum power density of 48.30 mW/m 3 and a current density of 375.67 mA/m 3 was produced for CW-MFC (GAC) under an organic loading rate of 890.11 g COD/m 3 -d. Keywords: multiple anode electrodes; wastewater treatment; bioelectricity generation; COD removal 1. Introduction Efficient management and treatment of wastewater is one of the prime environmental challenges today. Although various traditional technologies are currently being used to deal with this challenge, there is a prerequisite to exploring more efficient processes to combat future needs. These conventional wastewater treatment technologies demand an ample amount of energy for their operation, along with a high level of operational complexity. Thus, a low-cost, self-sufficient, easily operable, and low-maintenance technology can be a promising solution. Constructed wetlands (CWs) are one of the conventional wastewater treatment technologies that is advantageous in terms of low-cost, ease of operation, least maintenance requirement; however, they have slow treatment processes due to strongly dominated anaerobic reactions and thus require a large land area for treating wastewa- ter [1,2]. Meanwhile, bio-electrochemical systems such as microbial fuel cells (MFCs) have gained a lot of attention as wastewater treatment technology with simultaneous bioelec- tricity recovery as a by-product, but scaling up is the biggest challenge to incorporate into Energies 2023, 16, 784. https://doi.org/10.3390/en16020784 https://www.mdpi.com/journal/energies