A comprehensive overview of constructed wetland-microbial fuel cells for enhancing organic waste treatment and renewable energy production: From fundamentals to applications

Our society faces several challenges due to the scarcity of clean water and the depletion of non-renewable, fossil fuel-based energy resources. In this context, traditional wastewater treatment technologies open up opportunities to guarantee the availability of safe drinking water, prevent detrimental ecological impact, and address climate change by reducing greenhouse gas emissions. However, they require substantial financial and energy investment, limiting their adoption in resource-limited countries. Over the past few decades, bioelectrochemical systems, such as microbial fuel cells (MFCs), have gained great interest owing to their ability to detoxify waste streams and generate renewable energy (e.g., electricity). The distinguishing features of MFCs allow them to be a central component of several integrated wastewater treatment systems, including constructed wetland-microbial fuel cells (CW-MFCs), that have the capability to overcome the operating challenges associated with individual traditional technologies. Coupling MFCs with CWs enables the adjustment of redox activities and the balance of electron flow in both aerobic and anaerobic zones, thereby alleviating the constraint of the limited supply of electron acceptors and enhancing the capacity to manage its operation. In addition, CW-MFCs offer advantages compared to traditional wastewater treatment technologies, such as high chemical oxygen demand (COD) and nitrogen removal effectiveness, the ability to generate electricity, and the ability to remove persistent pollutants. This review article will critically assess the existing literature on the advantages and research opportunities of CW-MFCs for wastewater treatment and electricity generation. Furthermore, it provides an in-depth understanding of application guidance and the current key challenges of CW-MFCs.