Journal of Energy Bioscience 2024, Vol.15, No.3, 186-196 http://bioscipublisher.com/index.php/jeb 191 Yamane et al. (2021) demonstrated the chemical oxygen demand (COD) removal performance of microbial fuel cells (MFCs) at different hydraulic retention times (HRT). As can be seen from the figure, MFC has a significant effect in reducing COD, especially at lower HRT, and its removal efficiency is higher than that of non-reactor systems. Combined with single exponential regression and the Michaelis-Menten model, the COD degradation kinetics in MFC can be accurately described. Integrating MFC technology with existing wastewater treatment infrastructure can improve treatment efficiency and reduce energy consumption. MFC not only effectively removes organic matter, but also generates electricity at the same time, increasing the possibility of energy recovery for wastewater treatment, which is of great significance for improving the sustainability and economy of wastewater treatment. The potential of MFC to treat low-concentration wastewater is particularly high, helping to promote its use in a wider range of industrial applications. 5.3 Challenges and limitations in current MFC technologies Despite the promising advancements, several challenges and limitations hinder the widespread adoption of MFC technologies. One of the primary challenges is the low power density and high costs associated with MFC systems, which limit their economic viability for large-scale applications (Ardakani and Gholikandi, 2020). Additionally, issues such as membrane fouling, substrate cross-conduction, and the need for continuous process optimization pose significant hurdles (Zhuang et al., 2012). The complexity of microbial communities and the need for precise control over environmental conditions further complicate the operation of MFCs. Moreover, the integration of MFCs with existing infrastructure requires careful consideration of system compatibility and operational parameters to ensure optimal performance (Kumar et al., 2019). Addressing these challenges through continued research and technological innovation is crucial for the successful implementation of MFCs in wastewater treatment and energy recovery applications. 6 Case Study: Energy Recovery from Industrial Wastewater Using MFCs 6.1 Description of the industrial wastewater source The industrial wastewater used in this study was sourced from a petroleum refinery, which is known for its high chemical oxygen demand (COD) and the presence of specific contaminants such as oil, grease, phenol, and sulfide. Refinery wastewater (RW) poses a significant challenge due to its complex composition and high pollutant load, making it an ideal candidate for treatment using advanced technologies like MFCs (Zhao et al., 2021). 6.2 MFC system setup and operational parameters The MFC system employed for this study was a dual-chamber setup operated under continuous mode. The system was designed to handle high hydraulic retention times (HRT) of 8 to 16 hours, which is crucial for effective substrate degradation and energy recovery. The MFC was equipped with non-platinum air-cathodes to reduce material costs and enhance scalability. The system was operated at two different organic loading rates (ORLs) of 1.2 and 4.9 kg COD/m³/day to evaluate its performance under varying conditions (Srikanth et al., 2016) (Figure 2). Figure 2 The working principle of the MFC prototype (Adopted from Cecconet et al., 2018)
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