Recent Progress in Hybrid Microalgae-Electrocatalytic/Photocatalytic Technologies for Enhanced Wastewater Treatment

Abstract: Environmental pollution and the freshwater crisis are driving the need for innovative wastewater treatment solutions. Microalgal bioremediation has emerged as a sustainable technology for simultaneous contaminant removal (e.g., COD, nutrients, heavy metals) and biomass production. However, emerging contaminants, refractory pollutants, and complex wastewater matrices often inhibit microalgal growth and degradation efficiency. To address these challenges, this review systematically analyzes three hybrid integration strategies: (i) microalgal microbial fuel cells (MMFCs), (ii) microalgae-electrochemical advanced oxidation processes (EAOPs), and (iii) microalgae-photocatalytic systems. While existing literature extensively covers microalgal biotechnology, comprehensive analyses of its synergistic coupling with nanomaterial-based AOPs (electrochemical/photocatalytic) remain limited. This study elucidates the mechanisms, benchmarking performance, and novel enhancement strategies of these integrated systems, facilitating direct technology comparison. We highlight the multifunctional roles of microalgae in these hybrid systems, including bioelectricity generation (MMFCs), in situ oxygen supply (MMFCs and photocatalysis), and biodegradation to mitigate radical quenching (photocatalysis and EAOPs). The comparative advantages and limitations of each technology are critically evaluated, followed by forward-looking perspectives on system scalability, cost-efficiency, and real-world applicability.