Photocatalytic Bioreactors in Water Treatment: Mechanisms, Challenges, and Innovations in Microbial Inactivation

As freshwater resources become increasingly scarce, safe drinking water is critical to public health. However, emergent pollutants and pathogenic microorganisms threaten this goal, posing direct and indirect water quality risks. Photocatalysis offers a promising alternative disinfection strategy, overcoming many limitations of conventional methods by generating reactive oxygen species (ROS) capable of effectively deactivating microbial contaminants through targeted redox reactions. This review explores the photocatalytic disinfection process, detailing microbial inactivation mechanisms, and provides a comparative analysis of commonly used photocatalysts and their composites. Sources of microbial contamination, including bacteria, viruses, algae, fungi, and protozoa, are discussed to contextualize the challenges faced in water treatment. Key operational parameters influencing photocatalytic efficiency and an overview of practical bioreactor types optimized for varied disinfection needs are also addressed. This comprehensive review highlights the advancements and potential of photocatalytic bioreactors in safeguarding water quality and expanding accessible, efficient, and eco-friendly disinfection technologies.