Phage-Based Biofilm Control in Engineered Water Environments

Biofilms represent a predominant bacterial lifestyle and contribute to the ecological stability and biochemical functioning in water systems. Paradoxically, excessive biofilm formation threatens water security and public health by causing biofouling, harboring pathogens, and facilitating the transmission of antimicrobial resistance. Phage treatment offers a promising strategy for the targeted regulation of biofilm microecology without generating harmful disinfection byproducts. However, its performance in environmental settings can be constrained by spatiotemporal heterogeneity, suboptimal phage exposure, and the evolution of phage resistance in bacteria, creating additional challenges for engineering applications. Here, we synthesize phage-based biofilm control as a multilevel intervention paradigm organized by biological bottlenecks. We examine strategies that improve transport and host access, enhance targeting and productive lysis, induce biofilm disruption through prophage activation, and perturb biofilm communities through keystone-centered interactions. We then align these intervention principles with distinct biofilm scenarios and operational constraints in engineered water environments. Emerging technologies are evaluated according to their roles in target identification, validation under application-relevant conditions, and treatment monitoring. Finally, we propose a closed-loop framework encompassing system diagnosis, intervention design and validation, monitored deployment, and adaptive management. Overall, this Review provides an integrated roadmap for advancing scalable and sustainable phage-based biofilm control in engineered water environments.