Wastewater treatment protects public health, ecosystems, and economic prosperity by removing pollutants before water is released back into the environment. At the core of this process are complex microbial communities whose stability strongly affects energy use, treatment reliability, and infrastructure costs. However, engineers currently lack precise tools to control these microbial systems, relying instead on energy intensive operational adjustments such as aeration. This project addresses this challenge by developing new ways to harness bacteriophages or “phages”, which naturally infect and kill bacteria, as precision tools to stabilize wastewater treatment processes. By enabling phage-based control of problematic bacteria that cause sludge bulking or inefficient nitrogen removal, the research supports national priorities in efficient and robust water infrastructure, reduced energy consumption, and protection of waterways from nutrient pollution. The project advances science by transforming naturally occurring microbial diversity into programmable biological tools and contributes to advanced manufacturing by applying those tools to enable the provision of clean water, the recovery of nutrients from waste streams, and the generation of other value-added products. Additional benefits include training undergraduate and graduate students in synthetic biology, environmental engineering, and bioinformatics, thereby strengthening the workforce needed for the growing U.S. bioecono