AbstractBiological filtration (biofiltration) is the operational practice of managing, maintaining, and promoting biological activity on granular media in a filter to enhance the removal of organic and inorganic constituents before treated water is introduced into the distribution system. A major barrier to more widespread acceptance of biofiltration is the lack of recognized full‐scale experience available to utilities. To overcome this barrier, the Biofiltration Knowledge Base was developed (Water Research Foundation Project 4459). The Biofiltration Knowledge Base is a compendium of planning, design, operation, and monitoring experiences of 45 biofiltration facilities across North America with over 420 combined years of operational experience. This resource facilitates the exchange of knowledge, communicates the benefits of biofiltration, documents lessons learned, provides optimization strategies, and identifies needs for future research. Data demonstrate that biofiltration is widely used throughout North America and has been successful over a range of water qualities, design configurations, and operating conditions.