After the influent TOC is oxidized, O3-treated water is pumped to the ORTHOS BAF utilizing media-retaining ORTHOS Type D nozzles in an underdrain plate. Up to 96” of media (e.g., GAC, anthracite, sand) may be installed in the BAF to create 20+ minutes of empty bed contact time. Proteus™ pumps and compressor provide user-adjustable, concurrent air-water backwash, triggered manually or automatically based on headloss across the filter media, runtime, or turbidity.