Fixed film

Fixed Film Trickle Filtration is a process used to reduce Biological Oxygen Demand (BOD) and ammonia nitrogen levels. Trickling filters are composed of a bed of porous material (rocks, slag, plastic media, or any other medium with a high surface area and high permeability). Wastewater is distributed over the surface of the media, where it flows downward as a thin film over the media surface for aerobic treatment. The wastewater is then collected at the bottom through an under-drain system. The effluent is then settled by gravity to remove biological solids prior to being discharged.