BAF's get media attention

The Biological Aerated Filter is an accepted wastewater treatment option that has the advantage of treatment and solids separation in a single, compact reactor. Choosing the correct support media for the attached biomass is critical in the design and operation of the process to achieve the required effluent quality. This paper considers the physical properties of granular media, such as density, shape, size and surface structure in relation to biomass attachment and treatment efficiency. A pilot evaluation of downflow granular media BAF columns filled with media of different particle sizes, operated over a range of hydraulic and volumetric loading rates, is reported. Nitrification on the smallest 2-4 mm media was found to be inhibited at loading rates above 0.5 kg NH4-N and 2.5 kg BOD / m3media/d due to the greater hetrotrophic growth and enhanced wash requirement.