Air Flow Characteristics in Granular Biofilter Media

Pressure drop (Delta P) as a function of air velocity (V) is a key parameter controlling air cleaning biofilter cost efficiency. At present the V-Delta P relationship in biofilter materials must generally be determined experimentally, as no universal link between the V-Delta P relationship and material physical properties have been established. The objective of this study was, therefore, to investigate the link between the V-Delta P relationship, material particle size distribution, and wetting conditions for a common biofilter medium, Leca. Measurements of V-Delta P was carried out for 36 different Leca particle size fractions with different mean particle diameter (D-m) and particle size range (R) under both dry and wet conditions. Measurements showed that increasing Dm and decreasing R together with wetted conditions in the filter generally resulted in decreasing Delta P for the same V. A set of expressions allowing for accurate estimation of the V-Delta P relationship based on D-m, R. and wetting conditions were established, enabling reliable estimation of filter pressure drop (and operation costs) in Leca and similar granular materials. DOI: 10.1061/(ASCE)EE.1943-7870.0000640. (C) 2013 American Society of Civil Engineers.