Predicting the expansion behavior of filter media

As a result of the growing importance of granular media filtration in water and wastewater treatment, several studies dealing with various aspects of fluidization have been reported in the literature during the past two decades. The sphericity or angularity of the different filter media currently being used shows much variation and greatly influences the fixed bed head loss, the minimum fluidization velocity, and the expansion behavior of the media. This article attempts to elucidate the shortcomings of some expansion models and to correct certain concepts that have been presented in the literature, while complementing an earlier article.1