Abstract
A deep understanding of the relationship between the solids deposition and head losses is vital to optimize the backwashing in
biological aerated filters (BAFs). In this article, the deposition solids were classified into four types: heterotrophic biomass,
autotrophic biomass, inert biomass and extracellular polymeric substances (EPS). A concept model was developed to simulate
the solid deposition and the head loss development. The temporal and spatial distributions of the four types of solids mass were
modeled based on the Monod-type activated sludge model. The solid mass was converted into biofilm volume by using the
concept of space occupancy parameters. The filtration resistance and head loss were then calculated based on the Kozeny–
Carman equation. The model prediction was shown to be in reasonable agreement with experimental results. This suggests that
the modeling approach in this paper is valid in predicting the head loss development.