Deterministic-Based Model of Slow Sand Filtration. I: Model Development

Slow sand filtration (SSF) is widely used throughout the world for the treatment of drinking water. However, relatively little attention has been given to the development of a comprehensive process model. Previous studies have considered separate aspects of the SSF process, such as developing an improved representation of the schmutzdecke layer, and a more detailed description of the microbial dynamics. The objective of this work was to develop a deterministic simulation model of the SSF process incorporating fundamental physicochemical and biological dynamics within a classical filtration framework. The model was based on a temporal and spatial finite difference method and was calibrated and verified using operational data from pilot-scale SSF units. Results from the calibration showed that the model satisfactorily predicts headloss development in SSF units. There was no significant difference between many of the most sensitive model parameter values for two successive runs of the same filter. However, a few individual model parameters (e.g., in the fundamental headloss equations) were found to vary with filtration run and it is speculated that this is due to seasonal factors.