Computer-aided simulation of slow sand filter performance

Abstract

Although the modelling of deep bed filtration has progressed considerably in recent years, almost no attention has been given to simulating the process of slow sand filtration. The exception, to date, is the work of Woodward and Ta (1988) who have attempted to simulate slow sand filter performance via a simple, empirical headloss model; however, this model is not deterministic in nature and cannot predict filtrate quality nor the spatial headloss development with the filter. This paper describes the development and calibration of a computer-based numerical model based on assumed filtration coefficient and headloss relationships. The model structure includes a simple representation of biomass development but ignores the possible influence (currently uncertain) of a Schmutzdecke-surface skin. It is concluded that the spatial and temporal headloss development within the media bed can be simulated if certain combinations of headloss and filtration coefficient relationships are assumed.