  Slow sand filtration is most appropriate where there is funding to subsidize
the initial cost of the filter, available training for use and maintenance,
locally available sand, and a transportation network capable of moving the
filter. Since the experimental study of slow filtration is taking a long time,
theoretical analysis, modelling and simulation studies become important.
Theoretical models of slow filtration are not yet sufficiently developed.
Several reasons are hindering modelling and simulation: due to the complexity
of the interaction of water and pollution with filters and the lack of detailed
values for the kinetic coefficients in elementary processes. Multiphysics
modelling using Comsol, where a complex set of Navier-Stokes equations is
numerically solved together, with the molecular awareness for the kinetic
coefficients, was used to studying various geometries and construction types of
slow filtration.
