GPS-X Technical Reference

Sand Filtration Models 268
CHAPTER 9
Sand Filtration Models
INTRODUCTION
This chapter describes the deep bed granular filtration models available in GPS-X. The
continuous and massbalance models are based on empirical removal efficiencies. The simple1d
model is a mechanistic model based on continuity and kinetic equations that describe the removal
of suspended particles by deep bed granular filters.
CONTINUOUS MODEL
The basis for the continuous model is the direct specification of the filter performance through
two parameters: the backwash flow fraction and the backwash solids mass fraction (Figure
9-1). The backwashout connection (bottom left of object) is not used in this model.
The backwash flow fraction (frqbw) is the fraction of the incoming flow to the filter (input
connection - top left of object) that is used for backwash. Using this parameter, GPS-X will
calculate a continuous backwash flow (Q b) associated with the backwashout stream (top right of
the object):
Equation 9.1
The continuous output flow (bottom right of the object), is then calculated from the difference
between the input flow and the backwash flow:
Equation 9.2
GPS-X Technical Reference