A mathematical model for deposit detachment and removal during the bac
kwash of rapid gravity filters has been derived for a fluidising water
wash. The model consists of two parts; part 1 determines the volume o
f deposit dislodged into suspension at any instant, and part 2 determi
nes the change in concentration emerging from the filter bed at any st
age during the backwash. Initial conditions for the backwash model are
determined from a filtration model. (C) 1998 Published by Elsevier Sc
ience Ltd. All rights reserved.