Backwashing was studied when filtering a
sludge with a suspended solids concentration of
27 g:l and with an aeration rate of 1.8 m3:h.
During backwashing, the flow rate was 10%
higher than during filtration. The different conditions
of backwashing are summarized in Table 7.
In Fig. 12, the strong influence of backwashing
conditions appears clearly. Two conditions look
more efficient than the other conditions and they
are all the more efficient when the filtrate flux is
high. For instance, for a filtrate flux of 20 l:h.m2,
using backwashing reduces the hydraulic resistance to less than a third of its value without
backwashing.