Filter kinetics
Zero order reaction:
as=- kov 9
ifrJ
s1
kov
s=1--9·ll
St
(5.39)
(5.40)
(5.41)
where E is the treabnent efficiency This is shown in Fig 5.11. The expression applies,
of course, only to
kov
0<-·9<1
sl
Half order reaction:
as
kl-2v l, -=---9 -s
dri
s~
First order reaction:
as
-=-ktv9S
drJ
(5.42)
(5.43)
(5.44)
(5.45)
(5.46)
(5.47)
Each of these expressions for the relationship between treabnent efficiency and
retention time for different values of the respective reaction rates and influent
concentrations can be used independently A special case is, however, a filter with
biofilm diffusion because all three cases can occur at different levels in the same
filter. At the influent, the concentration may be sufficiently big for the medium to
diffuse to the bottom of the biofilm- a zero order reaction. After some treabnent, the
reduced concentration means that the biofilm becomes partially efficient - a half
order reaction. Further down in the filter the concentration outside the biofilm will
drop from values corresponding to a reaction of half order to values corresponding
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