Civil Engineering Reference
In-Depth Information
Pre-
s
e
d
i
men
tati
o
n
Rapid
Mi
x
Rapid
Mix
Floccu-
lation
Stabili-
zation
Disin-
fection
A
e
rat
i
on
Fl
o
c
c
ula
t
io
n
P
re
se
tt
l
i
n
g
Settling
Filtration
Option if
CO
2
>
10 mg/L
Options:
Excess lime
soda ash
caustic alum
polymer
Options:
Sand
Coal
Dual Media
Mixed Media
Options:
Recarbonation
HCl or H
2
SO
4
Polyphosphate
Option if Raw Water Turbidity > 3,000 NTU
Options:
Sludge
Recirculation
Split Treatment
Lime
Recirculation Option
Pre-Softening Options are Same
a
s f
o
r
S
ing
l
e
-
S
t
ag
e
S
of
t
e
n
i
ng
Rapid
Mix
Floccu-
lation
Recarb-
onation
Settling
Filtration
Disinfection
Options:
Alum
Polymer
Optional
Element
Bypass Flow
D
i
s
i
n
f
e
c
t
i
o
n
Two-Stage Softening
F
i
l
t
Excess Lime
Soda Ash
1st Stage
Recarbo-
nation
2 nd
Rapid
Mix
2 nd
Floccu-
lation
2nd Stage
Recarbo-
nation
Pre-Softening Options are Same
a
s
f
o
r
Si
n
g
l
e
-
S
t
ag
e
S
of
t
eni
ng
Rapid
Mix
Floccu-
lation
r
a
t
i
o
n
Settling
Settling
Options:
Alum
Polymer
Options:
Alum
Polymer
Options:
Sludge
Recirculation
D
i
s
i
n
f
e
c
t
i
o
n
Three-Stage Softening with Lime Recovery & Reuse
F
i
l
t
r
a
t
i
o
n
Lime for CaCO
3
Precipitation Only
Excess Lime
2nd
Rapid
Mix
2 nd
Floccu
-lation
1st Stage
Recarbo-
nation
2nd Stage
Recarbo-
nation
Pre-Softening Options are Same
a
s
f
o
r Si
ng
l
e
-
S
t
ag
e
S
of
t
eni
ng
Rapid
Mix
Floccu-
lation
Settling
Settling
Settling
R
ec
ir
c
u
l
ati
o
n
O
p
t
ion
Options:
Soda Ash
Caustic
Alum
Polymer
Options:
Coagulant
or Coagulan
Lime Recovery Option
R
ec
a
l
ci
na
ti
on
Aid
Fig. 13-5.
Softening flow patterns (From Culp, Gordon, and Williams, Robert,
Handbook of Public Water Systems.
Copyright
1986 by John Wiley & Sons, Inc. Reprinted by permission of John Wiley & Sons, Inc.)
