This document discusses water precipitation processes and facilities for water treatment. It describes precipitation of particles in batch and continuous settling tanks. It provides equations relating percentage of settled particles to time and settling velocity. It also shows schematics of horizontal, vertical, radial, and lamella settling tank designs. These include channels for inlet/outlet water and removal of settled sludge.

1. 1
III. Water Treatment
Topic III.3. Water Precipitation: Processes and
Facilities
Precipitation Processes
 Precipitation of spherical mineral particles in batch settler
(Stockes)
 Precipitation of natural particles (with arbitrary shapes and
dimensions) in batch settler
 Relationship between percentage of the settled particles -  and time of
settling - t
 Relationship between percentage of the settled particles -  and settling
velocity - u0
 Precipitation of natural particles in continuous flow settling tanks
with mean horizontal flow velocity - v and real settling velocity - u
; ;
2
.
.
.
18
1
d
g
u
w
w
p


 

0
0
0
0 .
30
. u
v
u
u
u
u


  0
.u
k
v  )
(
L
H
f
k 

2. 2
Precipitation Processes
 = f(t)  = f(u0)

3. 3
Precipitation Processes
Scheme of Horizontal Continuous Settling Tank
v - mean horizontal flow velocity; u0 - vertical precipitation velocity at batch conditions; w -
vertical component of pulse (arbitrary flow) velocity;
u - real settling velocity
, where F is the water mirror area, m2
, where k = 7,5 with L/H = 10; k = 10 with L/H = 15; k = 12 with L/H = 20
,where W is volume the setter, m3
0
.
6
,
3
.
u
Q
F


0
.u
k
v 
u
H
Q
t
Q
W .
6
,
3
/
.
. 


4. 4
Kinds of Settling Tanks
Scheme of Horizontal Settling Tank
1 - coarse water; 2 - sediments cleaning device; channel for floating particles removal;
5 - sludge removal pipe

5. 5
Kinds of Settling Tanks
Vertical Settling Tank
a - without flocculation chamber
б - with built-in flocculation chamber
1 - coarse water
2 - settled water
3 - sludge removal

6. 6
Kinds of Settling Tanks
Radial Settling Tank
1 - coarse water; 2 - sludge circulation; 3 - stilling chamber; 4 - settling zone; 5 - sludge
cleaner; 6 - sludge; 7 - settled water; 8 - mixer; 9 - reagents inlet pipe

7. 7
Kinds of Settling Tanks
Scheme of Lamella Settling Tank

8. 8
Kinds of Settling Tanks
Lamella Settling Tank
Prefabricated lamella settler Lamella modules