Sewage treatment plant for small towns
consists of the following units.
UNIT
FUNCTION
1. Rack
(1) Removes coarse floating matter
2. Grit chamber
(2) Removes grit
3. Imhoff tank
(3) Sludge, in lower chamber, settled
solids
are decomposed
4. Dosing tank
(4) Regulates head and discharge of nozzles
5. Trickling Filter
(5) Dissolved and finely divided organic
matter
is converted into Humus
6. Humus Tank
(6) Removes humus
7. Contact Beds
(7) Removes 80-90% of suspended solids and
60 to 75% of B.O.D
effluent obtained from
these beds are clear and odorless.
Objects/ Needs of sewage
treatment.
1.
To reduce the
sewage contents from the sewage
2.
To remove the
nuisance canting elements of the sewage.
3.
To change the
characteristics of the sewage
4.
To make the sewage
suitable for safe and final disposal.
TYPES OF TREATMENT (SEQUENCE OF
TREATMENT)
|
Sl.
No. |
UNIT |
IMPURITY REMOVED
|
% REMOVAL
OF |
|
SUSPENDED
SOLIDS |
BACTERIA |
B.O.D |
|
1 |
Screens |
(a)
PRIMARY REATMENT
Bulky
floating and suspended matter |
5-20 |
10-20 |
5-10 |
|
2 |
Skimming tank |
Oil
and grease |
|
|
|
|
3 |
Grit Chamber |
Heavy
and coarse suspended matter |
35-65 |
30-70 |
25-40 |
|
4 |
Sedimentary
tanks |
Suspended
Matter |
35-65 |
30-70 |
25-40 |
|
Sl.
No. |
UNIT |
IMPURITY REMOVED
|
% REMOVAL
OF |
|
SUSPENDED
SOLIDS |
BACTERIA |
B.O.D |
B. SECONDARY
TREATMENT |
|
1 |
Trickling filter
OR
Activated sluoga
process |
Colloidal
organic matter
Colloidal
organic matter |
70-90
85-90 |
90-95
90-95 |
80-90
75-95 |
C. FINAL
TREATMENT |
1
|
chlorinator |
Fins pathogenic
bacteria |
- |
90-95 |
98-99.2 |