3. Raw water is collected
from surface water or
from ground water.
For commercial purpose
only surface water is
used.
Surface water consist of
river water, pond water
or lake water.
3
5. Screening is the very first operation in the any water
treatment process.
Screen removes all the large sized suspended particles
and floating matter.
The materials collected in screening is grinded into
smaller sizes for easy disposal with the help of devices
such as comminutor and macerator.
It is of two types: FINE screen and COARSE screen
It is generally adopted for the treatment of surface water.
5
6. FINE
• These are in the form of
wire mesh and have a
spacing less than 20mm c/c.
• They get clogged easily and
hence increases the
operational and
maintenance cost.
• However the may be used
after coarse screen.
COARSE
• These are in the form of
parallel iron or aluminum
rod having spacing 20-
100mm c/c.
• Screens are always placed
inclined at an angle of 45-60
degree with horizontal in
the direction of flow.
• Diameters of rods is in the
range of 10-25mm.
6
8. Objectives Of Aeration
Removal of undesirables gases
such as H2S, NH3, CH4.
Increasing the dissolved
oxygen content in water.
Removal of volatile liquid like
phenol,humic acid etc.
Removal of iron & manganese
by converting into their
corresponding ppt.
8
9. All types of aerators work on the basic principle
of increasing the surface area of water in
contact with air.
Its types are
1. Cascade aerator
2. Spray nozzle aerator
3. Diffused bed aerator
4. Tray tower aerator.
9
11. • It is a process in which certain chemicals are added in
water to neutralise the negatively protected charged
suspended solid.
• It forms sticky and gelatinous ppt.which is capable of
sticking on to the surface of suspended solid forming
bigger size particles.
• High energy in the form of rapid mixing is given to
disperse the coagulants properly and to promote
particles collision.
11
12. 1. Alum- when alum is added in water it reacts with alkalinity
present in water. It forms sticky gelatinous ppt. of aluminum
hydroxide, which helps in removing the suspended particles.
Alum works in the ph range of 6.5 to 8.5, its usual doses is
b/w 10-30 mg/l.
There are many others coagulants other than alum
such as copperas(FeSO4.7H2O), chlorinated copperas
(FeCl3 + FeSO4) , Sodium Aluminate (Na2AlO4). But
these are not used in raw water treatment because
they have their own drawback.
12
14. • It is the process in which the particles are brought in
intimate contact with each other so as to promote
their agglomeration.
• After adding the flocculants, we generally do gentle
mixing to ensure that flocculants are completely
mixed in water in order to increase the opportunity
contact.
• There are two types of flocculation
1. Conventional
2. Tapered
14
16. It is a physical process in
which the particles settle
under the action of gravity.
It is based upon size and
specific gravity of particles.
Various types of settling may
be observed depending upon
concentration of suspended
solid in water.
16
17. 1. Type 1 or Discrete particle settling- it refers to settling
of discrete particles in suspension. Due to low concentration
of particles , the particles do not interfere with each other
while settling.
2. Type 2 or Flocculant settling- in this type of settling the
velocity field overlap and the particles may also comes in
contact with each other.
17
18. 3. Type 4 or Compression settling- it is observed in highly
concentrated suspension in which inter particles forces
hindered the settling of individual particles.
4. Type 4 or Compression settling- when solids are present
in excessive concentration such as at the bottom of
sedimentation tank, hence further settling occurs only by
compression caused due to expulsion of water due to weight
of particles constantly acting over it.
18
20. It is designed to effectively
remove suspended solid,
colloidal impurities, turbidity
,colour and microorganisms.
Types of filters are GRAVITY
& PRESSURE filter. For mass
filtration gravity filters are
used.
The most commonly used
medium is sand as it is widely
available ,cheap and effective
in removing impurities.
Nowadays activated carbon,
anthracite etc. are also used. 20
21. • Gravity filter are of two types
1. Slow Sand Filter- these filters consist of fine sand as
the filtering media. Filtering action mostly takes
place at or near the surface of the sand. It is said to
be ready for operation when SCHMUDTZDECKE
developed over the surface. For cleaning it, top 2-
3cm of the sand layer is removed. Its rate of
filtration is 100-200 l/h/m2.
21
22. 2. Rapid Sand Filter- the size of medium particles used
in it is comparatively bigger in size than SSF. Filtering
action takes place throughout the depth of filter,
hence impurities are present up to the bottom.
Surface cleaning like SSF is not sufficient here, so
cleaning is done by the process of backwashing.
Cleaning is done frequently to obtain high discharge,
it is completed in approximately in 30 minutes.
Rate of filtration is 3000-6000 l/h/m2.
RSF is adopted in INDIA.
22
24. Water disinfection means the removal, deactivation
or killing of pathogenic microorganisms.
Disinfectants should not only kill microorganisms. It
must also have a residual effect, which means that it
should remain active in order to protect from future
contamination.
Chlorine is generally used as disinfectant. It is
commercially adopted because chlorine is available
in various forms (solid, liquid,& gas).
24
25. • Chlorine is mostly used in liquid form. When it is
added it reacts with water to give HOCl and HCl.
• HOCl & HCl further dissociates into OCl- & Cl-
respectively.
• Cl2 ,HOCl & OCl- are capable of carrying out
disinfection & are called as freely available chlorine.
& since Cl- is stable it is not responsible for
disinfection.
• Freely available chlorine should not be left as residue
beyond 0.2 mg/l.
25
28. The purpose of distribution system is to deliver water to
consumer with appropriate, quality, quantity and pressure.
The distribution reservoir are designed to meet the
fluctuating demand with a constant rate of supply.
Requirements of Good Distribution System
1. Water quality should not get deteriorated in the distribution
pipes.
2. It should be capable of supplying the requisite amount of water
during firefighting.
3. The layout should be such that no consumer would be without
water supply, during the repair of any section of the system.
4. It should be fairly water-tight as to keep losses due to leakage to
the minimum. 28
29. TYPES OF DISTRIBUTION
SYSTEM
• It is of four types.
1. DEAD END OR TREE END: in this system main pipe
is divided into sub main, branches, & laterals. It is
usually followed in old towns.
ADVANTAGES:
1. it is economical as the pipe length required is less
as compared to other system.
2. it can be extended easily.
29
30. • DISADVANTAGES:
1. water can pass only through one route and hence, if
some faults occur complete water supply of the area gets
affected.
2. it has non-uniform distribution of pressure.
2. GRID IRON SYSTEM: in this system main, sub main &
branches are interconnected with each other.
ADVANTAGES:
1. Dead ends are completely eliminated & hence water
reach at a point through various points.
2. Pressure is almost uniform at all sections.
3. Water remains in continuous circulation and hence it
is not liable to contamination due to stagnation.
30
31. • DISADVANTAGES:
1. Its construction cost is intensive as it require more
length of pipeline, more nos. of joints & more nos.
of gate valve.
2. Its design id difficult and cannot be implemented in
an already established city.
3. ZONAL OR RADIAL SYSTEM: in this system a large
area is divided into several zones usually based
upon population. The water is pumped into the
distribution reservoir kept in the middle of each
zone.
ADVANTAGE: It gives quick service.
31
32. 4. RING OR CLOSED SYSTEM: in this system a closed
ring of main surrounds the whole area & is then
broken into sub main , branches & laterals. The flow
of water takes place ‘outside inn’.
32
