This presentation is made with a view to introduce various units & processes carried out in water treatment plant with various trains or say chains of units to meet Indian Standard criteria.

1. Bhagwan Mahavir College of
Engineering and Technology
PRESENTATION
ON

2. Prepared by : Ankit Gangani 140060106055

3. OUTLINE
 Introduction
 Objectives of water treatment
 Conventional water treatment plant layout
 Various Methods of purification of water
Screening
Plain Sedimentation
Sedimentation aided with coagulation
Filtration
Disinfection
Aeration
Softening

4. Introduction
Water treatment is the process of making water suitable or
acceptable for an end-use.
It removes existing water contaminants and so reduces their
concentration that the water becomes fit for its desired
application.
The amount & type of treatment process (Treatment Train )
depends upon quality of raw water and various standards required
after treatment.

5. Objectives of water treatment
The objectives of water treatment are to produce:
Water that is safe for human consumption
Water that is appealing aesthetically to the consumer
Water at a reasonable cost

6. Indian Standards for drinking water

7. Screening
Coagulation
Flocculation
Sedimentation
Filtration
Disinfection
Storage
Distribution
Raw water
Alum Cl2
sludge
sludge
sludge
7

8. Functions of Water Treatment Units

9. Selection of treatment process-Train
 The types of treatment required for different sources are given in the
following table:

10.  Removes large solids
logs
branches
rags
fish
 Simple process
may incorporate a mechanized trash removal system
 Protects pumps and pipes in Water Treatment Plants

11. Plain Sedimentation
 Sedimentation is the removal of suspended particles
by gravitational settling.
 Types of Sedimentation Tanks
1) Fill And Draw Type
2) Continuous Flow type

12. Shape of sedimentation tank
1. Rectangular
tank with
horizontal flow.
2. Circular tank
with radial or
spiral flow.
3. Hopper bottom
tank with
vertical flow.

13. SEDIMENTATION
13
 Water flows to a tank called a
sedimentation basin
 Gravity causes the flocs to settle to the
bottom
 It would take a very long time for all
particles to settle out and that would
mean we would need a very large
sedimentation basin.

14. Sedimentation aided with
coagulation
Addition of measured quantity of chemicals called
coagulants to water and their through mixing ( rapid
mixing ).
Formation of precipitate which coagulates and forms a
flow ( flocculation )
Sedimentation
 Sedimentation added with comprises of three step

15. Coagulants
 Aluminum Sulfate Al2(SO4)3
 Ferrous Sulfate FeSO4
 Ferric Sulfate Fe2(SO4)3
 Ferric Chloride FeCl3
 Lime Ca(OH)2
Aluminum salts are cheaper but
iron salts are more effective over
wider pH range
15

16. Aeration Unit
 Work : Diffusion of Air
 Removes odour and tastes
 Oxidizes iron and manganese, increases dissolved oxygen content in
water, removes CO2 and reduces corrosion and removes methane and
other flammable gases.
 Types of Aerators
1. Gravity aerators
2. Fountain aerators
3. Diffused aerators
4. Mechanical aerators.

17.  Gravity Aerators (Cascades): In gravity aerators,
water is allowed to fall by gravity such that a large area
of water is exposed to atmosphere, sometimes aided by
turbulence.
Aeration Unit

18.  Injection or Diffused Aerators : It
consists of a tank with perforated
pipes, tubes or diffuser plates, fixed
at the bottom to release fine air
bubbles from compressor unit. Time
of aeration is 10 to 30 min and 0.2 to
0.4 litres of air is required for 1 litre
of water.
Aeration Unit

19.  Fountain Aerators : These are also known as spray
aerators with special nozzles to produce a fine spray. Each
nozzle is 2.5 to 4 cm diameter discharging about 18 to 36
l/h. Nozzle spacing should be such that each m3 of water
has aerator area of 0.03 to 0.09 m2 for one hour.
Aeration Unit

20.  Mechanical Aerators : Mixing paddles as in
flocculation are used. Paddles may be either
submerged or at the surface.
Aeration Unit

21. Types of Mixing Devices
 Mixings basins with baffle walls
`

22.  Mixing Basins Equipped with Mechanical devicies

23. Flocculation
 Flocculation is a slow mixing or agitating process in which
the destablished colloidal particles are brought into
intimate contact in order to promote the floc formation .
 Rate of flocculation depends upon
 Types and amount of turbidity
 Types of coagulant
 Dosages of coagulant
 Mean velocity gradient in basin

24. Clariflocculator
Clarifier and flocculator are provided in single unit
called clariflocculator.
The flocculating chamber is provided in the centre
and clarifier component is formed by the peripheral
space.
Velocity of flow of water around 0.3 m/min.
Mechanical scrapper provided to remove sludge.

26. Filtration
The process of passing the water through the beds of
such granular material is known as filteraton
 Types of Filtration
Slow sand gravity filter
Rapid sand gravity filter
1. Rapid sand gravity filter
2. Pressure filter

29. Method of disinfection
 Physical method
By heat
By U.V. rays
 Chemical method
Oxidizing chemicals
Metal ions
Alkalis and acids
 Minor method
Boiling of water
Treatment with excess lime
Treatment with ozone
Treatment with iodine and bromine
Treatment with ultra-violet rays
Treatment with potassium permanganate

30. Water softening
 Water is said to be hard when it contains relatively large
amounts of bicarbonates, carbonates, sulphates and
chlorides of calcium and magnesium dissolved in it.
 Types of Hardness
 Temporary hardness
 Permanent hardness

31. Types of Hardness
 Temporary Hardness- caused by dissolved
bicarbonates of Ca and Mg.
-AKA ‘alkaline or carbonate hardness’
 Permanent Hardness – caused by dissolved
chlorides and sulphates of Ca, Mg, Fe and Al etc.

32. Removal of Hardness
 Removal of temporary hardness
1. Boiling
2. By adding lime
 Removal of temporary hardness
1. Lime-soda process
2. Zeolite process
3. Demineralization or De-ionization process

33. Disinfection
 The filtered water may
normally contain some
harmful disease producing
bacteria in it.
 These bacteria must be
killed in order to make the
water safe for drinking.
 The process of killing these
bacteria is known as
Disinfection or
Sterilization.

34. Methods of Disinfection
 Boiling: The bacteria present in water can be destroyed by boiling it for a long
time. However it is not.
 Treatment with Excess Lime: Lime is used in water treatment plant for
softening. But if excess lime is added to the water, it can in addition, kill the
bacteria also. Treatment like recarbonation for lime removal should be used
after disinfection.
 Treatment with Ozone: Ozone readily breaks down into normal oxygen, and
releases nascent oxygen. The nascent oxygen is a powerful oxidizing agent and
removes the organic matter as well as the bacteria from the water.
 Chlorination : The germicidal action of chlorine is explained by the recent
theory of Enzymatic hypothesis, according to which the chlorine enters the cell
walls of bacteria and kill the enzymes which are essential for the metabolic
processes of living organisms.

35. Reference
 Water & waste water Engineering -4th edition By
Mahajan Publishing House
 http://web.iitd.ac.in/~arunku/files/CVL100/L8.pdf
 http://nptel.ac.in/courses/105104102/Lecture%2020.ht
m
 http://www.sswm.info/sites/default/files/reference_at
tachments/SCHUTTE%202007%20Handbook%20for
%20the%20Operation%20of%20Water%20Treatment
%20Works.pdf