Water purification

1. Dr. Beena Negi
Water Purification Techniques
By
Dr. Beena Negi

2. Dr. Beena Negi
Potable and non potable water
Water that can be used for drinking and cooking purposes is called
potable water.
Water that can not be ingested is known as non-potable water.
Desalination
Process of removing dissolved salts from sea water to yield potable
water
Methods for desalination
1. Reverse osmosis
2. Electrodialysis
3. Distillation
4. Use of solar energy
5. Freezing

3. Dr. Beena Negi
Methods for desalination
Electrodialysis Reverse osmosis
High solute concentration to
low solute concentration

4. Dr. Beena Negi
Water purification techniques
1. Reverse osmosis or RO-UV
2. Filtration
3. Distillation
4. Heating/boiling
5. Chlorination
Water purification, or drinking water treatment, is the
process of removing contaminants from surface water
or groundwater to make it safe and palatable for human
consumption.

5. Dr. Beena Negi
In 2000 B.C., Sanskrit documents about medical concerns
were created called the Sus’ruta Samhita.
The Sus’ruta Samhita declares that “impure water” should
be purified by being boiled over a fire, or being heated
in the sun or by dipping a heated iron into it, or it may
be purified by filtration through sand and coarse gravel
and then allowed to cool.

6. Dr. Beena Negi
Reverse osmosis (RO) is a water
purification technology that uses a
semipermeable membrane.
In RO, an applied pressure is used to
overcome osmotic pressure.
The result is that the solute is retained
on the pressurized side of the
membrane and the pure solvent is
allowed to pass to the other side.
The purified water is also irradiated
using UV light which kills bacteria
and other organisms present in
water.
Reverse osmosis
Water flows from
high solute concentration to
low solute concentration

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In the normal osmosis
process, the solvent
naturally moves from an
area of low solute
concentration (High
Water Potential), through
a membrane, to an area
of high solute
concentration (Low
Water Potential).
Applying an external
pressure to reverse the
natural flow of pure
solvent, thus, is reverse
osmosis.
Osmosis

8. Dr. Beena Negi
 Improves taste, odour and appearance
 Highly effective
 Consume no energy
 Very convinient
 Flushes away pollutant, does not collect them
 Easy to clean
 Removes bacteria, virus, pesticide, hydrocarbon,
radioactive contaminant, colloidal matter, etc.
Benefits of RO water

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Impure water can be purified by distillation
In this process water is heated in a flask.
The steam generated is passed through a water cooled condenser.
The condensed water can be used as potable water.
It removes the widest variety of contaminants such as salts,
chemicals, bacteria and other micro-organisms from your water
supply.
Distillation

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Water is boiled for 20-25 minute in a container which coagulates
the suspended matter and kills bacteria and other organisms.
The resultant water can be cooled and filtered and can be used
for drinking purpose.
Heating

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Water is passed though a column packed with sand and gravel.
This treatment removes all suspended matter.
Filteration

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When chlorine is added to water it forms HCl & HOCl.
The disinfecting action of chlorine is mainly due to Hypochlrous
acid & to a small extent due to Hypochlorite Ions.
Chlorination

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Ozonation
Ozone (O3) is an effective, relatively harmless disinfection method,
but is expensive (and therefore less popular than chlorine).
Ozone is a strong oxidant, that produces hydroxyl free radicals that
react with organic and inorganic molecules in water to kill microbes.
Can result in a 99% reduction in the appearance of bacteria.
Acts as a strong disinfectant.

14. Dr. Beena Negi
Sewage water treatment
Tertiary treatment
Sewage waste
pass through
screens (remove
floating material)
Pass through a
chamber packed
with sand and
stones (freed
from dirt)
Filter and allow to stand in
sedimentation tank.
Particulate matter settles
down (sludge)
Sludge is removed and
processed as manure
Take water in another tank, air
is pumped, along with some
sludge (contains oxygen rich
bacteria)
Take it in another
sedimentation tank,
Sludge settles down
(generate methane gas)
Disinfection
tank
(chlorine)
Treatment by chemicals
(alum, flocculating agents)
Treat with chlorine
or ozone
RO, UV
electrodialysis
Primary treatment
Secondary treatment

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