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Water Tr eatment
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COAGULATION
SEDIMENTATION
FILTRATION DISINFECTION
STORAGE
COMPLETE CYCLEOF WATER TREATMENT:
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COAGULATION Coagulation removes dirt and other particles
suspended
in water. alum and other chemicals are added to water to
form
tiny sticky particles called floc which attract the dirt
particles. The combined weight of the dirt and the alums (floc)
becomes heavy enough to sink to the bottom during
sedimentation.
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SEDIMENTATION
WATER TOWARDS
FILTRATION
Coagulated particles fall, by gravity, through water in a
settling tank and accumulate at the bottom of the tank, clearing
the water of much of the solid debris and clear water moves to
filtration.
:
WATER FROM
COAGULATION
WATER FROM
COAGULATION
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FILTRATION, DISINFECTION &STORAGE
FILTRATION: The water passes through filters, some made of
layers of sand, and charcoal that help remove smaller
particles.
DISINFECTION: A small amount of chlorine is added or some other
disinfection method is used to kill microorganisms that may be in
the water.
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Water Disinf ecti on
Purpos e of d is infec t ion :
To make Drinking water free of any disease causing bacteria and
microbes.
Methods of disinfection:
There are 3 mainly used disinfection methods at large scale.
CHLORINATION OZONATION ULTRAVIOLET RADIATION
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CHLORINATION
Chlorine is applied to water in one of three forms: elemental
chlorine (chlorine gas), hypochlorite solution (bleach), or dry
calcium hypochlorite. All three forms produce free chlorine in
water
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The main advantages : It is the most efficient method of making
free chlorine
available to raw water.
It lowers the pH of the water slghtly. Control is simple;
testing simple; and it is not an expensivemethod.
The main disadvantages are: Chlorine gas is toxic and can
combine with other chemicals
to form combustible cysts (durab le seed-like stages) formed
by
parasitic protozoa such as C ryptosporidium
and G iardia can sur vive chlorine.
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The main advantages : Ozone is a much more powerful germicide
than chlorine
especially for fiscal bacteria. It reduces turbidity of water by
breaking down organic
constituents. The process is easily controlled. The
disadvantages are: Pure oxygen may not be readily available
locally.
Ozonized water is corrosive to metal piping. Ozone decomposes
rapidly into oxygen. Water has to be aerated prior to use to remove
the ozone
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UL TRAVI OL ET RADI ATI ON
When UV radiation penetrates the cell wall of an organism, it
damages genetic material, and prevents
the cell from reproducing.
Now a days emerging technology made UV radiation to find a place
in both household and large scale drinking water disinfection.
How is UV light generated?
Ultraviolet light is most typically generated from a low
pressure or a medium pressure lamp generating UV light.
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The main advantages of U-V treatment are: U-V rays in the range
of 2500-2600 Angstrom units
are lethal to all types of bacteria. There is no organoleptic,
chemical or physical changeto the water quality. Overexposure does
not have any ill effects.
The main disadvantages are: Electricity supply should be
reliable.
Turbidity reduces efficiency. Water may require prior treatment
like filtration. The unit requires regular inspection and
maintenance.
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COAGULATION
SEDIMENTATION
FILTRATION DISINFECTION
STORAGE
COMPLETE CYCLEOF WATER TREATMENT:
