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In
spite of a large part of the world being covered
with water, we do not get sufficient fresh
water. With the increased rate of
industrialization, even the available fresh
water sources are getting polluted day by day
making it unusable without proper treatment. The
level of ground water is also gradually going
down due to higher withdrawal of water from
ground and scanty rainfall.
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In
coastal regions, the availability of fresh water
is even scarcer as the ground water is also
saline. Fresh water resources are under pressure
in many cities and this will increase the demand
for recycled water. Development and
industrialization cannot sacrifice due to lack
of water availability. Some alternatives need to
be found which involve reducing use of water in
industry, conservation at different levels and
most importantly with the reuse of wastewater
after its proper treatment. This is where
wastewater recycling comes in.
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Three
types of processes are commonly used for
treatment and recycle of effluents. These are
physic-chemical, biological and membrane
/ion-exchange processes.
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Physic-chemical
processes are used to remove suspended and
colloidal impurities. These processes offer a
good pre-treatment to downstream biological and
membrane processes. Biological processes are
used to remove dissolved organics from effluent
and thus to reduce chemical and bio-chemical
oxygen demands (COD/BOD) of the effluent.
Biologically treated effluent containing
dissolved salts and residual impurities are
removed in processes such as membrane technology
base reverse osmosis, electro-dialysis or ion
exchange technique.
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