Water Treatment : Working Video Lecture - Class 8

in this video we will see how human
beings have added to the natural water
cycle you can see that in one of our
linked videos by taking water from
rivers for our use in towns and cities
humans began to interfere with the
natural water courses long ago wells
have been dug to access clean water for
drinking the Romans built aqueducts to
bring water to the cities and nowadays
we've built dams for irrigation and
hydroelectricity and we're taking a huge
amount of water from natural sources to
use in our homes and industries most
people in industrialized nations take
access to clean water for granted
however more than one person in 10
that's over 700 million people do not
have access to clean water and around
three and a half million people die each
year from water related disease the
average Britain uses a hundred and fifty
liters a day whilst each American uses
600 litres a day on average in contrast
many sub-saharan Africans at less than
20 liters of water a day and two-thirds
have no proper toilets for some people
water is a precious and scarce resource
only 3% of the water in the world is
fresh of this three-quarters is locked
up as ice in Antarctica and Greenland
and glaciers nearly another quarter is
underground only 1% is above-ground in
rivers and lakes we use the water mainly
for irrigation of crops and normally
this needs no further purification the
next biggest user is industry sometimes
for example in food preparation very
clean water is needed finally there is
domestic water some new housing estates
in industrialized countries have a dual
water supply where gray water collected
from rain and from effluent from basins
baths and showers is available for
flushing and watering the garden
and the purified water is only used for
washing and cooking however normally
only one pipe supplies water to our
homes and this water has to be a
drinking quality and is purified on an
industrial scale at the waterworks if
you do not have piped water where you
live you might have access to a well if
the well has a brick or concrete wall
and sides
the only water able to enter the well
will be water that has had to seep
through the surrounding rocks this means
that the water is likely to be pure and
safe to drink piped water from the
waterworks for those lucky enough to
have it originally comes from rivers
lakes reservoirs or underground aquifers
the grill will stop large floating
objects fish etc from entering the
waterworks next coagulants such as alum
are added which causes tiny particles in
the water to cluster in lumps which then
settle in the sedimentation process the
filter is made of fine sand to capture
any particles that are left
finally chlorine is added to kill any
bacteria if the water does not naturally
contain fluoride ions they are often
added as sodium fluoride as an aid to
building strong teeth in those that
drink the water but for the 700 million
people or so without access to clean
water
small-scale developments are beginning
to help if you are interested in these
developments look up clean drinking
water for the world and learn about the
LifeStraw BioSand filters and many more
so to summarize many people take clean
water for granted it comes in pipes
filtered and chlorinated to make it
disease-free from the waterworks however
there are almost a billion people
worldwide who do not yet have access to
safe drinking water