Water Freshens Up:An Eventful Journey Video Lecture | Science Class 7

hello friends this video on wastewater
story part 4 is brought to you by
example your calm no more fear from exam
so now we understood how the sewage gets
carried to the sewage treatment plant so
that part is free or not but now the
next question is how is Jewish treatment
down what happens inside the sewage
treatment plant that the wastewater gets
converted into clean water so what magic
happens inside so now we are going to
discuss about sewage treatment in detail
so sewage needs to be treated in sewage
treatment plants before disposal because
we cannot dispose the wastewater with
all the harmful chemicals and pesticides
and paints and harmful microorganisms it
will water directly that will pollute
the water of that entire water body so
that is why we first take them in to the
sewage treatment plant where all the
harmful substances are being removed and
then the clean water is disposed into
the water bodies so this process of
sewage treatment inside a plant is
carried out in four major stages and
these are called preliminary treatment
primary treatment secondary treatment
and tertiary treatment so these are the
four different stages in which the
entire process of sewage treatment
happens however this stages might be
different in different sewage treatment
plants so in some sewage treatment
plants the preliminary treatment and the
primary treatment they are both fused
together and it is called as primary
treatment in some sewage treatment
plants they really do not mention
tertiary treatment separately so in in
some of the counts they just have two
stages primary treatment and secondary
treatment but actually if you break it
down into proper four stages so these
are the four stages which through which
the sewage is sewage is passed through
so that it can get converted into clean
water so let us look at the entire
wastewater treatment plant
stepwise as I said so the first one is
preliminary treatment and
Neri treatment the sewage is passed
through bar screens and then grit and
sand remover tanks now we will discuss
about each of these in detail so you see
this is the preliminary treatment where
you have the buyer screens and the grid
and the sand removal tanks
this is followed by primary treatment
where you have water clarifiers and they
further help in clarifying water
removing dust and dirt from water which
is followed by secondary treatment where
we have aeration tanks here aerobic
microorganisms do a wonderful job
cleaning up the water and finally this
is followed by tertiary treatment which
is like final cleaning up of water and
here we make use of chemicals like
chlorine or other disinfectants to do
the final round of cleaning and at the
end of the airy treatment what we get is
a clean water so it is like very much
clean and it is so clean that you can
just dispositive directly into the
reverse so you see it's it's a wonderful
mechanism in order to reuse wastewater
now if we are able to reuse waste water
in this way we are actually going to you
know provide water to a lot of people
who are facing water scarcity and
therefore it is very very important that
sewage should always be treated before
it is being disposed off into a water
body
so now let us start with each treatment
one by one so like we first talked about
the preliminary treatment where we will
discuss about the bar screens so what
are bars things so this is the stage
where the entire sewage which contains a
huge amount of dust done will chemicals
how food substances solid particles
everything is there and then entire
wastewater is being passed through a
device like this where you have you see
rod like structures who are bar SE C bar
leg structures rod neck structures so
when you pass the sewage through this
all the solid particles get stuck so
kind of filtered so the solid bigger
solid particles if the solid particles
of a
tiny particles they will anyways pass
through but if they have big particles
they will get stuck and this step is for
removing the larger objects and larger
objects could be plastic could could be
packaged mistake scams ropes
it is funny surprising that people
through these kind of things also in the
sink because normally in sink you will
have that term that porous structure
because of which bigger objects will not
be able to pass through the same but a
lot of people they flush a lot of
substances like tissues steaks plastics
packets so all these are flushed so when
you flush all these things they actually
reach the sewerage and through the
sewerage it comes to the sewage
treatment plant so at the very first
first step all larger objects are being
removed so that is the first round of
cleaning water now from bar screens the
sewage is now passed on to the grit and
sand removal tank so here you have a big
tank like this where the water is not
allowed to move very fast so the speed
of the incoming wastewater is slowed
down so when the speed is slow down it's
like water spends a lot of time in this
tank and when you allow water to spend a
lot of time here what happens is the
heavier particles which is present in
that water
for example sand and grit so these kind
of particles they tend to settle down so
after some time what do you observe is a
lot of undesirable substances which were
present in the water in the form of sand
or grit they are all settled at the
bottom and therefore the clear water can
be taken up from the above so that is
the purpose of grit and sand removal
tank
so here smaller particles next time and
grit are removed and what does this
process termed as like if you leave a
liquid a liquid which
also contain some solid particles when
you need it undisturbed for something
what happens the heavier particles
settle down at the bottom and that
concept is known as that property is
known as sedimentation and the
substances which settle down at the
bottom that is down as the sediment so
here also the same concept of
sedimentation works in a grit and sand
removal tank and for sedimentation to
take place we need to lower the speed of
the incoming water because if water
passes through the stamp very fast if it
keeps going through the stand value fast
it will not get enough time for the sand
and grit to settle down so therefore we
reduce the speed of the water so the
water flows very slowly through the
stand and then gradually the heavier
particles will settle down at the bottom
so this is the second round of physical
removal now we only talked about this
entire process of sewage treatment we
will see that sewage treatment is not
only about physically removing unwanted
particles it involves physical removal
of particles it also involves biological
treatment where living organisms will
help in removing impurities it also
involves chemical treatment where
chemical substances are being used to
remove the unwanted substances so that
is why this treatment is a combination
of physical treatment chemical treatment
and biological treatment now these two
steps which have which we have discussed
so far that is the buyer screams and the
three times and removal tank these are
all physical treatment because here we
are physically removing unwanted
particles from the wastewater so we can
see that these these steps are physical
treatment but overall the entire process
of sewage treatment is a physical
chemical as well as biological treatment
so this was the preliminaries treatment
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