What is Water Pollution - Young Kun Park '76

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SOUTH MOUNTAIN SCHOOL LIBRAR1 - --~ ;- :.

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?-I any years :'l,_;- o ,fl1en y o ur fc1. t he r

was in your ar;e ,

he c ou l d g o t o a ri v er near a bic_; cit y f or s wi mn iin c;

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?-; ow , you

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a big ci ty .

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c<1.rrn ot sw i m or p l a y

Do y ou kn o w why

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in a

If y o u

w i l l t e l l you .

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The wa t e r

of

a riv e r

n ear a b i g ci t y ha s bad s me ll

and ma n y ge r ms wh ich ma ke you sick .

d i r t y 1¡,a ter " po ll uted wa ter ".

We call t h is

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The water of t r1e river be c ame d irty bec a us e

peop l e have dumped many d i rty was t e into th e r i ver.

Ma ny factories a lso dump t he i r d i r ty wa st e into the

river .

We c a ll t h is d irty waste "s e wage ".

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The g e r ms in a d irty wa ter make fis he s si c k .

If you eat a sick fi sh, you wi l l be c ome sick also .

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Do you k n ow h ow we c a n cle a n t he s ewag e ?

I will tell you the answer.

First, we must mea s u r e

how many germs are in the sewage.

The g erms are so

small that we cannot see them with our e yes.

Therefore,

we measure the amount of oxygen the g e rms e a t up.

large amount of oxygen is eaten up, we can tell that

there are many germs in the sewage.

l>y

We call the

amount of oxyg en eaten up/'--the germs "the biochemical

oxygen d emand".

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Second , if the r e are many g erms in t he sewage , we

must k ill t h em be for e we dump t he s e wage into t h e

river.

It is very difficult, and take s lots of

money to clean the sewage.

But, we must do it in

order to have clean rivers.

sewage "the s ewage treatment".

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We c all this cleaning of

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Step One :

screen .

and rags .

The sewag e wa ter pa sses through a

This catch es lar ge objects such as sticks

SEWAGE TREATMENT

There are t wo st eps i n sew age tr ea tment.

We

c a ll t h ese the pri mary treatment and t h e secondary

treatment.

By the primary treatment, we re move all

of solids such as sticks, g ravel, and sands.

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Step Two:

Next the sewage water f lows slowly

This allows

through a tank called "grit chamber".

sand, g ravel, and oth er h eavy objects to settle.

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The s e wage wa t e r

S te p T h r e e :

a l a r g e t a nk c a l l e d

" pr i mary settli ng t a n k " wh ere

T h e s o l i ds are d ivided

it st a nd s for a l ong t ime .

On e g roup s e ttl e s to t h e b ottom

into t wo g roup s .

of t he t a nk .

group r i se s

t hen flo ws i nto

1·ve c a l l t h is " sludg e" .

We c a l l

t o t h e top .

Th e other

th i s "scum" .

The

wa t e r b e t ween t h ese two gr ou ps is drain e d off .

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When t he sewa~e 1vat er l eav e s th e primary tr ea t me nt ,

it may b e d i s c har ge d into a river if it is clean .

If it ne e d s more cleaning , we pass t he m t h r ou gh the

secondary tre a t ment .

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S t ep One :

The sewag e water is spr a yed over stone s

in a tank and a llowed to trickle d own through them .

We call t h i s tank "t r ickling fi lter".

c atch t h e ge r ms in the sew age water .

The stones

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Step Two :

The sewage wa t er may t h en be s e nt to

another tank whe re it is allowed t o st a nd while

Thi s tank is c a lled "th e

remaining s o lids settle .

secondary settling tank" .

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S t ep T hr e e :

F inally 1ve may

add a gas c a l l ed

" chl or ine" to he l p k i l l g e rms.

"chlorina ti o n ".

We c a l l t his

The wa t er i s

then d ischarged into

a lake or a rive r.

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Now, many c i ti es a nd factories d o not have s u ch

This is why we h ave

sewag e treatment p lants.

such a dirty river ne a r

cities a nd factories.

It

is our job to b uil d such a sewage treatment plant

in order to h ave a clean river where we can swim

and fish.

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Park, Yo12m1 Ka.a

Wbat

water pollutioA?

Date Due

00011! MOUNTAIN SCHOOL LIBRARYMILLBU:RN, N. J.

00 Printed In U.S.A.