"More than one billion people in our country do not get safe drinking water.

"

★ "Jal Hai, To Kal Hai" your parents or teacher must have often advised you not to waste
water, because there is shortage of water.
★ Less than 1% of all the water on earth is fresh water that we can actually use. We use this
small amount of water for drinking, transportation, in industry and many other purposes.
1. Introduction
The dirty water which is produced in kitchens, bathrooms,
while washing cars or your bicycles and industrial wastes is
called wastewater. Wastewater is used water. What
happens to this dirty waste water in your homes? Where,
do you think that rain water runs, from the streets? What
happens to waste chemicals and other materials from
factories? Are there any harmful effects of the waste water?
In this chapter, we will get to know about the waste water.
Clean water
Clean water is a basic need of all of us. It is needed for several purposes - for drinking,
cooking food, bathing, washing clothes, growing crops and even for industries.
Unfortunately, clean water is not available for use, to many people.
As a result, people suffer from a number of water-related diseases like typhoid, cholera and
dysentery. Even deaths may take place.
Now not only the clean water is available in short supply, there is an acute shortage of
water as such.

1. Which period was proclaimed as the International Decade for action on "water for life" by
the United Nations?
2. Sewage
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 Sewage is the waste water from homes domestic liquid waste as well as from industries,
offices, hospitals and other places. All the wastewater that is released from various source
forms the sewage which contains suspended impurities. These impurities are called
contaminants.
The contaminants can be classified as follows:
Organic impurities Human faeces, animal waste, urine, oil,
pesticides, fruit and vegetable wastes, etc.
Inorganic Nitrates, phosphates, metals
impurities
Nutrients Phosphorus and nitrogen
Bacteria Those which cause cholera and typhoid
Other microbes Those which cause dysentery
Sewage, thus, is a complex mixture containing suspended solids, organic and inorganic
impurities, nutrients and disease - causing organism.

Sources of waste water

★ Water assists in many important function our bodies perform every day. Since it flows
through our organs and cells, water needs to be clean and free of disease, metals and
human and animal faeces.
3. Understanding our sewer system
Each time we wash something or flush our toilets, water containing paper, cloth, scrap,
detergent, oil, grease, food scrap, faeces, etc., goes down the drain. This water gets

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accumulated and forms sewage. In large cities, this is also known as municipal
wastewater. Let us take a look at the journey it makes before flowing into a water body.
The Sewer System
The sewer system is a channel of pipelines which carries out sewage from our houses. The
sewage leaves our houses through drain pipes and flows to the sewer mains of the city.
Waste flows easily through sewers due to a slight slope given to the drainage system.
Most sewer pipes are underground. So, what does one do if there is a leak or blockage in
any of these pipes? For this purpose, we have manholes. A manhole is a hole, usually with
a cover, through which a person may enter a sewer or drain to fix the faulty pipes.
What happens to the sewage after it flows through sewer mains? Where does it go? The
sewer mains flow into progressively larger pipes until they reach the wastewater
treatment plant.
In October 2007, Sulabh designed a system of cheap toilets that recycles human wastes into
biogas and fertilisers. For this, the founder of sulabh, Dr. Bindeshwar Pathak, has even been
awarded to Stockholm Water Prize of 2009.
In most cases, the local municipal bodies have laid a network of drainage pipes throughout
a city. Through this network, the sewage is released into nearby waterbodies i.e. lakes or
rivers.
In big cities or towns, however, the waste sewage water is first treated in waste water
treatment plants. Then, it is released in nearby rivers or lakes. People living downstream
often drink and use this water.

The sewer system

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★ Home → Drain pipes → Sewer system → Larger pipes → Waste water treatment plant →
Water bodies.

1. United Nations proclaimed the period 2005 - 2015 as International Decade for action on
"Water for life".

Study the sewage route in your home/school/building. Do the following.

Make a line diagram of the sewage route.
Walk down the street or survey the campus to find the number manholes.
If possible, observe open drain and record which living organisms are found in and around
it.
In case you do not have a sewerage system in your locality, find out how sewage is being
disposed off.

1. Why most of the diseases are caused by using open drain system?
4. Treatment of polluted water
Perform the following activity. It will help you understand the processes that take place at
the wastewater treatment plant.

Divide yourself into groups to perform the activity. Record observations at each stage.
Fill a large glass jar 3/4 full of water. Add some dirty organic matter such as grass pieces or
orange peels, a small amount of detergent and a few drops of an ink or any colour.

◾
Cap the jar, shake it well and let the mixture stand in the sun for two days.
After two days, shake the mixture and pour a small sample into test tube. Label

◾
this test tube “Before treatment; Sample 1”. How does it smell?
Use an aerator from an aquarium to bubble air through the sample in the glass jar.
Allow several hours for aeration; leave the aerator attached overnight. If you do not have

◾
an aerator, use a mechanical stirrer or a mixer. You may have to stir it several times.
The next day when aeration is complete, pour another sample into a second test
tube. Label it as “After aeration; Sample 2”.

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 ◾ Fold a piece of filter paper to form a cone. Wet the paper with tap water and then
insert the cone in a funnel. Mount the funnel on a support (as you have learnt in Class

◾
VI).
Place layers of sand, fine gravel and finally medium
gravel in the funnel figure. (An actual filtration plant
does not use filter paper, but the sand filter is several

◾
metres deep).
Pour the remaining aerated liquid through the
filter into the beakers. Do not allow the liquid to spill
over the filter. If the filtered liquid is not clear, filter it a

◾
few times till you get clear water.
Pour a sample of the filtered water into a third test

◾
tube labelled
Pour another sample of the filtered water into a fourth test tube. Add a small piece
of a chlorine tablet. Mix well until the water is clear. Label the test tube “Chlorinated;

◾
Sample 4”.
Observe carefully the samples in all the test tubes. Do not taste! Just smell them
5. Wastewater treatment plant (WWTP)

Wastewater treatment plant

A wastewater treatment plant is a facility that treats wastewater from industrial source.
There are basically three processes involved in treating wastewater: primary, secondary,
and tertiary.
Primary process: This is a mechanical process which involves screening and settling of
large particles. First the sewage is passed through screens of vertical bars to remove larger
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 impurities such as metal cans, plastic bags, cloth pieces, etc. The wastewater is then passed
through a grit and sand removal tank called the grit chamber.

Aeration tank
The speed of the incoming wastewater is reduced so that sand, grit, pebbles, etc. settle
down. The water is then passed through huge sedimentation tanks. Here solid waste such
as faeces is allowed to settle down and the light floatable waste such as soaps, oils, plastics
and greases rise. The material that settles at the bottom is referred to as sludge and the
material that rises to the top as scum.
Scum: Light floatable waste that rises to the top during wastewater treatment is called the
scum.
The water that comes out of the sedimentation tanks is called clarified water.
Effluent: Discharge of liquid waste from an industry is called effluents.

1. Diseases are caused by open drain system because it is a breeding place for flies,
mosquitoes and organisms.

1. Which removes the floatable solid like oil and greases?

2. Why should sewage be treated before being discharged in a water body?
3. Which sludge is used as manure?
Secondary process: This is a biological process in which
the organic matter in the sludge is broken down with the
help of bacteria. This process is called digestion and as a
result of this process biogas is produced. This biogas can
be used either as a fuel or to produce electricity. The
treatment at this stage can be speeded up by allowing
water to flow into large aeration tanks, where air is
blown into the sewage.
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 Tertiary process: This is basically a chemical process in which chemicals are used to
remove phosphorus and nitrogen from the water.
Addition of chlorine and exposure to ultraviolet light kills any remaining bacteria and
disinfects the water. The water is then discharged into water bodies.

What is the reason behind increasing scarcity of freshwater?

Explanation
The increasing scarcity of freshwater is due to population growth, pollution, industrial
development, mismanagement and other factors.

1. A skimmer removes the floatable solids like oil and greases.

2. Sewage should be treated before being discharge in a water body because there would be
lots of impurities present in it.
3. Dried sludge is used as manure.
6. Alternative arrangement for sewage disposal
Low cost onsite sewage disposal systems have been developed to take care of places where
there is no sewage system like in rural areas or in case of isolated buildings.
These systems include septic tanks and chemical toilets. A septic tank consists of a concrete
or metal tank with an outlet submerged in the ground. Domestic sewage enters the tank
through another inlet pipe. The solids settle down in the tank and the liquid flows through
the outlet pipe into the soil.
Biogas plant: Another method of waste disposal which is prevalent especially in village
and small towns in India is setting up of biogas plants. In this method, human and animal
excreta flow through covered drains into biogas plants. Microorganisms break down the
materials present in the waste and produce biogas. This biogas is then used to produce
electricity.
Vermi-composting Toilets: Recently vermi-composting toilets have been developed in
India as an alternative method for proper disposal of waste. It is based on an innovative

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 design in which earthworms are used to convert human excreta into compost. There is
minimal use of water and is a safe and hygienic way of processing human waste.

1. What is meant by vermi-composting toilet?

7. Become an active citizen
(i) Wastes should be disposed of properly and not thrown away anywhere.
(ii) Proper toilet facilities should be provided to rural people.
(iii) Chemical wastes from the factories should be properly treated before being released
into water.
(iv) Sewage from cities should not be discharged directly into rivers. It must be treated and
made harmless before release.
(v) Ensure that there are no leaking sewage pipes.
(vi) Ensure that there is no stagnant water in ponds and lakes. The clarity of water in a
stream, river or ocean is a key determinant in fostering a healthy and balanced aquatic
ecosystem. The clearer the water, the greater the ability of light to penetrate to aquatic
plants which generate the oxygen needed of aquatic life.

1. Vermi-composting toilet is a design of a toilet in which human's excreta is treated by

earthworms.
Better house keeping practices
• Chemicals like paints, insecticides and medicines should not be thrown in the drains.
These things may kill microbes that help to purify water.
• Used food remains, tea leaves, cotton sanitary towels should not be thrown in the
drains. These waste choke the drains and do not allow free flow of oxygen. This slows
down the degradation process. Such wastes should be thrown in the dustbin.
• Cooking oil and fats should not be thrown down the drain. These items on hardening
block the pipes. Oil and fats should be thrown in the dustbin.
• Reduce the quantity of waste production.

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1. Why should we plant eucalyptus trees all along sewage ponds?

What is the relation between sanitation and diseases?

Explanation
Poor sanitation and contaminated drinking water is the cause of a large number of
diseases. A vast number of our people are still without sewerage facilities. A very large
fraction of our people defecates in the open, on dry riverbeds, on railway tracks, near fields
and many a time directly in water. Untreated human excreta is a health hazard. It may cause
water pollution and soil pollution. Both the surface water and groundwater get polluted.
Groundwater is a source of water for wells, tubewells, springs and many rivers. Thus, it
becomes the most common route for water borne diseases. They include cholera, typhoid,
polio, meningitis, hepatitis and dysentery.
8. Sanitation at public places
In our country fairs are organised periodically. A large number of people participate in
them. In the same way railway stations, bus depots, airports, hospitals are very busy places.
Thousands of people visit them daily. Large amount of waste is generate here. It must be
disposed of properly otherwise epidemics could break out. The government has laid down
certain standards of sanitation but, unfortunately, they are not strictly enforced. However,
all of us can contribute in maintaining sanitation at public places. We should not scatter
litter anywhere. If there is no dustbin in sight, we should carry the litter home and throw it
in the dustbin.

1. We should plant eucalyptus trees all along sewage ponds because these trees absorb all
surplus wastewater rapidly and release pure water vapour into the atmosphere. Gradually,
water vapour is converted into its liquid form.
Basic terminology
1. Sewage – Sewage in the waste water from homes. (domestic liquid waste) as well as from
industry, offices, etc.
2. Contaminants – Generally suspended impurities are called contaminants.
3. Manholes - A manhole is a hole in sewer system usually with a cover, through which a
person enter to fire faulty pipes.

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4. WWTP – Waste water treatment plant.
5. Aeration – Aeration in process of adding air into waste wate to allow aerobic
biodegradation of organic materials.
6. Sludge – Impurities that settles at the bottom.
7. Scum - Impurities that rises to the tap is called scum.
Memory Map

Contaminants
Organic impurities
Other microbes
Bacteria
Nutrients
Inorganic impurities
Phosphorus
Nitrogen
Nitrates, Phosphates
Wine,
Animal waste
Causing typhoid, Cholera
Causing dysentery
Source of waste water
Agriculture
Domestic
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 activities
Industries
Construction of
buildings
Mining
Hospitals,
Hotels,
Offices
Sewer system
(Channel of pipelines, carries out sewage from our houses)
Important Terminology
Sewage
Scum
Sludge
Effluent
Incineration
Waste water story

Waste Water Treatment Plant

Primary Process
Tertiary Process
Secondary Process
Mechanical process,
involves screening and settling of large particles, objects
Biological process,
Involves breaking down of organic matter with the help of Bacteria
Chemical process, involves addition of chemicals to water for purifying
Alternatives of Sewerage System
(Septic tanks, Chemical toilets
Biogas Plant
Vermicomposting toilets

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