NCERT Environmental Studies (EVS) important notes Part 18 for AEES, KVS, NVS, DSSSB, UPTET, REET, CTET, BTET, MPTET, HTET and All other Teaching Exams

NCERT 

Environmental Studies

 Important Notes

Part 18

• Rich in lather, mixed with oil, black–
  brown water that goes down the drains
  from sinks, showers, toilets, laundries
  is dirty. It is called wastewater.
• Clean water that is fit
  for use is unfortunately
  not available to all. It
  has been reported that
  more than one billion of
  our fellow human beings
  have no access to safe drinking water.
  This accounts for a large number of
  water-related diseases and even deaths.
• The increasing scarcity of freshwater due to population growth,
  pollution, industrial development,
  mismanagement and other factors. 
• Realising the urgency of the situation
  on the World Water Day, on 22 March
  2005, the General Assembly of the
  United Nations proclaimed the period
  2005–2015 as the International Decade
  for action on “Water for life”. 
• All efforts “Water for life”.
  made during this decade aim to reduce
  by half the number of people who do
  not have access to safe drinking water.
• Cleaning of water is a process of
  removing pollutants before it enters a
  water body or is reused. This process of
  wastewater treatment is commonly
  known as “Sewage Treatment”. It takes
  place in several stages.
• Sewage is wastewater released by homes,
  industries, hospitals, offices and other
  users. It also includes rainwater that has
  run down the street during a storm or
  heavy rain. The water that washes off
  roads and rooftops carries harmful
  substances with it. Sewage is a liquid waste.
  Most of it is water, which has dissolved
  and suspended impurities. These
  impurities are called contaminants.
• Sewage is a complex
  mixture containing suspended solids,
  organic and inorganic impurities,
  nutrients, saprotrophic and disease
  causing bacteria and other microbes.

Organic impurities –Human faeces,
animal waste,
oil, urea (urine),pesticides,
herbicides, fruit
and vegetable
waste, etc.

 

Inorganic impurities – Nitrates,
Phosphates,
metals. 

 

Nutrients – Phosphorus
and Nitrogen. 

 

Bacteria – Such as which
cause cholera
and typhoid. 

 

Other microbes – Such as which
cause dysentery.

 

• In a home or a public building generally
  one set of pipes brings clean water and
  another set of pipes takes away
  wastewater. Imagine that we could see
  through the ground. We would see a
  network of big and small pipes, called
  sewers, forming the sewerage. It is like
  a transport system that carries sewage
  from the point of being produced to the
  point of disposal, i.e. treatment plant.

 

WASTEWATER TREATMENT PLANT
(WWTP)

 

Treatment of wastewater involves
physical, chemical, and biological
processes, which remove physical,
chemical and biological matter that
contaminates the wastewater.

1. Wastewater is passed through bar
screens. Large objects like rags,
sticks, cans, plastic packets, napkins
are removed.

 

2. Water then goes to a grit and sand
removal tank. The speed of the
incoming wastewater is decreased to
allow sand, grit and pebbles to settle
down.

 

 

 

3. The water is then allowed to settle in
a large tank which is sloped towards
the middle. Solids like faeces settle
at the bottom and are removed with
a scraper. This is the sludge. A sludge
skimmer removes the floatable solids
like oil and grease. Water so cleared
is called clarified water.

The sludge is transferred to a
separate tank where it is decomposed
by the anaerobic bacteria. The biogas
produced in the process can be used as
fuel or can be used to produce electricity.

 

 

 

4. Air is pumped into the clarified water
to help aerobic bacteria to grow.
Bacteria consume human waste,
food waste, soaps and other
unwanted matter still remaining in
clarified water. 

After several hours, the suspended
microbes settle at the bottom of the tank
as activated sludge. The water is then
removed from the top.

The activated sludge is about 97%
water. The water is removed by sand
drying beds or machines. Dried sludge
is used as manure, returning organic
matter and nutrients to the soil. 

The treated water has a very low level
of organic material and suspended
matter. It is discharged into a sea, a river
or into the ground. Nature cleans it up
further. Sometimes it may be necessary
to disinfect water with chemicals like
chlorine and ozone before releasing it
into the distribution system.

 

 

Become an active citizen

 

Waste generation is a natural part of
human activity. But we can limit the
type of waste and quantity of waste
produced. Often we have been repelled
by offensive smell. The sight of open
drains is disgusting. The situation worsens in the rainy season when the
drains start overflowing. We have to
wade through the mud pools on the
roads. Most unhygienic and unsanitary
conditions prevail. Flies, mosquitoes and
other insects breed in it.

You can be an enlightened citizen
and approach the municipality or the
gram panchayat. Insist that the open
drains be covered. If the sewage of
any particular house makes the
neighbourhood dirty, you should request them to be more considerate
about others’ health.

 

BETTER HOUSE KEEPING
PRACTICES

One of the ways to minimise or eliminate
waste and pollutants at their source is
to see what you are releasing down the
drain.

• Cooking oil and fats should not be
  thrown down the drain. They can
  harden and block the pipes. In an
  open drain the fats clog the soil pores
  reducing its effectiveness in filtering
  water. Throw oil and fats in the
  dustbin.
• Chemicals like paints, solvents,
  insecticides, motor oil, medicines
  may kill microbes that help purify
  water. So do not throw them down
  the drain.
• Used tealeaves, solid food remains,
  soft toys, cotton, sanitary towels, etc.
  should also be thrown in the dustbin. These wastes choke the drains. They do not allow free flow
  of oxygen. This hampers the
  degradation process.

 

SANITATION AND DISEASE

Poor sanitation and contaminated
drinking water is the cause of a large
number of diseases.

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.

 

Vermi-processing toilet

A design of a toilet in which humans excreta is treated by earthworms has been
tested in India. It has been found to be a novel, low water-use toilet for safe
processing of human waste. The operation of the toilet is very simple and hygienic.
The human excreta is completely converted to vermi cakes — a resource much
needed for soil. 

 

ALTERNATIVE ARRANGEMENT FOR
SEWAGE DISPOSAL

To improve sanitation, low cost onsite
sewage disposal systems are being
encouraged. Examples are septic tanks,
chemical toilets, composting pits. Septic
tanks are suitable for places where there
is no sewerage system, for hospitals, isolated buildings or a cluster of 4 to 5
houses.
Some organisations offer hygienic
on-site human waste disposal
technology. These toilets do not require
scavenging. Excreta from the toilet seats
flow through covered drains into a
biogas plant. The biogas produced is
used as a source of energy.

 

 

Important points to remember

• Used water is wastewater. Wastewater could be reused. 
• Wastewater is generated in homes, industries, agricultural fields and in
  other human activities. This is called sewage. 
• Sewage is a liquid waste which causes water and soil pollution. 
• Wastewater is treated in a sewage treatment plant. 
• Treatment plants reduce pollutants in wastewater to a level where nature
  can take care of it. 
• Where underground sewerage systems and refuse disposal systems are
  not available, the low cost on-site sanitation system can be adopted. 
• By-products of wastewater treatment are sludge and biogas. 
• Open drain system is a breeding place for flies, mosquitoes and organisms
  which cause diseases. 
• We should not defecate in the open. It is possible to have safe disposal of
  excreta by low cost methods.

 

 

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