EVS Pollution PPT.ppt

POLLUTION
 Pollution is the effect of undesirable changes in our
surroundings that have harmful effects on plants,
animals and human beings.
 When only short-term economic gains are made at the
cost of the long-term ecological benefits for humanity.
 No natural phenomenon has led to greater ecological
changes than have been made by mankind…!!!!!

 Pollutants that enter water have the ability to spread to distant
places especially in the marine ecosystem. From an ecological
perspective pollutants, classified as follows:
 Degradable or non-persistent pollutants: These can be rapidly
broken down by natural processes. Eg..?????
Eg: domestic sewage, discarded vegetables, etc.
 Slowly degradable or persistent pollutants: Remain in the
environment for many years in an unchanged condition and take
decades or longer to degrade. Eg..?????
Eg: DDT and some kinds of plastics.
 Non-degradable pollutants: Cannot be degraded by natural
processes. Once they are released into the environment they are
difficult to eradicate and continue to accumulate. Eg..?????
Eg: Toxic elements like lead or mercury.

Air Pollution
 Air
– Necessary for Existence
– Colorless, odorless mixture of gases
– Quality of air varies in different environments
 Urban vs. Rural
– Emission of Particulate matter from:
 Anthropogenic (Man-made) Sources (Industry)
 Natural Sources (Volcanoes, Forest Fires, Pollen)

Composition of Air
 Five Substances
– Nitrogen (N2) 78.1%(v/v)
– Oxygen (O2) 21.0%(v/v)
– Carbon Dioxide (CO2) 0.033%(v/v)
– Argon (Ar) 0.93%(v/v)
– Water (H2O) varies
– Other trace components 0.007%(v/v)

 Pollutants include solid, liquid or gaseous substances
present in greater than natural abundance produced due
to human activity, which have a detrimental effect on our
environment.
 An average human requires about 12 kg of air each day,
which is nearly 12 to 15 times greater than the amount of
food we eat.
 Thus even a small concentration of pollutants in the air
becomes more significant in comparison to the similar
levels present in food.

What is Air Pollution?
 Presence of undesirable solid or gaseous particles in the
air in quantities that are harmful to human health and the
environment.
 Air may get polluted by natural causes such as volcanoes,
which release ash, dust, sulphur and other gases, or by
forest fires that are occasionally naturally caused by
lightning.
 However, unlike pollutants from human activity, naturally
occurring pollutants tend to remain in the atmosphere for a
short time and do not lead to permanent atmospheric
change.

Types of Pollutants
 Pollutants that are emitted directly from identifiable sources are
produced both by natural events (for example, dust storms and volcanic
eruptions) and human activities (emission from vehicles, industries,
etc.). These are called Primary Pollutants.
 5 primary pollutants - 90 % of the global air pollution.
– Carbon oxides (CO & CO2), nitrogen oxides, sulfur oxides, volatile organic compounds
(mostly hydrocarbons) and suspended particulate matter.
 Pollutants that are produced in the atmosphere when certain chemical
reactions take place among the primary pollutants are called Secondary
Pollutants. Eg: sulfuric acid, nitric acid, carbonic acid, etc.

NATURAL SOURCES OF AIR
POLLUTION
 Natural Fires - Smoke
 Volcanoes - Ash and acidic components
 Sea Spray -
 Vegetation - Volatile organic compounds
 Bacterial Metabolism - Methane
 Dust
– Pollen
 Viruses and Bacteria

Conventional Pollutants
 Nitrogen Compounds
– Nitrogen oxides are reactive gases formed when
nitrogen is heated above 650o C in the presence
of oxygen, or when nitrogen compounds are
oxidized.
 Annual Emissions: 230 million metric tons

 Carbon Oxides
– Predominant form of carbon in the air is carbon
dioxide.
 Increasing levels due to human activities.
 Annual Emissions: 7-8 billion metric tons
– Carbon monoxide is a colorless, odorless, toxic
gas produced by incomplete fuel combustion.
 Annual Emissions: 1 billion metric tons

 Particulate Matter
– Atmospheric aerosols (solid or liquid)
 Respirable particles smaller than 2.5 micrometers are
among most dangerous.
– Anthropogenic particulate emissions amount to
about 362 million metric tons annually.

 Metals
– Many toxic metals occur as trace elements in fuel.
 Lead Emissions: 2 million metric tons.
– Mercury
 Bioaccumulation in aquatic ecosystems.
– Nickel, beryllium, cadmium, arsenic…
 Halogens (Fluorine, Chlorine, Bromine)
– CFC’s

 Volatile Organic Compounds
– Organic chemicals
 Generally oxidized to CO and CO2.
 Plants are largest source.
 Photochemical Oxidants
– Products of secondary atmospheric reactions
driven by solar energy.
 Ozone formed by splitting nitrogen dioxide.

Major toxic metals and their effects
Element Sources Health effects
Lead Auto exhaust (from gasoline),
paints, storage batteries, pipes
Neurotoxin, affects blood
system, behavioral disorders,
death
Cadmium Coal, zinc mining, incineration
of plastic containers, refining
of metals, tobacco smoke
Cardiovascular disease and
hypertension, interference
with zinc and copper
metabolism, kidney damages
Nickel Combustion of coal, diesel and
residual oils, tobacco smoke,
chemicals and catalysts, steel
and non ferrous alloys
manufacture
Respiratory symptoms, lung
cancer (as nickel carbonyl)
Mercury Combustion of fossil fuels,
evaporation from ore mining,
exhausts from metal smelters,
chloralkali cells, paints,
pharmaceuticals
Nerve and brain damage,
kidney damage

EFFECTS OF AIR POLLUTION
 Human Health
– EPA estimates each year 50,000 people die
prematurely from illnesses related to air
pollution.
 Likelihood of suffering ill health is related to intensity
and duration of exposure.
– Inhalation is the most common route, but absorption
through the skin and consumption via food can also occur.

Human Health
 Bronchitis
– Persistent inflammation of airways in the lung
that causes mucus build-up and muscle spasm,
constricting airways.
 Can lead to emphysema - irreversible chronic
obstructive lung disease in which airways become
permanently constricted and alveoli are damaged or
destroyed.

Plant Pathology
 Chemical pollutants can directly damage
plants, or can cause indirect damage by
disrupting normal growth and development
patterns.
– Certain environmental factors have synergistic
effects in which the injury caused by the
combination is more than the sum of the
individual exposures.
 Pollutant levels too low to cause visible effects may
still be damaging.

Acid Deposition
 pH and Atmospheric Acidity
– Unpolluted rain generally has pH of 5.6.
 Carbonic acid from atmospheric CO2.
– In industrialized areas, anthropogenic acids in the air often
outweigh natural sources of acid.

Acid Deposition
 Forest Damage
– Air pollution and depositions of atmospheric
acids are believed to be important causes of
forest destruction in many areas.
 Buildings and Monuments
– Limestone and marble are destroyed by air
pollution at an alarming rate.
– Corroding steel in reinforced concrete weakens
buildings, roads, and bridges.

Effects of Air Pollution
 Adverse effect of air pollution may be divided into two classes
– Acute effects
– Chronic effects
– Acute effects manifest themselves immediately upon short-
term exposure to air pollutants at high concentrations.
– Chronic effects become evident only after continuous
exposure to low levels of air pollution. The Chronic effects
are very difficult to demonstrate and or consequently less
obvious.
– The chief causes of deaths and causalities were vomiting,
violent coughing, eye infections (chemical conjuctivitis),
suffocation, cardiac failure and pulmonary disorders. The
full consequences are not yet known.
– Pollutants may enter the body by a number of ways. The can
cause eye and skin irritation; certain particulates may be
swallowed as a result of internal respiratory cleaning action
or certain pollutants could even be ingested. But the primary
mode of pollutant transfer into the human body is through
the respiratory system.

AIR POLLUTION CONTROL
 Reducing Production
– Particulate Removal
 Remove particles physically by trapping them in a
porous mesh which allows air to pass through but
holds back solids.
– Sulfur Removal
 Switch from soft coal with a high sulfur content to low
sulfur coal.

Air Pollution Control
 Nitrogen Oxides
– Best method is to prevent creation.
 Staged Burners
 Selective Catalysts
 Hydrocarbon Control
– Use closed systems to prevent escape of
fugitive emissions.

 Emission control equipment may be classified into two
general types:
– particulate control type, and
– gases and odours control type.
 The basic mechanisms of removing particulate matter from
gas streams may be classified as:
 (1) Gravitational settling
 (2) Centrifugal impaction
 (3) Inertial impaction
 (4) Direct interception
 (5) Diffusion
 (6) Electro static precipitation.

 Equipment presently available, which make use of one
or more of the above mechanisms, fall into the following
five broad categories:
 Gravitational settling chambers
 Cyclone separators
 Fabric filters
 Electrostatic precipitators
 Wet collectors (scrubbers)

Gravitational Settling Chambers
 Generally used to remove large, abrasive particles (usually
> 50 m) from gas streams. They offer low pressure drop
and require simple maintenance, but their efficiencies are
quite low for particles smaller than 50 m.

Settling chambers use the force of gravity to
remove solid particles. The gas stream
enters a chamber where the velocity of the
gas is reduced. Large particles drop out of
the gas and are recollected in hoppers.

Cyclone Separators
 The general principle of inertia separation is that the
particulate-laden gas is forced to change direction. As gas
changes direction, the inertia of the particles causes them
to continue in the original direction and be separated from
the gas stream.
 Cyclone separators utilize a centrifugal force generated by
a spinning gas stream to separate the particulate matter
from the carrier gas. The centrifugal force on particles in a
spinning gas stream is much greater than gravity
 Cyclones are effective in the removal of much smaller
particles than gravitational settling chambers, and require
much less space to handle the same gas volumes

COLLECTED FLY ASH
CLEANED GAS OUT
GAS IN
Cyclone Separators

Fabric Filter Systems
 Fabric filter systems typically consist of tubular bag or an
envelope, suspended or mounted in such a manner that
the collected particles fall into a hopper when dislodged
from the fabric. The structure in which the bags hang is
known as bag house. Generally, particle-laden gas enters
the bag at the bottom and passes through the fabric while
the particles are deposited on the inside of the bag.

DUSTY GAS IN
HOPPER LARGER PARTICLE
SEPERATION BY
CENTRIFUGAL ACTION
FILTER BAGS
CLEAN GAS
SHAKER MECHANISM
DUST OUTLET
Fabric Filter Systems

Electrostatic Precipitators (ESP)
 Removal of flyash from electric utility boiler emissions.
 The dust-laden gas is passed between oppositely charged
conductors and it becomes ionized as the voltage applied
between the conductors is sufficiently large (30,000 to 60,000
volts dependent on electrode spacing).
 As the dust-laden gas is passed through these highly charged
electrodes, both negative and positives ions are formed, the
latter being as high as 80%. The ionized gas is further passed
through the collecting unit, which consists of a set of vertical
metal plates. Alternate plates are positively charged and
earthed.
 The dust removed from the plates with the help of shaking
motion is collected in the dust hoppers.

 As the alternate plates are grounded, high intensity
electrostatic field exists between the plates. When the
charged dust particles are passed between the plates.
The deposited dust particles are removed from the
plates by giving the shaking motion to the plates with the
help of cam driven by external means

Electrostatic precipitator
1. Smoke particles pick up a negative charge.
2. Smoke particles are attracted to the collecting plates.
3. Collecting plates are knocked to remove the smoke particles

Wet Scrubbers
 Wet precipitations the principal mechanisms by which
atmospheric particles are removed by nature. This idea
has been exploited by industry to develop a variety of
liquid scrubbing equipment.
 Wet collectors have a number of advantageous over dry
collectors, such as simultaneous removal of particles
and gaseous pollutants but suffer from the problems of
corrosion and liquid waste disposal.

CLEAN GAS OUT
WATER IN
MIST ELIMINATOR
SPRAYS
DIRTY GAS IN
SLURRY OUT

Water Pollution
 Water is the essential element that makes life on earth possible.
 Without water there would be no life.
 We usually take water for granted. It flows from our taps when they
are turned on. Most of us are able to bathe when we want to, swim
when we choose and water our gardens. Like good health, we
ignore water when we have it.
 Although 71% of the earth’s surface is covered by water only a tiny
fraction of this water is available to us as fresh water.
 About 97% of the total water available on earth is found in oceans
and is too salty for drinking or irrigation. The remaining 3% is fresh
water. Of this 2.997% is locked in ice caps or glaciers.

 Thus only 0.003% of the earth’ total volume of water is easily
available to us as soil moisture, groundwater, water vapour and
water in lakes, streams, rivers and wetlands.
 In short if the world’s water supply were only 100 litres our usable
supply of fresh water would be only about 0.003 litres (one-half
teaspoon). This makes water a very precious resource.
 The future wars in our world may well be fought over water.
 By the middle of this century, almost twice as many people will be
trying to share the same amount of fresh water the earth has today.
 As freshwater becomes more scarce access to water resources will
be a major factor in determining the economic growth of several
countries around the world.

Water Availability on the Planet
 Water that is found in streams, rivers, lakes, wetlands and artificial
reservoirs is called surface water.
 Water that percolates into the ground and fills the pores in soil and
rock is called groundwater.
 Porous water-saturated layers of sand, gravel or bedrock through
which ground water flows are called aquifers. Most aquifers are
replenished naturally by rainfall that percolates downward through
the soil and rock. This process is called natural recharge.

 If the withdrawal rate of an aquifer exceeds its natural recharge
rate, the water table is lowered.
 Any pollutant that is discharged onto the land above is also
pulled into the aquifer and pollutes the groundwater resulting in
polluted water in the nearby wells.
 India receives most of her rainfall during the months of June to
September due to the seasonal winds and the temperature
differences between the land and the sea. These winds blow from
the opposite directions in the different seasons.
 They blow into India from the surrounding oceans during the
summer season and blow out from the subcontinent to the
oceans during the winter.
 The monsoon in India is usually reasonably stable but varies
geographically. In some years the commencement of the rains
may be delayed considerably over the entire country or a part of
it. The rains may also terminate earlier than usual. They may be
heavier than usual over one part than over another.

Causes of Water Pollution
There are several classes of common water pollutants.
 These are disease-causing agents (pathogens) which include
bacteria, viruses, protozoa and parasitic worms that enter water
from domestic sewage and untreated human and animal wastes.
 Human wastes contain concentrated populations of coliform
bacteria such as Escherichia coli and Streptococcus faecalis.
These bacteria normally grow in the large intestine of humans
where they are responsible for some food digestion and for the
production of vitamin K. These bacteria are not harmful in low
numbers.
 Large amounts of human waste in water, increases the number of
these bacteria which cause gastrointestinal diseases.

 Another category of water pollutants is oxygen-depleting wastes.
These are organic wastes that can be decomposed by aerobic
(oxygen requiring) bacteria. Large populations of bacteria use up the
oxygen present in water to degrade these wastes. In the process this
degrades water quality.
 The amount of oxygen required to break down a certain amount of
organic matter is called the biological oxygen demand (BOD).
 The amount of BOD in the water is an indicator of the level of
pollution. If too much organic matter is added to the water all the
available oxygen is used up. This causes fish and other forms of
oxygen dependent aquatic life to die.
 Anaerobic bacteria (those that do not require oxygen) begin to break
down the wastes. Their anaerobic respiration produces chemicals
that have a foul odour and an unpleasant taste that is harmful to
human health.

 Inorganic plant nutrients. These are water soluble nitrates and
phosphates that cause excessive growth of algae and other aquatic
plants. The excessive growth of algae and aquatic plants due to
added nutrients is called eutrophication. They may interfere with
the use of the water by clogging water intake pipes, changing the
taste and odour of water and cause a buildup of organic matter. As
the organic matter decays, oxygen levels decrease and fish and
other aquatic species die.
 The quantity of fertilizers applied in a field is often many times more
than is actually required by the plants. The chemicals in fertilizers
and pesticides pollute soil and water. While excess fertilizers cause
eutrophication, pesticides cause bioaccumulation and
biomagnification. Pesticides which enter water bodies are
introduced into the aquatic food chain. They are then absorbed by
the phytoplanktons and aquatic plants. These plants are eaten by
the herbivorous fish which are in turn eaten by the carnivorous fish
which are in turn eaten by the water birds. At each link in the food
chain these chemicals which do not pass out of the body are
accumulated and increasingly concentrated resulting in
biomagnification of these harmful substances.

 One of the effects of accumulation of high levels of pesticides
such as DDT is that birds lay eggs with shells that are much
thinner than normal. This results in the premature breaking of
these eggs, killing the chicks inside. Birds of prey such as hawks,
eagles and other fish eating birds are affected by such pollution.
Although DDT has been banned in India for agricultural use and
is to be used only for malaria eradication, it is still used in the
fields as it is cheap.

 A fourth class of water pollutants is inorganic
chemicals which are acids, salts and compounds of
toxic metals such as mercury and lead. High levels of
these chemicals can make the water unfit to drink,
harm fish and other aquatic life, reduce crop yields
and accelerate corrosion of equipment that use this
water.
 Another cause of water pollution is a variety of
organic chemicals, which include oil, gasoline,
plastics, pesticides, cleaning solvents, detergent and
many other chemicals. These are harmful to aquatic
life and human health. They get into the water directly
from industrial activity either from improper handling
of the chemicals in industries and more often from
improper and illegal disposal of chemical wastes.

Types of Water Pollutants and their
Effects
 The problem of water pollution due to discharge of
domestic and industrial wastes into aquatic systems
has already become a serious problem in the country.
Nearly 75 to 80% of India’s population is exposed to
unsafe drinking water
 To aid in a systematic discussion of water pollutants,
they have been classified into nine categories as
described below:

Oxygen Demanding Wastes
 Dissolved Oxygen (DO) is essential for sustaining the plant and
animal life in any aquatic system. For example, warm-water fish
requires a minimum DO level of at least 5 mg/l (5 ppm). If the DO
level drops below the level necessary to sustain normal life, then
the aquatic system is classified as polluted
 There are four processes which actually affect the DO content in
the Water: reaeration, Photosynthesis, respiration and the
oxidation of wastes
 Reaeration is the process by which oxygen in fresh water at
saturation point decreases with an increase in temperature
 Photosynthesis requires solar radiation. During the process, the
green plants such as algae utilize carbon dioxide and the
inorganic nutrients present in the water to synthesize organic
materials and liberate oxygen. Since the process occurs only in
the presence of sunlight, the DO level in the water increase during
the day

 At night the algae and the microorganisms compete with
each other for both dissolved oxygen and organic
compounds. This bacterial and algal respiration is
responsible for the production of carbon dioxide and
subsequent depletion of dissolved oxygen.
 Combination of the three effects of respiration,
photosynthesis and reaeration results in the diurnal
variation in dissolved oxygen concentration from the
values that may far exceed saturation during the day to
much lower values or depletion at night.
 The primary cause of deoxygenation of aquatic systems
is the presence of organic substances collectively called
oxygen-demanding wastes. When these substances
enter a waterway, dissolved oxygen is consumed in their
breakdown by microorganisms, so the organic
substances can be said to exert a demand on the
availability of dissolved oxygen. The more the oxygen is
required for the breakdown of the substance, the greater
will be the deoxygenation of the waterway. Pollution
results when the oxygen demand exceeds the available
oxygen.

 Although some inorganic substances are found in
the category of oxygen demanding wastes, most of
them are organic in nature. For example pollutants
in this category typically come from such sources
as sewage, food processing plants, pulp and paper
mills, tanning operations, and other organic waste
producing activities. These waste, in addition to
depleting the DO levels, produce-annoying odours,
impair domestic and livestock water supplies by
affecting its taste, odour and colour.

Biochemical Oxygen Demand
 The biochemical oxygen demand (BOD) is a
measure of the oxygen utilized by microorganisms
during the oxidation of organic materials. It is the
most widely known measure for assessing the
water pollution potential of a given organic waste.
On an average, the demand for oxygen is directly
proportional to the amount of organic waste.
Hence, BOD is a direct measure of oxygen
requirements and an indirect measure of
biodegradable organic matter

Disease Causing Agents
 Water is a potential carrier of pathogenic microorganisms; these
pathogens are carried into the water bodies by sewage and
wastes from farms and various industries, specially tanning and
meat packaging industries. Contact with the pathogens can be
made by drinking the water or through other activities involving
contact with water.
 Some bacteria are water-borne and these include those
responsible for causing cholera, typhoid, amoebic dysentery and
gastroenteritis. Viruses are also found in water including strains,
which are responsible for polio, infectious hepatitis, and
Coxsackie’s fever. Water may also contain some animal parasites
including the round worm, and the pork tapeworm. All these types
of organisms occur in faeces, and so present in sewage. Water
also plays an indirect but vitally important role in the transmission
of disease like malaria, yellow fever, filariasis, and schistomiasis

Synthetic Organic Compounds
 These include pesticides, synthetic organic chemicals and
detergents. These compounds, in contrast to the organic wastes,
are not biodegradable and may persist for long periods.
 These are great concern to environmentalists because most of the
synthetic compounds are accumulative toxic poisons and
ultimately may reach objectionable levels in water or in aquatic
life.

Plant Nutrients
 Nitrogen and phosphorous are essential elements which are
required by plants and animal for maintaining their growth and
metabolism. Small amount of nitrates and phosphates occur in
all aquatic systems and these are sufficient to maintain a
balanced biological growth.
 In wastewaters, these nutrients are present in abundance as
phosphates, nitrates, and ammonia or combined organic
nitrogen. These compounds may enter the water bodies
directly from the manufacture and use of fertilizers, and from
the processing of biological materials such as food and
textiles, or via domestic sewage treatment plants.
 When unusually large concentrations of nutrients are present
in water bodies, an excess growth of algae, known as and algal
bloom appears. This produces an unsightly green slime layer
over the surface of the water body and subsequently leads to
eutrophication.

 The slime layer reduces light penetration and restricts
atmospheric reoxygenation of the water. The dense algal
growth eventually dies and the subsequent biodegradation
produces an oxygen deficit, which can result in foul-smelling
anaerobic conditions.
 Birds feeding on the algae are killed by the powerful toxin
produced by the anaerobic bacterium Clostridium botulinum,
which flourishes in the environment.
 Other problems resulting from heavy algal growth are the
clogging of filters in water treatment plants and slowing down
of stream flow by filamentous weeds can trap solid particles
carried by a stream and if they are organic, a large decaying
mass accumulates which exerts a high oxygen demand.
 High concentrations of nitrate in drinking water. When it enters
the blood stream it becomes attached to hemoglobin, forming a
complex known as methaemoglobin. As a result, the oxygen
carrying capacity of blood is reduced producing a condition
called methaemoglobin anemia or the blue baby disease. In
young babies, it is frequently fatal. The nitrates can be further
converted to amines and nitrosoamines in the human body
leading to a possible cause of gastric cancer.

Sediments
 Sediments include soil, sand and mineral particles washed
into the aquatic environment by storms and floodwaters. In
addition, large deposits of sewage sludge, pulverized coal
ash, and various industrial solids are disposed off into
rivers and marine waters.
 The sediments erode pumping equipment and power
turbines, and have the effect of increasing turbidity and
consequently of reducing the amount of sunlight available
to green, water plants. In suspension, the solids may cause
thickening of fish gills, which may lead to eventual
asphyxiation of the fish. On the riverbed, the sediment may
interfere with spawning sites and decrease the amount of
food available for fish.

Radioactive Substances
 Very little is known about the threshold of radiation damage
to aquatic environment from wastes of uranium and
thorium mining and refining, from nuclear power plants,
and from industrial use of radioactive materials. The
refining of uranium ore is an important source of
radioactive waste producing radionuclides of radium,
bismuth, etc. Radium is the most significant waste product
and is considered to be hazard in drinking water.
 Water supplies must not contain more than 3 Pico curies
per litre of radium-226, nor more than 10 Pico curies per
litre of strontium-90

 Certain marine organisms have the capacity for
accumulating radionuclides from water. This
“biomagnifications” may cause objectionable radioactivity
in living organisms, although the radiation level in water
may be low enough to be considered safe.
Phytoplankton and fish may concentrate metal
radionuclides by factors of 102 to 105.
 Radioactive substances can enter humans with food and
water, and get accumulated in blood and certain vital
organs like the thyroid gland, the liver and bone and
muscular tissues. At present some low and medium level
wastes are sealed in containers and dumped into the
ocean. If there is any damage to, or leakage from the
containers, the nuclear wastes could escape and enter
the marine system. Then storms and ocean currents and
eventually reach coastal waters could circulate them.

Thermal Discharges
 Power plants and industry use large quantities of water for
cooling purposes. Used coolant water is usually discharged
directly into water bodies. This could result in increase in
temperature of the water bodies with deleterious
consequences for aquatic inhabitants.
 An increase in water temperature decrease the oxygen
saturation percentage, and at the same time accelerates
the lowering of DO levels. This is because the hot water
tends to form a separate layer above the cool water due to
density differences between the two. The hot layer, which
itself holds less oxygen than the cooler layer as it is denied
contact with the atmosphere. The DO level falls rapidly due
to normal biological functions in the lower layer and may
lead to anaerobic conditions.

Oil
 Oil is an important commodity involved in some way or
other in virtually every activity of contemporary life.
Therefore, there is obvious concern about its polluting
effects. Oil and oil wastes enter rivers and other water
bodies from several sources like industrial effluents, oil
refineries and storage tanks, automobile waste oil, and
petrochemical plants.
 Since oil is virtually insoluble in water, it floats and
spreads rapidly into a thin layer. The lighter, low
molecular weight elements, which are more toxic to
organisms, soon evaporate and others are degraded
biologically but only at slow rate. At sea, oil slicks are
responsible for the deaths of many birds. The oil
penetrates the bird feathers thereby affecting their
insulation and buoyancy. Thus the birds become colder
and more susceptible to diseases, and experience
difficulty in floating and flying.

The State of India’s Rivers
 India has always had a tradition of worshipping rivers. Most of the rivers
in India are named after gods, goddesses or saints. However a large
majority of the Indian population including those who worship the rivers
do not think twice before polluting a river.
 Urbanization, industrialization, excess withdrawal of water, agricultural
run-off, improper agricultural practices and various religious and social
practices all contribute to river pollution in India.
 Every single river in India be it the Ganga, Yamuna, Cauvery or the
Krishna have their own share of problems due to pollution. Waters from
the Ganga and the Yamuna are drawn for irrigation through the network
of canals as soon as these rivers reach the plains reducing the amount
of water that flows downstream.

 What flows in the river is water from small nalas, and streams that carry
with them sewage and industrial effluents. The residual freshwater, is
unable to dilute the pollutants and the rivers turn into stinking sewers.
 In spite of data from scientifically competent studies conducted by the
Central Pollution Control Board (CPCB), the Government has not been
able to tackle this issue. Sewage and municipal effluents account for
75% of the pollution load in rivers while the remaining 25% is from
industrial effluents and non-point pollution sources.
 In 1985, India launched the Ganga Action plan (GAP) the largest ever
river clean-up operation in the country. The plan has been criticized for,
overspending and slow progress. The GAP Phase II in 1991 included
cleaning operations for the tributaries of the Ganga, ie; the Yamuna,
Gomti and the Damodar.
 Thus the Yamuna Action Plan (YAP), Gomti Action Plan and the
Damodar Action plan were added.

 In 1995 the National River Conservation Plan (NRCP) was launched.
Under this all the rivers in India were taken up for clean-up operations. In
most of these plans, attempts have been made to tap drains, divert
sewage to sewage treatment plants before letting out the sewage into the
rivers.
 The biggest drawback of these river cleaning programs was that they
failed to pin responsibilities as to who would pay for running the treatment
facilities in the long run. With the power supply being erratic and these
plants being heavily dependent on power, most of these facilities lie
underutilized. Moreover the problem of river pollution due to agricultural
runoff has not been addressed in these programs.
 NRCP is scheduled to be completed by March 2005. The approved cost
for the plan is Rs. 772.08 crores covering 18 rivers in 10 states including
46 towns. The cost is borne entirely by the Central Government and the
Ministry of Environment and Forests is the nodal agency that co-
ordinates and monitors the plan.
 Under this plan the major activities include treating the pollution load from
sewer systems of towns and cities, setting up of Sewage treatment
plants, electric crematoria, low cost sanitation facilities, riverfront
development, afforestation and solid waste management.

Control Measures for Preventing Water
Pollution
 While the foremost necessity is prevention, setting up effluent
treatment plants and treating waste through these can reduce the
pollution load in the recipient water. The treated effluent can be
reused for either gardening or cooling purposes wherever
possible.
 A few years ago a new technology called the Root Zone Process
has been developed by Thermax. This system involves running
contaminated water through the root zones of specially designed
reed beds.
 The reeds, which are essentially wetland plants have the capacity
to absorb oxygen from the surrounding air through their stomatal
openings.
 The oxygen is pushed through the porous stem of the reeds into
the hollow roots where it enters the root zone and creates
conditions suitable for the growth of numerous bacteria and fungi.
These micro-organisms oxidize impurities in the wastewaters, so
that the water which finally comes out is clean.

Marine Pollution
 Marine pollution can be defined as the introduction of substances to
the marine environment directly or indirectly by man resulting in
adverse effects such as hazards to human health, obstruction of
marine activities and lowering the quality of sea water. While the
causes of marine pollution may be similar to that of general water
pollution there are some very specific causes that pollute marine
waters.
 The most obvious inputs of waste is through pipes directly discharging
wastes into the sea. Very often municipal waste and sewage from
residences and hotels in coastal towns are directly discharged into the
sea.
 Pesticides and fertilizers from agriculture which are washed off the
land by rain, enter water courses and eventually reach the sea.

 Petroleum and oils washed off from the roads normally enter the
sewage system but stormwater overflows carry these materials into
rivers and eventually into the seas.
 Ships carry many toxic substances such as oil, liquefied natural gas,
pesticides, industrial chemicals, etc. in huge quantities sometimes to
the capacity of 350,000 tonnes. Ship accidents and accidental spillages
at sea therefore can be very damaging to the marine environment.
Shipping channels in estuaries and at the entrances to ports often
require frequent dredging to keep them open. This dredged material
that may contain heavy metals and other contaminants are often
dumped out to sea.
 Offshore oil exploration and extraction also pollute the seawater to a
large extent.

Exxon Valdez oil spill
 Occurred in the Prince William Sound, Alaska, in 1989.
 One of the world's largest oil spills in terms of volume released
 Prince William Sound's remote location (accessible only by helicopter
and boat) made response efforts difficult
 The region was a habitat for salmon, sea otters, seals and seabirds
 The vessel spilled 10.8 million U.S. gallons (about 40 million litres) of
crude oil into the sea, and the oil eventually covered 11,000 square
miles (28,000 km2) of ocean.

Control Measures for Oil Pollution
 Cleaning oil from surface waters and contaminated beaches is a time
consuming labour intensive process.
 The natural process of emulsification of oil in the water can be
accelerated through the use of chemical dispersants which can be
sprayed on the oil. A variety of slick-lickers in which a continuous belt
of absorbent material dips through the oil slick and is passed through
rollers to extract the oil have been designed.
 Rocks, harbour walls can be cleaned with high pressure steam or
dispersants after which the surface must be hosed down.

Effects of Marine Pollution
 Apart from causing eutrophication a large amount of organic wastes can
also result in the development of red tides. These are phytoplankton
blooms of such intensity that the area is discolored.
 Many important commercially important marine species are also killed
due to clogging of gills or other structures. When liquid oil is spilled on
the sea it spreads over the surface of the water to form a thin film called
an oil slick.
 The rate of spreading and the thickness of the film depends on the sea
temperature and the nature of the oil.
 Oil slicks damage marine life to a large extent. Salt marshes, mangrove
swamps are likely to trap oil and the plants, which form the basis for
these ecosystems thus suffer. For salt marsh plants, oil slicks can affect
the flowering, fruiting and germination.

 If liquid oil contaminates a bird’s plumage its water repellent properties are
lost. Water thus penetrates the plumage and displaces the air trapped
between the feathers and the skin. This air layer is necessary as it
provides buoyancy and thermal insulation. With this loss the plumage
becomes water logged and the birds may sink and drown. Even if this
does not happen loss of thermal insulation results in exhaustion of food
reserves in an attempt to maintain body temperature often followed by
death. Birds often clean their plumage by preening and in the process
consume oil which depending on its toxicity can lead to intestinal, renal or
liver failure.
 Drill cuttings dumped on the seabed create anoxic conditions and result in
the production of toxic sulphides in the bottom sediment thus eliminating
the benthic fauna.
 Fish and shellfish production facilities can also be affected by oil slicks.
The most important commercial damage can however also come from
tainting which imparts an unpleasant flavour to fish and seafood and is
detectable at extremely low levels of contamination. This reduces the
market value of seafood.

Thermal Pollution
Sources
 The discharge of warm water into a river is usually called a thermal
pollution.
 It occurs when an industry removes water from a source, uses the
water for cooling purposes and then returns the heated water to its
source.
 Power plants heat water to convert it into steam, to drive the turbines
that generate electricity.
 For efficient functioning of the steam turbines, the steam is condensed
into water after it leaves the turbines. This condensation is done by
taking water from a water body to absorb the heat.
 This heated water, which is at least 15oC higher than the normal is
discharged back into the water body.

Effects
 The warmer temperature decreases the solubility of oxygen and
increases the metabolism of fish. This changes the ecological balance
of the river.
 Within certain limits thermal additions can promote the growth of
certain fish and the fish catch may be high in the vicinity of a power
plant.
 However sudden changes in temperature caused by periodic plant
shutdowns both planned and unintentional can change result in death
of these fish that are acclimatized to living in warmer waters.
 Tropical marine animals are generally unable to withstand a
temperature increase of 2 to 30C and most sponges, mollusks and
crustaceans are eliminated at temperatures above 370C.
 This results in a change in the diversity of fauna as only those species
that can live in warmer water survive.

Control Measures
 Thermal pollution can be controlled by passing the heated water through a
cooling pond or a cooling tower after it leaves the condenser.
 The heat is dissipated into the air and the water can then be discharged
into the river or pumped back to the plant for reuse as cooling water.
 There are several ways in which thermal pollution can be reduced. One
method is to construct a large shallow pond. Hot water is pumped into one
end of the pond and cooler water is removed from the other end. The heat
gets dissipated from the pond into the atmosphere.

 A second method is to use a cooling tower. These structures take up
less land area than the ponds. Here most of the heat transfer occurs
through evaporation. Here warm waters coming from the condenser is
sprayed downward over vertical sheets or baffles where the water flows
in thin films.
 Cool air enters the tower through the water inlet that encircles the base
of the tower and rises upwards causing evaporative cooling.
 A natural draft is maintained because of the density difference between
the cool air outside and the warmer air inside the tower. The waste heat
is dissipated into the atmosphere about 100 m above the base of the
tower.
 The cooled water is collected at the floor of the tower and recycled back
to the power plant condensers.
 The disadvantage in both these methods is however that large amounts
of water are lost by evaporation.

Soil Pollution
 We can no more manufacture a soil with a tank of chemicals than we
can invent a rain forest or produce a single bird.
 We may enhance the soil by helping its processes along, but we can
never recreate what we destroy.
 The soil is a resource for which there is no substitute. (Environmental
historian Donald Worster reminds us that fertilizers are not a substitute
for fertile soil).
 Soil is a thin covering over the land consisting of a mixture of minerals,
organic material, living organisms, air and water that together support
the growth of plant life. Several factors contribute to the formation of
soil from the parent material.

 This includes mechanical weathering of rocks due to temperature
changes and abrasion, wind, moving water, glaciers, chemical
weathering activities and lichens.
 Climate and time are also important in the development of soils.
Extremely dry or cold climates develop soils very slowly while humid and
warm climates develop them more rapidly.
 Under ideal climatic conditions soft parent material may develop into a
centimeter of soil within 15 years. Under poor climatic conditions a hard
parent material may require hundreds of years to develop into soil.
Mature soils are arranged in a series of zones called soil horizons. Each
horizon has a distinct texture and composition that varies with different
types of soils.
 A cross sectional view of the horizons in a soil is called a soil profile. The
top layer or the surface litter layer called the O horizon consists mostly of
freshly fallen and partially decomposed leaves, twigs, animal waste, fungi
and other organic materials. Normally it is brown or black. The uppermost
layer of the soil called the A horizon consists of partially decomposed
organic matter (humus) and some inorganic mineral particles. It is usually
darker and looser than the deeper layers.

 The roots of most plants are found in these two upper layers. As long as
these layers are anchored by vegetation soil stores water and releases it
in a trickle throughout the year instead of in a force like a flood. These two
top layers also contain a large amount of bacteria, fungi, earthworms and
other small insects that form complex food webs in the soil that help
recycle soil nutrients and contribute to soil fertility. The B horizon often
called the subsoil contains less organic material and fewer organisms
than the A horizon.
 The area below the subsoil is called the C horizon and consists of
weathered parent material.
 This parent material does not contain any organic materials. The chemical
composition of the C-horizon helps to determine the pH of the soil and
also influences the soil’s rate of water absorption and retention. Soils vary
in their content of clay (very fine particles), silt (fine particles), sand
(medium size particles) and gravel (coarse to very coarse particles). The
relative amounts of the different sizes and types of mineral particles
determine soiltexture. Soils with approximately equal mixtures of clay,
sand, silt and humus are called loams.

Causes of Soil Degradation
Erosion
 Soil erosion can be defined as the movement of surface litter and topsoil
from one place to another. While erosion is a natural process often
caused by wind and flowing water it is greatly accelerated by human
activities such as farming, construction, overgrazing by livestock,
burning of grass cover and deforestation. Loss of the topsoil makes a
soil less fertile and reduces its water holding capacity. The topsoil, which
is washed away, also contributes to water pollution clogging lakes,
increasing turbidity of the water and also leads to loss of aquatic life.
 For one inch of topsoil to be formed it normally requires 200-1000 years
depending upon the climate and soil type. Thus if the topsoil erodes
faster than it is formed the soil becomes a non-renewable resource.
Thus it is essential that proper soil conservation measures are used to
minimize the loss of top soil. There are several techniques that can
protect soil from erosion. Today both water and soil are conserved
through integrated treatment methods. Some of the most commonly
employed methods include the two types of treatment that are generally

Area Treatment Which Involves Treating the Land
 Drainage line treatment which involves treating the natural water
courses (nalas) continuous contour trenches can be used to enhance
infiltration of water reduce the runoff and check soil erosion. These are
actually shallow trenches dug across the slope of the land and along
the contour lines basically for the purpose of soil and water
conservation. They are most effective on gentle slopes and in areas of
low to medium rainfall. These bunds are stabilized by fast growing tree
species and grasses. In areas of steep slopes where the bunds are not
possible, continuous contour benches (CCBs) made of stones are used
for the same purpose. Gradonies can also be used to convert
wastelands into agricultural lands. In this narrow trenches with bunds on
the downstream side are built along contours in the upper reaches of
the catchment to collect run-off and to conserve moisture from the trees
or tree crops. The area between the two bunds is use for cultivation of
crops after development of fertile soil cover.
Some of the ways in which this can be achieved are:
Live check dams which barriers created by planting grass, shrubs and
trees across the gullies can be used for this purpose.
A bund constructed out of stones across the stream can also be used

Area Treatment
Purpose Treatment measure Effect
Reduces the impact of
rain drops on soils
Develop vegetative
cover on the non
arable land
Minimum displacement
and disturbance of soil
particles
Infiltration of water
where it falls
Apply water
infiltration measures
on the area
In situ soil and moisture
conservation
Minimum surface runoff Store surplus rain
water by constructing
bunds, ponds in the
area
Increased soil moisture
in the area, facilitate
ground water recharge
Ridge to valley
sequencing
Treat the upper
catchment first and
then proceed towards
the outlet
Economically viable,
less risk of damage and
longer life of structures
of the lower catchments

Drainage Line Treatment
Purpose Treatment Measure Effect
Stop further deepening of
gullies and retain
sediment run-off
Plug the gullies at
formation
Stops erosion, recharges
groundwater at the upper
level.
Reduce run-off velocity,
pass cleaner water to the
downstream side
Create temporary
barriers in nalas
Delayed flow and
increased groundwater
recharge
Minimum sedimentation
in the storage basins
Use various methods to
treat the catchments
Low construction cost Use local material and
skills for constructing
the structures
Structures are locally
maintained

 An Earthen checkbund is constructed out of local soil
across the stream to check soil erosion and flow of water.
 A Gabion structure is a bund constructed of stone and
wrapped in galvanized chainlink.
 A Gabion structure with ferrocement impervious
barrier has a one inch thick impervious wall of ferrocement
at the center of the structure which goes below the ground
level upto the hard strata. This ferrocement partition
supported by the gabion portion is able to retain the water
and withstand the force of the runoff water.
 An Underground bandhara is an underground structure
across a nalla bed to function as a barrier to check the
ground water movement.

Concept of Soil remediation
Protection of fertile soil is soil remediation.
 Waste water is treated adequately before land
disposal.
 Tree plantation at proper places is to be controlled
to prevent soil erosion.
 Natural fertilizers and biological agents for pest
management is used.
 Plough or mix the soil to improve aeration,
porosity and permeability.
 Water logging and salinity conditions is avoided.
 Grass only on polluted lands is cultivated.

Noise Pollution
 Noise may not seem as harmful as the contamination of air or water but
it is a pollution problem that affects human health and can contribute to
a general deterioration of environmental quality.
 Noise is undesirable and unwanted sound.
 Not all sound is noise.
 What may be considered as music to one person may be noise to
another.
 It is not a substance that can accumulate in the environment like most
other pollutants.
 Sound is measured in a unit called the ‘Decibel’.

Decibel Levels of Common Sounds
dB Environmental Condition
0 Threshold of hearing
10 Rustle of leaves
20 Broadcasting studio
30 Bedroom at night
40 Library
50 Quiet office
60 Conversational speech (at 1m)
70 Average radio
74 Light traffic noise
90 Subway train
100 Symphony orchestra
110 Rock band
120 Aircraft takeoff
146 Threshold of pain

Measurement of noise levels
It is measured in decibels.
Also in Noise exposure index (NEI)
NEI = t / T
Where t is total time of exposure at a particular noise
level.
T is total time of exposure permitted at that level.

Effects of Noise Pollution on Physical Health
 The most direct harmful effect of excessive noise is physical damage
to the ear and the temporary or permanent hearing loss often called a
temporary threshold shift (TTS).
 People suffering from this condition are unable to detect weak sounds.
However hearing ability is usually recovered within a month of
exposure.
 In Maharashtra people living in close vicinity of Ganesh mandals that
play blaring music for ten days of the Ganesh festival are usually
known to suffer from this phenomenon.

 Permanent loss, usually called noise induced permanent threshold shift
(NIPTS) represents a loss of hearing ability from which there is no
recovery.
 Below a sound level of 80 dBA hearing loss does not occur at all.
However temporary effects are noticed at sound levels between 80 and
130 dBA.
 About 50 percent of the people exposed to 95 dBA sound levels at work
will develop NIPTS and most people exposed to more than 105 dBA will
experience permanent hearing loss to some degree.
 A sound level of 150 dBA or more can physically rupture the human
eardrum.
 The degree of hearing loss depends on the duration as well as the
intensity of the noise. For example, 1hour of exposure to a 100 dBA
sound level can produce a TTS that may last for about one day.
However in factories with noisy machinery workers are subjected to high

 Exposure to 95 dBA for 8 hours everyday for over a period of 10 years
may cause about 15 dBA of NIPTS. In addition to hearing losses
excessive sound levels can cause harmful effects on the circulatory
system by raising blood pressure and altering pulse rates.
Effects of Noise Pollution on Mental Health
 Noise can also cause emotional or psychological effects such as
irritability, anxiety and stress.Lack of concentration and mental fatigue
are significant health effects of noise.
 It has been observed that the performance of school children is poor in
comprehension tasks when schools are situated in busy areas of a city
and suffer from noise pollution.

 As noise interferes with normal auditory communication, it may mask
auditory warning signals and hence increases the rate of accidents
especially in industries.
 It can also lead to lowered worker efficiency and productivity and higher
accident rates on the job.
 Thus noise is just more than a mere nuisance or annoyance. It definitely
affects the quality of life.
 It is thus important to ensure mitigation or control of noise pollution.

Ambient Noise Levels dB
Zone Day-time Night-time
Silent Zone 50 40
Residential Zone 55 45
Commercial Zone 65 55
Industrial Zone 70 70

Noise Control Techniques
There are four fundamental ways in which noise can be
controlled:
 Reduce noise at the source, block the path of noise, increase the path
length and protect the recipient.
 In general, the best control method is to reduce noise levels at the
source.
 Source reduction can be done by effectively muffling vehicles and
machinery to reduce the noise. In industries noise reduction can be done
by using rigid sealed enclosures around machinery lined with acoustic
absorbing material. Isolating machines and their enclosures from the floor
using special spring mounts or absorbent mounts and pads and using
flexible couplings for interior pipelines also contribute to reducing noise
pollution at the source.

 However one of the best methods of noise source reduction is regular and
thorough maintenance of operating machinery. Noise levels at construction
sites can be controlled using proper construction planning and scheduling
techniques. Locating noisy air compressors and other equipment away
from the site boundary along with creation of temporary barriers to
physically block the noise can help contribute to reducing noise pollution.
 Most of the vehicular noise comes from movement of the vehicle tires on
the pavement and wind resistance. However poorly maintained vehicles
can add to the noise levels.
 Traffic volume and speed also have significant effects on the overall
sound. For example doubling the speed increases the sound levels by
about 9 dBA and doubling the traffic volume (number of vehicles per hour)
increases sound levels by about 3 dBA. A smooth flow of traffic also
causes less noise than does a stop-and-go traffic pattern. Proper highway
planning and design are essential for controlling traffic noise.

 Establishing lower speed limits for highways that pass through
residential areas, limiting traffic volume and providing alternative routes
for truck traffic are effective noise control measures.
 The path of traffic noise can also be blocked by construction of vertical
barriers alongside the highway.
 Planting of trees around houses can also act as effective noise barriers.
 In industries different types of absorptive material can be used to
control interior noise. Highly absorptive interior finish material for walls,
ceilings and floors can decrease indoor noise levels significantly.

 Sound levels drop significantly with increasing distance from the noise
source. Increasing the path length between the source and the recipient
offers a passive means of control.
 Municipal land-use ordinances pertaining to the location of airports make
use of the attenuating effect of distance on sound levels. Use of earplugs
and earmuffs can protect individuals effectively from excessive noise
levels. Specially designed earmuffs can reduce the sound level reaching
the eardrum by as much as 40 dBA.
 However very often workers tend not to wear them on a regular basis
despite company requirements for their use.

SOLID WASTE MANAGEMENT:
Classification of Solid Waste
Urban waste: Includes domestic, muncipal and industrial
waste produts
Mineral waste: Includes waste from mining and mineral
processing.
Agricultural waste: Includes waste from farming, animals and
crops.
Industrial waste classified into process and non process
waste.
Process waste: complex and specific to industries.
 Rubber tyre industry generates rubber waste
 Plastic producing firm plastic waste.
Non process waste: Includes packaging, office and cafeteria
wastes similar to domestic and commercial wastes.

Characteristics of Municipal Solid
Waste
 Solid wastes are grouped or classified in several different ways. These
different classifications are necessary to address the complex challenges
of solid waste management in an effective manner.
 The term municipal solid waste (MSW) is generally used to describe most
of the non-hazardous solid waste from a city, town or village that requires
routine collection and transport to a processing or disposal site.
 Sources of MSW include private homes, commercial establishments and
institutions as well as industrial facilities.
 However MSW does not include wastes from industrial processes,
construction and demolition debris, sewage sludge, mining wastes or
agricultural wastes.
 Municipal solid waste contains a wide variety of materials. It can contain
food waste such as vegetable and meat material, left over food, egg
shells, etc which is classified as wet garbage as well as paper, plastic,
tetrapacks, plastic cans, newspaper, glass bottles, cardboard boxes,

Control Measures of Urban and Industrial
Wastes
An integrated waste management strategy includes three main
components:
1. Source reduction
2. Recycling
3. Disposal
 Source reduction is one of the fundamental ways to reduce waste.
This can be done by using less material when making a product, reuse
of products on site, designing products or packaging to reduce their
quantity. On an individual level we can reduce the use of unnecessary
items while shopping, buy items with minimal packaging, avoid buying
disposable items and also avoid asking for plastic carry bags.

 Recycling is reusing some components of the waste that may have
some economic value. Recycling has readily visible benefits such as
conservation of resources reduction in energy used during manufacture
and reducing pollution levels. Some materials such as aluminum and
steel can be recycled many times. Metal, paper, glass and plastics are
recyclable. Mining of new aluminum is expensive and hence recycled
aluminum has a strong market and plays a significant role in the
aluminum industry.
 Paper recycling can also help preserve forests as it takes about 17 trees
to make one ton of paper.
 Crushed glass (cullet) reduces the energy required to manufacture new
glass by 50 percent. Cullet lowers the temperature requirement of the
glassmaking process thus conserving energy and reducing air pollution.
 However even if recycling is a viable alternative, it presents several
problems. The problems associated with recycling are either technical or
economical.

 Plastics are difficult to recycle because of the different types of polymer
resins used in their production. Since each type has its own chemical
makeup different plastics cannot be recycled together. Thus separation
of different plastics before recycling is necessary.
 Similarly in recycled paper the fibers are weakened and it is difficult to
control the colour of the recycled product. Recycled paper is banned for
use in food containers to prevent the possibility of contamination. It very
often costs less to transport raw paper pulp than scrap paper.
Collection, sorting and transport account for about 90 percent of the cost
of paper recycling.
 The processes of pulping, deinking and screening wastepaper are
generally more expensive than making paper from virgin wood or
cellulose fibers.
 Very often thus recycled paper is more expensive than virgin paper.
However as technology improves the cost will come down.

Disposal of solid waste is done most commonly through a sanitary landfill
or through incineration.
A modern sanitary landfill is a depression in an impermeable soil layer that
is lined with an impermeable membrane.
The three key characteristics of a municipal sanitary landfill that
distinguish it from an open dump are:
 Solid waste is placed in a suitably selected and prepared landfill site in a
carefully prescribed manner.
 The waste material is spread out and compacted with appropriate heavy
machinery.
 The waste is covered each day with a layer of compacted soil.
• The problem with older landfills are associated with groundwater
pollution.
• Pollutants seeping out from the bottom of a sanitary landfill (leachates)
very often percolate down to the groundwater aquifer no matter how
thick the underlying soil layer.

 Today it is essential to have suitable bottom liners and leachate collection
systems along with the installation of monitoring systems to detect
groundwater pollution.
 The organic material in the buried solid waste will decompose due to the
action of microorganisms.
 At first the waste decomposes aerobically until the oxygen that was
present in the freshly placed fill is used up by the aerobic microorganisms.
 The anerobes take over producing methane which is poisonous and
highly explosive when mixed with air in concentrations between 5 and 15
percent. The movement of gas can be controlled by providing
impermeable barriers in the landfill. A venting system to collect the
blocked gas and vent it to the surface where it can be safely diluted and
dispersed into the atmosphere is thus a necessary component of the
design of sanitary landfills.

 Even though landfilling is an economic alternative for solid waste
disposal, it has become increasingly difficult to find suitable landfilling
sites that are within economic hauling distance and very often citizens
do not want landfills in their vicinity.
 Another reason is that no matter how well engineered the design and
operation may be, there is always the danger of some environmental
damage in the form of leakage of leachates.
 Incineration is the process of burning municipal solid waste in a
properly designed furnace under suitable temperature and operating
conditions.
 Incineration is a chemical process in which the combustible portion of
the waste is combined with oxygen forming carbon dioxide and water,
which are released into the atmosphere. This chemical reaction called
oxidation results in the release of heat.
 For complete oxidation the waste must be mixed with appropriate
volumes of air at a temperature of about 815o C for about one hour.

 Incineration can reduce the municipal solid waste by about 90 percent
in volume and 75 percent in weight. The risks of incineration however
involve airquality problems and toxicity and disposal of the fly and
bottom ash produced during the incineration process.
 Fly ash consists of finely divided particulate matter, including cinders,
mineral dust and soot. Most of the incinerator ash is bottom ash while
the remainder is fly ash.
 The possible presence of heavy metals in incinerator ash can be
harmful. Thus toxic products and materials containing heavy metals
(for example batteries and plastics) should be segregated.
 Thus extensive air pollution control equipment and high-level technical
supervision and skilled employees for proper operation and
maintenance is required.
 Thus while sanitary landfills and incinerators have their own
advantages and disadvantages, the most effective method of solid
waste management is source reduction and recycling.

Vermi – Composting
 Nature has perfect solutions for managing the waste it creates, if left
undisturbed.
 The biogeochemical cycles are designed to clear the waste material
produced by animals and plants. We can mimic the same methods that
are present in nature.
 All dead and dry leaves and twigs decompose and are broken down by
organisms such as worms and insects, and is finally broken down by
bacteria and fungi, to form a dark rich soil-like material called compost.
 These organisms in the soil use the organic material as food, which
provides them with nutrients for their growth and activities. These
nutrients are returned to the soil to be used again by trees and other
plants.
 This process recycles nutrients in nature. This soil can be used as a
manure for farms and gardens.

Steps for Vermi-Compost
• Dig a pit about half a meter square, one meter deep.
• Line it with straw or dried leaves and grass.
• Organize the disposal of organic waste into the pit as and when generated.
• Introduce a culture of worms that is now produced commercially.
• Ensure that the contents are covered with a sprinkling of dried leaves and soil
everyday.
• Water the pit once or twice a week to keep it moist.
• Turn over the contents of the pit over 15 days.
• In about 45 days the waste will be decomposed by the action of the
microorganisms.
• The soil derived is fertile and rich in nutrients.

Hazardous Wastes
 Modern society produces large quantities of hazardous waste which are
generated by chemical manufacturing companies, petroleum refineries,
paper mills, smelters and other industries.
 Hazardous wastes are those that can cause harm to humans or the
environment.
 Wastes are normally classified as hazardous waste when they cause or
significantly contribute to an increase in mortality or an increase in
serious irreversible or incapacitating reversible illness or pose a
substantial present or potential hazard to human health or the
environment when improperly treated, stored, transported or disposed
of.

Characteristics of Hazardous Wastes
 A waste is classified as a hazardous waste if it exhibits any of the four
primary characteristics based on the physical or chemical properties of
toxicity, reactivity, ignitability and corrosivity. In addition to this waste
products that are either infectious or radioactive are also classified as
hazardous
 Toxic wastes are those substances that are poisonous even in very
small or trace amounts. Some may have an acute or immediate effect on
humans or animals causing death or violent illness. Others may have a
chronic or long term effect slowly causing irreparable harm to exposed
persons. Acute toxicity is readily apparent because organisms respond to
the toxin shortly after being exposed. Chronic toxicity is much more
difficult to determine because the effects may not be seen for years.
Certain toxic wastes are known to be carcinogenic, causing cancer and
others may be mutagenic causing biological changes in the children of
exposed people and animals.
 Reactive wastes are those that have a tendency to react vigorously with
air or water, are unstable to shock or heat, generate toxic gases or
explode during routine management. For example, gunpowder,

 Ignitable wastes are those that burn at relatively low temperatures
(less than 600C) and are capable of spontaneous combustion during
storage, transport or disposal. For example, gasoline, paint thinners,
and alcohol.
 Corrosive wastes are those that destroy materials and living tissue by
chemical reaction. For example, acids and bases.
 Infectious wastes include human tissue from surgery, used bandages
and hypodermic needles, microbiological materials, etc.
 Radioactive waste is basically an output from the nuclear power plants
and can persist in the environment for thousands of years before it
decays appreciably.

Environmental Problems and Health Risks Caused By
Hazardous Wastes
 As most of the hazardous wastes are disposed of on or in land the
most serious environmental effect is contaminated groundwater.
 Once groundwater is polluted with hazardous wastes it is very often
not possible to reverse the damage. Pesticides are used increasingly
to protect and increase food production.
 They form residues in the soil which are washed into streams which
then carry them forwards. The residues may persist in the soil or in
the bottom of lakes and rivers. Exposure can occur through ingestion,
inhalation and skin contact resulting in acute or chronic poisoning.
 Today we have an alternative to the excess use of pesticides through
the use of Integrated Pest Management (IPM). The IPM system uses
a wide variety of plants and insects to create a more natural process.

 The natural balance between climate, soil and insect populations can
help to prevent an insect from overpopulating an area and destroying a
particular crop.
 Lead, mercury and arsenic are hazardous substances which are often
referred to as heavy metals. Lead is an abundant heavy metal and is
relatively easy to obtain. It is used in batteries, fuel, pesticides, paints,
pipes and other places where resistance to corrosion is required. Most
of the lead taken up by people and wildlife is stored in bones.
 Lead can affect red blood cells by reducing their ability to carry oxygen
and shortening their life span. Lead may also damage nerve tissue
which can result in brain disease.
 Mercury occurs in several different forms. Mercury is used in the
production of chlorine. It is also used as a catalyst in the production of
some plastics. Industrial processes such as the production of chlorine
and plastics are responsible for most of the environmental damage
resulting from mercury. Our body has a limited ability to eliminate
mercury.

 In the food web mercury becomes more concentrated as it is taken up
by various organisms. In an aquatic environment, mercury can be
absorbed by the plankton which are then consumed by fish. In addition,
fish take up mercury through their gills and by eating other fish
contaminated with mercury.
 Generally older the fish greater is the mercury concentration in its
body. Birds that eat the fish concentrate even more mercury in their
bodies.
 It is a cumulative poison ( it builds up in the body over long periods of
time) and is known to cause brain damage.
 Thousands of chemicals are used in industry everyday.

 When used incorrectly or inappropriately they can become health
hazards. PCBs (Polychlorinated biphenyls) are resistant to fire and do
not conduct electricity very well which makes them excellent materials
for several industrial purposes. Rainwater can wash PCBs out of
disposal areas in dumps and landfills thus contaminating water. PCBs
do not break down very rapidly in the environment and thus retain their
toxic characteristics.
 They cause long term exposure problems to both humans and wildlife.
PCBs are concentrated in the kidneys and liver and thus cause
damage. They cause reproductive failure in birds and mammals.
 Vinyl chloride is a chemical that is widely used in the manufacture of
plastic. Usually people are only exposed to high levels of vinyl chloride
if they work with it or near it but exposure can also occur from vinyl
chloride gas leaks. After a long continuous exposure (one to three
years) in humans, vinyl chloride can cause deafness, vision problems,
circulation disorders and bone deformities.

 Vinyl chloride can also cause birth defects. It is essential to substitute
the use of PCBs and vinyl chloride with chemicals that are less toxic.
Polyvinyl chloride use can be lowered by reducing our use of plastics.
 Thus by reducing waste, encouraging recycling and using products that
are well made and durable we can greatly reduce our consumption of
these chemicals thus curtailing our exposure to these substances.
 We may not realize it but many household chemicals can be quite toxic
to humans as well as wildlife.
 Most of the dangerous substances in our homes are found in various
kinds of cleaners, solvents and products used in automotive care.
 When these products are used incorrectly they have the potential to be
harmful.

EVS Pollution PPT.ppt

More Related Content

Similar to EVS Pollution PPT.ppt (20)

Recently uploaded (20)

EVS Pollution PPT.ppt