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EEES CLASS NOTES
Introduction to energy scenario
Energy is an important input for development. It aims at human welfare covering
household, agriculture, transport and industrial complexes like other natural resources.
Conventional sources of energy coal, petroleum, natural gas are the common sources.
These account for about 89.4% of the world‘s production of commercial energy, hydro
electric and nuclear power accounting for only 10.6%, oil – 39.5%, Natural gas – 19.6%,
Coal – 30.3%, Hydro-electric – 6.7%, Nuclear – 3.9%.
More than 80% of the total world consumption of energy is by developed world
which account for only 30% of the world production. On the other hand, 20% of the
energy is consumed by 70% of the world population in developing and social countries.
In India commercial energy constitutes 38.5% and 31.7% in industrial and
transport sectors respectively. Oil constitutes 71.2% in household sector, 61.8% in
agriculture and 47.6% electricity that are important.
Conventional and non-conventional resources of energy
i) Conventional energy sources: As most of the fuel wood is consumed for
domestic purposes, mainly in rural areas, very little of it is available to
industrial sector. Thermal coal, already in use in industries becomes a highly
priced source. It was then supplemented by mineral oil. Likewise the use of
hydroelectricity (water energy) becomes dearer, the areas where running water
and needed technology is not readily available.
After world war–II yet another source of energy, nuclear power was
developed. All these sources of energy are known as conventional sources of
energy, among which coal still occupies a central position.
ii) Non Conventional energy sources: Efforts were made to develop new sources
of energy. These are called non-conventional sources of energy and include
urban waste, agriculture waste, energy plantations, animal and human wastes,
solar energy, wind-energy, tidal energy, geothermal energy, ocean, biogas etc.
These are pollution-free, environmentally clean and socially relevant.
Renewable energy
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Renewable energy is energy which comes from natural resources such
as sunlight, wind, rain, tides, and geothermal heat, which are renewable (naturally
replenished). In 2008, about 19% of global final energy consumption came from
renewables, with 13% coming from traditional biomass, which is mainly used for heating,
and 3.2% from hydroelectricity. New renewables (small hydro, modern biomass, wind,
solar, geothermal, and bio-fuels) accounted for another 2.7% and are growing very
rapidly.The share of renewables in electricity generation is around 18%, with 15% of
global electricity coming from hydroelectricity and 3% from new renewables.
Resource energy or non-renewable energy is the energy taken from a source which is
depleted by extraction. It rely on consumable materials. Non-renewable energy sources
come from the earth and appear as either solids, liquids, and gases.
Energy sources that are almost always classified as non-renewable:
Fossil fuels
Coal
Petroleum
Natural gas
Fossil fuel
Fossil fuels are fuels formed by natural resources such as anaerobic
decomposition of buried dead organisms. The age of the organisms and their
resulting fossil fuels is typically millions of years and sometimes exceeds 650
million years. The fossil fuels, which contain high percentages of carbon,
include coal, petroleum, and natural gas. Fossil fuels range from volatile
materials with low carbon:hydrogen ratios like methane, to liquid petroleum to
nonvolatile materials composed of almost pure carbon, like anthracite coal.
Methane can be found in hydrocarbon fields, alone associated with oil, or in the
form of methane clathrates. It is generally accepted that they formed from the
fossilized remains of dead plants and animals by exposure to heat and pressure in
the Earth's crust over millions of years. This biogenic theory was first introduced
by Georg Agricolain 1556 and later by Mikhail Lomonosov in the 18th century.
Coal
Coal is a combustible black or brownish-black sedimentary rock normally
occurring in rock strata in layers or veins called coal beds or coal seams. The harder
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forms, such as anthracite coal, can be regarded as metamorphic rock because of later
exposure to elevated temperature and pressure. Coal is composed primarily
of carbon along with variable quantities of other elements, chiefly sulfur,
hydrogen, oxygen and nitrogen.
Coal begins as layers of plant matter accumulate at the bottom of a body of water.
For the process to continue the plant matter must be protected from biodegradation and
oxidization, usually by mud or acidic water. The wide shallow seas of the
Carboniferous period provided such conditions. This trapped atmospheric carbon in the
ground in immense peat bogs that eventually were covered over and deeply buried by
sediments under which they metamorphosed into coal. Over time, the chemical
and physical properties of the plant remains (believed to mainly have been fern-like
species antedating more modern plant and tree species) were changed by geological
action to create a solid material.
Petroleum
Petroleum {L. petroleum, from Greek: petra (rock)+ Latin: oleum (oil)} or crude
oil is a naturally occurring, flammable liquid consisting of a complex mixture
of hydrocarbons of various molecular weights and other liquid organic compounds, that
are found in geologic formations beneath the Earth's surface. Petroleum is recovered
mostly through oil drilling. It is refined and separated, most easily by boiling point, into a
large number of consumer products, from gasoline and kerosene to asphalt and chemical
reagents used to make plastics and pharmaceuticals.
The term petroleum was first used in the treatise De Natura Fossilium, published
in 1546 by the German mineralogist Georg Bauer, also known as Georgius Agricola. In
the 19th Century, the term petroleum was frequently used to refer to mineral oils
produced by distillation from mined organic solids such as cannel coal (and later oil
shale) and refined oils produced from them; in the United Kingdom storage (and later
transport) of these oils were regulated by a series of Petroleum Acts, from the Petroleum
Act 1862 c. 66 onward.
Natural gas
Natural gas is a gas consisting primarily of methane, typically with 0-20% higher
hydrocarbons (primarily ethane). It is found associated with other fossil fuels, in coal
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beds, as methane clathrates, and is an important fuel source and a major feedstock for
fertilizers.
Most natural gas is created by two mechanisms: biogenic and thermogenic.
Biogenic gas is created by methanogenic organisms in marshes, bogs, landfills, and
shallow sediments. Deeper in the earth, at greater temperature and pressure, thermogenic
gas is created from buried organic material.
Before natural gas can be used as a fuel, it must undergo processing to remove
almost all materials other than methane. The by-products of that processing include
ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons,
elemental sulfur, carbon dioxide, water vapour and sometimes helium and nitrogen.
Indian Scenario
India is one of the countries where the present level of energy consumption, by
world standards, is very low. The estimate of annual energy consumption in India is about
330 Million Tones Oil Equivalent (MTOE) for the year 2004. Accordingly, the per capita
consumption of energy is about 305 Kilogram Oil Equivalent (KGOE). As compared to
this, the energy consumption in some of the other countries is of the order of over 4050
for Japan, over 4275 for South Korea, about 1200 for China, about 7850 for USA, about
4670 for OECD countries and the world average is about 1690.
In so far as electricity consumption is concerned, India has reached a level of
about 600-kilowatt hour (kwh) per head per year. The comparable figures for Japan are
about 7,800, for South Korea about 7,000, for China about 1380, for USA about 13,000,
for OECD countries about 8050 and world average are about 2430. Thus, both in terms of
per capita energy consumption and in terms of per capita electricity consumption, India is
far behind many countries, and as a matter of fact, behind even the world average.
Therefore, to improve the standards of living of Indian people and to let them enjoy the
benefit of economic development, it is imperative that both energy consumption and
electricity consumption level is enhanced. India is targeting a growth rate of 9 – 10%,
having already reached a level of almost 8%. To sustain the double-digit growth rate for
next 10-15 years, it would be essential that the level of energy availability and
consumption, and electricity consumption in particular, is enhanced substantially.
In the profile of energy sources in India, coal has a dominant position. Coal
constitutes about 51% of India‘s primary energy resources followed by Oil (36%),
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Natural Gas (9%), Nuclear (2%) and Hydro (2%). To address the issue concerning energy
consumption, and more particularly, the need for enhancing the energy supply, India has
accorded appropriate priority to both - supply side management and demand side
management.
Non Conventional Energy Sources
Indian Government has accorded very high priority to develop and expand
installed capacity base through non-conventional sources of electricity generation. There
is a separate Ministry in the Government of India to exclusively focus on this important
area of power generation. National Electricity Policy notified in 2005 in pursuance of the
Electricity Act, 2003, prescribes that State Electricity Regulatory Commissions should
prescribe a proportion of power which should be produced and supplied to the grid
through the non-conventional sources. Some of the Regulatory Commissions have come
out with specific policy guidelines with a different approach on tariff for these plants in
order to encourage these technologies and plants. National Electricity Tariff Policy
mandates that State Commissions should fix such minimum percentage latest by April,
2006. India has very high potential for these capacities:
It may be seen from the above that India has achieved substantial success on wind turbine
based power generation. Ministry of Non-conventional Energy Sources (MNES) has set a
target of achieving at least 10,000 MW capacity through various non-conventional
sources, by the year 2012.
Conventional Sources of Electricity Generation
Fossil fuel based thermal power, hydro-electric, and nuclear constitute the
conventional sources of power. Non-conventional sources are less than 5% of total
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installed capacity in India. The present installed capacity (as in March 2006) is about
1,25,000 MW, consisting of coal based plants (56%), gas based plants (10%), hydro-
electric (26%), nuclear (3%) non-conventional (5%).
Indian Power Sector was opened up for private power generation in 1991. In
terms of ownership structure, the profile consists of Central Government owned
companies (32%), State Government owned companies/Electricity Boards (57%) and
Private Sector (11%). 100% FDI is permitted in all segments of electricity industry – viz.
Generation, Transmission, Distribution, Trading.
In the last three years far-reaching structural changes have been introduced in the
Indian Electricity Sector. Electricity Act 2003 is an historic legislative initiative with
powerful potential to transform the power sector industry and market structure.
Most important features of the Electricity Act 2003 are as follows:
1. The Act creates a liberal and transparent framework for power development
2. It facilitates investment by creating competitive environment and reforming
distribution segment of power industry.
3. Entry Barriers have been removed/reduced in following areas:
• Delicensed generation.
• Freedom to captive generation including group captive
• Recognizing trading as an independent activity
• Open access in transmission facilitating multi buyer and seller model.
4. Open access to consumers above 1 MW within five years commencing from 27th
January, 2004 (date of enforcement of amendment to Electricity Act) Regulators
have been mandated to ensure this.
5. Multiple licenses in distribution in the same area of supply so that competition
could yield better services to consumers.
6. Regulatory Commissions – to develop market and to fix tariff.
National Grid
The energy potential in the country is concentrated in certain pockets. Coal
reserves are located in a few states and similarly huge hydro-electric potential is located
in a few states. This poses a challenge to embark upon massive inter-regional
transmission capacity.
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Augmentation of National Grid
1. Intra-regional expansion of transmission capacity is linked to generation projects.
2. Inter-regional connectivity has been planned with hybrid systems, consisting of
HVDC, Ultra High Voltage AC (765 KV) & Extra High Voltage AC (400 KV)
lines.
3. Present Inter-regional transfer capacity is 9,500 MW, being enhanced to 17,000
MW by 2007.
4. 37,000 MW by 2012.
Table 1.1 : Projected Capacity Addition for 2007-12 (XI Plan)
May be revised to 67,000 MW, depending on the availability of Gas/LNG in
required quantities and right prices.
1. In addition, 5000 MW through Non-conventional Energy Sources.
2. Captive capacity not included.
Clean Development Mechanism
1. India is emerging as one of the largest potential source of Carbon Emission
Reduction (CER)
2. Designated National Authority is fully functional
3. Focus areas in Energy Sector:
R&M of old plants
Conversion of LT to HT lines
Supercritical Thermal Power Projects
Hydro projects
Distribution Sector Reform
The Government of India‘s Accelerated Power Development and Reform
Programme (APDRP) being implemented through the X Plan (2002-07) aims at
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comprehensive reform of electricity distribution in urban/industrial centres. Revamping,
augmenting and modernizing the distribution network and system for improved reliability
of power supply, reducing technical and commercial losses, and improving financial
health of distribution utilities are the main objectives of the scheme.
Utility and Waste management of thermal and Hydraulic energy
Thermal power plant is very much suitable for base load. They use coal,
petroleum and natural gas to produce the electricity. These sources are of mineral origin
and also called fossil fuels. They are exhaustible and polluting. Electricity, is the most
convenient and versatile form of energy. This is great demand in industry, agriculture,
transport and domestic sectors. Both big and small thermal power stations are scattered all
over the country. Electricity produced by them is fed into regional grids. It is proposed to
have a single national. The grids receive electricity produced from all the four major
sources - coal, oil, water and nuclear.
Hydro – Power
Fig. 1.1 (A) : Hydro Electric Power Station
Water-energy is most conventional renewable energy source and obtained from
water flow, water falling from a height. Hilly and highland areas are suitable for this
purpose, where there is continuous flow of water in large amounts falling from high
slopes.
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Fig. 1.1 (B) : Hydro Electric Power Station
It is clean, non-polluting source of energy. It can be transmitted to long distance
though wires and cables. Hydro-electric power generation is expected to upset the
ecological balance existing on earth. Hydro projects are responsible for catchments
degradation and soil erosion.
Solar Energy
Energy produced and radiate by sun is known as solar energy. This solar energy can be
converted directly or indirectly into other forms of energy such as heat and electricity.
Fig. 1.2 : Solar Pond Electric Power Plant
India receives 5000 Trillion KW/hr of sun shine in an year. India receives
abundant sunshine with about 1648-2108 KWhr/m2/yr with nearly 250-300 days of useful
sunshine in a year. The daily solar energy incidence is between 4 to 7 KWhr/m2.
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Energy radiated by the sun as electromagnetic waves (Wavelength 0.2 to 0.4 um).
Due to absorption and scattering in the atmosphere the maximum flux density is 1
KW/sq.m. 45% energy in the form of visible rays and 44% as infra-red radiation.
The enormous solar energy resource may be converted into other forms of energy
through thermal photovoltaic conversion routes. The solar thermal route uses radiation in
the form of heat in turn may be converted to mechanical electrical or chemical energy.
Application of solar energy
a) Solar Water heating.
b) Solar Heating of Building.
c) Solar – Distillation
d) Solar Furnaces
e) Solar Cooking
f) Solar Electric Power Generation (Photovoltaic System)
g) Solar Thermal Power Production.
h) Production of Power through Solar Ponds.
i) Solar Green Houses.
Environmental Implications
1. The sites to be selected as such that it should not reduce the forest cover.
2. Cadmium used in fabricating thin film solar cells, is both poisonous and a possible
carcinogen since only small quantities of cadmium are released from discarded
PV panels, the danger involved are not so serious.
3. Carbon dioxide produced while forming silicon from silica may increase the
atmospheric temperature causing green house effect.
4. Silicon dust is also an important occupational hazard.
Wind – Energy
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Fig. 1.3 (A) : Wind Power Direct Feed to Main Power line
Wind result from air in motion due to pressure gradient. Wind is basically caused
by the solar energy irradiating the earth. This is why wind utilization is considered a part
of solar technology.
Fig. 1.3 (B) : Wind Power Direct Feed to Main Power line
Energy of wind can be economically used for the generation of electrical energy.
Winds are caused from two main factors:
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1) Heating and cooling of the atmosphere which generates convection currents.
Heating is caused by the absorption of solar energy on the earth‘s surface and in
the atmosphere.
2) The rotation of the earth with respect to atmosphere and its motion around the
sun. Wind mill consists of wind turbine head, transmission and another supporting
structure. Wind energy conversion devices like wind turbines are used for
converting wind energy into mechanical energy.
Wind turbine consists basically of a few sails, vans and blades radiating from a
central axis when wind blows against the blades or vans they rotate about the axis. The
rotational motion is utilized to perform some useful work. By connecting the wind turbine
to an electric generator wind energy can be converted into electric energy.
Wind densities upto 10 KW/m3/day are available. More than 20,000 MW
electricity can be generated in India from wind.
Three factors which determine the output from a wind energy converter:
1. The wind speed.
2. The Cross-section of wind swept by rotor.
3. Conversion efficiency of the rotor transmission system and generator or pump.
A. Horizontal axis
B. Vertical axis
Biomass Based Energy
A) Petro-plants: There are attempts to identify potential plant species as sources of
liquid hydrocarbons, a substitute for liquid fuels. The hydrocarbons present in
such plants can be converted into petroleum hydrocarbons. The plants belong to
Euphorbiaceae, Apocynaceae, Sapotaceae and over 385 species have been
screened for hydrocarbon content. The Indian Institute of Petroleum, Dehradun
has done excellent work in this area, particularly on hydro-cracking of the crude
products. The products obtained from their latex processed biocrude were gases
naphtha, kerosene, gas oil, coke.
(B) Biomass Energy: A green plant converted into organic matter is biomass.
Biomass fermented is aerobically to produce biogases.
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Biogas is mixture of methane (CH4) (70%) and Carbon dioxide (CO2), Hydrogen
(H2), Nitrogen (N2). This is an environmentally clean technology.
At 40% methane content calorific value is 3214 Kcal/m3, at 50% is 4429 Kcal/m
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and at 55% is 4713 Kcal/m3. In biogas technology, the important factors are dung
excrement and availability, gas yield, calorific value and appliance efficiency.
In order to make best use of biogas technology, two things are relevant; restricted
use of water and better strains of methane generating bacteria. For normal microbial
activity 90% water content is needed, whereas in bovine-manure and human waste this
value is 80%.
Thus, we need additional water which may be critical to this technology in drier
areas of the country. There is need to be developed a dry process, that requires less of
water. Also there is need for methanogens, able to operate at temperatures lower than
20ºC, land area is also a factor. Biogas can also be generated from sludge obtained from
primary treatment of raw sewage and one such plant is in operation at Okhla, Delhi.
Besides gas, the rest matter from sewage is good manure. If biogas is used in boilers it
will reduce the air pollution.
Hydrogen Energy
An ecologically-friendly fuel which uses electrochemical cells or combusts in
internal engines to power vehicles and electric devices. It is also used in the propulsion of
spacecraft and can potentially be mass produced and commercialized for passenger
vehicles and aircraft.
In a flame of pure hydrogen gas, burning in air, the hydrogen (H2) reacts with
oxygen (O2) to form water (H2O) and heat. It does not produce other chemical by-
products, except for a small amount of nitrogen oxides. Hence a key feature of hydrogen
as a fuel is that it is relatively non-polluting (since water is not a pollutant). Pure
hydrogen does not occur naturally; it takes energy to manufacture it. Once manufactured
it is an energy carrier (i.e. a store for energy first generated by other means). The energy
is eventually delivered as heat when the hydrogen is burned. The heat in a hydrogen
flame is a radiant emission from the newly formed water molecules. The water molecules
are in an excited state on initial formation and then transition to a ground state, the
transition unleashing thermal radiation. When burning in air, the temperature is roughly
2000°C. Hydrogen fuel can provide motive power for cars, boats and aeroplanes, portable
fuel cell applications or stationary fuel cell applications, which can power an electric
motor.
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Fig. 1.4 : Hydrogen Energy
The current leading technology for producing hydrogen in large quantities is
steam reforming of methane gas (CH4). In addition, obtaining hydrogen from electrolysis
using renewable resources is being studied as a viable way to produce it domestically at a
low cost. This process involves the use of wind—or solar—generated electricity to power
an electrolyzer which would split water into hydrogen and oxygen. Other methods are
discussed in the Hydrogen Production article. Primarily because hydrogen fuel can be
environmentally friendly, there are advocates for its more widespread use. At present,
however, there is not a sufficient technical and economic infrastructure to support
widespread use. The proposed creation of such an infrastructure is referred to as the
hydrogen economy.
At the gas pressure at which hydrogen is typically stored, hydrogen requires four
times more storage volume than the volume of gasoline that produces the equivalent
energy, but the weight of this hydrogen is nearly one third that of the gasoline. With
regard to safety from unwanted explosions, hydrogen fuel in automotive vehicles is at
least as safe as gasoline. The advantages and disadvantages of hydrogen fuel compared to
its competitors are discussed at hydrogen economy.
Geothermal Energy
Geothermal energy is the heat energy deep within the earth. Huge amount of
(energy) heat are stored in the lower layer of the earth‘s crust. A temperature of 200ºC –
300ºC normally occur only at the depth of 10 km.
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US geological survey defines geothermal sources as ―all heat stored in the earth‘s
crust above 15ºC to a depth of 10 km.‖
Fig. 1.5 : Geothermal Reservoir
Sources:
1. Hydrothermal convenient systems
a) Vapour dominated or dry steam fields.
b) Liquid dominated system or wet steam field.
c) Hot water fields.
2. Geo-pressure resources.
3. Petro-thermal resources.
4. Magma resources.
5. Volcanoes.
Advantages of Geothermal Energy:
1. This energy is least polluting in comparison of other energy resources.
2. It is renewable source of energy.
3. It is cheaper source of energy.
Disadvantages:
1. Overall efficiency of power production is low.
2. Drilling operation is noisy.
3. Large areas are needed for exploitation of geothermal energy.
4. The steam and hot water coming out of earth may contain H2S, CO2, NH3, radon
etc. If these gases are vented into the air, may cause air pollution.
Hot molten rock called magma is present 25-40 km. depth in the core of the earth.
When the ground water finds its way into such a rock having molten in lava then it gets
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heated up by the heat of the rock and molten magma and comes to the surface of the earth
as steam and hot water 200ºC to 300ºC. This hot water or Steam is used to operate
turbines to generate electricity. A cold storage unit and 5 MW Power plant have been set
up a Manikaran (H.P.). At present nearly 350 geothermal springs have been located in the
country.
The International Geothermal Association (IGA) has reported that 10,715 MW of
geothermal power in 24 countries is online, which is expected to generate 67,246 GW of
electricity in 2010. This represents a 20% increase in online capacity since 2005.
Tidal Energy
The term tide is used for the periodic rise and fall of water of ocean and produced
by the attraction of moon and the sun. The tidal wave result by the gravitational pull on
ocean water by the moon and sun on ocean water and are effected by:
1. Spinning of earth around its axis.
2. Relative position of the earth, moon and sun.
About 70% of the tide producing force is due to the moon and 30% due to sun.
Thus the moon is the major factor in tide force.
Small tidal power plants have been constructed in China and North Asia. The
more important application of tidal power is an electricity generation.
Principle: The large scale up and down movement of sea water represents on unlimited
source of energy.
Advantage:
1. It is pollution free in nature.
2. These power plants do not demand large area of valuable land.
3. Peak power demand can be effectively met when it works in combination with
thermal or hydroelectric system.
Disadvantage:
1. This energy is variable in nature.
2. Sea water is corrosive and it was feared that the machinery may get corroded.
3. Construction in sea is difficult.
4. Cost is not favourable compared to other source of energy.
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A lot of energy is inherent in the twice a day rise and falls of the tides. Tidal
power is eternal and pollution free.
Fig. 1.6 : Tidal Power Generation
The incoming tide following through the turbines generated power. As the tide
shifts the blade may be reversed so that out flowing water continuously generates power.
A fluctuation of at least 6 meters in needed between the high tide and low tide.
Wave Energy:
Waves are formed by the wind action over the sea water surface, the incessant
motion of the sea surface in the form of wind waves. About 1.5% of the incoming
energy from sun is converted into wind energy. Part of this is transferred to sea surface
resulting in the generation of wave‘s breach.
Wave energy is concentrated through the interaction of the wind and the free
ocean surface.
A multipurpose wave regulator system in the form of a long barrier results in the
formation of a calm pool between the barrier and shore and this can be used as harbor.
Space of aquaculture space for coastal transport with light and faster crafts shore
protection against the erosion by sea. It is pollution free.
Nuclear Power Energy
This is of course a main source of energy. When the fossil fuel reserves are
depleting very fast. A small quantity of radioactive material can produce an enormous
amount of energy. For instance, one ton of Uranium235
would provide as much energy as
by 3 million tons of coal or 12 million barrels of oil. Besides electricity, atomic power is
also used as fuel for marine vessels, heat generation for generation for chemical and food
processing plants and for spacecrafts.
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For atomic energy, we need a nuclear reactor. The decay of fusion-able matter
produces enormous heat. This is used to make steam and channel through a turbine
connected to an electric generator. There are different types of nuclear reactor.
a) Light Water Reactor: Here we use ordinary water for cooling and moderation.
These are of two basic types (i) Boiling water reactor (ii) Pressurized Water
Reactor.
There are also high temperature gas cooled reactors (HIGCR) which are basically
of LWR types.
Fig. 1.7 : Nuclear Reactor Power Generator
b) Heavy Water Reactor: Here we use heavy water. The most popular one has been
Canadian Deuterium – Uranium (CANDU) reactor. Here the design is different
from that of LWR type. The fuel is arranged horizontally rather than vertically as
in LWR.
c) Liquid Metal Fast Breeder Reactor (LMFBR): Here we use liquid sodium as
coolant. Radioactive Pollutants released from nuclear power plants are chronically
hazardous. The dangerous radio waste cannot be buried in land without the risk of
polluting soil and underground water. Now the waste can be dumped into the river
without polluting aquatic life and human beings as well.
Electromagnetic Energy:
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It consists of visible light, Radio waves, heat, ultraviolet rays, X-rays.
Velocity of light C = ν λ
When λ = wave length
ν = number of peaks parting a fixed point in space
Unit time = wave frequency
Microwave 1 mm to 1 m. wave length, Radio wave length
1. Non-ionizing radiation, Microwave shorter than 10 cm are absorbed by the skin
that can be felt by heating of the surface.
2. 10 to 30 cm. can penetrate the epidermis and felt layer of the skin.
3. Longer than 30 cm. can penetrate deep tissues of dermis causing the skin hot.
Microwave Reflectors Disk, like reflections used to guide microwave beam.
Microwave oven, the cooking is done without converting heat by short electromagnetic
waves known as microwaves. That pan virtually under finished through many materials
such as glass, plastic papers and chin. When microwave comes in contact with food they
are absorbed their energy is converted into heat and they cook or heat the food from the
inside out.
Infrared energy waves have shorter wave length than microwaves. Recently the
hazardous level for microwave power density in United States installations, has been set
at 0.01 W/cm2 with a special limit of 0.01 W/cm
2 for eye exposure, around 10 cm
wavelength.
4. Russians have set lower exposure limits claiming that microwaves result in skin-
burns, fatigue, dizziness, headache, eye-injuries and cataracts, below heat injury
levels in man.
Radar Hazards
The radar hazards particularly in high-power installation, come mainly from the
acute heating effects these effects cause headache, fatigue, nervousness, and skin
diseases. In small power installations, radar hazards result in other severe diseases such as
disrupting artificial pacemakers for the heart (40,000 to 30,000,000 vibration / sec.)
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Effects of Radio Frequency Radiations
Recently an investigative agency of US congress reported that the current levels of
micro-wave and radio-frequency radiations in air pose severe hazards to human health.
Non-ionizing radiations of longer wave length cause a common thermal effect. These
radiations induce thermal agitation in molecules of the matter to produce heat.
A variety of non-thermal effects are potentially more dangerous as they pose acute
physiological effects. Non-thermal effects may be linked to the electric and magnetic
fields associated with the electromagnetic radiation. *
*[That the change in environmental magnetic field causes physiological effects is
corroborated by the discovery of I.O. Hays and N.O. Opdyke of the Lamont – Doherty
Geological Observatory, U.S.A. Who observed that reversal in the direction of magnetic
field of earth kills a large number of sea-animals.]
Waste Management of Different Power Plants
1. Thermal Plant: For every 1 MW of installed capacity about one acre of land is
needed for the disposal of ash generated. The material accumulating to a height of
8-10 meters converts fly ash into brick, cement. 85-90% of ash collecting in the
nearby ash pond. 10% is lost as fallout from the chimney.
2. Hydro Power Plant:
1. Big dam is dangerous to environments.
2. Catchments degradation.
3. Soil Erosion.
4. Deforestation.
3. Nuclear Power Plants: Radioactive waste generated by Nuclear Power Plants.
Low level radioactive liquid wastes
Radio active wastes in solution coming from power plants contaminate with
aquatic life. These radioactive elements are eventually conveyed to man from water
suppliers to food chain through soil, vegetation and live stock. Gaseous and particulate
radioactive waste. Radio – isotopes H3 – C14 , Kr85, I129. When these radio isotopes are
inhaled by man, they get concentrated in specific organs posing health effects. Fission
Fragments Radio nuclides Sr-90, I-131, Cs-137, Co-58. Induced radio nuclides P-32, Fe-
59, Zn-65 are released into the river, detaches, waste holding ponds, aquatic environment.
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Sr-90 concentrates in the aquatic food web. Become distributed to an altitude of about 10
km in the atmosphere and in the ocean to a depth of 13 km emanating radiation in the
environment. Heat relative Uranium produces enormous heat causing thermal pollution
and water bodies.
ECOSYSTEM
The Segments of Environment
Today the atmosphere is 78% nitrogen, 21% oxygen, and 0.93% argon. The
remaining 0.07% is made up of water vapor, carbon dioxide, ozone (a form of oxygen in
which three oxygen atoms bond chemically) and noble gases. The noble gases, including
argon and neon are noted for their lack of reactivity, meaning that they are extremely
resistant to chemical bonding with other elements.
Nitrogen also tends to be unreactive and the reason for its abundance in the
atmosphere lies in the fact that it never attempted to bond with other elements. Therefore,
nitrogen along with the noble gases, is simply "hanging in the air" (literally), left over
from the time when volcanoes hurled it into the atmosphere several billion years ago. By
contrast, oxygen (both in O2 and O3 or ozone molecules) and the other elements in air are
vital to life. Furthermore, oxygen is one of two elements, along with hydrogen, that goes
into the formation of water.
Overlap Between Subsystems
The present atmosphere would not exist without the biosphere. In order to put
oxygen into the air, there had to be plants, which take in carbon dioxide and release
oxygen in the process of photosynthesis. This resulted from an exceedingly complex
series of evolutionary developments from anaerobic or non-oxygen-breathing single-cell
life-forms to the appearance of algae. As plant life evolved, eventually it put more and
more oxygen into the atmosphere, until the air became breathable for animal life. Thus,
the atmosphere and biosphere have sustained one another.
Such overlap is typical and indeed inevitable where the open earth subsystems are
concerned and examples of this overlap are everywhere. For instance, plants (biosphere)
grow in the ground (geosphere), but to survive they absorb water (hydrosphere) and
carbon dioxide (atmosphere), nor are plants merely absorbing they also give back oxygen
22
to the atmosphere, and by providing nutrition to animals, they contribute to the biosphere.
At the same time, the many components of the picture just described are involved in
complex biogeochemical cycles, which we look at later.
Water and the Hydrologic Cycle
As any backyard horticulturist knows, plants need good soil and water. In the
course of circulating throughout Earth, water makes its way through organisms in the
biosphere as well as reservoirs housed within the geosphere. It also circulates
continuously between the hydrosphere and the atmosphere. This movement known as the
hydrologic cycle, is driven by the twin processes of evaporation and transpiration.
The first of these processes, of course, is the means whereby liquid water is
converted into a gaseous state and transported to the atmosphere, while the second
process by which plants lose water through their stomata, small openings on the
undersides of leaves. Scientists usually speak of the two as a single phenomenon,
evapotranspiration. The atmosphere is just one of several "compartments" in which water
is stored within the larger environment. In fact, the atmosphere is the only major reservoir
of water on Earth that is not considered part of the hydrosphere.
Accounting for Earth's Water Supply
The water that most of us see or experience is only a very small portion of the
total. Actually, that statement should be qualified the oceans, parts of which most people
have seen, make up about 5.2% of Earth's total water supply. This may not sound like a
large portion, but in fact, the oceans are the second-largest water compartment on Earth.
If the oceans are such a small portion yet rank second in abundance, two things are true
there must be a lot of water on Earth, and most of it must be in one place.
In fact, the vast majority of water on Earth is stored in aquifers or underground
rock formations that hold 94.7% of the planet's water. Thus, deep groundwater and oceans
account for 99.9% of the total. Glaciers and other forms of permanent and semipermanent
ice take third place, with 0.065%. Another 0.03% appears in the form of shallow
groundwater, the source of most local water supplies. Next are the inland surface waters,
including such vast deposits as the Great Lakes and the Caspian Sea as well as the
Mississippi-Missouri, Amazon, and Nile river systems and many more, which
collectively make up just 0.003% of Earth's water.
23
Atmospheric Moisture and Weather
That leaves only 0.002% which is the proportion taken up by moisture in the
atmosphere: clouds, mist and fog, as well as rain, sleet, snow, and hail. While it may seem
astounding that atmospheric moisture is such a small portion of the total, this fact says
more about the vast amounts of water on Earth than it does about the small amount in the
atmosphere. That "small" amount, after all, weighs 1.433 × 1013
tons (1.3 × 1013
tonnes)
or 28,659,540,000,000,000 pounds (12,999,967,344,000,002 kg).
This moisture in the atmosphere is the source of all weather, which clearly has an
effect on Earth's life-forms. (Weather is the condition of the atmosphere at a given time
and in a given place, whereas climate is the pattern of weather in a particular area over an
extended period of time.) On the one hand, rain is necessary to provide water to plants
and desert conditions can sustain only very specific life-forms; on the other hand,
storms, icy precipitation, and flooding can be deadly.
Our biosphere is the global sum of all ecosystems. It can also be called the zone
of life on Earth, a closed (apart from solar and cosmic radiation) and self-regulating
system. From the broadest biophysiological point of view, the biosphere is the
global ecological system integrating all living beings and their relationships, including
their interaction with the elements of the lithosphere, hydrosphere and atmosphere. The
biosphere is postulated to have evolved, beginning through a process
of biogenesis or biopoesis, at least some 3.5 billion years ago.
Atmosphere
Sources and sinks of most gaseous components are situated at the land or sea
surface, often by mediation of the biosphere and biological activity. This is true for the
case of carbon dioxide, oxygen and water, as well as for most anthropogenic gases and
greenhouse gases such as methane (CH4). However, water stands out as the only one
whose phase transition occurs in the temperature range of the (lower) atmosphere itself,
resulting in a sink by condensation within the air column and a residence time which is
short relative to the mixing and transport rates within the atmosphere.
The vertical distribution of mass in the atmosphere is basically controlled by
gravity and described by pz = po
exp (-z/H) where po
and pz are the pressures at
groundlevel and at altitude z, respectively; H is the scale height, about 8.4 km in the
24
lower troposphere. The vertical temperature distribution shown in Fig. 2.1 controls the
vertical motions and also the partitioning of the atmosphere into discrete spheres.
In the lower atmosphere, the troposphere, a noticeable convection driven by the
heating of the Earth's surface by absorption of solar radiation results in mixing of the air
column. The thermally driven convection is dampened at a height of about 8 to 15 km,
where the temperature lapse rate is reduced, a region called the tropopause. At a height of
about 15 to 25 km, the atmosphere is further heated by absorption of UV radiation. The
resulting rise in temperature with height imparts stability to this part of the atmosphere,
the stratosphere, against vertical motions.
Fig. 2.1 : Structure of Atmosphere
The vertical distribution of the water vapour content in the atmosphere is also
primarily controlled by temperature. However, since both sources and sinks of water
reside in the troposphere and its lower boundary, and as the residence time of water is
short compared to the air mixing rates, there is a large variability in the amount of water
in the lower atmosphere in both space and time.
Horizontal motion in the atmosphere results primarily from the revolution of the
earth and proceeds along bands of latitude. However it is modified by the differential
pressure fields which respond to the unequal heating of the surface and the resultant
convective motions.
25
Characteristic residence times in the atmosphere are given. These are turbulent
systems where molecular diffusion is not the dominant process, except in the upper
atmosphere, the exosphere, where the atmosphere is rarefied and at the lower boundary
near the ground surface where the turbulent motion is suppressed. This has far reaching
consequences regarding the source term of the gases above the sea.
Lithosphere
The word lithosphere is derived from the word sphere, combined with the Greek
word lithos, meaning rock. The lithosphere is the solid outer section of Earth, which
includes Earth's crust (the "skin" of rock on the outer layer of planet Earth), as well as the
underlying cool, dense, and rigid upper part of the upper mantle. The lithosphere extends
from the surface of Earth to a depth of about 44–62 mi (70–100 km). This relatively cool
and rigid section of Earth is believed to "float" on top of the warmer, non-rigid, and
partially melted material directly below.
Fig. 2.2 : Composition of Lithosphere
Earth is made up of several layers. The outermost layer is called Earth's crust. The
thickness of the crust varies. Under the oceans, the crust is only about 3–5 mi (5–10 km)
thick. Under the continents, however, the crust thickens to about 22 mi (35 km) and
reaches depths of up to 37 mi (60 km) under some mountain ranges. Beneath the crust is a
layer of rock material that is also solid, rigid and relatively cool, but is assumed to be
made up of denser material. This layer is called the upper part of the upper mantle, and
varies in depth from about 31–62 mi (50–100 km) below Earth's surface. The
26
combination of the crust and this upper part of the upper mantle, which are both
comprised of relatively cool and rigid rock material is called the lithosphere.
Below the lithosphere, the temperature is believed to reach 1,832°F (1,000°C),
which is warm enough to allow rock material to flow if pressurized. Seismic evidence
suggests that there is also some molten material at this depth (perhaps about 10%). This
zone which lies directly below the lithosphere is called the asthenosphere, from the Greek
word asthenes, meaning weak. The lithosphere, including both the solid portion of the
upper mantle and Earth's crust, is carried "piggyback" on top of the weaker, less rigid
asthenosphere, which seems to be in continual motion. This motion creates stress in the
rigid rock layers above it, forcing the slabs or plates of the lithosphere to jostle against
each other, much like ice cubes floating in a bowl of swirling water. This motion of the
lithospheric plates is known as plate tectonics, and is responsible for many of the
movements seen on Earth's surface today including earthquakes, certain types of volcanic
activity, and continental drift.
Hydrosphere
A hydrosphere in physical geography describes the combined mass
of water found on, under, and over the surface of a planet.
The total mass of the Earth's hydrosphere is about 1.4 × 1018
tonnes, which is
about 0.023% of the Earth's total mass. About 20 × 1012
tonnes of this is in the Earth's
atmosphere (the volume of one tonne of water is approximately 1 cubic metre).
Approximately 75% of the Earth's surface, an area of some 361 million square kilometres
(139.5 million square miles), is covered by ocean. The average salinity of the Earth's
oceans is about 35 grams of salt per kilogram of sea water (3.5%)
27
Fig. 2.3 : Hydrosphere
A thick hydrosphere is thought to exist around the Jovian moon Europa. The outer
layer of this hydrosphere is almost entirely ice, but current models predict that there is an
ocean up to 100 km in depth underneath the ice. This ocean remains in a liquid form
because of tidal flexing of the moon in its orbit around Jupiter. The volume of Europa's
hydrosphere is 3 × 1018
m3, 2.3 times that of Earth.
It has been suggested that the Jovian moon Ganymede and the Saturnine
moon Enceladus may also possess sub-surface oceans. The ice covering is expected to be
thicker on Jupiter's Ganymede than on Europa.
Hydrological cycle
Insulation, or energy (in the form of heat and light) from the sun, provides the
energy necessary to cause evaporation from all wet surfaces including oceans, rivers,
lakes, soil and the leaves of plants. Water vapor is further released as transpiration from
vegetation and from humans and other animals.
Aquifer draw-down or over-drafting and the pumping of fossil water increases the
total amount of water in the hydrosphere that is subject to
transpiration and evaporation thereby causing accretion in water vapour and cloud
cover which are the primary absorbers of infrared radiation in the Earth's atmosphere.
Adding water to the system has a forcing effect on the whole earth system, an accurate
estimate of which hydro-geological fact is yet to be quantified.
ECO-SYSTEM
An ecosystem consists of the biological community that occurs in some locale and
the physical and chemical factors that make up its non-living or abiotic environment.
28
There are many examples of ecosystems -- a pond, a forest, an estuary, a grassland. The
boundaries are not fixed in any objective way, although sometimes they seem obvious, as
with the shoreline of a small pond. Usually the boundaries of an ecosystem are chosen for
practical reasons having to do with the goals of the particular study.
The study of ecosystems mainly consists of the study of certain processes that link
the living, or biotic, components to the non-living, or abiotic, components. Energy
transformations and biogeochemical cycling are the main processes that comprise the
field of ecosystem ecology. As we learned earlier, ecology generally is defined as the
interactions of organisms with one another and with the environment in which they occur.
We can study ecology at the level of the individual, the population, the community, and
the ecosystem.
Studies of individuals are concerned mostly about physiology, reproduction,
development or behavior, and studies of populations usually focus on the habitat and
resource needs of individual species, their group behaviors, population growth and what
limits their abundance or causes extinction. Studies of communities examine how
populations of many species interact with one another, such as predators and their prey, or
competitors that share common needs or resources.
Components of an Ecosystem
You are already familiar with the parts of an ecosystem. You have learned about
climate and soils from past lectures. From this course and from general knowledge, you
have a basic understanding of the diversity of plants and animals, and how plants and
animals and microbes obtain water, nutrients, and food. We can clarify the parts of an
ecosystem by listing them under the headings "abiotic" and "biotic".
ABIOTIC COMPONENTS BIOTIC COMPONENTS
Sunlight Primary producers
Temperature Herbivores
Precipitation Carnivores
Water or moisture Omnivores
Soil or water chemistry (e.g., P, NH4+) etc. Detritivores etc.
All of these vary over space/time
29
By and large, this set of environmental factors is important almost everywhere, in
all ecosystems.
Usually, biological communities include the "functional groupings" shown above.
A functional group is a biological category composed of organisms that perform mostly
the same kind of function in the system; for example, all the photosynthetic plants or
primary producers form a functional group. Membership in the functional group does not
depend very much on who the actual players (species) happen to be, only on what
function they perform in the ecosystem.
Processes of Ecosystems
This figure with the plants, zebra, lion, and so forth illustrates the two main ideas
about how ecosystems function: ecosystems have energy flows and ecosystems cycle
materials. These two processes are linked, but they are not quite the same (see Figure 2.5)
Fig. 2.4 : Energy flows and material cycles.
Energy enters the biological system as light energy, or photons, is transformed
into chemical energy in organic molecules by cellular processes including photosynthesis
and respiration, and ultimately is converted to heat energy. This energy is dissipated,
meaning it is lost to the system as heat; once it is lost it cannot be recycled. Without the
continued input of solar energy, biological systems would quickly shut down. Thus the
earth is an open system with respect to energy.
During decomposition these materials are not destroyed or lost, so the earth is a
closed system with respect to elements (with the exception of a meteorite entering the
system now and then). The elements are cycled endlessly between their biotic and abiotic
states within ecosystems. Those elements whose supply tends to limit biological activity
are called nutrients.
The Transformation of Energy
30
The transformations of energy in an ecosystem begin first with the input of energy
from the sun. Energy from the sun is captured by the process of photosynthesis. Carbon
dioxide is combined with hydrogen (derived from the splitting of water molecules) to
produce carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine
triphosphate, or ATP.
The prophet Isaah said "all flesh is grass", earning him the title of first ecologist,
because virtually all energy available to organisms originates in plants. Because it is the
first step in the production of energy for living things, it is called primary production.
Herbivores obtain their energy by consuming plants or plant products, carnivores eat
herbivores, and detritivores consume the droppings and carcasses of us all.
Fig. 2.5 : Food Chain
A simple food chain, in which energy from the sun, captured by plant
photosynthesis, flows from trophic level to trophic level via the food chain. A trophic
level is composed of organisms that make a living in the same way, that is they are all
primary producers (plants), primary consumers (herbivores) or secondary consumers
(carnivores). Dead tissue and waste products are produced at all levels. Scavengers,
detritivores, and decomposers collectively account for the use of all such "waste" --
consumers of carcasses and fallen leaves may be other animals, such as crows and
beetles, but ultimately it is the microbes that finish the job of decomposition. Not
surprisingly, the amount of primary production varies a great deal from place to place,
31
due to differences in the amount of solar radiation and the availability of nutrients and
water.
Usually when we think of food chains we visualize green plants, herbivores, and
so on. These are referred to as grazer food chains, because living plants are directly
consumed. In many circumstances the principal energy input is not green plants but dead
organic matter. These are called detritus food chains. Examples include the forest floor
or a woodland stream in a forested area, a salt marsh, and most obviously, the ocean floor
in very deep areas where all sunlight is extinguished 1000's of meters above. In
subsequent lectures we shall return to these important issues concerning energy flow.
Finally, although we have been talking about food chains, in reality the
organization of biological systems is much more complicated than can be represented by
a simple "chain". There are many food links and chains in an ecosystem, and we refer to
all of these linkages as a food web. Food webs can be very complicated, where it appears
that "everything is connected to everything else", and it is important to understand what
are the most important linkages in any particular food web.
Controls on Ecosystem Function
Now that we have learned something about how ecosystems are put together and
how materials and energy flow through ecosystems, we can better address the question of
"what controls ecosystem function"? There are two dominant theories of the control of
ecosystems. The first, called bottom-up control, states that it is the nutrient supply to the
primary producers that ultimately controls how ecosystems function. If the nutrient
supply is increased, the resulting increase in production of autotrophs is propagated
through the food web and all of the other trophic levels will respond to the increased
availability of food (energy and materials will cycle faster).
The second theory, called top-down control, states that predation and grazing by
higher trophic levels on lower trophic levels ultimately controls ecosystem function. For
example, if you have an increase in predators, that increase will result in fewer grazers,
and that decrease in grazers will result in turn in more primary producers because fewer
of them are being eaten by the grazers. Thus the control of population numbers and
overall productivity "cascades" from the top levels of the food chain down to the bottom
trophic levels.
So, which theory is correct? Well, as is often the case when there is a clear
dichotomy to choose from, the answer lies somewhere in the middle. There is evidence
32
from many ecosystem studies that both controls are operating to some degree, but that
neither control is complete. For example, the "top-down" effect is often very strong at
trophic levels near to the top predators, but the control weakens as you move further
down the food chain. Similarly, the "bottom-up" effect of adding nutrients usually
stimulates primary production, but the stimulation of secondary production further up the
food chain is less strong or is absent.
Thus we find that both of these controls are operating in any system at any time
and we must understand the relative importance of each control in order to help us to
predict how an ecosystem will behave or change under different circumstances, such as in
the face of a changing climate.
Summary
Ecosystems are made up of abiotic (non-living, environmental) and biotic
components, and these basic components are important to nearly all types of
ecosystems. Ecosystem Ecology looks at energy transformations and
biogeochemical cycling within ecosystems.
Energy is continually input into an ecosystem in the form of light energy, and
some energy is lost with each transfer to a higher trophic level. Nutrients, on the
other hand, are recycled within an ecosystem, and their supply normally limits
biological activity. So, "energy flows, elements cycle".
Energy is moved through an ecosystem via a food web, which is made up of
interlocking food chains. Energy is first captured by photosynthesis (primary
production). The amount of primary production determines the amount of energy
available to higher trophic levels.
The study of how chemical elements cycle through an ecosystem is termed
biogeochemistry. A biogeochemical cycle can be expressed as a set of stores
(pools) and transfers, and can be studied using the concepts of "stoichiometry",
"mass balance", and "residence time".
Ecosystem function is controlled mainly by two processes, "top-down" and
"bottom-up" controls.
A biome is a major vegetation type extending over a large area. Biome
distributions are determined largely by temperature and precipitation patterns on
the Earth's surface.
Biogeochemical Cycles
33
Water is not the only substance that circulates through the various earth systems.
So, too, do six other substances or, rather, chemical elements. These elements are
composed of a single type of atom, meaning that they cannot be broken down chemically
to make a simpler substance, as is the case with such compounds as water. The six
elements that cycle throughout Earth's systems are hydrogen, oxygen, carbon,
nitrogen, phosphorus, and sulfur. The two following lists provide rankings for their
abundance. The first shows their ranking and share in the entire known mass of the
planet, including the crust, living matter, the oceans and atmosphere. The second list
shows their relative abundance and ranking in the human body.
Abundance of Selected Elements on Earth (Ranking and Percentage):
1. Oxygen (49.2%)
9. Hydrogen (0.87%)
12. Phosphorus (0.11%)
14. Carbon (0.08%)
15. Sulfur (0.06%)
16. Nitrogen (0.03%)
Abundance of Selected Elements in the Human Body (Ranking and Percentage):
1. Oxygen (65%)
2. Carbon (18%)
3. Hydrogen (10%)
4. Nitrogen (3%)
6. Phosphorus (1%)
9. Sulfur (0.26%)
Note that the ranking of all these elements (with the exception of oxygen) is relatively
low in the total known elemental mass of Earth, whereas their relative abundance is
much, much higher within the human body. This is significant, given the fact that these
elements are all essential to the lives of organisms. All six of these elements take part in
biogeochemical cycles, a term used to refer to the changes that a particular element
undergoes as it passes back and forth through the various earth systems and particularly
between living and nonliving matter.
Nitrogen Cycle
The nitrogen cycle is the process by which nitrogen is converted between its
various chemical forms. This transformation can be carried out via both biological and
34
non-biological processes. Important processes in the nitrogen cycle include fixation,
mineralization, nitrification, and denitrification. The majority of Earth's atmosphere
(approximately 78%) is nitrogen, making it the largest pool of nitrogen. However,
atmospheric nitrogen has limited availability for biological use, leading to a scarcity of
usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest
to ecologists because nitrogen availability can affect the rate of key ecosystem processes,
including primary production and decomposition. Human activities such as fossil fuel
combustion, use of artificial nitrogen fertilizers, and release of nitrogen in waste water
have dramatically altered the global nitrogen cycle.
Fig. 2.6 : Nitrogen Cycle
The processes of the nitrogen cycle
Nitrogen is present in the environment in a wide variety of chemical forms
including organic nitrogen, ammonium (NH4+), nitrite (NO2
-), nitrate (NO3
-), and nitrogen
gas (N2). The organic nitrogen may be in the form of any living organism, or humus, and
in the intermediate products of organic matter decomposition or humus built up. The
processes of the nitrogen cycle transform nitrogen from one chemical form to another.
Many of the processes are carried out by microbes either to produce energy or to
accumulate nitrogen in the form needed for growth. The diagram above shows how these
processes fit together to form the nitrogen cycle.
Nitrogen fixation
35
Atmospheric nitrogen must be processed, or "fixed" to be used by plants. Some
fixation occurs in lightning strikes, but most fixation is done by free-living or symbiotic
bacteria. These bacteria have the nitrogenase enzyme that combines gaseous nitrogen
with hydrogen to produce ammonia, which is then further converted by the bacteria to
make their own organic compounds. Most biological nitrogen fixation occurs by the
activity of Mo-nitrogenase, found in a wide variety of bacteria and some Archaea. Mo-
nitrogenase is a complex two component enzyme that contains multiple metal-containing
prosthetic groups. Some nitrogen fixing bacteria, such as Rhizobium, live in the root
nodules of legumes (such as peas or beans). Here they form a mutualistic relationship
with the plant, producing ammonia in exchange for carbohydrates. Nutrient-poor soils can
be planted with legumes to enrich them with nitrogen. A few other plants can form such
symbioses. Today, about 30% of the total fixed nitrogen is manufactured in ammonia
chemical plants.
Conversion of N2
The conversion of nitrogen (N2) from the atmosphere into a form readily available to
plants and hence to animals and humans is an important step in the nitrogen cycle, which
distributes the supply of this essential nutrient. There are four ways to convert N2
(atmospheric nitrogen gas) into more chemically reactive forms:
1. Biological fixation: some symbiotic bacteria (most often associated with
leguminous plants) and some free-living bacteria are able to fix nitrogen as
organic nitrogen. An example of mutualistic nitrogen fixing bacteria are the
Rhizobium bacteria, which live in legume root nodules. These species are
diazotrophs. An example of the free-living bacteria is Azotobacter.
2. Industrial N-fixation: Under great pressure, at a temperature of 600 C, and with
the use of an iron catalyst, atmospheric nitrogen and hydrogen (usually derived
from natural gas or petroleum) can be combined to form ammonia (NH3). In the
Haber-Bosch process, N2 is converted together with hydrogen gas (H2) into
ammonia (NH3), which is used to make fertilizer and explosives.
3. Combustion of fossil fuels: Automobile engines and thermal power plants, which
release various nitrogen oxides (NOx).
4. Other processes: In addition, the formation of NO from N2 and O2 due to photons
and especially lightning, can fix nitrogen.
Assimilation
36
Plants get nitrogen from the soil, by absorption of their roots in the form of either
nitrate ions or ammonium ions. All nitrogen obtained by animals can be traced back to the
eating of plants at some stage of the food chain.
Plants can absorb nitrate or ammonium ions from the soil via their root hairs. If
nitrate is absorbed, it is first reduced to nitrite ions and then ammonium ions for
incorporation into amino acids, nucleic acids, and chlorophyll. In plants that have a
mutualistic relationship with rhizobia, some nitrogen is assimilated in the form of
ammonium ions directly from the nodules. Animals, fungi, and other heterotrophic
organisms obtain nitrogen as amino acids, nucleotides and other small organic molecules.
Ammonification
When a plant or animal dies, or an animal expels waste, the initial form of
nitrogen is organic. Bacteria, or fungi in some cases, convert the organic nitrogen within
the remains back into ammonium (NH4+), a process called ammonification or
mineralization. Enzymes Involved:
GS: Gln Synthetase (Cytosolic & PLastid)
GOGAT: Glu 2-oxoglutarate aminotransferase (Ferredoxin & NADH dependent)
GDH: Glu Dehydrogenase:
Minor Role in ammonium assimilation.
Important in amino acid catabolism.
Nitrification
The conversion of ammonium to nitrate is performed primarily by soil-living
bacteria and other nitrifying bacteria. The primary stage of nitrification, the oxidation of
ammonium (NH4+) is performed by bacteria such as the Nitrosomonas species, which
converts ammonia to nitrites (NO2-). Other bacterial species, such as the Nitrobacter, are
responsible for the oxidation of the nitrites into nitrates (NO3-). It is important for the
nitrites to be converted to nitrates because accumulated nitrites are toxic to plant life.
Due to their very high solubility, nitrates can enter groundwater. Elevated nitrate in
groundwater is a concern for drinking water use because nitrate can interfere with blood-
oxygen levels in infants and cause methemoglobinemia or blue-baby syndrome. Where
groundwater recharges stream flow, nitrate-enriched groundwater can contribute to
eutrophication, a process leading to high algal, especially blue-green algal populations
and the death of aquatic life due to excessive demand for oxygen. While not directly toxic
37
to fish life like ammonia, nitrate can have indirect effects on fish if it contributes to this
eutrophication. Nitrogen has contributed to severe eutrophication problems in some water
bodies. As of 2006, the application of nitrogen fertilizer is being increasingly controlled
in Britain and the United States. This is occurring along the same lines as control of
phosphorus fertilizer, restriction of which is normally considered essential to the recovery
of eutrophied waterbodies.
Denitrification
Denitrification is the reduction of nitrates back into the largely inert nitrogen gas
(N2), completing the nitrogen cycle. This process is performed by bacterial species such
as Pseudomonas and Clostridium in anaerobic conditions. They use the nitrate as an
electron acceptor in the place of oxygen during respiration. These facultatively anaerobic
bacteria can also live in aerobic conditions.
Anaerobic ammonium oxidation
In this biological process, nitrite and ammonium are converted directly into
elemental nitrogen (N2) gas. This process makes up a major proportion of elemental
nitrogen conversion in the oceans.
Human influences on the nitrogen cycle
As a result of extensive cultivation of legumes (particularly soy, alfalfa, and
clover), growing use of the Haber-Bosch process in the creation of chemical fertilizers
and pollution emitted by vehicles and industrial plants, human beings have more than
doubled the annual transfer of nitrogen into biologically-available forms. In addition,
humans have significantly contributed to the transfer of nitrogen trace gases from Earth to
the atmosphere, and from the land to aquatic systems. Human alterations to the global
nitrogen cycle are most intense in developed countries and in Asia, where vehicle
emissions and industrial agriculture are highest.
N2O (nitrous oxide) has risen in the atmosphere as a result of agricultural
fertilization, biomass burning, cattle and feedlots and other industrial sources. N2O has
deleterious effects in the stratosphere, where it breaks down and acts as a catalyst in the
destruction of atmospheric ozone.
N2O in the atmosphere is a greenhouse gas, currently the third largest contributor
to global warming, after carbon dioxide and methane. While not as abundant in the
atmosphere as carbon dioxide, for an equivalent mass, nitrous oxide is nearly 300 times
more potent in its ability to warm the planet.
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NH3 (ammonia) in the atmosphere has tripled as the result of human activities. It
is a reactant in the atmosphere, where it acts as an aerosol, decreasing air quality and
clinging on to water droplets, eventually resulting in nitric acid (HNO3) acid rain.
Atmospheric NH3 and HNO3 damage respiratory systems.
Water Cycle
The water cycle, also known as the hydrologic cycle or H2O cycle, describes the
continuous movement of water on, above and below the surface of the Earth. Water can
change states among liquid, vapour and ice at various places in the water cycle. Although
the balance of water on Earth remains fairly constant over time, individual water
molecules can come and go, in and out of the atmosphere. The water moves from one
reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by
the physical processes of evaporation, condensation, precipitation, infiltration, runoff and
subsurface flow. In so doing, the water goes through different phases: liquid, solid and
gas.
The hydrologic cycle involves the exchange of heat energy, which leads to
temperature changes. For instance, in the process of evaporation, water takes up energy
from the surroundings and cools the environment. Conversely, in the process of
condensation, water releases energy to its surroundings, warming the environment.
The water cycle figures significantly in the maintenance of life and ecosystems on
Earth. Even as water in each reservoir plays an important role, the water cycle brings
added significance to the presence of water on our planet. By transferring water from one
reservoir to another, the water cycle purifies water, replenishes the land with freshwater,
and transports minerals to different parts of the globe. It is also involved in reshaping the
geological features of the Earth, through such processes as erosion and sedimentation. In
addition, as the water cycle also involves heat exchange, it exerts an influence on climate
as well.
Description
The sun, which drives the water cycle, heats water in oceans and seas. Water
evaporates as water vapor into the air. Ice and snow can sublimate directly into water
vapor. Evapotranspiration is water transpired from plants and evaporated from the soil.
Rising air currents take the vapor up into the atmosphere where cooler temperatures cause
it to condense into clouds. Air currents move water vapor around the globe, cloud
particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as
39
snow or hail, and can accumulate as ice caps and glaciers, which can store frozen water
for thousands of years. Snowpacks can thaw and melt, and the melted water flows over
land as snowmelt. Most water falls back into the oceans or onto land as rain, where the
water flows over the ground as surface runoff. A portion of runoff enters rivers in valleys
in the landscape, with streamflow moving water towards the oceans. Runoff and
groundwater are stored as freshwater in lakes. Not all runoff flows into rivers, much of it
soaks into the ground as infiltration. Some water infiltrates deep into the ground and
replenishes aquifers, which store freshwater for long periods of time. Some infiltration
stays close to the land surface and can seep back into surface-water bodies (and the
ocean) as groundwater discharge. Some groundwater finds openings in the land surface
and comes out as freshwater springs. Over time, the water returns to the ocean, where our
water cycle started.
Fig. 2.7 : Water Cycle
Precipitation
Condensed water vapor that falls to the Earth's surface . Most precipitation occurs
as rain, but also includes snow, hail, fog drip, graupel, and sleet. Approximately 505,000
km3 (121,000 cu mi) of water falls as precipitation each year, 398,000 km
3 (95,000 cu mi)
of it over the oceans.
Canopy interception
40
The precipitation that is intercepted by plant foliage and eventually evaporates
back to the atmosphere rather than falling to the ground.
Snowmelt
The runoff produced by melting snow.
Runoff
The variety of ways by which water moves across the land. This includes both
surface runoff and channel runoff. As it flows, the water may seep into the ground,
evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural
or other human uses.
Infiltration
The flow of water from the ground surface into the ground. Once infiltrated, the
water becomes soil moisture or groundwater.
Subsurface Flow
The flow of water underground, in the vadose zone and aquifers. Subsurface water
may return to the surface (e.g. as a spring or by being pumped) or eventually seep into the
oceans. Water returns to the land surface at lower elevation than where it infiltrated,
under the force of gravity or gravity induced pressures. Groundwater tends to move
slowly, and is replenished slowly, so it can remain in aquifers for thousands of years.
Evaporation
The transformation of water from liquid to gas phases as it moves from the ground
or bodies of water into the overlying atmosphere. The source of energy for evaporation is
primarily solar radiation. Evaporation often implicitly includes transpiration from
plants, though together they are specifically referred to as evapotranspiration. Total
annual evapotranspiration amounts to approximately 505,000 km3 (121,000 cu mi) of
water, 434,000 km3 (104,000 cu mi) of which evaporates from the oceans.
Sublimation
The state change directly from solid water (snow or ice) to water vapor.
Advection
The movement of water - in solid, liquid, or vapor states - through the atmosphere.
Without advection, water that evaporated over the oceans could not precipitate over land.
Condensation
41
The transformation of water vapor to liquid water droplets in the air, creating
clouds and fog.
Transpiration
The release of water vapor from plants and soil into the air. Water vapor is a gas
that cannot be seen.
Carbon Cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged
among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.
It is one of the most important cycles of the earth and allows for carbon to be recycled
and reused throughout the biosphere and all of its organisms.
The carbon cycle was initially discovered by Joseph Priestley and Antoine Lavoisier, and
popularized by Humphry Davy. It is now usually thought of as including the following
major reservoirs of carbon interconnected by pathways of exchange:
The atmosphere.
The terrestrial biosphere, which is usually defined to include fresh water systems
and non-living organic material, such as soil carbon.
The oceans, including dissolved inorganic carbon and living and non-living
marine biota.
The sediments including fossil fuels.
The Earth's interior, carbon from the Earth's mantle and crust is released to the
atmosphere and hydrosphere by volcanoes and geothermal systems.
The annual movements of carbon the carbon exchanges between reservoirs, occur
because of various chemical, physical, geological and biological processes. The ocean
contains the largest active pool of carbon near the surface of the Earth, but the deep ocean
part of this pool does not rapidly exchange with the atmosphere in the absence of an
external influence, such as a black smoker or an uncontrolled deep-water oil well leak.
The global carbon budget is the balance of the exchanges (incomes and losses) of
carbon between the carbon reservoirs or between one specific loop (e.g., atmosphere ↔
biosphere) of the carbon cycle. An examination of the carbon budget of a pool or
reservoir can provide information about whether the pool or reservoir is functioning as a
source or sink for carbon dioxide.
42
Fig. 2.8 : Carbon Cycle
Carbon exists in the Earth's atmosphere primarily as the gas carbon dioxide (CO2).
Although it is a small percentage of the atmosphere (approximately 0.04% on a molar
basis), it plays a vital role in supporting life. Other gases containing carbon in the
atmosphere are methane and chlorofluorocarbons (the latter is entirely anthropogenic).
Trees and other green plants such as grass convert carbon dioxide into carbohydrates
during photosynthesis, releasing oxygen in the process. This process is most prolific in
relatively new forests where tree growth is still rapid. The effect is strongest in deciduous
forests during spring leafing out.
The carbon cycle is the biogeochemical cycle by which carbon is exchanged
among the biosphere, pedosphere, geosphere, hydrosphere and atmosphere of the Earth. It
is one of the most important cycles of the earth and allows for carbon to be recycled and
reused throughout the biosphere and all of its organisms.
Genetic and Plant Biodiversity
Meaning: The sum total of various types of microbes, plants and animals present
in a system is referred to as Bio-diversity.
OR
Complex beyond understanding and valuable beyond measure biological diversity
is the total variety of life on our planet.
The biosphere comprises of a complex collection of innumerable organisms,
which constitutes the vital life support for the survival of human race. As per in the
43
convention on Biological Diversity held at Rio-De-Janeiro (Brazil) in 1992, the
Biological Diversity is defined as ―The variability among living organisms from all
sources including, interalia, terrestrial, marine and other aquatic ecosystems and the
ecological complexes of which they are part. This includes diversity within species,
between species and of eco-systems.
Nature has developed complex spectrum of life forms over 600 million years. It is
understood that anywhere between 10 to 80 million species exist on earth.
I. Diversity of Biotic Communities and Ecosystem: Different types of ponds,
lakes, rivers, wetlands, meadows, grass-lands, forests etc., represent diverse
ecosystems with their own characteristic biotic community. Ex: A pond may
possess different sets of flora and fauna as compared to another ecosystem such as
river.
II. Diversity of Species Composition within a Community: The Biotic
components of an ecosystem composed of a number of species consisting of
plants, microbes, and animals which interact with each other on one hand and
interact with the abiotic factors of the environment on the other. The richness of
species in an ecosystem is called ―species diversity‖.
III. Diversity of Genetic Organization within a Species: Within a species, we can
find several varieties or strains or races which slightly differ from each other in
one or more characteristics namely size, shape, quality of their respective product,
resistance against pests, insects, diseases etc., and resilience to survive under
adverse environmental conditions. These differences are due to slight variation in
their genetic organization. Such diversity in the genetic make-up of a species is
called ―genetic diversity‖. A species having large numbers of varieties, strains or
races is considered as rich and more diverse in its genetic organization.
IV. Diversity within a Landscape: This type of diversity refers to size and
distribution of several ecosystems and their interactions across a given land
surface.
Importance of Biodiversity
Bio-sphere is life support system for human-race. Plants and animals have been
exploited by human since time immemorial for need of food, clothing, shelter etc. So far
about 1.5 million species of plants (10% of existing plants) have been recorded similarly
many living organisms are yet to be recognized.
44
A huge wealth of biological resources is yet to be tapped by the mankind. The
price we might have been paying for this neglect may be illustrated by the fact that if
“penicillium” or “cinchona” would have been extinct before their curative properties
were discovered, what would have been the plight of mankind.
Work to be done:
1. The ―Ecosystem services‖ provided to us by nature is ―gratis‖ also consists supply
of fresh water, generating soils, supply of plant pollinators, and maintaining a
huge ―genetic library‖.
2. In many cultures, maintenance of mountains and other diverse landforms are of
religious significance.
3. A diversity of biological communities such as parks, gardens, natural animal
habitats, forests, mountains, sea-shores, etc. are useful for educational, picnicking
and other recreational activities.
4. The vast insect fauna contains large number of species which is potentially
superior crop pollinators, weed-control agents and are parasites of insect pests.
5. In a simple ecosystem, loss of even one or a few species could be disastrous
because of the lack of alternatives.
There are several examples of genetic modifications:
a) A wild variety of rice grown in U.P. saves millions of hectares of paddy crop from
‗grassy stand‘ virus.
b) The kans grass known as “saccharum spontaneum‖ from Indonesia provided
genes for resistance to red rot diseases of sugar cane.
c) The genes from a wild melon grown in U.P. helped in imparting resistance to
powdery mildew in musk melons grown in California.
d) Maintaining the Bio-Diversity helps in preservations of socio-economic, aesthetic
cultural and religious values of ecosystems.
El-Nino Phenomenon
Under normal circumstances the water of the eastern pacific off Ecuador, Peru and
Northern Chile are surprisingly cold, as much as 10ºC cooler than the waters of the
western pacific. This part of the eastern pacific is teeming with fish, since here cold
waters, rich in nutrients, well up from the deep ocean.
But once every five to ten years from December to March, the waters of the
Eastern Pacific warm up a little (28ºC i.e., 4ºC higher than normal) which disrupts the
45
upwelling of the rich, cold water. This in turn disrupts the anchovy fishery, Key to
Peruvian economy.
This phenomenon is called El-Nino (Spanish term for ―The Christ Child) since it
starts in December. El-Nino is not a regular event as it takes place once every five years
on the average. But when it occurs, the local environment suffers from enormous
disruption. The anchovy fish die for shortage of food, followed by birds that normally
feed off the anchovy.
Since the 1950‘s with off-shore fishing, the Peruvian fishery became the world‘s
largest, by weight. The anchovies are also dried and ground up into fish meal for animal
feed, especially for poultry forms. A major El-Nino can wreck the Peruvian economy and
send world fish meal prices soaring.
El-Nino struck Chile and Peru in mid-1970s and 1982. El-Nino affected climate
over half the globe.
In the late 1960‘s it was found that El-Nino events coincided with the southern
oscillation, an irregular but recurrent relationship between atmosphere pressures and sea-
surface temperatures over the south-eastern pacific and the Indian oceans, particularly
between Darwin, Australia and the Pacific island of Tahiti. These two events, El-Nino and
the southern oscillation, are called ENSO by climatologists. They usually last for 12
months from December to December. They bring with them impacts for Peruvian
anchovies. The most notorious ENSO event was in 1982 making full impact all around
the globe. There were droughts in north-eastern Brazil (14 million people affected) India
(food production dropped by 4%), north china (grain, yield reduced by 10%), Indonesia
(350 starvation deaths) and eastern Australia as well as major floods in Ecuador, Bolivia
and Peru.
The science of El-Nino / ENSO process is not yet fully understood. Its relationship
with greenhouse effect remains to be established. In order to forecast ENSO event it is
necessary to monitor regularly sea-surface temperatures of Peru and atmospheric pressure
differences between Tahiti and Darwin. A team of scientists have been conducting
research on El-Nino under the sponsorship of the permanent south-pacific commission,
which supports oceanographic research and governs maritime policy in Chile, Colombia,
Ecuador and Peru. The commission co-ordinates the work of 17 scientific organizations.
They have fitted in the seas all along the equator more than 200 buoys which are
equipped with wind sensors, satellite transmitters and thermostats. The experts keep track
46
of ocean temperature, salinity levels, and wind patterns and thus are in a position to
forecast the approach of El-Nino several months before it hits South America.
AIR POLLUTION & SOUND POLLUTION
„Air Pollution is the excessive concentration of foreign matter in the air which
adversely affects the well being of individual or causes damage to property‟
American Medical Association
Older people are highly vulnerable to diseases induced by air pollution. Those
with heart or lung disorders are under additional risk. Children and infants are also at
serious risk. Studies have estimated that the number of people killed annually in the US
alone could be over 50,000.
Because people are exposed to so many potentially dangerous pollutants, it is
often hard to know exactly which pollutants are responsible for causing sickness. Also,
because a mixture of different pollutants can intensify sickness, it is often difficult to
isolate those pollutants that are at fault.
Many diseases could be caused by air pollution without their becoming apparent
for a long time. Diseases such as bronchitis, lung cancer, and heart disease may all
eventually appear in people exposed to air pollution.
Air pollutants such as ozone, nitrogen oxides, and sulfur dioxide also have
harmful effects on natural ecosystems. They can kill plants and trees by destroying their
leaves, and can kill animals, especially fish in highly polluted rivers.
Defining ―air pollution‖ is not simple. One could claim that air pollution started
when humans began burning fuels. In other words, all man-made (anthropogenic)
emissions into the air can be called air pollution, because they alter the chemical
composition of the natural atmosphere. The increase in the global concentrations of
greenhouse gases CO2, CH4 and N2O, can be called air pollution using this approach,
even though the concentrations have not found to be toxic for humans and the ecosystem.
One can refine this approach and only consider anthropogenic emissions of harmful
chemicals as air pollution.
Air pollution is the presence of substances in air in sufficient concentration and
for sufficient time, so as to be, or threaten to be injurious to human, plant or animal life,
or to property, or which reasonably interferes with the comfortable enjoyment of life and
property.
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Air pollutants arise from both man-made and natural processes. Pollutants are also
defined as primary pollutants resulting from combustion of fuels and industrial operations
and secondary pollutants, those which are produced due to reaction of primary pollutants
in the atmosphere. The ambient air quality may be defined by the concentration of a set of
pollutants which may be present in the ambient air we breathe in. These pollutants may be
called criteria pollutants. Emission standards express the allowable concentrations of a
contaminant at the point of discharge before any mixing with the surrounding air.
There are many health effects of air pollution including irritation of the eyes, nose,
mouth, and throat, chest pain, labored breathing, and increased susceptibility to lung
infection. At its least severe levels, air pollution is a nuisance to healthy individuals and a
burden to those with respiratory diseases.
Millions of tons of harmful gases and pollutants are released into the air each year.
Once inhaled, polluted air weakens the lungs natural defenses against harmful
contaminants. In fact, lung tissue has no reliable defense against air pollution, and
therefore, is gradually destroyed by invasive pollutants
Pollutants
1. Primary Pollutants
2. Secondary Pollutants
S.No. Primary Pollutants Secondary Pollutants
1. Carbon monoxide (CO) Ozone (O3)
2. Nitrogen Oxide (NOx) Peroxyactyl nitrate (PAN)
3. Sulphur Oxide (SOx) Aldehydes
4. Hydrocarbon (HC) Ketones
5. Particulates Sulphur trioxide
Primary air pollutants are emitted directly into the air from sources. They can have
effects both directly and as precursors of secondary air pollutants (chemicals formed
through reactions in the atmosphere).
1. Primary Pollutants:
I . CO (Carbon monoxide)
II. NOx (Nitrogen Oxide)
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III. SOx (Sulphur Oxide)
IV. HC (Hydrocarbon)
V. Particulates
I . CO (Carbon monoxide)
It is odourless, colourless and tasteless gas. It is insoluble of water. It is
96.5% as heavy as air. It is produced by incomplete combustion of fuel. It
burns in air or oxygen with blue flame.
2C+ O2 2 CO
Dissociations of CO2 at high temperature
CO2 CO + O
Sources
1. Natural Sources – volcano, electric discharge during storms, marsh gas .
2. Transportation – motor vehicle, aircraft, rail.
3. Industrial activities – petroleum, paper and steel industries
4. Miscellaneous – forest fire, agricultural waste
Harmful effects
CO can cause oxygen deprivation (hypoxia), displacing oxygen in bonding with
hemoglobin, causing cardiovascular and coronary problems, increasing risk of stroke, and
impairing learning ability, dexterity and sleep. CO is mostly hazardous in relatively
confined areas such as tunnels under bridges and overpasses, and in dense urban settings.
In unconfined areas or away from population centres, it will stabilize into CO2 before
damage to human health is likely.
It circulate directly into blood through lungs. Carbon monoxide binds to
hemoglobin (Hb) in red blood cells, reducing their ability to transport and release oxygen
throughout the body because of Carboxy hemoglobin (CO Hb). The affinity of Carboxy
hemoglobin is 210 times greater to that of oxygen. Low exposures can aggravate cardiac
ailments, while high exposures cause central nervous system impairment or death. It also
plays a role in the generation of ground-level ozone.
Hb + CO CO Hb
Controls
49
1. Development of exhaust systems.
2. Modifications of internal combustions systems
3. Development of substitute fuel for gasoline
Sulfur dioxide
Sulfur dioxide is a colourless gas with a pungent odour. It is a liquid when under
pressure. Sulfur dioxide dissolves in water very easily. It cannot catch fire.
Sources
1. Volcanic eruptions.
2. Burning of fossil fuels.
3. Copper smelting.
4. Manufacture of sulfuric acid.
5. Manufacture of paper.
6. Food preservatives industries.
7. Manufacture of fertilizers.
Once released into the environment, sulfur dioxide moves to the air. In the air,
sulfur dioxide can be converted to sulfuric acid, sulfur trioxide, and sulfates. Sulfur
dioxide dissolves in water. Once dissolved in water, sulfur dioxide can form sulfurous
acid.
Harmful effects
1. Body absorb sulfur oxide through lungs. It can easily and rapidly enter
bloodstream through your lungs and it breaks down to sulfate.
2. Exposure to 100 ppm is considered immediately dangerous to life and health,
copper mine developed burning of the nose and throat, breathing difficulties.
3. Lung function changes have been observed in some workers exposed to 0.4–3.0
ppm.
4. Studies in animals support the human data regarding respiratory effects of sulfur
dioxide.
5. Children may be exposed to more sulfur dioxide than adults because they breathe
more air for their body. Long-term exposed studies reduced breathing ability.
6. It also causes to damage crops.
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7. SO2 dissolves in cloud droplets and oxidizes to form sulfuric acid (H2SO4) which
can fall to Earth as acid rain or snow or form sulfate aerosol particles in the
atmosphere.
Controls
1. Development of substitute fuel for gasoline.
2. Use of low sulphur fuel.
3. Removal of SOx from fuel gases.
Nitrogen Oxides
Nitric oxide (NO) which is colourless, odourless gas and Nitrogen dioxide (NO2) which
is radish brown, pungent are main primary pollutants.
Sources
Coal Burning.
Motor vehicle exhausts.
Fixation of lighting.
Bio mass burning.
Emission from acid manufacturing.
Harmful effects
1. Respiratory disease like bronchitis.
2. Formation of smog in acid humid condition.
3. Acid rain when NO2 combines with water.
Control
There are only two way to reduce NOx emissions:
Modifying combustion processes to prevent NOx formation.
Treating combustion gases after flame to convert NOx to N2.
Combustion Modification
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This is the most widely used approach to NOx control. Combustion modification
involves mixing part of the combustion air with the fuel and burning as much of the fuel
that the air will allow. Then, some of the heat from the flames is transferred to whatever
is being heated. Next, the remaining air is added and combustion is finished. This is
known as two-stage combustion or reburning .
One of the major advantages to this technique is that it is cheap. The
disadvantages are that it requires a larger firebox without a higher combustion rate. Also,
it is difficult to get complete burning of the fuel in the second stage. Therefore, the
amount of unburned fuel and/or carbon monoxide in the exhaust gas increases.
Post-Flame Treatment
Many of these processes require the addition of a reducing agent to the
combustion gas stream to take oxygen away from NO. In automobile engines, a platinum-
rhodium catalyst is used. The reaction is:
2NO + 2CO + p-r catalyst-----------> N2 + 2CO2
On the other hand, for power plants and other large furnaces, there are many
choices of reducing agents. However, the most popular is ammonia. The desired
conversion reaction is:
6NO + 4NH3 -------------> 5N2 + 6H2O
However, there is always some oxygen present. This oxygen causes reactions like
the following:
4NO + 4NH3 +O2 ---------> 4N2 + 6H2O
If the above reaction occurs, the NO2 is reduced by the following reaction:
2NO2 + 4NH3 +O2 ---------> 3N2 + 6H2O
All of these reactions are expensive to carry out. They can occur either over a
zeolite catalyst or in a gas stream in a part of a furnace where the temperature is between
1600 and 1800 degrees Fahrenheit. If the temperature is greater than 1800 degrees, the
NO content increases rather than decreases, which exactly what we don't want. The
dominant reaction is:
NH3+O2 ---------> NO + 3/2H2O
52
Particulate Matter Pollution
The term Particulate Matter (PM) includes both solid particles and liquid droplets
found in air. Many man-made and natural sources emit PM directly or emit other
pollutants that react in the atmosphere to form PM. These solid and liquid particles come
in a wide range of sizes. Particles less than 10 micrometers in diameter tend to pose the
greatest health concern because they can be inhaled into and accumulate in the respiratory
system. There different type of particulate matters like
1. Dust.
2. Fumes.
3. Mist.
4. Smoke.
5. Aerosol.
6. Fog.
7. Coarse particles.
Sources
1. Volcanic eruptions.
2. Motor vehicles.
3. Power plants.
4. Wood burning.
5. Crushing or grinding operations.
6. Dust from paved (Cemented) or unpaved roads.
7. Harvesting and trashing of crops.
8. Constructions works.
Harmful effects
1. It has found that numerous health effects arise from both fine and coarse particles
when they accumulate in the respiratory system.
2. When exposed to even small levels of PM, people with existing heart or lung
diseases-such as asthma.
3. Exposure to fine particles is associated with several serious health effects, and it
will cause death.
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4. Chronic obstructive pulmonary disease, congestive heart disease are at increased
risk of premature death.
5. Children and people with existing lung disease may not be able to breathe as
vigorously as they normally would, and they may experience symptoms such as
coughing and shortness of breath when exposed to levels of PM.
Controls
1. Gravity Setting Chamber : This is the simplest of all separation equipment. It
has big box, with the inlet and outlet streams way up at the top, and as the fluid
flows through, the particles fall out. If the box is long enough, then all the
particles should fall out. This brings us back to the settling velocity; if the flow
rate through is too fast for the size of the box you are using, then not all the
particles, if any, are going to settle.
Fig. 3.1 : Gravity setting chamber
2. Mechanical Collectors – It is also known as cyclone collector. Mechanical
collectors use the inertia of the particles for collection. The particulate-laden gas
stream is forced to spin in a cyclonic manner. The mass of the particles causes
them to move toward the outside of the vortex. Most of the large-diameter
particles enter a hopper below the cyclonic tubes while the gas stream turns and
exits the tube.
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Fig. 3.2 : Top Inlet cyclone
3. Wet Scrubbers –
There are a number of major categories of particulate wet scrubbers such as Ventures
Impingement and Sieve Plates.
Spray Towers.
Mechanically Aided.
Condensation Growth.
Packed Beds.
Ejector.
Mobile Bed.
Caternary Grid.
Froth Tower.
Oriented Fiber Pad.
Wetted Mist Eliminators.
Spray Tower Scrubbers
A typical spray tower scrubber is shown in figure 3.3. This is the simplest type of
particulate wet scrubber in commercial service. Sets of spray nozzles located near the top
of the scrubber vessel generate water droplets that impact with particles in the gas stream
as the gas stream moves upwards.
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Fig. 3.3 : Spray Tower Scrubbers
4. Electrostatic Precipitator
An electrostatic precipitator is a large, industrial emission-control unit. It is
designed to trap and remove dust particles from the exhaust gas stream of an industrial
process. Precipitators are used in Electric, Cement , Chemicals, Metals, Paper industries .
Fig. 3.4 : Electrostatic Precipitator
Hydrocarbon
Hydrocarbons are natural chemical compounds made up of carbon and hydrogen.
Hydrocarbon are mainly two types - saturated and unsaturated.
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Saturated hydrocarbons: They have no double, triple, or aromatic bonds between
carbons.
Unsaturated hydrocarbons: They have at least one aromatic ring of carbons, they have
at least one double or triple bond between carbons, polycyclic aromatic hydrocarbons
(PAH).
Sources
1. Natural sources like CH4.
2. Coal.
3. Wood.
4. Petroleum Products.
Harmful Effects
1. Irritation on mucus secretions
2. They undergo chemical reactions in the presence of sunlight and nitrogen oxides.
They form photochemical oxidants leading to photochemical smog.
3. This causes irritation in the eyes and lungs leading to respiratory diseases.
Table – 1
Pollutants Sources Environmental Effects
Carbon
Monoxide
(CO)
Natural Sources –
volcano, electric
discharge during
storms, marsh gas .
Transportation –
motor vehicle,
aircraft, rail.
Industrial activities –
petroleum, paper and
steel industries.
Forest fire,
agricultural waste.
It binds with Hb in red blood cells, reducing
their ability to transport and release oxygen
throughout the body because of Carboxy
hemoglobin (CO Hb). The affinity of Carboxy
hemoglobin is 210 times greater to that of
oxygen. Low exposures can aggravate cardiac
ailments, while high exposures cause central
nervous system impairment or death.
Nitrogen
Oxides
(NOx)
Combustion of oil,
coal, gas.
Combustion of
Decreased visibility due to yellowish
colour of NO2.
NO2 contributes to heart and lung
57
automobiles.
Bacterial action in
soil.
Forest fires.
Lightning volcanic
action.
problems.
NO2 can suppress plant growth.
Decreased resistance to infection.
May encourage the spread of cancer.
Sulfur oxide
(SOx)
Volcanic eruptions.
Burning of fossil
fuels.
Copper smelting.
Manufacture of
sulfuric acid.
Manufacture of
paper.
Food preservatives
industries.
Manufacture of
fertilizers.
Nose and throat, breathing difficulties.
Lung function changes have been
observed.
Studies in animals support the human data
regarding respiratory effects of sulfur
dioxide.
Long-term exposed studies reduced
breathing ability.
It also causes to damage crops.
SO2 dissolves in cloud droplets and
oxidizes to form sulfuric acid (H2SO4),
which can fall to Earth as acid rain or
snow or form sulfate aerosol particles in
the atmosphere.
Hydrocarbon
(HC)
Natural sources like.
CH4 .
Coal.
Wood.
Petroleum Products.
Irritation on mucus secretions.
They undergo chemical reactions in the
presence of sunlight and nitrogen oxides.
They form photochemical oxidants
leading to photochemical smog.
This causes irritation in the eyes and lungs
leading to respiratory diseases.
Particulate
Matters (PM)
Volcanic eruptions.
Motor vehicles.
Power plants.
Wood burning.
Crushing or grinding
Accumulate in the respiratory system.
Heart or lung diseases-such as asthma.
Exposure to fine particles is associated
with several serious health effects, and it
will cause death.
58
operations.
Dust from paved
(Cemented) or
unpaved roads.
Harvesting and
trashing of crops
Constructions works.
Children and people with existing lung
disease may not be able to breathe as
vigorously as they normally would, and
they may experience symptoms such as
coughing and shortness of breath.
Volatile
Organic
Compounds
(VOCs)
Evaporation of
solvents.
Evaporation of fuels.
Incomplete
combustion of fossil
fuels.
Naturally occurring
compounds like
terpenes from trees.
Eye irritation.
Respiratory irritation.
Some are carcinogenic.
Decreased visibility due to blue-brown
haze.
Ozone (O3) Formed from
photolysis of NO2 .
Sometimes results
from stratospheric
ozone intrusions.
Bronchial constriction.
Coughing, wheezing.
Respiratory irritation.
Eye irritation.
Decreased crop yields.
Retards plant growth.
Damages plastics.
Breaks down rubber.
Harsh odour.
Peroxyacetyl
Nitrates (PAN)
Formed by the
reaction of NO2 with
VOCs (can be formed
naturally in some
environments).
Eye irritation.
High toxicity to plants.
Respiratory irritation.
Damaging to proteins.
59
Causes of Air Pollution
Carbon dioxide is one the main pollutants that causes air pollution. This is because
although living beings do exhale carbon dioxide, this gas is harmful when emitted from
other sources, which are caused due to human activity. An additional release of carbon
dioxide happens due to various such activities. Carbon dioxide gas is used in various
industries such as the oil industry and the chemical industry. The manufacturing process
of most products would require the use of this gas. There are various human activities that
add to the increased proportions of carbon dioxide in the atmosphere. The combustion of
fossil fuels and the harmful effects of deforestation have all contributed towards the same.
Show that amongst the various gasses emitted during a volcanic eruption, carbon dioxide
remains to be at least 40% of the emission. Scientists have now therefore identified
carbon dioxide as one of those elements that have contributed to global warming.
Causes of air pollution are not limited to this. The combustion of fuels in
automobiles, jet planes etc all cause the release of several primary pollutants into the air.
The burning of fossil fuels in big cities which is seen at most factories, offices and even a
large number of homes, it is no wonder that air pollution is increasing at an alarming rate.
The release of other harmful gases all adds to the state that we see today. Although
carbon dioxide plays an important role in various other processes like photosynthesis,
breathing an excess of the same also causes harmful effects towards one‘s health.
The various causes of air pollution that releases harmful gases into the atmosphere
are caused due to the increasing number of power plants and manufacturing units or
industries that mostly have activities related to the burning of fuels. Besides, as
mentioned earlier, most automobiles, marine vessels, activities that involve the burning of
wood, fumes that are released from aerosol sprays, military activities that involve the use
of nuclear weapons, all are the numerous causes of air pollution.
Carbon monoxide is another such gas which although was present in the
atmosphere earlier, is now considered to be a major pollutant. An excess of the same has
a harmful effect on our system. There are many reasons why carbon monoxide can be
released into the atmosphere as a result of human activities. This is also produced due to
any fuel burning appliance and appliances such as gas water heaters, fireplaces,
woodstoves, gas stoves, gas dryers, yard equipments as well as automobiles, which add to
the increased proportion of this gas into the atmosphere.
60
Sulfur dioxide is yet another harmful pollutant that causes air pollution. Sulfur
dioxide is emitted largely to the excessive burning of fossil fuels, petroleum refineries,
chemical and coal burning power plants etc. Nitrogen dioxide when combined with sulfur
dioxide can even cause a harmful reaction in the atmosphere that can cause acid rain.
Nitrogen dioxide is one more gas that is emitted into the atmosphere as a result of
various human activities. An excess of nitrogen dioxide mainly happens due to most
power plants seen in major cities, the burning of fuels due to various motor vehicles and
other such sources, whether industrial or commercial that cause the increase in the levels
of nitrogen dioxide. These and a number of other hazardous air pollutants are emitted
with the various numbers of activities that we carry out during the day which are the main
causes of air pollution.
Fig. 3.5 : Air pollution
Secondary Air Pollutants
These types of pollutants are formed in the atmosphere by chemical reaction
between primary pollutants and atmospheric constituents. Oxidation reactions, hydrolysis
reaction and photochemical reactions are takes place during interaction. There are
following type of secondary pollutants
1. Ozone.
2. Peroxyactyl nitrate (PAN).
3. Aldehydes.
4. Ketones.
5. Sulphur trioxide.
61
Ozone Layer
Fig. 3.6 : Ozone Layer
The ozone layer is a deep layer in the stratosphere, encircling the Earth that has
large amounts of ozone in it. The layer shields the entire Earth from much of the harmful
ultraviolet radiation that comes from the sun.
"The ozone layer" refers to the ozone within stratosphere, where over 90% of the
earth's ozone resides. Ozone is an irritating, corrosive, colorless gas with a smell
something like burning electrical wiring.
Ozone is a special form of oxygen, made up of three oxygen atoms rather than the
usual two oxygen atoms. It usually forms when some type of radiation or electrical
discharge separates the two atoms in an oxygen molecule (O2), which can then
individually recombine with other oxygen molecules to form ozone (O3).
O2 + O O3
Sources
1. Lighting.
2. Forest Fire.
3. Vehicles exhaust.
Harmful effects
1. Increased concentration of ozone effect RNA & DNA.
2. Lung Cancer.
3. Loss of immune system.
62
4. It retarded the growth of vegetation.
5. It also effect the food production.
Ozone Depletion
Arctic Ozone
The maximum depletion is generally less severe than that observed in the
Antarctic, with no large and recurrent ozone hole taking place in the Arctic.
Since the 1980's, scientists at ESRL have been participants in field, theoretical and
laboratory research to demonstrate some of the key processes that contribute to the
observed difference between the depletion of ozone in the Arctic and Antarctic.
Ozone-Depleting Substances
Certain industrial processes and consumer products result in the atmospheric
emission of ozone-depleting gases. These gases contain chlorine and bromine atoms,
which are known to be harmful to the ozone layer. Important examples are the CFCs and
hydro- chloro-fluoro-carbons (HCFCs), human-produced gases once used in almost all
refrigeration and air conditioning systems. These gases eventually reach the stratosphere,
where they are broken apart to release ozone-depleting chlorine atoms.
Photochemical Smog
Photochemical smog is produced when sunlight is mixed with various pollutants
like nitrogen dioxide or hydrocarbons. The photochemical smog is often colorless and
invisible. However, it can cause various problems like eye irritation, respiratory problems
and so on. Smog is caused when smoke released from vehicles and factories gets mixed
with fog. This smog (smoke + fog) becomes heavy and remains on the surface of the land
rather than moving up, which causes a number of accidents and respiratory problems.
This harmful smog may contain any of the following:
NOx.
Various harmful organic compounds.
Aldehydes.
Peroxyacyl Nitrate (PAN).
O3 .
63
Fig. 3.7 (A) : Photochemical Smog
Smog is often used as a generic term for any kind of air pollution that reduces
visibility, especially in urban areas. However, it is mainly two types:
1. Industrial smog.
2. Photochemical smog.
Events like the London smog of 1952 are often referred to as industrial smog because
SO2 emissions from burning coal play a key role. Typically, industrial smog also called
gray or black smog develops under cold and humid conditions. Cold temperatures are
often associated with inversions that trap the pollution near the surface allows for rapid
oxidation of SO2 to form sulfuric acid and sulfate particles.
64
Fig. 3.7 (B) : Photochemical Smog
London smog occurred in the industrial towns of Liege, Belgium, in 1930, killing
more than 60 people and Donora, Pennsylvania, in 1948, killing 20. Today coal
combustion is a major contributor to urban air pollution in China, especially from
emissions of SO2 and aerosols.
Air pollution regulations in developed countries have reduced industrial smog
events, but photochemical smog remains a persistent problem, largely driven by vehicle
emissions.
Photochemical smog forms when NOx and VOCs react in the presence of solar
radiation to form ozone. The solar radiation also promotes formation of secondary aerosol
particles from oxidation of NOx, VOCs, and SO2. Photochemical smog typically develops
in summer (when solar radiation is strongest) in stagnant conditions promoted by
temperature inversions and weak winds.
Nevertheless, people have started taking some measure to reduce the harmful
effects of photochemical smog. Tight control on emissions throughout the world is one
such excellent example of this. Many countries have banned the usage of a few harmful
65
chemicals that create photochemical smog. Most governments have started taking such
measures and have started monitoring air quality to gauge the increase level.
Acid Rain
Rain is acidified by oxides of sulfur and nitrogen. Acid rain is formed when
pollutants called oxides of sulfur and nitrogen, contained in car exhaust, power plant,
smoke, and factory smoke, react with the moisture in the atmosphere.
Acid rain is formed when sulfur dioxide and nitrogen oxides reach the air and are
transformed into sulfate or nitrate particles. When combined with water vapour, they are
converted into sulfuric or nitric acids. Acid rain can adversely affect aquatic life, erode
stone buildings and marble statues, and seriously threaten trees and crops.
Power plants that burn coal to generate electricity are a chief cause of acid rain.
Coal burning releases sulfur dioxide into the air. Sulfur dioxide then combines with free
oxygen and water vapour to form small quantities of sulfuric acid in our rain.
Nitrogen oxide emissions from cars also contribute to acid rain. Nitrogen oxide
controls are also required for new municipal waste incinerators and power plants.
NOx + O2 HNO3
SOx + O2 H2SO4
Harmful Effects of Acid Rain
1. It has been found that acidification causes adverse effects on aquatic animals.
2. Ancient monuments, structure, building, bridges, roads are weakens due to attack
of acid.
3. Corrosive effect on steel or iron windows and doors.
4. Hair, skin and lungs are affected by acid rain.
5. Acidification damage to crops and forest.
6. Acid rain causes a cascade of effects that harm or kill individual fish, reduce fish
population numbers, completely eliminate fish species from a water body, and
decrease biodiversity.
66
Fig. 3.8 – Acid Rain
Controls
1. By using catalytic converter to emit less pollutant in the environment.
2. By using bio fuels instead of gasoline or diesel.
3. Developing more efficient vehicles to reduce the harmful gases.
4. It is also observed that neutralize the acid with lime but this is expensive.
Global Warming
The heat balance of the earth is defined as the ratio of energy received by the earth
from the sun to the energy the earth loses by reflection and by radiation is form of heat.
This ratio is essentially unit. That is, the earth loses as much heat energy as it receives. As
a result, a near steady state of the average of global temperature has been maintained.
Although there have been imbalances in local regions, the average temperature of
the earth has remained more or less constant over a span of millions of years.
The atmosphere plays a significant role in maintaining the heat balance of the
earth. It is through the atmosphere that the earth radiates back the heat energy or reflects
back solar radiations. On an average 33% of the solar radiations received from the sun are
reflected back, primarily by clouds and partially by snow and ice sheets on the earth‘s
surface. The reflecting capacity of the earth is called albedo. The remaining 67% of the
solar energy is absorbed of this one-fourth is absorbed by the atmosphere, three-fourth by
the earth‘s surface. Ultimately both the atmosphere and the earth‘s surface radiate back
67
the absorbed energy as heat. The amount of heat energy radiated into the outer space
almost equals 67%. The heat gain and loss factors are thus balanced over the global scale.
It is feared that human activities are likely to disturb the delicate heat balance of
the earth. Industrial operations have induced large amounts of greenhouse gases, like
carbon dioxide, ozone, nitrous oxide, methane and water vapours into the atmosphere.
These gases tend to increase the average global temperature. The industrial operations
have also injected particulate load into the atmosphere. The particulates tend to counter
the warming effect of green house gases.
The current global trends in deforestation along with increased combustion of
fossil fuels have a cumulative effect on the net increase in carbon dioxide content. From
previous 283 ppm to present 356 ppm (0.03%) and it will be 600 ppm in future. However,
the rate of increase of CO2 is only about 50% of the expected magnitude. The removal
mechanisms, i.e., due to sinks of carbon dioxide photosynthesis & ocean are shown in fig.
3.9
Fig. 3.9 : Global Warming
The major sink is the ocean which contains the bulk of dissolved carbon dioxides
as bicarbonate.
It has been estimated that this combined effect will bring about a 3ºC rise in
surface temperature for a doubling of the carbon dioxide concentration, which may occur
around 2050 A.D.
It may be noted that a slight increase in surface temperature, say 1ºC, can
adversely affect the world food production. Thus the wheat growing zones in the northern
latitude will be shifted from the North Asia and Canada to the poles, i.e., from fertile to
poor soils. The biological productivity of the ocean would also decrease due to warming
of the surface layer, which in turn reduces the transport of nutrients from deeper layers to
the surface by vertical circulation.
68
Another effect is the rise in sea levels. Since oceans act as reservoirs of heat, it
could result in rise of sea levels by as much as 2 meters due to expansion of sea water at
increased temperatures, partial melting of glaciers, ice-gap of Greenland and also polar
ice caps. This rise of sea levels would threaten coastal countries some 60 odd island
nations who face deep inroads by the sea, like the Maldives, Bangladesh may be totally
submerged. In India coastal cities such as Chennai, Goa may meet similar fates.
On the other side without carbon dioxide the earth would be as cold as the moon.
By trapping the heat radiating from the earth‘s surface, carbon dioxide regulates global
temperature to life-sustaining 15ºC. But if its quantity increases too much, the earth may
share the fate of its neighboring planet Venus with surface temperature of 450ºC.
Although scientist agree on the theory of green house warming, debate continues
as to whether the increase in these greenhouse gases have actually begun to warm the
global climate. They hope to settle the question with measurements of the speed of sound
by sending pulses of underwater sound around the world through all five of its ocean
basins.
The potential of a greenhouse gas to cause greenhouse warming is expressed by
―Global warming potential‖ (GWP), originally defined by the United Nations
Intergovernmental panel on climate change, which is a function of both the infra-red
sorption characteristics and the lifetime of the gas. The greenhouse gases can be arranged
in GWP sequence as follows:-
10000x 150x 25x
CFC > N2O > CH4 > CO2
In other words, CFC is 38 million times stronger, N2O 3800 times and CH4 25
times stronger than CO2 in terms of GWP.
69
Ozone Hole
The major culprit in ozone depletion consists of CFC compounds, commonly
known as ―Freons‖. The extreme chemical stability and non-toxicity of CFC‘s enable
them to persist for years in the atmosphere and to enter, the stratosphere. In the
stratosphere CFC‘s are subjected to photochemical dissociation by intense UV radiation.
Fig. 3.10 : Ozone Layer Depletion
The net result is regeneration of Cl. radical which sustains the chain reaction.
It is known that one Cl. atom / radical can destroy one lakh O3 molecules. CFC‘s
have lifetimes of the order of 100 years.
The Antarctic Ozone Hole appears during Antarctic‘s late winter and early spring
of severely depleted ozone (upto 50%) over the polar region. The reasons why this occurs
are related to the normal effect of NO2 in limiting Cl –atom -catalyzed destruction of
ozone by combining with ClO
ClO + NO2 -------------- ClONO2
But these NOx gases in Antarctica are removed along with water by freezing in
polar stratospheric clouds at temperatures below –70ºC as HNO3.3H2O. Furthermore
Chlorine species can be liberated from ClO.NO2 and other chlorine compounds such as
HCl by reactions in the cloud, followed by photo-dissociation to yield ozone destroying
Cl
ClO.NO2 + H2O ----------- HOCl + HNO3
ClO. NO2 + HCl ------------- Cl2 + HNO3
HOCl + hv -------------- HO. + Cl
Cl2 + hv ------------------ Cl + Cl
70
The destruction of O3 by Cl involves an intermediate ClO., which should be
observed if Cl is the cause of O3 depletion. Satellite measurements have confirmed the
presence of ClO. (radical) in both the Arctic Antarctic atmospheres during periods of
severe O3 depletion.
CFC Substitutes
The frequency used CFCs are CFC-11 (CFCl3) and CFC-12 (CF2Cl2). As a
Safeguard against ozone depletion, the recommended CFC substitutes are hydrohalo-
alkanes, compounds containing at least one H atom–HCFCs (Hydro chloro flouoro
carbons) or HFCs (hydrofluorocarbons).
Typical such compounds are HCFC-22 (CHClF2), HCFC-142 (CH3CClF2), HFC –
134a (CH2FCF3) and HFC – 152a (CH3CHF2). Each of such molecules has an H-C bond,
susceptible to attack by HO.. In the troposphere thereby eliminating the compound with
its potential to produce O3 – depleting Cl atom before it reaches the stratosphere. All
these substitutes have low O3 depletion. Potential, short tropospheric so lifetime so that
the compound is destroyed before migrating to the stratosphere.
Human Activity and Meteorology
Our activities have some impact on the climate, although we may not be aware of
it. Meteorology, the science of atmosphere phenomenon, involves the study of physical
parameters such as temperature, wind, moisture and movement of air masses in the
atmosphere. It is, however, affected by the chemical properties of the atmosphere and the
chemical reactions going on it.
The pattern of air circulation governs the dispersal of air pollutants. In this context
temperature inversion has an important role. It happens when a warm air mass is above a
cold air mass, resulting in air stagnation and trapping of air pollutants in localized areas.
Thus occurs when warm air blows over a mountain range and flows over cool air on the
other side of the range. Such a phenomenon is observed in Denver, Colorado, USA, on
the east of the Rocky Mountains.
Human activities are partly responsible for changing the meteorology of the earth.
1. Deforestation and depletion of forest cover.
2. Shifting of surface water and ground water in massive amounts.
3. Release of heat from energy –producing sources.
71
4. Emission of particles and trace gases into the atmosphere.
5. Release of carbon-dioxide into the atmosphere by combustion of fossil fuels.
6. Effect of transportation system on land surface and effect of their emissions upon
the lower and upper atmosphere.
An approximate calculation shows that if the particle loading in the atmosphere
increases by 50%, the average temperature of the earth will decrease by 0.5 to 1ºC. The
same order of temperature drop will result from particle – induced cloud formation. This
partly counterbalances temperature increase due to the greenhouse effect.
Green House effect
When sunlight reaches Earth's surface some is absorbed and warms the earth and
most of the rest is radiated back to the atmosphere at a longer wavelength than the sun
light. Some of these longer wavelengths are absorbed by greenhouse gases in the
atmosphere before they are lost to space. The absorption of this longwave radiant energy
warms the atmosphere. These greenhouse gases act like a mirror and reflect back to the
Earth.Some of the heat energy which would otherwise be lost to space. The reflecting
back of heat energy by the atmosphere is called the "greenhouse effect".
The major natural greenhouse gases are water vapor, which causes about 36-70% of the
greenhouse effect on Earth (not including clouds), carbon dioxide CO2, which causes 9-
26%, methane, which causes 4-9%, and ozone, which causes 3-7%. It is not possible to
state that a certain gas causes a certain percentage of the greenhouse effect, because the
influences of the various gases are not additive. Other greenhouse gases include, but are
not limited to, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons
and chlorofluorocarbons.
72
Fig. 3.11 : Green House Effect
Causes of green house effects
1. Choloroflouro carbon.
2. Carbon dioxide.
3. Methane.
4. Ozone.
5. Nitrogen oxide.
Harmful effects
1. Global temperatures are rising. Observations suggest that the average land surface
temperature has risen 0.45-0.6°C in the last century.
2. Rising global temperatures are expected to raise sea level, change precipitation
and local climate conditions. This could affect forests, crop fields, and water
supplies. It could also harm human's health, birds, fish and ecosystems. Deserts
may expand and some national parks may be affected.
3. Human's health depend largely on local climate. Extreme temperatures can cause
the loss of life. Several diseases only appear in warm areas.
4. People with heart problems are vulnerable in this case.
73
5. Air and water pollution, caused by warm temperatures can harm human health as
well. Higher air temperatures also increase the concentration of ozone at ground
level and this is a harmful pollutant at this level.
6. it can cause problems for people with asthma and other lung diseases. As well as
chest pains, nausea, and pulmonary congestion.
7. Death rates increase during extremely hot days, especially in cities. We can
prevent this by installing air conditionings and by acclimatising ourselves.
8. Diseases spread by insects are more prevalent during the warmer temperatures, for
example malaria, dengue fever, yellow ever, and encephalitis.
9. Global warming could have many impacts on fish and other aquatic species.
Water may become too warm for the fish to inhabit it, but warmer temperatures
may also enable fish in cold oceans to grow more rapidly.
10. Climate changes are likely to have both direct and indirect effects on birds. Higher
temperatures can directly affect their life cycles. The loss of their habitats could
have an indirect effect by making some regions less hospitable to birds.
Controls
1. Reducing the emission of gases those are responsible for green house effect.
2. Less burning crude oil and coal.
3. Use non renewable sources of energy.
4. Government should subsidies solar energy.
Sound Pollutions
In simple terms, noise is unwanted sound. Sound is a form of energy which is
emitted by a vibrating body and on reaching the ear causes the sensation of hearing
through nerves. Sounds produced by all vibrating bodies are not audible. The frequency
limits of audibility are from 20 HZ to 20,000 HZ.
A noise problem generally consists of three inter-related elements- the source, the
receiver and the transmission path. This transmission path is usually the atmosphere
through which the sound is propagated, but can include the structural materials of any
building containing the receiver.
Noise may be continuous or intermittent. Noise may be of high frequency or of
low frequency which is undesired for a normal hearing. For example, the typical cry of a
74
child produces sound, which is mostly unfavourable to normal hearing. Since it is
unwanted sound, we call it noise.
Noise is harmful. Damage caused by noise can range from bursting of eardrum,
permanent hearing loss, cardiac and cardiovascular changes, stress, fatigue, lack of
concentration, deterioration in motor and psychomotor functions, nausea, disturbance of
sleep, headaches, insomnia, and loss of appetite and much other damage is caused.
Pregnant women exposed to high noise levels may be at risk. Psychological
disturbances and emotional distress also occur - violent conduct by persons continuously
exposed to unbearable noise.
The National Physical Laboratory has found that Delhi, Bombay and Calcutta are
the noisiest cities in the world. Even the Election Commission has recognized the
harmful effects of noise and banned use of loudspeakers during the
elections. Widespread ill effects of Noise Pollution such as high blood pressure,
increased acidity and peptic ulcer formation, deafness, mental agitation and disturbance
of sleep generally became known to people in early 1980s. So far Bombay Police Act
1951 and Bombay Municipal Corporation Act 1888 considered noise as just a nuisance,
now it is known as major health hazard. We in India are exposed not only to noises,
common to most countries, but in addition we have to face misuse of loudspeakers, loud
and shrill vehicle horns, noisy crackers, etc, which are firmly put down in most countries.
Sound Pollution
The Human ear receives sound waves which setup oscillation in the ear drum
(tympanic membrane). These oscillation induce movements of three fossils or small
bones in the middle ear behind the ear drum.
The oscillation or sounds are identified and interpreted in the brain, which can
select mixed sounds into different categories – thus it can differentiate speech from
background noises.
The ear has the capacity to analyze sounds into frequency components. A person
with normal hearing has audio range between 20 Hz and 20,000 Hz (1 Hz = 1 cycle/sec. =
unit of frequency).
The audio sense is most sharp in the frequency range 2000-5500 Hz.
Sound waves travel through the medium from the source to the recipient or
listener. The rate of the oscillations of the medium is known as the frequency of the
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sound, the unit being Hertz (Hz) or cycles per second. The frequency is a measure of the
pitch of the sound received by the listener. High frequency imply high pitched sounds
which are more irritating to the indeciduate than low frequencies. The second parameter
of sound is sound pressure, which is measured in Newtons per sq. meter (N/m2). The third
parameter of sound is its intensity, expressed in watts per sq. meter (W/m2) i.e., the
quantum of sound energy that flows through unit area of the medium is unit time. Sound
is also sometimes expressed in terms of loudness.
The common scientific acoustic unit is the Decibel (dB). It is not an absolute
physical unit like volt, meter etc., but it is a ratio expressed as a logarithacic scale relative
to a reference sound pressure level.
1 decibel (dB) = 10 log10 intensity measure/reference intensity.
The reference intensity used is the threshold of hearing which means sound which
can be first heard at a sound pressure of 2x10–5 Newton m2
or sound intensity of 10–12
watts m2.
The dB scale is limited in the sense that it is not related to the human ear
frequency response and environmental circumstances in which noise is produced. This
has necessitated design of noise measuring meters which reduce the response to low and
very high frequency, characteristics of Human ear capacity.
These meters record the dBA scale which is commonly used for measurement of
general noise levels.
Intensity Wm2–
Pressure (un2–
) dB Sound source
100 200,000 200 Satum rocket takeoff
1.0 20 120 Boiler shop
10–2
2.0 100 Siren at 5 m.
10–4
0.2 80 Heavy machinery workshop
10–6
0.02 60 Normal conversation at 1 m.
10–8
0.002 40 Public library
10–10
2 x 10–5
0 Threshold of hearing
Noise Classification
1. Transport Noise.
2. Occupational Noise.
3. Neighbourhood Noise.
The Central Pollution Board (India) has prescribed permissible sound levels for
cities divided into four zones :-
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Table 3.1
ZONES DAY NIGHT
Industrial 75 dB(A) 65 dB(A)
Commercial 65 dB(A) 55 dB(A)
Residential 50 dB(A) 45 dB(A)
Sensitive areas upto 100m.
around hospitals
educational institutions.
50 dB(A) 40 dB(A)
Occupational noise levels are:
Table 3.2
PARTICULARS dB
Steel Plate riveting 130
Oxygen Torch 126
Boiler Maker‘s shop 120
Textile loom 112
Circular Saw 110
Farm Tractor 103
Newspaper press 101
Bench Lathe 95
Milling Machine 90
High Speed Drill 85
Key Press Machine 82
Super Market 60 (dBA)
Noise Pollution Hazards
Noise is air-borne mechanical energy shrinking the Human eardrum while 65
dB(A) is the noise level for conversation heard at a distance of one meter, 125 dB(A)
gives the sensation of plain in the ear and 150 dB(A) might kill a Human being.
In addition to progressive hearing loss there may be instantaneous damage or
aquatic trauma.
77
Sonic booms or over-pressure from supersonic air liners are impulse type noise,
which can have hazardous effects on the ears.
High frequencies or ultrasonic sound above the normal audible range can affect
the semicircular canals of the inner ear and make one suffer from nausea and dizziness.
Again very low frequency noise can produce resonance in the body organs giving
the effects of reduced heart beat, variants in blood pressure and breathing difficulties.
Mid-audible band frequencies can generate resonance in the skull and hence affect
the brain and nervous system having inspect on thinking and co-ordination of the limbs.
Moderate vibration can lead to pain, and cyanosis (blue-colouration) of fingers
while severe vibration results in damage to bones and joints in the hands with swelling
and stiffness.
One exposed to the constant tapping of a typewriter in office or the noise of a
generator on the streets runs the risk of physical and mental damage.
Children exposed to excessive noise show signs of behavioral disorders which in
later age manifest themselves in destructive nature.
Electroencephalogram records reveal distorted brainwaves and blurry of vision at
a level of 125 dBA.
The impact of noise pollution on migratory birds is exemplified in Alipore Zoo at
Kolkutta. The high-rise buildings near the Alipore Zoological Garden and the resultant
noise pollution is discouraging the annual visit of the migratory birds to the lake of the
zoo.
Sources of Noises
The noise pollution has two sources, i.e. industrial and non- industrial. The
industrial source includes the noise from various industries and big machines working at a
very high speed and high noise intensity. Non- industrial source of noise includes the
noise created by transport/vehicular traffic and the neighborhood noise generated by
various noise pollution can also be divided in the categories namely-natural and
manmade. Most leading noise sources will fall into the following categories: roads traffic,
aircraft, railroads, construction, industry, noise in buildings and consumer products.
78
1. Road Traffic Noise
In the city, the main sources of traffic noise are the motors and exhaust system of
autos, smaller trucks, buses, and motorcycles. This type of noise can be
augmented by narrow streets and tall buildings.
2. Air Craft Noise
The problem of low flying military aircraft has added a new dimension to
community annoyance, as the nation seeks to improve its nap-of the- earth aircraft
operations over wilderness areas and other areas previously unaffected by aircraft
noise has claimed national attention over recent years.
3. Noise from railroads
The noise from locomotive engines, horns and whistles, and switching and
shunting operation in rail yards can impact neighboring communities and railroad
workers.
4. Construction Noise
The noise from the construction of highways, city streets and buildings is a major
contributor to the urban scene. Construction noise sources include pneumatic
hammers, air compressors, bulldozers, loaders, dump trucks and pavement
breakers.
5. Noise in Industry
Although industrial noise is one of the less prevalent community noise problems,
neighbors of noisy manufacturing plants can be disturbed by sources such as fans,
motors and compressors mounted on the outside of buildings. Interior noise can
also be transmitted to the community through open windows and doors, and even
through building walls. These interior noise sources have significant impacts on
industrial workers, among whom noise- induced hearing loss is unfortunately
common.
6. Noise in building
Apartment dwellers are often annoyed by noise in their homes, especially when
the building is not well designed and constructed. In this case, internal building
noise from plumbing, boilers, generators, air conditioners and fans can be audible
and annoying. Improperly insulated walls and ceilings can reveal the sound off-
amplified music, voices, footfalls and noisy activities from neighbouring units.
External noise from emergency vehicles, traffic, refuse collection, and other city
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noises can be a problem for urban residents, especially when windows are open or
insufficiently glazed.
7. Noise from Consumer products
Certain household equipment, such as vacuum cleaners and some kitchen
appliances have been and continue to be noisemakers, although their contribution
to the daily noise dose is usually not very large.
Harmful effects
Annoyance: It creates annoyance to the receptors due to sound level fluctuations.
The aperiodic sound due to its irregular occurrences causes displeasure to hearing
and causes annoyance.
Physiological effects: The physiological features like breathing amplitude, blood
pressure, heart-beat rate, pulse rate, blood cholesterol are affected.
Loss of hearing: Long exposure to high sound levels cause loss of hearing. This
is mostly unnoticed, but has an adverse impact on hearing function.
Human performance: The working performance of workers/human will be
affected as they'll be losing their concentration.
Nervous system: It causes pain, ringing in the ears, feeling of tiredness, thereby
affecting the functioning of human system.
Sleeplessness: It affects the sleeping there by inducing the people to become
restless and lose concentration and presence of mind during their activities.
Damage to material: The buildings and materials may get damaged by exposure
to infrasonic / ultrasonic waves and even get collapsed.
Control
The noise pollution can be controlled at the source of generation itself by
employing techniques like-
1. Reducing the noise levels from domestic sectors: The domestic noise coming
from radio, tape recorders, television sets, mixers, washing machines, cooking
operations can be minimised by their selective and judicious operation. By usage
of carpets or any absorbing material, the noise generated from felling of items in
house can be minimised.
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2. Maintenance of automobiles: Regular servicing and tuning of vehicles will
reduce the noise levels. Fixing of silencers to automobiles, two wheelers etc., will
reduce the noise levels.
3. Control over vibrations: The vibrations of materials may be controlled using
proper foundations, rubber padding etc. to reduce the noise levels caused by
vibrations.
4. Low voice speaking: Speaking at low voices enough for communication reduces
the excess noise levels.
5. Prohibition on usage of loud speakers: By not permitting the usage of
loudspeakers in the habitant zones except for important functions. Now-a-days,
the Urban Administration of the metro cities in India, is becoming stringent on
usage of loudspeakers.
6. Selection of machinery: Optimum selection of machinery tools or equipment
reduces excess noise levels. For example selection of chairs, or selection of certain
machinery/equipment which generate less noise (sound) due to its superior
technology etc. is also an important factor in noise minimization strategy.
7. Maintenance of machines: Proper lubrication and maintenance of machines,
vehicles etc. will reduce noise levels. For example, it is a common experience that
many parts of a vehicle will become loose while on a rugged path of journey. If
these loose parts are not properly fitted, they will generate noise and cause
annoyance to the driver/passenger. Similarly in the case of machines, proper
handling and regular maintenance is essential not only for noise control but also to
improve the life of machine.
8. Design of building: The design of the building incorporating the use of suitable
noise absorbing material for wall/door/window/ceiling will reduce the noise levels.
9. Green belt development: Green belt development can attenuate the sound levels.
The degree of attenuation varies with species of greenbelt. The statutory
regulations direct the industry to develop greenbelt four times the built-up area for
attenuation of various atmospheric pollutants, including noise.
10. Using protection equipment: The various steps involved in the noise
management strategy are illustrated. Protective equipment usage is the ultimate
step in noise control technology.
11. Exposure reduction: Persons who are working under such conditions will be
exposed to occupational health hazards. The schedule of the workers should be
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planned in such a way that, they should not be over exposed to the high noise
levels.
12. Hearing protection: Equipment like earmuffs, ear plugs etc. are the commonly
used devices for hearing protection. Attenuation provided by ear-muffs vary
widely in respect to their size, shape, seal material etc.
Measurement
A decibel is the standard for the measurement of noise. The zero on a decibel
scale is at the threshold of hearing, the lowest sound pressure that can be heard, on the
scale according to Smith, 20 db is whisper, 40 db the noise in a quiet office, 60 db is
normal conversation, 80 db is the level at which sound becomes physically painful.
The Noise quantum of some of the cities in our country indicate their pitch in
decibel in the nosiest areas of corresponding cities, e.g. Delhi- 80 db, Kolkata -
87,Bombay-85, Chennai-89 db etc.
WATER POLLUTION
Water Pollution
Water is an essential constituent for all types of life on earth. Next to air, water is
the most important substance for the existence of life on the earth. The pure water is one
which is free from impurities. Today water resources have been the most exploited
natural systems since man‘s existence on the earth. Pollution of water resources are
increasing due to rapid population growth, industrialization, urbanization, modernization
and wide spread human activities. Ground water, river, seas, lakes, ponds and streams are
founding it more and more difficult to escape from pollution.
Water pollution can be defined as the presence of some foreign substances or
impurities in water and by which lowing the water quality and making it unfit for use.
Thus ―Any physical or chemical changes in surface water or underground water that can
adversely affect living organisms is called water pollution.‖ The term water pollution is
also derived from latin word ‗pollus‘ which means before ‗wash‘. Before washing, water
contains impurities and hence the term water pollution is indicated contamination or
making foul the natural water resources like river, pond etc.
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Types of water Pollution – On the basis of nature of impurities, water pollution can be
classified into following four categories –
1. Physical Pollution.
2. Chemical Pollution.
3. Biological Pollution.
4. Physiological Pollution.
1. Physical Pollution – Physical pollution of water is due to the change in physical
properties of water such as colour, odour, taste, turbidity and thermal properties.
Colour of water is changed by industrial coloured waste materials like paper and
pulp, textile, and tanneries etc. Change of colour in water is harmful because it is
due to toxic chemicals.
Taste and odour is produced in water due to various salts, Fe, Mn, H2S,
Chlorine, Phenols and Unsaturated Hydrocarbons. Some micro organism like
bacteria and algae can also cause the taste and odour in water. Industrial water
containing Fe, Mn, free chlorine, phenols create bed taste and odour in water.
Decomposed organic matter, algae, fungi, bacteria and pathogens also cause bad
taste in water.
Turbidity of water comes from colloidal matter, fine suspended particles
and by soil erosion. This water becomes unsuitable for domestic and industrial
uses because it contains Fe, Mn, Co, Ni, Pb, Sb, Bi, etc which many cause stain on
cloths, sinks and baths.
The cooling water use in thermal power plants and nuclear power plants
discharges unutilized heat into the water which causes the depletion of dissolved
oxygen (D.O.) level.
Foam of water is also included in this category. The pollution of water by
foam may be serious because water containing foam is likely to carry suspended
matter and also includes pathogenic bacteria.
2. Chemical Pollution – Chemical Pollution of water is due to the change in
chemical properties of water like acidity, alkalinity or pH of water etc. It is caused
by presence of organic and inorganic chemicals, toxic dissolved and suspended
inorganic and organic compounds and gases like O2 or CO2. Organic pollutants
include fats, proteins and carbohydrates discharged from domestic and industrial
wastes. Inorganic pollution is caused by water of industrial use like fertilizers, gas
liquors, coke ovens, alkali producing industries, etc. toxic inorganic pollutants are
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free chlorine, chloramines, H2S, NH3 and salts of many metals such as Pb, Ni, Cu,
Hg, AS, Cr, U, Ba etc.
3. Biological Pollution – Biological pollution of water is mainly due to presence of
pathogenic bacteria, fungi, protozoa, viruses, parasitic worms, etc. The main
sources of biological pollutants are domestic sewage and industrial wastes, solid/
liquid human excreta and decomposable organic matter such as vegetables, fruits
etc. Contaminated water supplies frequently create infections of the intestinal
tract, polio and hepatitis, cholera etc.
4. Physiological Pollution - Physiological Pollution of water is caused by some
chemical agents like chlorine, sulphurdioxide, hydrogen sulphide, ketones,
phenols, amines, mercaptans and hydroxy benzene. Actually chlorine converts the
phenol to ortho or para chloro phenol which tastes like medicine and gives
offensive odour.
Sources of water pollution - Sources of water pollution can be divided into two
categories-
1. Point Sources.
2. Non Point Sources.
1. Point Sources – These sources are measurable discharge points. These are easily
identifiable at a single location. The point sources are industries, municipal
sewage, treatment plants, combined sewer overflow and raw sewage discharges.
This type of pollution sources can be controlled.
2. Non Point sources – These sources are diffused (plume) sources. These are the
sources of generalized discharge of water whose location can not be identified.
Ex. run-off from agriculture lands, forestry, mining, construction, urban off,
hydrologic modification and residual waste. This type of discharge of water
cannot be easily controlled.
Types of Water Pollutants and Their Adverse Effects
The Substances which are responsible for water pollution are known as water
pollutants. These pollutants can be organic, inorganic, radioactive, oxygen demanding
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wastes etc. These pollutants give adverse effect on environment. Various water pollutants
may be divided into following categories-
1. Organic pollutants.
2. Inorganic pollutants.
3. Suspended solids and sediments.
4. Radioactive pollutants.
5. Thermal pollutants.
1. Organic Pollutants – Most of the substances of which living things are composed
are organic compounds. The main source is food stuff (eg. Proteins,
carbohydrates, fats etc) a number of materials and substances necessary for
modern life style (e.g. cotton, petroleum, rubber, antibiotics etc) are organic
compounds. Their presence in water is not desirable as they impart taste, odour
and colour to water and some of them may be toxic and carcinogenic also. These
organic pollutants enter into the water system through domestic sewage, industrial
waste from paper mill, water from slughter house, meat packing plants, food
processing plants, run off from crop lands and decomposition products of organic
compounds. These pollutants may be suspended or dissolved from in water.
Suspended organic matter is due to presence of certain industrial waste or
vegetable or animals. Vegetable are in the form of algae, decayed leaves, fungi
etc, they impart acidity, green or brown colour and teste to water. Dead animals
and insects are responsible for growth of bacteria in water. This water contains
large quantity of albuminoidal ammonia, free ammonia, chlorides and different
types of bacteria and viruses. Organic pollutants may be divided as –
1. Natural organic pollutants - They came in water from decomposition of
naturally occurring organic compounds like leaves, plants, dead animals etc.
Various types of aquatic micro-organisms releasing organic compounds into a
water body through their metabolic processes also comes in this category.
All these wastes require dissolved oxygen (D.O.) for their degradation which
depletes the D.O. level of water. This reduction in D.O. level is harmful for
aquatic organization.
2. Sewage – Municipal and domestic sewage and effluents such as food processing
unit, paper mills, tanneries etc. contains a large number of organic pollutants
sewage makes water anesthetic , totally unfit for drinking domestic use sewage
contains various oxidizable and fermentable matter which cause lowing of
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anesthetic, totally unfit for drinking and domestic sewage. which affects the
aquatic for severely. Lowering of D.O. in also come objectionable odour in water.
When D.O. reaches 4-5 ppm fisher starts to die suspended matter of sewage create
a blanket on the water thereby interfering in the spawning of fish and reduces the
aquatic biota.
3. Industrial effluents- Industrial effluents are also contain various organic
compounds like tetrachloride (used as fire extinguisher), tetrachloroethylene (used
as solvent), pesticides, herbicides and many other chemicals use in industrial
process such as ethylbenzene, styrene and toluene. Most of these chemicals are
toxic to plants, animals and human beings. PCB‘s and dioxins cause cancer.
Industrial effluents containing methyl mercaptan and pentachloro phenol lowers
the photosynthetic rate of aquatic plants by hindering sunlight penetration.
Disinfectants added in water to kill algae and bacteria may persists in water bodies
and may cause mortality of fish, planktons and diatoms.
4. Synthetic organic pollutants - They are the man made materials such as
pesticides, detergents, food additives, insecticides, paints, elastomers, plasticizers,
plastics and other industrial chemicals. Most of these are toxic to plants, animals
and humans. DDT is highly stable and can persist for a long time in the
environment. It enters into the food chain becomes highly dangerous. It cause
heart, kidney etc. diseases in man. PCBs (Polychlorinated bi phenyls) are
generally used as dielectrics, lubricants and plasticizers are similar to DDT and
cause several physiological disturbances.
5. Disease-causing pollutants - They are pathogenic micro organisms which enters
into the water bodies through waste water coming from hotels, restaurants,
residential areas, human faeces matters, animal wastes, etc. They include bacteria,
viruses, protozoa, algae and helminthes. These pathogens are very dangerous for
human health and life. Various health problems caused by these pathogens are
listed below in Table 4.
Table 4.1 Health Problems Caused by Various Pathogens
S.No. Group/Name of Pathogen Disease Caused
(1) Bacteria
a. Salmonella typhosa.
Typhoid fever
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b. Salmonella Schottmulleri.
c. Vibrio Cholerae.
d. Enteropathogenic E.Coli.
e. Shigella.
f. Mycobacterium tuberculosis.
g. Other mycobacteria.
Gastroenteritis
Cholera
Gastroenteritis
Bacillary dysentery
Tuberculosis
Pulmonary illness
(2) Viruses
a. Polioviruses.
b. Coxsackie Viruses A and B.
c. Reoviruses.
d. Hepatitis A viruses.
Poliomoyelitis
Aseptic meningitis
Upper respiratory and
gastrointestinal illness
Hepatitis
(3) Protozoa
a. Balantidium Coli.
b. Entamoeba Histolytica.
c. Giardia lamblia.
Dysentery
Amoebic dysentery
Giardiasis
(4) Algae (blue green)
a. Anabaena flos-aquae.
b. Microcystis aeruginosa.
c. Schizothrix calciola.
Gastroenteritis
Gastroenteritis
Gastroenteritis
(5) Helminths
a. Dracunculus medinensis.
b. Echinococcus.
c. Schistosoma.
Dracontiasis
Echinococcosis
Schistosomiasis
6. Oil - Oil is a naturally occurring mixture of thousands of different hydrocarbon
compounds. Water pollution due to oil takes place because of oil spills from cargo
oil tankers on the seas, losses during off shore exploration and production of oil,
accidental fires in ships and oil tankers, and leakage from oil pipe lines. Insoluble
oils spreads over the water surface, and forms a layer which restricts light
transmission through surface waters, thereby reducing the photosynthesis of
marine plants. This reduces the D.O. level and cause a deleterious effect on
marine organisms. While soluble oil forms a milky emulsion which is quite stable
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and non-destroyable. These emulsion coat the gills of fish affecting their
respiration.
7. Organic pollutants - It can also be divided into two categories-
(i) Biodegradable (ii) Non-biodegradable
Biodegradable Organics - The organic compounds which degrade very rapidly in
a natural environment or man-made environment are called biodegradable
organics. Biodegradable organic pollutants include proteins, fats, carbohydrates,
polymers, resins, coal, oil and various other organic substances found in domestic
and industrial wastes.
Impact of Biodegradable Organics in Water - The most common biodegradable
organics are fats, proteins and carbohydrates. They are introduced into the water
through domestic sewage, industrial wastes from paper mills and tanneries, waste
from slaughter house, meat packing plants and food processing plants. They can
be either in the suspended from or dissolved from. Suspended vegetables such as
algae, decayed leaves, fungi, etc., impact acidity, green or brown colour and taste
to water. Suspended animals such as insects and dead animals are responsible for
the growth of bacteria and even viruses. This water contains large quantity of
albuminoidal ammonia, but small quantity of free ammonia and chlorides.
Thermal decomposition of fats, oils and glycerol forms various aldehydes
such as acetaldehyde, benzaldehyde, formaldehyde, furfural and vanillin, etc.
These compounds cause odour in water, inhibit algal growth and are toxic to fish
and other aquatic animals.
(i) Non-biodegradabie Organics - The organic compounds which do not degrade
naturally or degrade at a very slow rate are termed as non-biodegradable organics.
They remains in the aquatic ecosystem for a long time. They are pesticides,
fungicides, herbicides, insecticides, rodenticides etc. Theses non-biodegradable
organics are toxic and once they found their way from crops to nearby water
sources can cause a serious pollution problem.
8. Inorganic Pollutants - Inorganic water pollutants consist inorganic salts, metallic
compounds and complexes, mineral acids, organo metallic compounds and poly
phosphates detergents. Inorganic pollutants may be categorized in following
categories-
(i) Acids and Alkalis - Industries manufacturing hydrochloric, nitric, sulphuric,
phosphoric acids, sulphur dioxide, oxides of nitrogen, chlorine, ammonia and
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bases of Na, K, Ca etc., discharge a huge amount of acids and alkalis in water
system. These acids and alkalies destroy the bacteria and other micro organisms in
water.
(ii) Toxic Inorganic Compound - These are derived from industrial wastes of
industries producing fertilizers, coke ovens, gas liquors, alkalis, etc. They includes
salts containing anions of carbonate, acetate, nitrate, nitrite, fluoride, chloride,
sulphate, phosphate and sulphides of Cu, Cd, Zn, Mn, Pd, Sn, Fe and As etc.
Toxic compounds also include free chlorine, H2S, NH3.
(iii) Toxic Metals – Traces of heavy metals such as Hg, Cd, Pb, As Co, Mn, Fe and
Cr have deleterious effects on aquatic ecosystems and human health. They are
introduced into the water bodies from industrial processes, domestic sewage land
run off and fossil fuel burning. Detrimental effects of some toxic metals are
discussed below.
Mercury (Hg) is highly toxic, its compounds which are very volatile or
soluble cause potential hazards to man. It cause well known Minamata disease.
Lead (Pb) comes in water from steel and paint industries burning of
gasoline (containing TEL). Lead when enters into the food chain may cause death
of children and of infants due to brain damage. In adults it can cause anemia,
kidney, mental retardation, abnormal pregnancy, etc.
Cadmium even in concentrations less than 1 mg /l it is toxic. It presents in
water as suspended particles of hydroxides sulphates, etc. Cd can accumulate in
lever and kidney and can cause hypertension, emphysema, kidney damage and
weakening of bones.
9. Suspended solids and sediments - Soil erosion by natural and anthropogenic
processes (such as mining agricultural and constructional activities) deposits a
large amount of sediments in water. Industrial effluents contains various organic
and inorganic particles or immiscible liquids remains suspended in water and
effects its turbidity. The suspended solids effects taste, odour and colour of water
while bottom sediment can cause anaerobic conditions. Bottom sediments are
deposition of trace elements and heavy metal. These particles reduce direct
penetration of sunlight which reduces photosynthesis in aquatic plants and hence
decreases the D.O. in water. Toxic metals like Hg, Cd, Pb, can attack sulphur
bond in enzymes of aquatic and cause immobilizing effect.
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10. Radioactive pollutants - Radioactive pollutants enter into water bodies from
nuclear power plants, nuclear reactors, nuclear installations, fission and fusion
product nuclear tests etc. Extremely toxic radioactive Pu, Np, Cm, Cs, Zr, Ru, etc.
are produced from neutron bombardment of atomic fuel. Though all of radioactive
pollutants are carcinogenic the radio nuclides of most concern are Uranium 235,
238, Radium 226 and 228, radon and Thorium 230 and 232. In aquatic animals
radiation damage makes cell permeable membranes, which results in temporary or
permanent injury in them. The radioactive pollutant deactivate enzymes by
breaking S-H-S hydrogen bonds, due to this enzyme inhibition, cell division may
be stopped.
11. Thermal pollutants - Water is the most commonly used coolant in various
industries because of its low cost and good thermal properties. This heated water
when discharged to water bodies causes thermal pollution. These pollutant include
waste from atomic, nuclear and thermal power plants. The discharge of this
unutilized heat adversely affects the aquatic environment. The amount of
dissolved oxygen in water decreases with the rise in temperature, while activity of
biological life is more at higher temperature hence requires more D.O. This may
be fatal for aquatic life. Some animals and aquatic animals are killed outright by
hot water. It cause direct fish mortality due to failure of respiratory or nervous
system. High temperature accelerates the activities of pathogenic organisms,
which makes pathogens more virulent and fishes less resistant. It causes rapid
settling of sediments which affects the aquatic food supply.
Eutrophication
The phenomenon of becoming rivers and lakes highly productive is known as
eutrophication. The word eutriphication has been derived from the Greek word eutrophou
means well nourished or enriched. Entrophication of a water body may takes place by
both natural and anthropogenic sources.
Ponds and lakes during their early stage of formation are relatively barren and
nutrient deficient, thus supporting no or very poor aquatic life. In this state water bodies
are known as oligotrophic. Nutrient content of water body increases slowly by natural
processes such as surface run-off, organic debris plant's excreta and marine organisms
excreta. Bacteria and blue green algae fix atmospheric N and P in bottom rocks becomes
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soluble in water due to microbial activity. At this stage a moderate population of plants
animals and microbes develops in the system, which further increases with nutrient
enrichment. This process of natural eutrophication is accelerated by addition of domestic
and industrial sewage and agricultural run-off (mainly fertilizers containing phosphates
and nitrates). This accelerates the growth of algae and other water plants and the whole
system becomes highly productive i.e. eutrophic. Due to this accelerated eutrophication
water system turns into a shallow muddy pond, then to a marsh and finally into a dry
land.
CHARACTERISTIC OF WASTE WATER
Physical characteristics -Various physical characteristics of waste water are discussed
below.-
(i) Turbidity – Sewage in normally turbid resembling dirty dish water or waste from
baths, having other floating matter like pieces of paper, cigarette-ends, match –
sticks, greases, fruit skins etc. Turbidity of waste water shows that some amount
of solid matter is present in suspension it also indicates stag of sewage, the
turbidity increases as sewage becomes stronger.
(ii) Colour and Odour :- Colour and odour indicates the condition of sewage as it is
fresh stale or septic. Colour of fresh domestic sewage is grey. If the colour is
black or dark brown it indicate stale or septic sewage. Fresh sewage is practically
odourless. It starts to give offensive smell of hydrogen sulphide after 2 to 6 hours
when it become stale.
(iii) Temperature – The temperature of sewage is slightly higher than ordinary water.
The temperature effect on the biological activity of bacteria presents in sewage.
The average temperature of sewage is 20 to 25oC which is an ideal temperature for
the biological activities.
(iv) Solids – Generally sewage contains 99.9% of water and 0.1% solids in the form
of suspended solid dissolved soild colloidal solid and settleable solids. Suspended
solids are those solids which remains floating in sewage dissolved solids are those
which remains dissolved in sewage. Colloidal solid are finely divided solids
remaining either in solution or in suspension. Settles solids are that portion of
solid matter which settles out, if sewage is remain undisturbed for a period of 2
hours.
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Chemical characteristics - Various chemical characteristics of waste water are discussed
below-
(i) pH value – pH value determine whether sewage is acidic or alkaline. Fresh
sewage is generally alkaline having pH value in the range of 7.3 - 7.5 . But after
some time, its pH value lowers due to formation of acids by bacterial action.
However after oxidation, when sewage become relatively stable, it again
becomes alkaline. pH value of sewage helps in determination of amount of
coagulant and disinfectant needed and in its biological treatment.
(ii) Dissolved oxygen (D.O) – Oxygen is one of the most commonly dissolved gases
in water. Dissolved Oxygen (D.O) represents the amount of oxygen dissolved in
water. Oxygen can be dissolved in water through-
(a) Atmosphere , by natural aeration.
(b) Photosynthesis, by algae.
(c) Mechanical equipments during treatment of water.
Natural water always contains some amount of oxygen dissolved in it. The
solubility of oxygen is directly proportional to the pressure and inversely proportional to
the temperature. Solubility of oxygen also decreases with amount of salt contain in water.
The measurement of D.O. helps to determine purity of water. Clean surface waters
are generally saturated with D.O. while sewage generally has no D.O. presence of D.O. in
sewage indicates either it is fresh or its considerable oxidation has occurred due to sewage
treatment methods.
Dissolved oxygen (D.O.) is essential for the support of fish and other aquatic life
in water bodies. D.O. content in water can be determine by using Winkler‘ methods,
which is an oxidation- reduction process carried out chemically to liberate iodine in
amount equivalent to the dissolved oxygen.
All the wastes undergo decomposition and degredation due to bacterial activity
and deplete the dissolved oxygen (D.O.) from the water D.O. is a fundamental
requirement for the maintenance of aquatic life. Decrease in D.O. is an indication of
water pollution. Depletion of D.O. is disastrous as it destroys fish as well as other aquatic
animals including their habitat.
(iii) Biochemical oxygen demand (BOD) - BOD represents the quantity of oxygen
required by bacteria and other micro-organisms during the biochemical
degradation and transformation of organic matter present in waste under aerobic
conditions.
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The biochemical oxygen demand is a measure of oxygen utilized by the
micro-organisms during the oxidation of organic materials. BOD is a direct and
the most widely known measure for oxygen requirements and an indirect measure
of biodegradable organic matter. Inspite of its inherent limitations BOD test is still
valued as the best test for assigning organic pollution, it is considered as the major
characteristic used in stream pollution control. It gives very valuable information
regarding the purification capacity of streams and serves as a guideline for the
regulatory authorities to check the quality of effluent discharged into water bodies.
The BOD test essentially consists of measurement of dissolved oxygen
content of the sample before and after incubation at 200C for 5 days. if the sample
does not contain oxygen is supplied to it and BOD is measured.
= post O2/ million parts of sample
Limitations of BOD Test
1. Before BOD test the pre - treatment of sewage is necessary it is also contains toxic
wastes.
2. The test is applicable only in the case of biodegradable organic matter.
3. A high concentration of active bacteria is necessary to be present in the sample of
sewage.
4. Before applying BOD test the effects of nitrifying organisms are to be reduced.
5. The time required for the test is long as well as arbitrary.
6. There is no validity of the test after the soluble organic matter present in the
sewage sample is utilized.
Chemical oxygen demand (COD)
The chemical oxygen demand is a measurement of oxygen equivalent to that
portion of organic matter present is the waste-water sample that is susceptible to
oxidation by potassium dicromate.
The COD test is carried out to measure the content of organic matter of sewage
and natural waters. The test gives a good idea of the amount of organic matter present in a
stream.
The test involves the oxidation of organic matter in the sample with a known
excess of K2 Cr2 O7 in a 50% H2SO4 solution in the presence of AgSO4 (as catalyst) and
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HgSO4 (to eliminate interference to chlorine). It is then boiled for two hours. It is then
cooled and the excess dichromate is measured by titrating with a standard solution of
ferrous ammonium sulphate.
Sample + K2Cr2O7 AgSO4 (Catalyst) CO2 + Water + Ammonia
(From (in excess) HgSO4 (for suppression of chlorine)
Sewage) H2SO4 (for acidic medium)
K2Cr2O7 + Ferrous Ammonium Titration Salt
(remaining) Sulphate
(of normality N)
COD is measured (calculated) by the formula
COD in mg/L = (V1-V2)N x 8 x 100
X
Where V1 and V2 are volumes of Ferrous Ammouium Sulphate (of Normality N and X is
the volume of sample taken).
WASTE WATER TREATMENT
The objective of waste water treatment is removing the pollutants from water
before discharging it into a steam. After the treatment of waste water it can be reused or
discharged into a receiving stream. The waste water treatment processes are expensive
and depend upon the quality of water required. The waste water treatment processes are
usually classified as -
1. Primary Treatment (Physical treatment).
2. Secondary Treatment (Biological treatment).
3. Tertiary Treatment (Chemical treatment).
Primary treatment (Physical treatment) - It is a mechanical process in which waste
water passes through a screen for filtering sticks, stones and floating or suspended
materials. Suspended solids of waste water are settled down in the form of sludge in the
sedimentation tank. By this treatment 60% of suspended solid, 30% of oxygen demanding
waste, 20% of nitrogen compounds, 10% of phosphorus compounds are removed. This
process involves the following steps:
1. Screening. This process is used for removing suspended impurities. Grit- settling
chamber is used after screening. Removal of gross solids is generally
accomplished by passing waste water through mixed moving screens. These
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screens are present in the different forms such as screen hand raked screen, drum
screen etc. the raw water is passed through screen, having large number of holes
when floating matters retained by them. (fig. 4.1)
2. Sedimentation – Gravitational settling is employed to separate settle able solids.
The process is carried out in a large tank where the solids settle at the bottom in
the form of a sludge is removed either by various sections or mechanical means.
The clear liquid formed is known as the overflow which done not contain any
settle able solid.
Fig. 4.1 : Grit Chamber
Sedimentation is a process of allowing water to stand undisturbed in high tanks,
about 5 m deep, when most of the suspended particles settle down at the bottom, due to
the force of gravity. The clear supernatant water is then drawn from tanks with the help of
pumps. The retention period in sedimentation tank is from 2-6 hrs. When water contains
fine clay particle and colloidal matter, it becomes necessary to apply sedimentation with
coagulation for removing such impurities.
Fig. 4.2 : Sedimentation Tank
Parallel bar
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Sedimentation tanks
Sedimentation operation in waste treatment applications may be carried out in
rectangular, horizontal flow, circular radial flow or vertical basins. In first types tanks,
feed is introduced at one end along the width of the tank and the overflow is collected at
the surface. An endless conveyor scrapes the floating material into a screen through while
it also pushes the settled solids into a sludge hopper. The settling of particles in a
suspension depends upon their concentration and their flocculating properties.
1. Flotation - Flotation process is used for the treatment of industrial waste water. It
contains finely divided suspended solids and oily matter. Sedimentation process is not
allowed for all small particles whose densities are close to water. In this case the effluent
is aerated and the solid particles float to the surface and can be easily removed. Chemical
coagulants are used to help in this process.
Fig. 4.3 : Primary treatment
Secondary treatment (Biological treatment) - In a biological treatment, aerobic bacteria
is used to remove biodegradable organic wastes. It remove up to 90% of the oxygen
demanding wastes. The degraded material settles out in secondary settling tanks. The
96
sediment containing the microbial growths and their by product is called secondary
sludge or activated sludge. The treated water is then discharge in the nearby water bodies.
Some of the sludge is returned to aeration tanks where it is recycled with incoming waste.
Aerobic and anaerobic biological treatment are used to complete biological treatment.
Fig. 4.4 : Secondary treatment
Biological Treatment
Aerobic treatment Anaerobic treatment
Oxidation Aerated Trickling Activated Single digester Septic tanks
Pond lagoon filter sludge
(1) Aerobic Treatment – In this process micro- organism like bacteria, algae, fungi
etc. consume organic substances as a food and converted into biomass. In the
waste water different types of matters are present hence they need different
microbes for their proper treatment. Aerobic biological treatment may be
completed by the following process:
(a) Oxidation pond - Waste water is purified with the help of algae and aerobic
bacteria in the oxidation pond. In this pond aerobic bacteria decompose organic
matter where as algae consume the food and decrease BOD of waste water by
release of oxygen gas. This pond is not useful for Indian climate.
(b) Aerated lagoon - Effluents from primary treatment process are collected. Aerated
lagoon are aerated by floating aerators. Floating aerator maintains aerobic
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environment for preventing the biomass to settle. By this method good flocculent
sludge is formed and 90% BOD can be removed. This process is oldest process.
Fig. 4.5 : Aerated lagoons
(c) Trickling filter - This consists bed of coarse material (stones, salts, PVC). The
waste water is distributed overt the surface of stone by a rotating arm. The filter is
arranged in a fashion by which air can entire at the bottom. Aerobic bacteria
purify sewage by forming a bacterial film around the particles of the filtering
media. Sufficient quantity of oxygen supplied for providing suitable aeration to
the filter. The microbial film formed is very sensitive to temperature and the
efficiency of the filter depends upon the composition of the waste, pH depth of the
filter etc. The effluent obtained from this is used by the secondary sedimentation
tank. Filter are effectively used for the treatment of dairy, distillery, food
processing, slaughter house, pharmaceutical wastes etc. The effluent of filter is
nitrified and removes about 70-80% of BOD.
Disadvantage
1. Decrease in efficiency by increasing load of waste water.
2. Cost of construction.
3. Need for ventilation ducts for the under-drain system.
(d) Activated Sludge process – In this process a mixture of waste water and
microorganisms are agitated and aerated. By this process an active mass of
microbes is formed which is called activated sludge. The aerobic bacteria bring
about biological digestion of the waste into CO2 and H2O, the effluent from the
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aerated tank is separated from the sludge by setting and discharged from it. Some
part of this sludge is recycled to the aerated tank for further microbial process. A
BOD removed to the extent of 90-95% can be achieved by this process. It is best
method for biological treatment.
Fig. 4.6 : Trickling filter
Advantage
1. By this process no fly or odour nuisance occurs.
2. Minimum area required for this process.
3. It gives clear sparkling treated liquid.
4. By this loss of heat is minimum.
Fig. 4.7 Activated sludge plant
Disadvantage
1. It needs maintenance and careful attention.
2. It has high sensitivity to shock loads of toxic and organic substances.
(2) Anaerobic Treatment
In anaerobic process 95% biodegradable carbon is decomposed into biogas and
5% into biomass.
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(i) Sludge Digesters - In this process complex organic matter of sludge is changed
into simple-compound through bio-chemical reactions. Sludge constituents
undergo slow fermentation process by anaerobic reaction. Microbes which are
responsible for anaerobic treatment are actinomycities, aerobector, lactobacillus
etc. By this process different fractions are obtained which are :
1. Digested Sludge . this is settled at bottom of the tank and used as a
2. Decomposition gases such as CH4 ,CO2, NO2,H2S and used as a fuel in
power generation.
3. Supernatant liquid –It is a solid matter present and used for irrigation.
Fig. 4.8 Anaerobic sludge digestion process.
60-70% of suspended smatter is settled as bottom of the tank. Organic matter of
sludge is decomposed interfere liquid, offensive smell occurs due to the digestion
process. It removes about 90% of BOD. Working of septic tank is unpredictable and the
uniform.
Advantage of anaerobic treatment
1. Anaerobic digestion reduces waste volume by 65%.
2. Digested sludge is used as manure.
100
Fig. 4.9 : Flow Chart of Secondary Treatment
3. Gases obtained from this treatment can be used as a fuel and for power generation.
4. The operation and maintenance costs are less in this treatment.
Tertiary Treatment (Chemical Treatment)
Tertiary treatment or advanced treatment is a process by which specific quantity
of pollutants can be reduced. By the tertiary treatment fine suspended solid particles,
microorganism, dissolved and solids inorganic and organic chemicals are removed. A
many techniques are available which depends upon the nature of pollutions . In the
tertiary treatment process following steps can be used -
(i) Coagulation : Certain chemicals are rapidly dispersed in waste water to change
the characteristics of the suspended particles. Due to this, particles coalesce and
from flocs which sink rapidly. Negatively charged colloidal suspensions are
removed by coagulation. Coagulation is most effective and economical means to
remove impurities.
For industrial waste water coagulation is used for oily emulsions, a settle
able solids such as pigments, paper, fiber, tannery effluents. The most widely used
coagulants for waste water treatment are Hydrated lime alum
(K2SO4.Al(SO4)3.24H2O) Ferric chloride, chlorinated coppers mixture of ferric
sulphate and chloride. At high pH these coagulants produce insoluble Al2 (OH)3
or Fe (OH)3flocs.
101
2 4 3 2 3 2 4
2 4 3 2 4 2 3
2 3 2 2
2 4 3 3 2 3 4 2
( ) 6 2 ( ) 3
3 3 ( ) 3 6
6 6 6
( ) 3 ( ) 2 ( ) 3 6
Al SO H O Al OH H SO
H SO Ca HCO CaSO H CO
H CO CO H O
Al SO Ca HCO Al OH CaSo CO
At low concentration of colloidal matter flock formation is difficult. In
these cases coagulants (Polyelectrolyte‘s) are added to promote flock formation.
Coagulation and flocculation can remove both suspended and colloidal solids.
After flock formation the solution is transferred to settling tank where
flocks are settled down.By the filtration flock can be removed. In this way several
filters of different porosity graded in the direction of water flow are used.
Fig. 4.10 : Tertiary Treatment
(ii) Chemical oxidation . In this method oxidizing agents such as chlorine, ozone etc.
are widely used for disinfection. Removing organic material which produces
hypochlorous acid which is powerful germicide. This hypochlorous acid reacts
with reducing agent and destroys pathogenic bacteria.
2 2
3 2 2
.
Cl H O HCl HOCl
NH HOCl NH Cl H O
Bacteria HOCl Killed pathogenic Bacteria
Ozone is also powerful oxidizing agent and acts and as an efficient disinfectant.
It is used for removal of colour, taste, odour of waste water. Ozone is effective in
the oxidation of many complex organic materials such pesticides, surfactants etc.
But this process is costly.
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(iii) Ion Exchange - It is effectively used in removing hardness and Mn, Fe salts from
potable water. Trace metals Cu, Cr, Pb, Ni, etc. present in industrial waste water
can be removed by ion exchange method. It is economical only when the
recovered salts are reused in the process. Special ion exchangers are used for
retrieval of toxic metal ions from industrial waste water. Except these methods
some other methods are also used for advanced treatment of waste water. These
are Evaporation, Adsorption, Reverse Osmosis, Chemical precipitation method
etc.
Industrial Waste Water Treatment
Industrial waste water which mainly contents toxic and non-biodegradable
chemicals can be purified by two methods which are as follows:
(i) Filtration by Activated charcoal/Synthetic Resins – Activated charcoal with
large surface area is quite and effective filter medium for adsorption of organic
compounds. It can reduce concentration of chlorinated hydrocarbons by 99%.
Synthetic organic ion exchange resins are used for removal.
(ii) Membrane Techniques- The ion exchange membrane techniques are used for
removal toxic wastes by ultra filtration or reverse osmosis. In ultra filtration, the
solution is pushed under pressure through a membrane which contains pores of
size 2 to 10,000 mm, which stops big molecules make effluent free of them. In
reverse osmosis, the membrane pores are much smaller 0.04 to 600 mm in size.
These techniques are used for purification of waste from metal textile, paper, pulp
and food industries. Electro dialysis is another membrane technique which is used
to reduce concentration of ions.
Some common industries, pollutant contained in their waste water and their
treatment are discussed below-
(1) PAPER AND PULP INDUSTRY
Waste – The raw material for paper industries are cellulosic materials such as wood,
bamboo, cotton liners, bags , straw, jute and hemp. Various operations of these industries
such as raw materials preparation, pulping, washing bleaching, chemicals recovery,
screening of pulp and paper making utilizes, various chemicals such as sulphites, phenols,
free chlorine, methyl mercaptan, pentachlor phenol. All these chemicals are found is then
effluent. Waste water from paper industries is dark brown in colour, highly alkaline has
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high content of suspended and dissolved solids high COD (about 1500 mg/l) and contains
lignin which is highly resistant to biological oxidation.
Harmful effects
(1) Chemicals present in waste water are harmful to flora and fauna of water streams.
(2) Dark brown colour of effluent due to lining compounds, inhibits photosynthesis
and other natural self purification processes of water stream.
(3) High oxygen demand depletes D.O. level to a dangerous value.
Treatment – First of all lignin is recovered as a useful by-product by chemical recovery.
The waste water is then chemically treated with lime for colour removal. Activated
carbon at pH lower then 3 can also be used for this purpose. Most of the suspended
particles can be removed by screening, coagulation, sedimentation and flocculation.
Dissolved organic matter can be removed by lagooning and activated sludge process.
Fertilizer Industries
Wastes- Fertilizer industrial waste contain various nutrients, e.g. P,N,K and their
salts and various acids (such as H2SO4, HNO3,H3PO4 and HCl). They also contains high
amount of F (over 1000 mg/l), Cr, Cyanide and NH3, AS and oils. Fertilizers such as urea,
ammonium sulphate, ammonium nitrate, super phosphate etc.
Harmful Effects
(1) Acids and alkalies can destroy the normal aquatic life.
(2) Arsenic, flourides and ammonia salts are toxic to the fishes.
(3) Amines besides being toxic to the fishes also deplete the dissolved oxygen of the
water body.
(4) Nitrogen and other nutrients present in waste water encourage growth of aquatic
life which further reduces D.O. level of water body.
(5) Make the water body unfit for use as a source of drinking water in the downstream
side.
Treatment - NH3 can be removed by sedimentation, neutralization, waste segregation
and biological methods. F and P can be removed by precipitating with chalk, lime or
double lime treatment. Cr can be removed by its reaction with SO2 in acid medium
followed precipitation of Cr(OH)2 by lime treatment. Urea can be removed by thermal or
enzymatic hydrolysis.
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Sugar Industry
Wastes- Main wastes of sugar industries are carbonaceous matter, acids and suspended
solids. They comes into the effluent by spillage from sugarcane juice extraction, wash
water from filters, floor washing and spillage from pan boiling. The effluent has variable
pH, high B.O.D. and odour.
Harmful Effects
(1) High pH value disturbs the natural ecosystem of water.
(2) High B.O.D. results in depletion of D.O. Carbonaceous matter provides nutrient
for algae growth.
(3) Suspended solids impart turbidity.
Treatment - pH value can be balanced by neutralization, while B.O.D. can be remove by
aerobic oxidation. To remove various organic matters suspended or dissolved lagoons and
oxidation ponds can be used.
Leather Industry
Wastes - Effluent from leather tanning industries is highly acidic, contains a lot of NaCl.
It also contains alkalis, sulphides, lime, CaCO3. dirt, dung, organic matter such as animal
skin, flesh, hair etc. These organic matters and suspended solid impart dark colour and
bad odour. It has high B.O.D. in the range of 4000-9000mg/l and sometimes up to
12000mg/l.
Harmful Effects
1. The acidic or alkaline effluent are corrosive to concrete and metal pipes.
2. Water contains high NaCl can not be used for irrigation.
It imparts dull brown colour to receiving water, makes it anesthetic.
3. Suspended solids such as animal flesh, hair and CaCO3 may choke the sewage
pipes. They also interfere with the photosynthesis of aquatic flora.
4. Chromium and sulphide salts are highly toxic to micro organisms.
5. Dissolved protein such as albumin, imparts repulsive odour.
Treatment - Suspended impurities like animal hairs, flesh and CaCO3 can be removed in
primary treatment using screens and then sedimentation. Secondary treatment includes
chemical coagulation (without neutralization). This is followed by a biological treatment,
in which anaerobic lagoon may be followed by an aerated lagoon.
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Textile Industry
Wastes - Waste water from textile industries contains starch, polyvinyl alcohol, various
acids and alkalis, organic solvents, resigns, dyes, oils, phenols chromium salts, etc. This
water possesses a high B.O.D. and C.O.D.
Harmful Effects
1. This water has high pH value which is dangerous to aquatic life.
2. High B.O.D. due to of starch sulphides and nitrites, duplets the D.O. level.
3. Dyes impart colour and interfere with the photosynthesis of phytoplankton.
4 Oil film also interfere with oxygenation of water streams .
5 Colloidal and suspended impurities cause turbidity.
6. Dissolved impurities cause corrosion of metallic parts of the sewage treatment
plants.
Treatment - Coarse suspended matter can be removed by using screens while grease and
oil can be removed by using skimming tanks. Colour causing impurities can be removed
by chemical coagulation. Finely suspended and colloidal impurities can be removed by
aerobic biological treatment (e.g. trickling filter activated sludge process). Tertiary
treatment can also be given, if required to reduce the acidity or alkalinity of waste water,
it have to be neutralized. This is known as neutralization. Acidic wastes can be
neutralized by using lime stone or lime slurry or caustic soda while alkaline waste may be
neutralized by using H2SO4 or CO2 or boiler flue gases.
Distilleries
Wastes - Distilleries (wines alcohols and brandy producing industries) waste water is
highly brownish yellow coloured. It contains high concentration of chloride and
sulphates. Their BOD is very high.
Treatment - Waste contains very high polluted yeast sludge. It requires biological
anaerobic and aerobic treatment.
Pharmaceutical Industries
Waste - They producing antibiotics and synthetic drugs reject waste which may be either
acidic or alkaline. It contains high total solids, BOD and COD.
Treatment – It consists neutralization with lime, anaerobic digestion and conventional
aerobic biological processes.
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Some case studies of water pollution
The problem of water pollution due to discharge of domestic and industrial wastes
into an aquatic system has already become a serious problem in the country. Nearly 80%
of Indian‘s population is exposed to unsafe drinking water. In many capitals millions of
liters of sewage and industrial effluents are being discharged into the sea and water
courses without any treatment. In the last stretch of the Kally river near Kalyan town,
water becomes highly acidic with a pH of 1.5. Similar acute conditions prevail in many
rivers at other industrial zone e.g. Hooghly near Kolkata, Damodar near Asansol and
Durgapur, Gomati near Lucknow, Kanpur, and Yamuna near Agra and Delhi.
Water borne diseases such as infective hepatitis, poliomyelitis, cholera, diarrhea,
typhoid, dysentery etc. have been successfully controlled in the developed countries but
these are still assuming epidemic proportion in India. These diseases are due to the water
pollution.
Indian Drinking Water Standards
Indian standard for drinking water as per ISO: 10500- 1991 are given in Table 4.1
Table 4.1 Physical and Chemical Standards for Drinking Water
S.
No.
Characteristics Acceptable Tolerable in the absence of
alternative and better source up to
1. Turbidity (NTU units) <10 25
2. Colour (Hazen Scale) <10 50
3. Taste and odour Unobjectionable objectionable
4. pH 7.0-8.5 6.5-9.2
5. Total dissolved solids (TDS) 500 1500
6. Total Hardness (CaCO3)(Mg/l) 200 600
7. Chlorides (Cl-)(Mg/l) 200 1000
8. Sulphates (SO-4) (Mg/l) 200 400
9. Fluorides (F)(Mg/l) 1.0 1.5
10. Calcium (Ca)(Mg/l) 75 200
11. Nitrates (NO-3) (Mg/l) 45 45
12. Magnesium (Mg) (Mg/l) <30 Depends upon sulphates (Both are
related)
13. Iron (Fe) (Mg/l) 0.1 1.0
14. Manganese (Mn) (Mg/l) 0.05 0.5
107
15. Copper (Cu) (Mg/l) 0.05 1.5
16. Zinc (Zn) (Mg/l) 5.0 15.0
17. Phenolic compounds 0.001 0.002
18. Anionic detergents (MBAS) 0.2 1.0
19. Mineral oil 0.01 0.3
Toxic Materials
1. Arsenic (As) (Mg/l) 0.05 0.05
2. Cadmium (Cd) (Mg/l) 0.01 0.01
3. Chromium (Cr6+
) (Mg/l) 0.05 0.05
4. Cyanides (CN-) (Mg/l) 0.05 0.05
5. Lead (Pb) (Mg/l) 0.1 0.1
6. Selenium (Se) (Mg/l) 0.01 0.01
7. Mercury (Hg) (Mg/l) 0.001 0.001
8. Polynuclear aromatic
Hydrocarbon (PAH) (Mg/l)
0.2mg/l
(mg/l micro
gram/lit)
0.2mg/l
Radioactivity
1. Gross Alpha activity 3 pci/l 3 pci/l
2. Gross Beta activity 30 pci/l 30 pci/l
SAMPLING
The significance of a chemical analysis depends to a large extent on the sampling
programme. An ideal sample should be one which is both valid and representative. These
conditions are met by collection of samples through a process of random selection. This
ensures that the composition of the sample is identical to that of the water body from
which it is collected and the sample shares the same physiochemical characteristics with
the sampled water at the time and site of sampling.
Table 4.2 : Typical analysis of some surface and ground waters :
Constituents ppm A B C
Silica 9.5 1.2 10
Iron (III) 0.07 0.02 0.09
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Calcium 4.0 36 92
Magnesium 1.1 8.1 34
Total hardness 14.6 123 169
Sodium 2.6 6.5 8.2
Potassium 0.6 1.2 1.4
Bicarbonate 18.3 119 339
Sulphate 1.6 22 84
Chloride 2.0 13 9.6
Nitrate 0.41 0.1 13
Total dissolved solid 34 165 434
The relevant factor for any sampling program are (a) Frequency of sample
collection (b) Total No. of samples (c) Size of each sample. (d) Site of sample
collection (d) Method of sample collection (e) Data to be collected with each sample
(f) Transportation and care of samples prior to analysis.
For analyzing of Natural and Waste water, two principal types of sampling
procedures are employed:
1. Spot or grab samples are discrete portions of water, samples taken at a given time.
A series of grab samples.
2. Composite samples are essentially weighted series of grab samples, the volume of
each being proportional to the rate of flow of the water stream at the time and site
of sample collection.
Preconcentration techniques:
1. Carbon absorption method.
2. Freeze Concentration.
3. Solvent Extraction.
4. Ion Exchange.
Treatment of extractable metal is done as follows : At the time of collection, the
water sample is acidified with conc. HNO3 (5 ml/l) before analysis the sample is well
mixed and 100 ml aliquot is taken in a beaker or flask. 5 ml of red distilled HCl is added.
The sample is heated to near boiling for 15 mins. and then filtered. The volume of the
filtrae is made up to 100 ml with distilled water and subsequently analyzed by AAS.
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Preservation
It is essential to protect samples from changes in composition and deterioration
with aging due to various interactions. The optimum sample-holding times range from
few for parameters such as pH, temperature and D.O. to one week for metals.
These are essential for retarding biological action, hydrolysis of chemical
compounds and complexes and reduction of volatility of constitutes. It is desirable for
accurate results, that analysis must be undertaken within 4 hrs., for some parameters and
24 hrs for other from the time of collection, and it must be concluded within a week.
The bottles for sample collection should be thoroughly cleaned by water with 8M
HNO3, followed by repeated washing with deionized distilled water for bacteriological
examination.
Soil Pollution
Soil is defined as the naturally occurring unconsolidated mineral or organic
material at the surface of the earth. The word ‗soil‘ has derived from Latin word ‗solum‘
which means floor or ground. It is the top covering of the solid crust of the earth's land
mass, it is made up of broken down rock materials, of various kinds of changed in varying
degree from the parent rocks by action of different agencies. Soil is defined as more or
less loose and crumby part of the outer earth crust.
Soil is one of the most significant ecological factor. It is a store of minerals, a
reservoir of water, a conserver of soil fertility, a producer of vegetative crops, a home of
wild life and livestock. The food that we eat, the fiber which makes our cloths, the
materials used in making of house and buildings, all are originated from the plants, that
grow in the soil. It also provides nutrients, water, minerals to these plants. The soil
facilitates homes and environmental conditions for living beings. It also helps in
decomposition of organic wastes by various soil micro organisms. Thus all life essentially
depends upon the soil, there can be no life without soil.
Soil Pollution – Soil or land pollution refers to ―Alteration in physical /chemical
/biological properties of soil, which interferes its beneficial use. Thus soil pollution is
defined as the build-up in soils of persistent toxic compounds, chemicals, salts,
radioactive matter, disease causing micro organisms, which have adverse effects on plants
growth and animal health‖.
110
Soil pollution is the contamination of soil system by considerable quantities of
chemical or other substances, resulting in the reduction of its fertility or productivity with
respect to qualitative as well as quantitative yield of the crops.
Soil Profile
At any place where parent material is weathering over a period of time, here develop
layers of soil one over the other in progressive state of maturity. The vertical section of
such type of soil is called soil profile. This is characteristic of mature soil and are made
up of different horizons. These horizons vary in thickness, colour, texture, structure,
acidity, porosity and composition. Soil have mainly four horizontal layers. They are -
1. Horizone O or Litter zone - The uppermost horizon of soil is called O or litter
zone. It is usually not present in the soils of deserts, grassland, cultivated field, it
is present in soils of forests.
2. Horizon A or Top soil - After O zone top soil of Horizon A is present in the
soil which contains under composed partially decomposed and completely
decomposed humus. It is generally sandy.
3. Horizon B or Subsoil - It is formed by clay soil and contains little humus.
4. Horizon C Weather land - It is at the bottom of soil profile and contains
weathered rock of parent material. It is light coloured and is virtually lacking in
organic material.
5. Horizon R unweathered land - It includes unweathered bad is rocks and
present below the C Horizon.
Fig. 4.11 : Soil Profile
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Sources of soil pollution
Soil Pollution is an extremely complicated process. It may occur-directly by dumping
and disposal of wastes. and application of agro-chemicals indirect effect of air pollution
Ex. acid rain. The main soil pollutants are-
1. Industrial Wastes - Both solid and liquid wastes of industries are dumped over
the soil. The wastes contain a number of toxic chemicals like Hg, Pb, Zn, Cd, Cu,
cyanides, thiocynates, cromates, acids, alkalies and other organic substances.
Some toxic chemicals added in the soil by mining operations also.
2. Pesticides - In present time a number of chemicals are used to kill insects, fungi,
algae, rodents, weeds, herbs etc. to improve agriculture, forestry and horticulture.
They are sprayed on the plants in the form of fine mist or powder. Most of the
pesticides has a broad spectrum and effect all types of life. Thus they are therefore
also called biocides. Pesticides reduce the number of species of living as well as
micro organisms, thus effect the structure and fertility of soil. Some pesticides and
their degraded products are absorbed by plants which in turn may affect the entire
food chains and food webs.
3. Fertilizers and Manures - Fertilizers are added to the soil for increasing crop
yield. Excessive use of these chemicals and fertilizers decreases strength of useful
bacteria and crumb structure of the soil. It also increases salt content of the soil
and reduces productivity of the soil.
The excretory products of people and live stock and digested sewage sludge used
as manure which pollute the soil. A number of pathogens are present in these type
of wastes contaminate the soils and their crops and cause serious health hazards
for man and animals.
4. Discarded Materials - Most of the discarded materials are dumped on the soil by
man. These include concrete, asphalt, ruged, leather, cans, plastics, glass,
discarded food, paper and carcasses.
5. Radioactive waste - Radioactive elements from mining and nuclear power plants
find their way into water and than into the soil.
6. Other Pollutants - Many air pollutants (acid rain) and water pollutions ultimately
becomes part of the soil. The soil also receive some toxic chemicals during
weathering of certain rocks.
112
Adverse Effects of Soil Pollution
The effect of pollution on soil are quite alarming and can cause huge disturbances
in the ecological balance and health of living creatures on earth. Nearly 80% of the
diseases, can be limited with soil and water. The solider highly polluted by several
pathogenic organism and hazardous industrial effluents. Soil pollution is the result of
urban – technology revolution and speedy exploitation of every bit of natural resources.
Some of the most serious soil pollution effects are mentioned below -
1. Decrease in soil fertility and soil yield.
2. Loss of soil and natural nutrients present in it and result in soil erosion.
3. Disturbance in the balance of flora and fauna residing in the soil.
4. Increase is in salinity of the soil thus cause salination of soil problem, which
makes it unfit for vegetation, thus making it useless and barren.
5. Crops can not grow and flourish in a polluted soil, if some crops manage to grow,
then those would be poisonous.
6. To cause health problems in consuming people.
7. Creation of toxic dust leading is another potential effect of soil pollution.
8. Unpleasant smell due to industrial chemicals and gases might result in headaches,
fatigue, nausea, vomiting etc.
9. Changed soil structure cause death of many essential organisms.
10. Soil pollution runs off into rivers and cause water pollution by which kills the fish,
plants and other aquatic life.
11. May poison children playing the soil polluted area.
Controlling measure of soil pollution
The following steps have been suggested to control soil pollution –
1. Reducing chemicals use - Fertilizers and pesticides use. Other biological
methods of pest control can also reduce the use of pesticides.
2. Reusing of materials – Materials such as glass containers, plastic bags, papers,
cloths etc. can be reused at domestic levels instead of disposed, reducing solid
waste pollution.
3. Recycling and recovery of materials - Materials such as papers, plastics and
glass can and are being recycled. Thus can minimize the volume of refuse and
helps in the conservation of natural resource Ex. Recovery of 1 tone paper can
save about 17 trees.
113
4. Reforesting – Control of land loss and soil erosion can be attempted by restoring
forest and grass cover to check west lands and soil erosion.
SOCIETY AND ETHICS
Impact of Waste on Society
Solid waste generation in one form is associated with human activities. Among
the various problems resulting due to consequences of urbanization, management of solid
waste is one of them. Management of solid waste in urban centers is becoming very
complex. Solid is the material generated from various human activities and which is
normally disposed as unless and unwanted. Thus ―Any unwanted or discarded material
from residential, commercial, industrial, mining and agricultural activities that cause
environmental problem may be termed as solid waste.‖ It consist of the highly
heterogeneous mass of discarded materials from the urban community as well as the more
homogeneous accumulation of agricultural, industrial and mining wastes. Improper
handling of this solid waste can pose direct threats to both the public health as well as
quantity of environmental resources.
Increasing urbanization, industrialization and population growth, the solid waste
has been a problem in past has become a serious threat in recent years and situation is
going to be worse if appropriate measures are not taken immediately. Dumping the waste,
has two negative points. One is it pollutes the air, water and soil resulting in diseases and
destruction of human habitat and other one is, it deprives us of a powerful resource
material for producing energy, electricity and manure etc.
Urban solid waste management continuous the remain as one of the most
neglected areas of urban development in India. Unplanned land fills have caused an
environmental disaster poising health hazards both to workers and to other population. It
is to be expect that only 1 cubic meters of garbage can produce more than two million
flies, which is the carrier of many diseases, eg. bacillary dysentery. Second most
important vector of human diseases due to solid waste is rat. Rats, destroy property as
well as infect by direct bite, they are dangerous as carrier of insects and cause various
human diseases.
Solid waste are also responsible for water and soil pollution. It generate from a
refuse dump enters surface and ground water and pollute it. Uncontrolled burning of these
wastes in open dumps can contribute to air pollution. Besides all these adverse effects
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open dumps of solid waster are also responsible for spoiling aesthetic beauty of the local
area.
Thus every activity of the man from birth to death has its impact on the
environment. Some of the major impacts are listed below-
Solid Waste Management
As solid waste can neither be transported any where nor can be dispersed in the
atmosphere. If it has to be dumped on land which besides occupying precious land
resources destroys the aesthetic beauty of the region. It is also an open food source for
various rodents and parasites, which cause a number of diseases. Disposal of solid waste
has many problem like technical, environmental, administrative, political and economical
difficulties. To overcome this type of difficulties the concept of solid waste treatment is
generated called as "solid waste management‖. The main aim of this is to minimize the
adverse effects caused by solid wastes to reduce difficult is of future. Solid waste
management comprises of purposeful and systematic control of the generation, storage,
collection, transport, separation, processing, recycling, recovery and disposal of the solid
waste.
Classification of Solid Waste
Waste produced in the society is from different sources and are of various types
depending upon their physical, chemical and biological properties. On the basis of their
source and nature wastes are classified mainly into following categories -
1. Nuclear Waste.
2. Thermal Waste.
3. Plastic Waste.
4. Bio- Medical Waste.
5. Agricultural waste.
6. Domestic waste.
7. E - waste.
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Table – 5.1 Man-made activities and their impact on environment.
Activity Impacts
Agricultural Water pollution, soil erosion discharge of nutrients and water
burden on water resources. Discharging of pesticides, fertilizers
and other chemicals to environment and ecosystem.
Transportation Deforestation for constructing roads and railways, decreased the
agriculture land. Air pollution, noise pollution disruption of wild
life habitats.
Industries Water pollution, air pollution and noise pollution. Pressure on
land, natural resources and transport system.
Energy power plants Thermal power plants create water, air and thermal pollution, they
require coal, oil, etc. Hydropower plants submerged of valuable
lands deforestation, disturbances in wild life. Nuclear power
plants create air and water pollution and risk of radioactive
hazards.
Mining Global warming, acid rain deforestation, water pollution and soil
erosion.
Urbanization Solid waste generation, water burden, environmental problems
like air water and noise problems. Sanitation problem, traffic
related and social problems.
Religions Spread of disease, water burden transport and sanitation problems
1. Nuclear waste - Nuclear waste comprises a variety of material that contains
radioactive nuclei, such as C-14, U-235, U-238, U-239, Ra-226 etc. The emission
of energy from radioactive substances in the environment is often called as
―Radioactive or nuclear pollution‖.
The sources of radioactivity are classified into natural and man-made. The natural
sources includes -
i. Cosmic rays coming from outer space.
ii. Emission from radioactive material from earth‘s crust.
Low level of radiations are exposed from these natural sources but man-made
sources are very poising to mankind which produced during the -
i. Mining and processing of radioactive ores.
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ii. Use of radioactive material in nuclear power plants.
iii. Use of radioactive isotopes in medical industrial and research applications.
iv. Use of radioactive material in nuclear weapons.
The effect of radioactive pollutants depend upon the half life, energy releasing
capacity, rate of deposition of contaminants. According to the amount and types
of radioactivity in them, they are classified as-
i. Low level waste – It contains small amounts of short lived radioactive it is buried
in shallow landfill sites. Its sources are hospitals, laboratories, industries etc.
World wise it comprises 90% of the volume but only 1% of the radioactivity
present in of all waste.
ii. Intermediate level waste – It contains higher amount of radioactivity and may
require special type treatment. Usually short lived waste is buried, but long lived
waste will be disposed at deep underground. It comprises resins, chemical sludge
and reactor components. World wise if makes up 7% of the volume and has 4% of
the radioactivity of all waste.
iii. High level waste – It contains the highly fission products and some heavy
elements with long lived radioactivity. It requires special shielding during
handling and transportation. Only 3% of the volume of all waste holds 95% of the
radioactivity.
Four main technical processes are available for treatment of waste are-
evaporation, chemical precipitation, flocculation solid phase separation and ion
exchange. These treatment are well established and widely used. Evaporation is a
proven good method for the treatment of liquid radioactive waste.
2 Thermal waste – It refers to the release of heat into any of the component of
environment. The pollution related with this heat is called thermal or heat
pollution. Thermal pollution can be sudden, long term or acute event process.
Sudden heat releases due to some natural events like forest fires and human
created like fire storms. The main sources of thermal waste are –
(i) Nuclear Power Plants – The emissions of nuclear reactors, fission and fusion
reactions, processing, are responsible for rising temperature of nearby water
bodies. Out of this drainage from hospitals, research centre etc. emit a large
amount of unutilized heat and traces of nuclear radio substances into nearby water
body and pollute them thermally.
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(ii) Industrial Effluents – Power generating industries like hydro electric power plant,
coal power plant etc. require large amount of water as a coolant and other
industries like textile, sugar, paper and pulp also release heat in water.
(iii) Domestic Sewage – The municipal water sewage has a increased temperature as
compared to receiving water. These increased temperature of receiving water,
causes decrease in D.O. and hence anaerobic conditions will setup and create foul
and offensive gases in water.
Increased temperature decreases the level of D.O., the decrease in D.O. can harm
aquatic animals like fish, amphibians etc. Higher temperature of water can change the
natural conditions and finally disturb the aquatic ecosystem. Fish spawning cycles may be
disturbed and fishes may be susceptible to the diseases.
3. Plastic waste – Plastic has many advantages – It is durable, light weight,
economic etc., these quality makes its increased demand but due to its non
biodegradable nature, plastic is now a serious environmental problem. The growth
in the consumption of plastics is to such an extent that plastic is now considered as
environmental hazardous due to the throw away culture. In India it is estimated,
about 10,000 tones of plastic waste is generated daily.
The sources of plastic wastes are. House hold (carry bags, bottles,
containers etc), Hospitals and Medicals (disposable syringes, glucose bottles,
surgical gloves, blood and euro packets etc), Hostels (packaging items, minerals
water bottles plastic plates, glasses, spoons etc) Air or rail travels (mineral water
bottles, plastic plates, glasses, plastic bags etc.).
Plastic is a high molecular weight polymer compound, it is of two types –
Thermoplastics and Thermosets. Thermoplastics soften and melt on heating and
they are recyclable. Ex. Polyvinyl chloride (PVC), Polytetrafluroethylene or
Teflon (PTFE) etc. Thermosets not soften on heating they stay solid and cannot be
recycled.
Various environmental problems are increases due to this plastic waste
like; it reduce rate of rain water percolating, thus resist the recharge of
underground water. On burning of plastic waste, they emit polluting gases and
cause air pollution. The soil fertility is also affected when plastic bags form part of
manure. If animals feed garbage containing plastic, sometimes die. Plastics also
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infected water bodies. Plastics present an ugly and unhygienic seen and thus spoil
beauty of the landscape and make polluted public places.
4. Biomedical waste - The waste generated from hospitals, health centers, medical,
veterinary, laboratories, nursing homes, funeral homes and other associated areas
constitute biomedical wastes. The above material are considered as biomedical
waste like biological cultures, anatomical wastes, discarded medicines, bandages
human excreta, blood cells, organs and tissues, chemotherapeutic wastes,
pathological wastes, waste from surgery and autopsy used syringes, gloves,
blades, instruments and gas containers, stocks of infectious agents etc.
Medical waste is generated during the diagnosis, treatment or
immunization of human beings or animals. This waste is highly infectious and
can be a serious threat to human health if it is not managed in a scientific manner.
It has been estimated that 4 kg of waste generated 1 kg would be infected of them.
Biomedical waste should be strictly classified as infectious or bio-
hazardous and they spread of infectious diseases. Hence biomedical waste should
be placed in specially labelled bags and containers for removal by bio- medical
waste transporters. Another waste should not be mixed with it. Generally
incineration method is used for the treatment.
5. Agricultural waste – Agricultural waste is waste, that produce as farm as a result
of farming activities. Nowadays agricultural practices have also been modernized,
to create a revolution in agriculture huge quantity of chemicals, fertilizers and
pesticides are used. The long term effects of these chemicals have proved very
dangerous and undesirable. They pollute environment in the term of soil and water
pollution to a great extent. Agricultural wastes are -
(i) Fertilizers – They contain plant nutrients like N, P, K etc and its derivatives.
Excessive use of these in the soil, they can reach the ground water by leaching and
can wash out to surface water (river, lakes etc.) by natural draining.
(ii) Pesticides – There are chemicals, used to kill pests. Pests are undesirable parasites
are worms or insects or birds like nematodes (that feed on roots and plant tissues)
bacteria, fungi and viruses weeds (flowering plant with crops) vertebrates ( that
feed on fruit and grain).
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Pesticide can be classified as –
1) Insecticides –It use to kill or suppress unwanted insects. Ex. DDT, Malathian,
Aldrin, Endrin etc.
2) Fungicides – These are used to kill fungi. Ex. FOPLET, CAPTAN etc.
3) Herbicides – It used to suppress the growth of weeds. Ex. Atrazine, mounuron
etc.
4) Rodenticides – These are used to kill rodents. Ex. Norbomide, Strychnine etc.
These different types of pesticides are polluting the natural environment. The
residues of these chemical substance remains in soil and reach in other life form
through food chain and affect them.
iii) Soil Conditioners and other chemical effects- They are used to increase and
protect the soil fertility. They contain some toxic metals like Cd, Hg, As, Pb etc.
When used these compounds to a land, they will accumulate in the soil
permanently and introduced into a food chain through growing crops.
6. Domestic waste – These wastes are generated after household activities of human
beings. It includes-
i) Garbage – All kind of solid waste from household. It can be recycled and reused.
To prevent creation of these waste it should be thrown into the dustbins by
community.
ii) Organic waste – It includes kitchen waste, vegetables, flowers, leaves, fruits etc.
iii) Toxic waste – Chemicals, paints, containers, fertilizers, pesticides, batteries, old
medicines etc.
iv) Recyclable – Like paper, glass, metals, plastic etc.
v) Soiled – Hospital waste i.e. cloth soiled with blood and other body fluids.
As population is increased, the amount of waste generated is also increasing. In
India, it is estimated in 1997 solid waste was about 48 million tones. About 30%
of municipal solid waste is not collected, and now it becoming unmanageable. The
local corporations have adapted different methods for the disposal of waste – open
dumps, landfills, incineration, landfills etc. But composting treatment is good out
of these.
8. E – waste – E – waste is electrical and electronic products nearing the end of their
―useful life‖. It describe loosely discarded, surplus, obsolete or broken electrical
and electronic devices like T.V. sets, VCRs, stereos, copiers, fax machine,
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computer monitor, digital cameras, laptops, scanners, printers, telephone, mobile
phone, CD – Rom, refrigerators, plastics, wires and other high tech goods and
sophisticated medical equipments are the major sources of e –waste. Generally in
working condition these equipments are not risky but these products contain Hg,
CD, Pb, Sb, Ag, Cr, Zn, As, plastic and other toxic compounds and cause serious
health problems when released in landfill disposal and incineration. These e-
waste is largest contributor of heavy metals.
Thus all E – waste is toxic and hazardous. If it dispose in landfill, toxic
chemicals of e-waste can leach in to the land and then atmosphere and impact
nearby communities and the environment. If incineration method is used for the
treatment of e-waste. It having heavy metals like Pb, Hg, Cd etc. thus they spread
into the air. Adverse effects from the E- waste include DNA damage, asthmatic
bronchitis, mental retardation in children. Contaminated soil and water are
becoming carcinogenic and toxins and cause birth defects, infant mortality,
tuberculosis, blood diseases and other respiratory problems.
If incineration method used to dispose waste they released into the
atmosphere and can accumulate in the food chain. Plastics, PVC, released toxic
dioxins and furan pollutes the environment. Reuse and recycling are good
methods to minimize the e-waste many old products are exported to developing
countries and can increase a products lifespan.
Solid Waste Management:
a) Bio-Concentrative Wastes: Industries using Cadmium, Mercury or Polychlorinated
biphenyl (PCB) expelled these as wastes. These are bio-concentrative and hot
readily adjustable to atmosphere.
b) Toxic Wastes: These are waste that may affect living organisms either by ingestion
through the food chain, respiratory system or through the surface of skin.
c) Flammable wastes: They are those materials which are at specific conditions
become flammable and cause hazards.
d) Explosive wastes: It may be any material which would have possibility of explosive
determination with or without ignition.
e) Reactive wastes.
f) Irritating or sensitizing wastes.
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Some common Industrial wastes:
Fertilizers - Ammonia, Arsenic
Coke ovens - Phenol, Cyanide, Thio-cyanide, Ammonia
Metallurgical - Heavy metals e.g., Copper, Cadmium
Electroplating - Hexa-valent chromium, Cadmium, Copper & Zinc
Synthetic Wool - Acrylonitrile, Acetonitrate
Petrochemicals - Phenol, Heavy metals, Cyanide
Any unwanted or discarded material from residential, commercial, industrial,
mining and agricultural activities that cause environmental problems may be termed as
solid waste.
3Rs & 4Rs of solid waste management:
Recovery Reduction
Recycle Recovery
Reuse Recycle
Reuse
Solid waste management comprises of purposeful and systematic control of the
generation, storage, collection, transport, separation, processing, recycling, recovery, and
disposal of solid waste.
Fig. 5.1 : Material flow
Collection of Municipal Solid Wastes (MSW):
a) Community storage Point: The municipal refuse the taken to fixed storage bins
and stored tile the waste collection agency collects it daily for disposal in a
vehicle.
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b) Curbsides Collection: In advance of the collection time, the refuse is brought in
containers and place on the footway.
c) Block collection: Individuals bring the waste in containers and hand it over to the
collection staff that empties it into the waiting vehicle and returns the container to
the individuals.
Fig. 5.2 (A) : Separation of MSW
Before the solid waste is ultimately disposed off it is processed in order to
improve the efficiency of solid waste disposal system and to recover unable resources out
of the solid wastes.
Before disposal collection of municipal solid wastes and industrial solid waste:
collection, transportation, transfer station, storage discharge state activities are performed
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due to heterogeneity of the city refuse it is important to select the most appropriate solid
waste disposal method keeping in view the following objectives:
Fig. 5.2 (B) : Separation of MSW
a) It should be economically viable i.e., the operation and maintenance costs must be
carefully assessed.
b) It should not create a health hazard.
c) It should not cause adverse environmental effect.
d) It should not be aesthetically unpleasant i.e., it should not result in offending
sights, odours and noises.
e) It should preferably provide opportunities for recycling of materials.
The methods of reduction commonly used are:
1. Salvage or manual separation.
2. Compaction or mechanical volume reduction.
3. Stationary compactor.
4. Incineration or thermal volume reduction.
Fig. 5.3 : Incineration of MSW
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If solid waste will burn it can be incinerated. Highly combustible wastes like
plastics, cardboard, paper, rubber and combustible wastes like cartons, wood, scrap, floor
sweepings, food wastes etc. are subjected to incineration i.e., burning at very high
temperatures.
Incineration results in air pollution and so proper control equipment need to be
installed to avoid contamination of environment. The heat generate during incineration is
usefully utilized by generating steam or by putting a waste heat boiler on the incinerator
thereby partly recovering the lost of waste collection and disposal.
1. Open dumping: Open dumping of solid wastes is done in low lying areas and
outskirts of the towns and cities.
2. Sanitary land filling or controlled tipping: Sanitary land filling involves the
disposal of municipal wastes on or in the upper layers of the earth‘s mantle
especially in degraded areas in need of restoration.
In land filling, the solid wastes are compacted and spread in thin layers, each layer
being uniformly covered by a layer of soil. The layer is covered by a final cover of about
one meter of earth to prevent rodents from burrowing into the refuse and scattering.
This is a biological method of waste treatment and bacterial refuse digestion
results in decomposition products like CO2, CH4, NH3, H2S and H2O which can be
harnessed as renewable sources of energy.
Advantages of land filling:
1. Simple
2. Economical
3. Cheap equipment and plant is required.
4. Skill labour not required.
5. Separation of different types of solid wastes is not required.
6. No residue or by product.
7. Low lying areas can be reclaimed and put to better use.
Disadvantages
Large land area is required continuous evolution of foul smell at the site of
disposal. Use of insecticide is required. Covering of waste solid with good earth may
sometimes difficult. It may also cause ground water pollution.
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Pyrolysis or Destructive Distillation
It is the process in which certain waste can be pyrolysed. If it can yield valuable
gases or liquids as by products, pyrolysis might be suitable in under anaerobic conditions.
The organic components of the solid wastes split up into gaseous liquid and gaseous
fractions (CO, CO2, CH4, Tar, Charred Carbon). Unlike the highly exothermic process of
combustion, pyrolysis is a highly endothermic process and that is why it is also called
destructive distillation.
Composting or Biodegradation
It includes waste like organic refuse such as kitchen waste, leaves, grass and
handling these wastes in such a way that naturally occurring bacteria and other micro-
organisms will break these down and produce safe, clean and soil like material called
compost. It can occur in the presence of air or in a closed container or underground.
Receiving Pits - Send to hopper - Rotary vibrating screens --- Magnetic separator
---- Sorting belt / table ------- Mixing of sludge -------- window pits ----------
Rolls --------- Screen -------- Market.
Preparation of fine intermediate and coarse humus. Bacterial decomposition of the
organic compound of the municipal solid wastes result in formation of humus or compost
and the process is known as composting. It consists of waste preparation, Digestion and
Product up gradation. Types of composting covers by trenching, open window
composting, mechanical composting.
Shredding: Preparation of solid waste requires, reduction and uniformity in size for
future use for this a process called shredding is devised. Shredded waste can be best
utilized every use, There are number of different types of size reduction machines which
can handle industrial wastes. They are rolling ring crushes, jar crushes, hammer mills,
shredder and hags. The rolling ring crushes and roll crushes use impact shearing and
compression, and hammer mills use impact and shearing.
Hammer Mills: This is most common type of industrial size reduction equipment. The
hammer mill consists of large motor driven rotor to which are hinged a number of heavy
hammers that pivot on these hinges and turn with the motor like to many blades of a saw.
Hammer mills can have rigid or flexible hammers, light or heavy hammers according to
the desirability of work. Breaker plate used to bear or absorbed crushing force and it is
manufactured in a way to promote shearing action.
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Bio-methanisation Technology
The organic portion is removed this position goes into bioreactor which are closed
with bacteria in it. The bacteria in the garbage produce organic manure and biogas.
Organic manure is used as inputs in chemical fertilizers and biogas can be used to
produce electricity.
Ethics and moral values
Ethics is also known as moral philosophy. Ethics word has originated from ‗ethos‘
means character or manners. The term ‗ethical‘ as concerning principle of human
conduct. It can be understand by the following ways-
Ethics as a matter of fact, deals with certain standard of conduct and moral.
Ethics is an indirect governing force behind every human conduct.
Ethics is human behavior and differentiate between proper/improper, right/wrong
or fair/unfair human actions. It can be defined as a theory or a system of moral
values. It can be used as synonymous for morally correct. Ethics is an activity and
area of inquiry. It involves defining, analyzing, evaluating and resolving moral
problems and developing moral criteria to guide human behavior. Ethics is
basically used to use the knowledge for the protection of safety and welfare of
public and also to treat all others in a way similar to now you and yourself would
like to be treated.
Morals
Morals refers to personals behavior. It refers to any aspect of human action.
Morals are those customs, the violation of which is regarded in the community as
definitely wrong in the word, they are Morals. The moral code is that of body of rules in
which the individual conscience upholds as constituting right or good. The physician who
destroys a monstrously deformed baby, for example may violate the community‘s moral
code, but he remains true to his own moral convictions. For most of morals codes vary
from person to person, but the morals characterize the group or the community.
Values
Man had social nature is his fundamental attribute. Human values are conceptions
of basic categories of desires. Values are needs/desires. Values are the rules by which we
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make decisions about right and wrong, should and shouldn‘t, good and bad. It is the link
that ties together the personal perceptions, judgments, motives and actions. These needs
are not necessarily self- centered and some of them might be abstract like liberty,
conformity, prosperity etc. Values are more important and primary than facts in forming
and understanding all kinds of human purpose. Five human values (Truth, Care, Peace,
Duty and Justice) are universal, though values are not always held in the sense of being
followed, they are everywhere held in esteem.
Ethical Situations – Some doing our best is not good enough, we must do what is
required. A variety of situation can occur that require a consideration for possible ethical
consequences of an action or practice. The most frequently cited ethical dilemmas fell in
to the following categories.
Meta Ethics Normative Ethics Applied Ethics
Situation 1: You are applying for a job. Would you put on your resume that you had been
debarred for three years by the university in a cheating case.
Situation 2: Your employer has called you to enquire about the role of a particular
person in an undesirable incident occurred in the organization. You know that the person
was responsible for the incident. Do you answer only the questions asked or tell the whole
truth. The person is a good friend of yours and everyone loves him.
Situation 3: You, as the Principal of the institute, have been solicited by a new vending
machine company and, in return, offered a free holiday trip. Would you accept the offer?
Situation 4: By mistake, the teacher has given you a higher grade in the Exam. It is
unlikely that it would ever be discovered. Would you report it to the teacher?
Situation 5: A teacher is a tough grader. Would you, as the principal, change a grade for
an outstanding student who is seeking a scholarship?
There are many ways for making decision, but few guides to indicate when
situation might have an ethical implication. These examples show how ethical problem
arise most often when there is difference of judgment or exceptions as to what constitutes
the true state of affairs or a proper course of action.
The simple way to act in typical situation, after recognizing it is to use generic
indictors as compelling guides for an active conscience. Strictly say this is not absolute
rules or values. Instead, they are more like a rough measurement where an exact one is
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not possible. They often conflict with each other and some will trump with each others in
some conditions. According to principle, that need to be considered, they should constant.
Objective of Ethics and its study
Ethics is a code of values to guide our actions. They are related with each field of
human life like personality, education and occupation. Ethics, in its full range of meaning
includes developing the appropriate sensibilities – moral, cultural spiritual and the ability
to make proper judgment and decision in life. Ethics an activity and act on enquiry.
Resolving moral issues and justifying moral judgment to guide professionals.
How should be live life well?
How to find happiness?
How to make others happy?
How to make decisions in diverse situations?
How to behave and communicate with others?
How to manage all kind of people with happiness?
The study of ethics, thus, is essentially ‗man making and ‗character building‘.
Take the case of two brilliant and very qualified scientists- one invents a life – saving
drug, both have a great deal of academic brilliance but the scientist with ethics and high
moral values creates something that can save thousands of lives; whereas, on the contrary,
the other scientist creates something that can take thousands of lives and cause pain and
deformities even in future generations.
There is only one fundamental alternative in the universe existence or non
existence. The existence of inanimate matter is unconditional, the existence of life is not,
it depends upon the specific course of action. Matter is indestructible, it changes, its
forms, but it cannot cease to exist. It is only a living organism that faces a constant
alternative- the issue of life or death. Life is a process of self – sustaining and self
generated action. If an organism fails in that action, it dies, its chemical element remains,
but its life goes out of existence.
Preliminary Studied Regarding Environmental Protection Act
It is a moral responsibility for and looking after the environment for ourselves, our
family, friends and society. The act places a general environmental duty on every one in
not to harm the environment.
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Indian constitution has a number of provisions directing the responsibility of the
central government and state for ―Environmental Protection‖. The state‘s responsibility
has been laid down under article 48 – A which states- The state shall endeavor to protect
and improve the environment and safeguard the forests and wildlife of the country.
Environmental Protection has been made a fundamental duty of every person under
article 51 –A which states. It shall be the duty of every person of India to protect and
improve the natural environment like wildlife, forest, lakes, rivers etc. Article 21 reads as
– No person shall be deprived of his life or personal liberty.
According to section 2 (a) of Environmental Protection Act (1986). It
includes - (i) water air and land (ii) the inter relationship which exists among and between
(1) water, air and land (2) human beings, other living creatures, plants, micro organisms
and property. It Includes-
Water and air pollution
1. The water (prevention and control of pollution) Act, 1974.
2. The water (prevention and control of pollution) Rules, 1975.
3. The Air (prevention and control of pollution) Act, 1981.
4. The Air (prevention and control of pollution) Rules, 1982.
5. The Air (prevention and control of pollution) (union territories) Rules, 1983.
6. Environment protection.
7. The Environment (protection) Act, 1986.
8. The Environment (protection) Rules, 1986.
9. Environment (sitting for industrial projects) Rules, 1999 Coastal stretches.
10. Declaration of coastal stretches as Coastal Regulation Zone (CRZ).
11. Hazardous process and organisms.
12. The rules for the manufacture, use, import, export and storage of hazardous.
13. Microorganism genetically engineered organisms or cells 1989.
14. The manufacture, storage and import of Hazardous chemical rules, 1989.
15 The Hazardous waste (management and handling) Rules, 1989.
16. Dumping and disposal of fly ash discharged from coal of lignite based thermal
power plants on land, 1999.
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Noise Pollution
1. The noise pollution (Regulation and control) (Amendment) Rules.
2. Noise pollution (Regulation and control) Rules, 2000.
Wild life and Forests
1. The Indian wildlife (protection) Acts, 1972.
2. The wildlife (protection) Rules, 1995.
3. Forest (conservation) Acts, 1980.
4. The Indian forest Act, 1927.
5. Guidelines for diversion of forests lands for non – forest purpose under the forest
(conservation) Act, 1980.
Forest Conservation act, 1980
‗Non Forest Purpose‘ means the breaking up of cleaning of any forest, land or
portion there of for the cultivation of tea, coffee, spices, rubber, palms, oil bearing plants,
horticultural crops, medicinal plants or plantation crops.
It is well known that breaking up the soil or clearing of the forest land affects
seriously reforestation up the soil or clearing of the forest land affects seriously
reforestation or regeneration of forests and therefore, such breaking up of soil can only be
permitted after advantages and disadvantages to the economy of the country.
Environmental conditions, ecological imbalance that is likely to occur, its effect on the
flora and the fauna in the areas, etc., it was therefore thought that the entire control of the
forest areas should vest in the central government. With that end in view, Section 2
provided that prior approval of the central government should be obtained before
permitting the use of the forest land for non- forest purpose.
Current Requirements that should be met before declaring an area into a wild Life
Sanctuary/ National Park under Forest Act.
1. The state government may by notification in the office declare the provision of
their chapter to any forest land or waste land which is not include in a reserve
forest, but which is the property of government.
2. The forest land and waste land included in any such notification shall be called a
‗protected forest‘.
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3. No such notification shall be made unless the nature and extent of the rights of
government and of private persons in or over the forest land or waste land
comprised therein have been enquired into and recorded at a surveyor settlement,
or in such other manner as the state government thinks sufficient.
Environmental Impact Assessment (EIA)
Environmental Pollution has become a global problem and random urbanization
and industrialization have made the situation critical. Recent estimate shows that coal
based power generation units in India alone contribute about 13 million tones of fly ash,8
million tones particulates, 4,80,000 tones of COx, 2.80 .000 tones of NOx, 1600 tones
CO and 5.000 tones of HCs to the atmosphere annually. Water pollution and solid waste
disposal are also causes for great concern. The situation in mainly due to the lack of
proper planning before project implementation.
EIA is an effort to anticipate, measure and weight the socio economic and
biophysical change that may result from a proposed project. This involves a multi-
disciplinary approach. Ex. for EIA study of a dam, the team may include expertise from
the areas of geology. forestry, wildlife, anthropology, chemistry, engineering, economics,
agricultural science and social Science.
In 27th
Jan 1994, EIA was carried out under administrative guidelines which
required the proponents of major irrigation. Projects, River Vally Project, Power valley
Project. Power station Ports etc. to secure a clearance from the union ministry of
Environment Forest (MOFE).
Natural environment is balanced in itself. Ecological ethics limit social as well as
individual freedom. The belief in environment is governed by the following laws-
1. Role of man in nature is to create final order, harmony and balance.
2. Man can engineer nature and modify it for his benefits.
3. Man has a moral obligation to protect and preserve the environment.
4. A life support system in its wilds state is necessary for the survival of human
begins.
5. Environment is beautiful, magnificent powerful and un predictable.
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Steps involved in EIA – The following steps are involved in EIA process-
1. Project Screening – In this step planner studied the plan and decide whether to
conduct a comprehensive EIA study or not. The world Bank has placed all the
projects in following categories, on the basis of environmental impacts-
(i) Water resources developmental project.
(ii) Highway Project.
(iii) Thermal power project.
(iv) Petrochemical project.
(v) Fertilizers project.
(vi) Residential construction project.
(vii) Minining project etc.
Comprehensive studies of EIA have to be conducted for identifying the significant
environmental impact. If impact are negative, such projects are screened off right in the
beginning.
2. Scope of Assessment – It is stressed on determining, at an early stage and project
specific issues and impacts are to be assessed.
3. Consideration of Alternatives – In this step it has to ensure that the promoter has
also considered on other alternative project locations, scales, processes, layouts,
operating conditions etc.
4. Identification of Impact – It includes the both present and future state of the
environment. It also ensures that all the significant EIA are identified and taken
into account in the process.
5. Prediction of Impacts – It identify the magnitude and other dimension of
identified change in the environment with a project by comparison with the
situation without that project.
6. Interpretation and Evaluation of Impacts – Object of this is to assess the
relative significance of the predicted impacts to allow a focus on main adverse
impacts.
7. Mitigation – It involves the introduction of measures to avoid, reduce, remedy or
compensate for any significant adverse impacts.
8. Public Consultation – It aims to assure the quality and effectiveness of the EIA
to consider in decision making process.
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9. EIS Reporting – It is a vital step of the process. It EIS done badly, much good
work in the EIA may be.
10. Review – It is a systematic appraisal of the quality of the EIS, as a contribution to
the decision making process.
11. Decision making – It involves a consideration by the relevant authority of the EIS
together with other material considerations.
12. Post decision monitoring – In this step involves the recording of out comes
associated with development impact, after a decision to proceed.
13. Auditing – It follows from monitoring. It can provide actual out comes and the
effectiveness of mitigation.
Benefits of EIA
EIA offered a many benefit some of them are-
(1) Reduced time and cost of project implementation.
(2) Increased projected acceptance.
(3) Improved project performance and quality.
(4) Lost saving modifications in project design.
(5) Avoiding impacts of law and rules regulations.
(6) Avoiding waste treatment.
(7) It provide healthy environment.
(8) It reduces pollution in some extent.
(9) Improved human health.
(10) It decreased resource over use.
(11) It increased community skills and knowledge about environment.