AIR
POLLUTION
DEPARTMENT: SOIL AND ENVIRONMENTAL MANAGEMENT
FACULTY: AGRICULTURE AND
NATURAL RESOURCE MANAGEMENT
COURSE CODE: SEM
564
COURSE TITLE: POLLUTION
CONTROL
TABLE OF CONTENTS
Introduction
Sources
of Air Pollutant
Natural Sources of Pollution
Effects
of air pollution
Effects
on Human beings
Acid
rain
Ozone
layer
Green
house effects
Effects
on Vegetation
Air
Quality Standards
Prevention
and Control of Air Pollution
Gaseous Matter
Particulates Matter
Settling
Chambers
Cyclone
Separation
Wet
Collectors (Scrubbers)
Bag
Filter
Electrostatic
Precipitators
References
INTRODUCTION
Air pollution is one of the current
environmental challenges even in Nigeria. Our environment is under attack,
because of time the air we breathe, the water we drink, the seas we fish in.
the soil we farm, the forest animals and plants which surround us are in
danger.
Air is one the five essentials (air,
water, food, heat and light) for the human beings man breath nearly 22000 times
a day and inhales approximately 15kg of air per a day.
Air pollution can be defined as the introduction of
the contaminants in the outdoor atmosphere in a sufficient quantity and
duration which is injurious to human health and welfare plant and animals life
and interfere with the enjoyment of life and property.
Air pollution can be defined as the excessive presence
or concentration of foreign material in the air which adversely affects the
well being of the individual and causes, damage to the property (American
Medical Association).
Air pollution is the presence in the ambient air/
atmosphere of substances is generally resulting form the activities of man in
sufficient concentration present for a sufficient time and under circumstance
which interferes significantly with he comfort health or welfare of persons or
with the rule use of enjoyment of property.
The presence in the earth’s atmosphere of man-caused
or man made, contaminant, which may adversely affect property, or eh lives of
plants animals, or humans common on pollutant include carbon dioxide, carbon
monoxide, lead, nitrogen oxide, ozone, smoke, and sulphure dioxide
(pollutants).
Air pollution generally is as a result of man’s
activities in the environment such as burning of a substance in the air which
produces what is known as air pollutant and causes pollution. Examples includes
carbon dioxide, carbon monoxide, nitrogen oxide, ozone, smoke and sulphur
dioxide e.t.c
SOURCES OF AIR POLLUTANT
Air pollutant enter the atmosphere
by various natural man made activities such as dust storm volcanic emption,
industrial pollution this air pollutant may be present in any form in other
words solid, liquid and gas (Raju 1998).
Based on the mode of generation of
pollutants, the sources are classified as natural source and (ii) man-made
sources.
NATURAL SOURCES OF POLLUTION ARE
(a) Forest fires- In the areas of tropical
region or areas of high temperature throughout the year, forest fires is a
common features very large quantities of smoke and particulate matter are
liberated during their broadcast.
(b) Volcanic eruptions- During the eruption
of volcano lava is produced along with release of manual solid particles gases
and radiation.
(c) Dust storms by movement of hot wind
(d) Pollen Grains production of pollen causes
energy is (Pollution)
MAN –MADE ACTIVITIES THAT ARE
RESPONSIBLE FOR THE POLLUTION CAN BE CLASSIFIED UNDER THE FOLLOWING HEADS
(a) Domestic
pollution – The use of insecticides in homes for clearing, burning of fuel in
home for cooking purpose are primary source of pollution in domestic areas.
(b) Industrial
Pollution of oil industries refinery mainly the flaring during extraction of
crude oil.
(c) Vehicular pollution from vehicles
exhaust.
BASED ON SHAPE OF ENTRY OF POLLUTANTS
INTO THE ATMOSPHERE
Classified as
(i) Point source (singly entry of pollutant)
(ii0 Line source: entry through a source of
wine shape
(iii) Area/Volume source. They may be two types
instantaneous and continuous.
Based on the origin of pollutants
They
are classified as (i) Primary pollutant and
(ii)
Secondary pollutants
(a) Primary
Pollutants:- they are the pollutants which are directly malted into the
atmosphere form the various pollutants sources eg. Smoke release from burning of coal.
(b) Secondary
pollutants they are the pollutants which are formed by the chemical reactions
of two or more primary pollutants the photochemical reactions are responsible
for the formation of secondary pollutants eg. Formation of PAN (Peroxy Acetyl
Nitrate).
Base
on the chemical composition of pollutants they are classified as (i) Organic
pollutant and (ii) Inorganic Pollutants.
Based
on the state of matter in which they exist in the atmosphere they are
classified is (i) Particulate matter
(ii) Gaseous Pollutants
(a) Particulate
matter: They are the finely divided solid and liquid particle present in the
atmosphere which are L generated as a
result of combustions their size vanes from 500 microns to 0.0002 micron. They
are highly reactive in chemical properties and are mostly carried through the
smoke, dust etc.
(b) Gaseous
Pollutants- Pollutants, which are present in the form of gases. Are known as gaseous
pollutants eg carbon di-oxide, sulphur-di-oxide etc particulate matter can be
classified as:
* Aerosols-they
are air suspensors having particles of dust smoke and funds. These particles
may be solid, liquid or gas depending upon the state of matter in which they
exist .
* Dust – 122000m Irregular shape
particles.
* Smoke-
Suspension of V. Fine carbon piles resulting from incomplete combustion of coal
wood ash.
* Soot incomplete combustion of wood in
pregnanted with far
* Fumer 0.03 to 1mmew
Effects of air pollution
1. Effect of air pollution on Human beings
2. Effects of air pollution on vegetation
3. Effect of air pollution on materials
4. Effects of air pollution in some
particular material
Effects on human beings
Particles
include nitrates, sulphates carbon and acid aerobe are a complete grouping
pollutants. The living contains more than 40 different km of cells. Air
pollutions can change the cells in the lung by damaging those that are most
susceptible.
Asthma is perhaps the most popular
disease with an increase incidence, but other disease, such as allergies
reaction, bronchitis and respiratory infections also have been increasing to
add to the problem, assess pollutants including ozone sulfur dioxide, nitrogen
dioxide and carbon monoxide often are present in the atmosphere As per the
recent studies, Babies exposed air pollutions during the maturation of them
organs may suffer permanent changes to those organs studies using newborn rats
showed that carbon monoxide exposure could cause changes in the heat muscle
tissue.
pollutants
|
Effect
on the heath
|
beryllium
|
Fatal
to heart and manufacture of house lungs
|
manganese
|
Damages
nerves and reproductive system
|
Benzene
|
Leukemia/
chromosomal damage
|
pesticide
|
Leukemia,
Chromosomal damage
|
Arsenic
|
Toxic
|
The
table 4.1 below shows various health effects due to different air pollutants
Pollutants
|
Effect
on the heath
|
Sulphur
dioxide
|
Irritation
of eyes and respiratory system,
increase mucus production crash and shortcuts of breath,
|
Oxides
of nitrogen
|
Irritation
of pulmonary tract affecting functions of lungs
|
Carbon
monoxide
|
Reduction
in oxygen carrying capacity of blood
|
Hydrocarbons
chlorine
|
Lung
cancer irritation of mucous membrane
|
Ammonia
|
Irritation
of mucous membrane
|
Hydrogen
sulphide
|
Excessive
inhalation leads to death
|
Acids
and aldyhdes
|
Eyes,
nose, throat irritation
|
Suspeude
particulate matter (SPM)
|
Respiratory disease
|
Dust
|
Silicosis
|
Asbestos
|
Asbestosis
|
Lead
|
Cumulative
poison, impairment
|
Domestic pollution:- The worst form of air pollution could be the wood
smoke inhaled by women while cooking.
Automobile pollution-The magnesium from a gasoline- powered engine are
mainly carbon monoxide (Co) unburned hydrocarbon HC orders of nitrogen (Nox)
and other like paraldehyde, acetaldehyde, acrolin and benzaldehyde lead is the
major significant toxic compound Indian petrol contain a high % of lead whose
emission leads to lung diseases and cancer.
Thermal power stations:- All thermal power plants are coal fuel. The major
affluent form these plants are fly ash, soot and sulphur dioxide. Fly ash from
power station reduces visibility and contains traces of chromium. Arsenic,
cadmium orcum, lead, manganese etc once again, these affect human health.
Acid rain:- Acid rain is the outcome of the emission form
industries releasing sulphur and oxides of nitrogen. When these oxides came
into contact with water vapour acids result with dramatic effects. There is an
increased acidity of the soil damage to crops and forests and frequently the death of fish is an increased
acidity of the soil, damage to crops and forests and frequently the death of
fish in lakes and rivers is observed acid rain indirectly mobilizes heavy metal
such as cadmium and mercury, which are absorbed by plants and enter the food
chain.
Ozone layer:- The earth is protected form the sun’s uv radiation by
a layer of ozone high up in the stratosphere without this layer of ozone, life
would have been impossible. But again due to human intervention there is a
disruption of the ozone layer leading to certain types of skin cancer some of the factors which lead to the disruption
of the ozone layer are the increased releases of nitrogen oxides into the
atmosphere the increase of suspension aircraft (SSTs) and the presence in the
atmosphere of chlorofluorocarbons (CFCs) which are used as refrigerants in fire
extinguishers and as propellant is aerosol spray cans.
Green house effects:- The effects of carbon dioxide on the temperature of
the earth is what is termed the “Green House effect” it behaves like the glaze
in a green house. According the heat form the sun to pass through the earthen
but preventing some of it from being radiated back through the atmosphere
carbon dioxide traps more heat and thereby increases the earth’s temperature
scientists pear that if the temperature rises by even a few degrees it will
melt the solar ice caps which in turn will submerge vast areas of land.
EFFECTS ON VEGETATION
Disease
of plant caused by the air pollution which are emitted as a result of
anthropogenic activities
Theses
diseases are
(a) Necrosis:-
It is the kicking of tissues or destruction of leaf tissue or seven drying.
(b) Chlorosis:-
It is the killing tissues or destruction
of leaf tissue or sever drying.
(c) Epinasty:-
The curving down of the leaf on the upper surface is known as epinasty.
(d) Acute
injury:- It is the injury caused to plant due to the exposure of pollutants in
high concentration.
Effects on materials
The
principal effects which are associated with the effect of pollutions on the
material are,
1. Loss of mechanical strength eg. Sand
stone and lime stone.
2. Leakage eg in pipes may water or oil.
3. Loss of detail in carving eg clay
material
4. Failure of protective coatings eg. In
lime stone
5. Pipe corrosion Eg like metal pipe
Effects
in particular materials
(a) Zinc
and Copper:- Dissolution of protective corrosion products leads to increases
deterioration rates.
(b) Rock -Stone
used for building is characterized by different textures, structures and
composition calcareous stone such as limestone or marble is very susceptible to
deposition by sulphur doxiode through transformation of the original calcium
carbonate to gypsum and calcium sulphate.
(c) Organic
Material: Rubber tyres and paints, degradation is usually associated with ozone
in conjunction with temperature and solar radiation.
(d) Stained Erlase: Cause by harmful
corrosion attack of air pollutants.
AIR QUALITY STANDARDS
The most common air pollutants are sulphur dioxide (So2),
Nitrogen Oxides (NO and No2) carbon monoxide (co) suspended
particulate matter (SPM) and lead Industrial production are responsible for the
release of So2 Nitrogen oxides and SPM in the atmosphere along with the pollutants
like Co2, Ozone and certain trace elements which are consanguine in
nature.
On the basis of land use,
urbanization and industrialization, the various areas of a state are classified
into three zones industrial, sensitive and residential and rural areas are
given in Table.
Ambient status Mg/M3
(Microgram per cubic meter of ambient air)
Annual Mean Concentration Range (Mg/M3)
|
||||
Pollution Level
|
Industrial
|
Residential
|
||
|
SO2
& NO2
|
SPM
|
SO2
& NO2
|
SPM
|
Low
(L)
|
0.40
|
0.180
|
0.30
|
0.70
|
Moderate
(M)
|
40-80
|
180-360
|
30-60
|
70-140
|
High
(H)
|
80-120
|
360-540
|
60-90
|
140-210
|
Critical
(C)
|
>120
|
>540
|
>90
|
>210
|
MINAS (Minimum National Air)
Pollutant
|
Quality standard
|
|||||
|
Sulphur
dei-oxide So2
|
Nitrogen
di-oxide No2
|
Standard
(SPM)
|
|||
Time
weighted average
|
Annual
average
|
24-hours
average
|
Annual
average
|
24
hours average
|
Annual
average
|
24
hours average
|
Industrial
area
|
80ug/M3
|
120ug/
M3
|
80ug/
M3
|
120ig/
M3
|
300ug/
M3
|
500ug/
M3
|
Residential
and rural area
|
60ug/
M3
|
80ug/
M3
|
60ug/
M3
|
80ug/
M3
|
140ug/
M3
|
200ug/
M3
|
Sensitive
area
|
15ug/
M3
|
30ug/
M3
|
15ug/
M3
|
30ug/
M3
|
370ug/
M3
|
100ug/
M3
|
PREVENTION AND CONTROL OF AIR POLLUTION
Prevention of air pollution is not
so simple. It is any impracticable to provide at reasonable cost. All the
growing need and amenities of modern life are causing some air pollution for
example. It is difficult to run an industry on what causing some air pollution it
is not possible to run a thermal plant without fouling the atmosphere.
Air
pollution can be particulates or gaseous difficulty techniques for controlling
these pollutants are as under
(A) GASEOUS
MATTER
(i) Combustion
(ii) Absorption
(iii) Adsoption
(i) This techniques is used when the
pollutants are in the form of organic gases or vapour during flame combustion
or catalytic process. These organic pollutants are converted into water vapour
and relatively less harmful products such as carbon dioxide
(ii) Absorption
In this techniques the gaseous effluent
are passed through scrubbers or absorbers. These contain a suitable liquid
absorbent, which removes a modifiers one or more of the pollutants present in
two gaseous effluents
(iii) Adsorption
The gaseous effluents are passed
through porous solid adsorbent kept in suitable containers. The organic and
inorganic constituents of the effluent gases are trapped at the interface of
the solid adsorbent by physical absorbent.
B.
PARTICULATES MATTER
Methods of removal particles, matter may be
classified into five types as given: settling chamber
Cyclone separators
Wet
collator (scrubbers)
Bay
filters
Electrostatic
precipitation
SETTLING CHAMBERS
They are closes tanks having inlet
and outlet arrangement the polluted gas is allowed to enter into chamber where
the velvety of gas is reduced sufficiently to minimize the turbulence nearer to
laminar flow condition which may allow the particulates to settle by gravity
and separates form the gas stream. To ensure uniform velocity, baffle or mesh
screens may be suspended in the chamber. A copper bottom with 1:1 scope is
provide at the bottom of settling zone to collect the settled particulates
matter. The flow velocity is usually in the range of 0.5; to 3 m/sec. the minimum
size of particles which can be removed is 10 microns efficiency is high for
removal of particles for eaten them or equal to 50 microns.
CYCLONE SEPARATION
A cyclone separator is an enclosed vertically placed
cylinder with an inverted cone at the base. The inlet is arranged with a
tangential entry and an outlet arrangement at the top of the cylinder through
the tangentially inlet which given a whirl motion. The polluted gas pushes
towards the periphery of the cylinder de to centrifugal action, the heavy
particle move towards the edge of cyclone. These the particle slide down into a
conical collector the gas further proceeds downwards and reaches the bottom of
the conical section. There the gas moves upwards as a small inner spiral, which
is concentric to the first spiral. After reaching the top of cylinder, the
clean gas leaves the cylinder through an outlet pipe.
WET COLLECTORS (SCRUBBERS)
Wet collectors are the enclosed tanks with a separate
inlet and outlet arrangement for polluted gas and a scrubbing liquid the
particulates are removed form the gas with the help of a liquid (Scrubbing)
generally water is used as the scrubbing liquid.
Separation of particles from the gas
occurs when the particulates are made to strike a liquid surface within the wet
collector.
They can be used as pre-cleaner.
Depending on the provision of contact made between the gas and the liquid the
wet collection are commonly classified into four different types
_ Spray Tower
- Cyclone Scrubbers
- Venturi Scrubbers, and
- Packed Bed or Floating Bed Tower.
BAG FILTER
Bag
filter are used for the removal of particles of size range of less than 10
microns these are reliable efficient system for particulate removal. These are
arranged in an encloser called “Bag
House” The size of each bah is 120 to 400m in diameter and 2 to 10 m long,
which are suspended. The outlet ends of the bags are open alternatively and
attached to manifold. The gas flow into the bags and leaves through the outlet
pipe. The particulate matter retained on the inside of the bag and forms a cake
will be clean with shaping mechanism, causing the filter cake to be loosened. This
loosened lake will fall into the hopper, which is provided at the button of bag
house.
ELECTROSTATIC PRECIPITATORS
Electrostatic
precipitators are widely popular for the removal of very small size
particulates matter. The polluted gas is allowed to pass between two electrodes
one is negative charged high voltage electrode and the other is positively
changed plate or a cylinder the potential difference is maintained between
them. Because of high potential difference a powerful ionizing field is formed.
This creates an active glow zone very close to negative electrode which is
called as “CORONA” as the negative ions migrate towards the collecting electrode
(Low Potential electrode) they also change the passing particulates. The
electric field attracts the particulates toward the collecting electrode and
deposited there.
Federal of Nigeria enacted a law
called Associated Gas Re-injection Act, CAP 20, LFN 2004. It deals with gas
flaring activities of oil and gas companies in Nigeria. The following sections
are relevant to air pollution prevention –section 3(1) prohibits without lawful
permission any oil and gas company from flaring gas in Nigeria section 4
stipulates the penalty for breach of permit conditions
REFERENCES
Abbasi, S.A, and Vinthan S. “Environmental Impact of
Industries on Environment”. Discovery Publishing House, 2000.
Barton, Philips K. and Atwater, James W. “Nox
Emissions and anthropogenic Nitrogen in wastewater and solid waste”, journal of
Environmental Engineering, American society of civil engineers (Volume-128, No.
2 February 2002.
Bhatia, H.S. “a Texbook of Environmental Pollution and
Control”, Galgotia Publications Limited, New Delhi, 1998.
Bhaitia, S.C. “Environmental Pollution and Control in
Chemical Process Industries”. Khanna Publishers, New Delhi, 2001.
Bibberro, R.J. and Young, I.G. “Systems Approach to
air Pollution Control”, Wiley – Inter Science Publication (John Wiley and
Sons), New York, 1984.
Carney, G.C. and Pandey, G.N. “Environmental
Engineering” Tata – Mata _McGraw hill Publishing Company Limited, New Delhi,
1989.
Chatterjee, A.K. “Water supply, Waste Disposal and
Environmental engineering”, Khanna Publishers, New Delhi, 1998.
Dhar, T.K. “Coal Ash Management and utilization – A
Challenge”. Employment News, 9-15 November 2002.
Information Collected from Environment Management
Group, Badarpur Thermal Power Station (BTPS), New New Delhi (2001-02).
Kamavisdar, a and Sirociya, R.S. Assessment of Sulphur
Content of Coal From Soaner Coal Mines”, Indian Journal of environmental
Health, national environmental Engineering Research Institute (volume 42, No
3), July 2000
Khitoliya, R.K. and Rao, S.V. “risk assessment and
Environmental Pollution control”, National Conference on Pollution control and
Industrial Ecology, Maduari (February 27-28, 2002)