AIR POLLUTION CONTROL | SOIL AND ENVIRONMENTAL MANAGEMENT

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.

The table 4.1 below shows various health effects due to different air pollutants

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)

MINAS (Minimum National Air)

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. “No_x 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)