Environmental pollution may be defined as, “the unfavorable alteration of our surroundings”. It...

ENVIRONMENTAL

POLLUTION

INTRODUCTION

Environmental pollution may be defined as, “the unfavorable alteration of our surroundings”. It changes thequality of air, water and land which interferes with the health of humans and other life on earth.

Pollution are of different kinds depending on the nature of pollutant generated from different sources.

Example : Industry, automobiles, thermal power plants, farming, nuclear reactors, generate different types of pollutants causing pollution to air, water bodies and land.

1. Biodegradable pollutants

Biodegradable pollutants decompose rapidly by natural processes.

Non-degradable pollutants do not decompose or decompose slowly in the environment. Slowly decomposed materials are more dangerous because it is more difficult to remove them.

2. Non-degradable pollutants

Classification of Pollution

Different kinds of pollution that affects the environment are,

(i) Air Pollution(ii) Water Pollution(iii) Soil Pollution(iv) Marine Pollution(v) Noise Pollution(vi) Thermal Pollution and(vii) Nuclear hazards.

AIR POLLUTION

Definition

Air pollution may be defined as, “the presence of one or more contaminants like dust, smoke, mist and odour in the atmosphere which are injurious to human beings, plants and animals”.

Rapid industrialization, fast urbanization, rapid growth in population, drastic increase in vehicles on the roads and other activities of human beings have disturbed the balance of natural atmosphere.

Chemical Composition of Atmospheric Air

During several billion years of chemical and biological evolution, the composition of earth’s atmosphere has varied. Today, about 99% of the volume of air we inhale consists of two gases: Nitrogen and Oxygen.

Constituents %Nitrogen 78

Oxygen21

Argon (Ar)< 1

CO2 0.037

Water vapourRemaining

O2, He, NH3 Trace amount

Chemical composition of atmospheric air

Indian ambient air quality standards

Air quality standards are legal limits, placed on the concentration of air pollutants in a community where people and things are exposed.

Ambient air quality standards are permissible exposure of all living and non-living things for 24 hours per day, 7 days per week. Indian Ambient air quality standards are given in table.

Indian Ambient air quality standards

Category

Area

Concentration in ug/m3

SPM SO2 NOX CO

A Industrial and mixed use 500 120 120 5,000

B Residential and rural 200 80 80 2,000

CSensitive (hill stations,

tourist resorts, monuments

100 30 30 1,000

Sources of Air Pollution

1. Natural sources

2. Man-made (anthropogenic) activities

Volcanic eruptions, forest fires, biologicaldecay, pollen grains, marshes, radioactivematerials etc.

These pollutants are caused by the natural sources.

Thermal power plants, vehicular emissions, fossil fuel burning, agricultural activities etc.,

Sources of air pollution are of two types

Classification of Air Pollutants

Depending upon the form (origin) of pollutants present in the environment, they are classified as

(i) Primary air pollutants.

(ii) Secondary air pollutants.

1. Primary air pollutants

Primary air pollutants are those emitted directly in the atmosphere in harmful form.

CO, NO, SO2, etc.,

Indoor Air Pollutants

1. Radon gas is emitted from the building materials like bricks, concrete, tiles, etc., which are derived from soil containing radium.

Indoor air pollutants are primary air pollutants. The most important indoor air pollutant is radon gas.

Sources (causes) of indoor air pollutants

2. It is also present in natural gas and ground water and is emitted indoors while using them.

3. Burning of fuels in the kitchen, cigarette smoke, liberates the pollutants like CO, SO2, formaldehyde, BAP (benzo-(a) pyrene).

2. Secondary air pollutants

Some of the primary air pollutants may react with one another or with the basic components of air to form new pollutants. They are called as secondary air pollutants.

(HNO3/NO3) etc.,Moist

NO/NO2

Common air pollutants sources (causes)and their effects

According to the World Health Organization (WHO), more than 1. 1 billion people live in urban areas where outdoor air is unhealthy to breathe. Some of the common air pollutants are described below.

1. Carbon monoxide (CO)

Description

It is a colourless, odourless and is poisonous to air-breathing animals. It is formed during the incomplete combustion of carbon containing fuels.

2C + O2 2CO

Health Effects

Reacts with heamoglobin in red blood cells and reduces the ability of blood to bring oxygen to body cells and tissues, which causes headaches and anemia. At high levels it causes coma, irreversible brain cell damage and death.

Environmental Effects

It increases the globe temperature.

Human Sources (causes)

Cigarette smoking, incomplete burning of fossil fuels. About 77% comes from motor vehicle exhaust.

2. Nitrogen dioxide (NO2 )

It is a reddish-brown irritating gas that gives photochemical smog. In the atmosphere it can be convertedinto nitric acid (HNO3).


Fossil fuel burning in motor vehicles (49%) and power industrial plants (49%).

NO2+ Moisture (H 2O) HNO3

Health Effects

Lung irritation and damage.Environmental Effects

Acid deposition of HNO3 can damage trees, soils and aquatic life in lakes, HNO3 can corrode metals and eat away stone on buildings, statues and monuments. NO2 can damage fabrics.

3. Sulphur dioxide (SO2)

It is a colourless and irritating gas. It is formed mostly from the combustion of sulphur containing fossil fuels such as coal and oil. In the atmosphere it can be converted to sulphuric acid (H2SO4)which is a major component of acid deposition


Coal burning in power plants (88%) and industrial processes (10%).

Health Effects

Breathing problems for healthy people.


Reduce visibility, acid deposition of H2SO4 can damage trees, soils and aquatic life in lakes.

4. Suspended particulate matter (SPM)

It includes variety of particles and droplets (aerosols).They can be suspended in atmosphere for short periods to long periods.


Burning coal in power and industrial plants (40%), burning diesel and other fuels in vehicles (17%), agriculture, unpaved roads, construction etc.,

Health EffectsNose and throat irritation, lung damage,

bronchitis,asthma, reproductive problems and cancer.


Reduces visibility, acid deposition and H2SO4 droplets can damage trees, soils and aquatic life in lakes.

5. Ozone (O3)

Highly reactive irritating gas with an unpleasant odour that forms in the troposphere. It is a major component of photochemical smog.


Chemical reaction with volatile organic compounds (emitted mostly by cars and industries) and nitrogen oxides.

Environmental Effect

Moderates the climate.

6. Hydrocarbons (aromatic and aliphatic)

Hydrocarbons especially lower hydrocarbons get accumulated due to the decay of vegetable matter.


Agriculture, decay of plants, burning of wet logs.

Health Effects

Carcinogenic.

Environmental effect

It produces an oily film on the surface and do not as such causes a serious problem until they react to form secondary pollutants. Ethylene causes plant damage even at low concentrations.

Control Measures of air pollution

The atmosphere has several built-in self cleaning processes such as dispersion, gravitational settling, flocculation, absorption, rain washout and so on, to cleanse the atmosphere

In terms of a long range control of air pollution, control of contaminants at their source is a more desirable and effective method through preventive or control technologies.

Control methods for removing particulates from exhaust gases

I. Source control.

Since we know the substances that causes air pollution, the first approach to its control will be through source reduction. Some actions that can be taken in this regard are as follows:

1. Use only unleaded petrol.

2. Use petroleum products and other fuels that have lowsulphur and ash content.

3. Reduce the number of private vehicles on the road by developing an efficient public-transport system and encouraging people to walk or use cycles.

4. Ensure that houses, schools, restaurants and places where children play are not located on busy streets.

6. Industries and waste disposal sites should be situatedoutside the city centre preferably downwind of the city.

7. Use catalytic converters to help control the emissions of carbon monoxide and hydrocarbons.

II. Control measures in industrial centers

1. The emission rates should be restricted to permissible levels by each and every industry.

2. Incorporation of air pollution control equipments in the design of the plant layout must be made mandatory.

5. Plant trees along busy streets because they removeparticulates and carbon monoxide, and absorb noise.

Equipments used to control air pollution

Air pollution can be reduced by adopting the following approaches.

(i) To ensure sufficient supply of oxygen to the combustion chamber and adequate temperature so that the combustion is complete, eliminating much of the smoke consisting of partly burnt ashes and dust.

3. Continuous monitoring of the atmosphere for the pollutants should be carried out to know the emission levels.

The four figures (figure) are commonly used control methods for removing particulates from the exhaust gases of electric power and industrial plants.

(ii) To use mechanical devices such as scrubbers, cyclones, bag houses and electro-static precipitators, reducing particulate pollutants

All these methods retain hazardous materials that must be disposed of safely. The wet scrubber can also reduce sulphur-di-oxide emissions.

(iii) Chemical treatment to deal with factory fumes. The disposal of the collected air pollutants is equally important for successful control of air pollution.

CHEMICAL AND PHOTO CHEMICAL REACTIONS IN THE ATOMSPHERE

Formation of smog

Smog is a mixture of smoke and fog in suspended droplet form. The Brownish smoke like appearance that frequently forms on clear, sunny days over large cities with significant amounts of automobile traffic.

Types of smog

There are two types of smog.

1. London smog

2. Los Angles smog (or) Photochemical smog.

1. London Smog

It is a coal smoke plus fog. Fog mainly consists of mixture of SO2 + SO3 + humidity. It is bad in morning hours and becomes worse after sun rise. This is due to sunlight induced oxidation of SO2 + SO3, followed by reaction with humidity giving sulphuric acid and aerosd.

SO2 + (O) SO3

SO3+H2O H2SO4

2. Los Angles Smog (or) Photochemical smog

It is not related to smoke (or) fog. It is formed by the combination of NO, NO2, CO2, H2O, CO, SO2 and unburnt hydrocarbon particles. The important reaction is dissociation of NO2 in sunlight.

Hydrocarbon + O2, O, O3, NO2, NO Oxidized hydrocarbons.

These oxidised hydrocarbons with ozone in the presence of humidity causes photochemical smog.

Health effects of smog

1. It causes irritation to eyes and lungs.

2. It damages plants.

3. It irritates nose, throat, etc.,

4. It also causes bronchial irritation.

Environmental effects of smog

1. It produces acid rain.

2. It damages plants and trees.

3. Smog can reduce visibility.

Remedial measures of smog

1. By decreasing nitrogen oxides and hydrocarbonlevels in the air.

2. By using unleaded petrol in automobiles.

PAN

(Peroxy Acetyl Nitrates)(Lachrymatory substance)

Description

Peroxy acetyl nitrates is a secondary pollutant present in photochemical smog. It is a lachrymatory substance. It is thermally unstable and decomposes into peroxy ethanoyl radicals and nitrogen dioxide gas. It is an oxidant and more stable than ozone.

At higher concentrations

Production of PAN

They are formed by the photochemical reaction between hydrocarbons, nitrogen oxides and light. It occurs in two steps

Cause extensive damage to vegetation, causing skin cancer

Health effect

At lower concentrations

It is a powerful respiratory and eye irritants, toxic in nature.

Unburnt hydrocarbons undergo oxidation to give aldehydes, ketones and dicarbonyl compounds, which creates peroxyacyl radicals.

STEP I

Peroxyacyl radicals combine with nitrogen dioxide to form peroxyacyl nitrates.

Sources

1. It comes from the degradation of isoprene, hydrocarbon, acylation.

2. Blended gasoline with ethanol.

STEP II

Environmental effects

1. Damages plants and art.

2. React explosively.

3. Plays a very large role in photochemical smog.

4.3.3 Acid Rain (or) Acid Precipitation

Normal rain water is always slightly acidic because of the fact that CO2 present in the atmosphere gets dissolved in it. Because of the presence of SO2 and NO2 gases as pollutants in the atmosphere, the pH of the rain water is further lowered. This type of precipitation of water is called acid rain (or) acid deposition.

The pH scale

Acid rain means the presence of excessive acids in rain water. The thermal power plants, industries and vehicles release nitrous oxide and sulphur dioxide into atmosphere due to burning of coal and oil.

When these gases react with water vapour in the atmosphere, they form acids and descend on to earth’s “acid rain” through rain water.

Effects (impacts) of Acid Rain

Due to the drifting of these gases in the atmosphere by the wind, their presence are felt as far as 2,000 kilometers. The air pollution of one nation could cause acid rain for another nation.

Acid rain causes a number of harmful effects. Some of the adverse effects are as follows.

I. Effects of acid rain on human beings

1. Acidic rain has been found to be very dangerous to the living organisms as it can destroy life. Human nervous system, respiratory system and digestive system are affected by acid rain.

2. It also causes the premature death from heart andlung disorders such as asthma and bronchitis.

II. Effects of acid rain on buildings

1. The Taj Mahal in Agra suffering at present due to SO2 and H2SO4 acid fumes released from Mathura refinery. Crystals of CuSO4 & MgSO4 are formed as a result of corrosion caused by acid rain.

2. Acid rain corrodes houses, monuments, statues, bridges and fences. British parliament building also suffered damage due to H2SO4 rains.

3. Acid rain and dry deposition of acidic particles contribute to the corrosion of metals, and the deterioration of paint and stone. These effects seriously reduce the value of buildings, bridges and cultural objects.

4. Dry deposition of acidic compounds can also dirty buildings and other structures, leading to increased maintenance costs.

III. Effects of acid rain on terrestrial and lake ecosystem

1. The effect of acid precipitation on terrestrial vegetation reduces rate of photosynthesis and growth and increased sensitivity to drought and disease.

2. Acid rain severely retards the growth of crops such as beans, raddish, potato, spinach and carrots etc.,

3. Acid rain causes a number of complications in ponds, rivers and lakes where it accumulates as acid snow. It causes a significant reduction in fish population

4. Black flies, mosquitoes, deer flies and the aquatic worms occur abundantly where fishes are eliminated due to acid deposition.

5. The activity of the bacteria and other microscopic animals is reduced in acidic water. So the dead materials and other accumulated substances lying on the bottom of lakes are not rapidly decomposed. Thus essential nutrients such as nitrogen and phosphorus stay locked up in dead wastages. Biomass production is reduced and fish population declines.

Other names of Acid rain

Acid fog, acid snow and acid precipitation

Control measures of Acid Rain

1. Improvement in technologies and switching to clean combustion technologies are highly essential in order to monitor the air pollution.

2. Emissions of SO2 and NO2 from industries and power plants should be reduced by using pollution control equipments.

3. Coal with lower sulphur content is desirable to use in thermal plants. Replacement of coal by natural gas would also reduce the problem.

4. Liming of lakes and soils should be done to correct the adverse effects of acid rain.

5. The real solution is to cut back on the use of fossil fuels by reducing our dependency on motor vehicles and unnecessary utility of motor articles.

4.3.4 Oxygen and Ozone chemistry

A. Oxygen chemistry

The word oxygen comes from Greek words “oxy” and “genes”, which together means acid forming. Our atmosphere currently contains about 21% of free oxygen. It plays an important role in sustaining life without oxygen, animals would be unable to breathe and consequently die.

Production of oxygen

Oxygen is produced in various ways.

1. Photochemical dissociation

Photochemical dissociation of water molecules by UV rays produces about 1 - 2% of our oxygen.

2. Photosynthesis

Photosynthesis is performed by plants, which involves the following general reaction

CO2 + H2O + hv (Sunlight) Carbohydrate + O2

3. Industrial production

Oxygen is industrially produced by fractional distillation of liquefied air.

Structure of O2

It is a colourless, odourless gas. Electronic configuration of oxygen is 1s2 2s2 2p4 and its valency is 2. It is paramagnetic.Hence its structure is

B. Ozone chemistry

O2 molecule is not elemental form of oxygen. Another form of (allotrope) oxygen is ozone (O3)

Production of ozone

Formation of ozone involves the following two steps

In the presence of lightning or spark of light, O2 molecules dissociate to form oxygen atoms.

STEP I

These oxygen atoms react with O2 molecules to form ozone (O3)

Structure of ozone

Ozone is an unstable compound with a sharp, pungent odour. Its structure is shown below.

Oxygen (O2) and Ozone (O3) are examples of allotropes,having different chemical and physical properties.

STEP II

Table 4.3 Properties of allotropes of oxygen

Properties Oxygen(O2) Ozone (O3)

Melting point - 218.750C -192.50C

Boiling point -182.960C - 110.50C

Density (at 200C) 1.331 g/lit 1.998 g/lit

O - O bond order 2 1.5

O - O bond length 0.1207 nm 0.1278 nm

Properties of ozone

Ozone under goes slow decomposition to give oxygen.

At lower concentrations

At higher concentration

At lower concentration ozone is relatively pleasant.

At higher concentration ozone leads to coughing, rapid beating of the heart, chest pain and general body pain.

4.3.5 Ozone Layer Depletion (Ozone hole)

Ozone is a gas (O3) found throughout the atmosphere, but most highly concentrated in the stratosphere between 10 and 50 km above sea level, where it is known as the ‘ozone layer’.

Importance of ozone layer

Without the ozone layer, life on the earth’s surface would not be possible. It protects us from the damaging ultraviolet radiation of the sun. In particular it filters out UV-B radiation.

Fig. 4.4 Ozone layer depletion

Recent evidence has shown that certain parts of the ozone layer are becoming thinner and ozone ‘holes’ have developed.

The consequence of any thinning of the ozone layer is that more UV-B radiation reaches the earth’s surface.

UV-B radiation affects DNA molecules, causing damage to the outer surface of plants and animals. In humans it causes skin cancer, and eye disease.

Mechanism of Ozone layer depletion (or) Formation (or) Causes of ozone hole

In 1970, it was found that the ozone layer was attacked by chlorofluoro carbons (CFCs) which are released into atmosphere by refrigeration units, air conditioning systems, aerosol sprays and cleaning solvents.

Chlorofluoro carbons release chlorine which breaks ozone into oxygen.

The following reactions will then occur

Each chlorine atom is capable of attacking several ozone molecules. So that a long chain process is involved. A 1% loss of ozone results in a 2% increase in UV rays reaching the earth’s surface.

Ozone Depleting Substances

The ozone depleting substances essentially consists of chlorine or bromine atoms which are extremely reactive while they are in the free state. The following gases are accumulated in the atmosphere and are found to be instruments in ozone depletion.

1. Chloro Fluoro Carbon (CFC)

Sources

Refrigerants (freon) in refrigerators, propellent in aerosol spray cans, blowing agent, foam plastic blowing agent.

2. Hydro Chloro Fluoro Carbon (HCFC)

Refrigerants, blowing agents.

3. Bromo Fluoro Carbons (BFC)

Sources

Sources Fire extinguishers.

4. Other Chemicals

1. Certain halogen compounds are potential ozone destroyers upto ten times more powerful than the CFCs.

2. Sometimes the atmospheric sulphur dioxide is converted into sulphuric acid which greatly increases the rate of ozone depletion.

Effect (or) Environmental impact (or) consequencesof Ozone Layer Depletion

As the ozone layer gets deteriorated the harmful UV rays will reach the ground and cause various adverse effects.

I. Effect on human health

(i) The UV-rays damage genetic material in the skin cells which cause skin cancer.

(ii) For the fair skinned people life long exposure to the high level radiation of UV rays increases the riskof non melanine skin cancer.

(iii) Prolonged human exposure to UV-rays may lead toslow blindness called actinic keratitis. Enhanced level of UV-ray could lead to more people suffering from cataracts.

(iv) Human exposure to UV-rays can suppress the immune responses in humans and animals. It also reduces human resistivity leading to a number of diseases such as cancer, allergies and some other infectious diseases.

II. Effect on Aquatic Systems

(i) UV rays directly affect the aquatic forms such asphytoplankton, fish, larval crabs.

(ii) The phytoplankton consumes large amount of CO2.

Decrease in population of phytoplankton could have more amount of CO2 in the atmosphere which contributes to the global warming.

III. Effect on Materials

Degradation of paints, plastics and other polymeric material will result in economic loss due to effects of UV radiation.

IV. Effect on Climate

The ozone depleting chemicals can contribute to the global warming i.e., increasing the average temperature of the earth’s surface

Measurement of Ozone (Dobson Unit)

The amount of atmospheric ozone is measured by‘Dobson spectrometer’ and is expressed in Dobson units (DU).1 DU is equivalent to a 0.01 mm thickness of pure ozone at the density it posses if it is brought to the ground level (1 atm) pressure.

In temperate latitude its concentration is 350 DU.

In tropics its concentration is 250 DU.

In subpolar region its concentration is 450 DU.

Control Measures

1. Replacing CFCs by other materials which are less damaging.

2. Use of gases such as methyl bromide which is a crop fumigant also to be controlled.

3. Manufacturing and using of ozone depleting chemicals should be stopped.

4.4 PROPERTIES OF TERRESTRIAL AND MARINE WATER

4.4.1 Terrestrial (or) Surface water

The water, which is coming out directly through precipitation and does not percolate down into the ground or does not return to the atmosphere by evaporation is called terrestrial (or) surface water.

(Or)

The water stored on the surface of earth is called terrestrial (or) surface water.

Types of terrestrial water

Terrestrial water (or) surface water exists in two forms.

1. Standing water bodies

2. Flowing water bodies.

I. Standing Water Bodies

1. Lakes

(a) Oligotropic lakes: These are generally deep, clear and deficient in nutrients without much biological activity.

(b) Eutrophic lakes: These are the lakes having more

nutrients and are more turbid and support more life.

(c) Dystrophic lakes: These are shallow and coloured lakeswith a low pH and clogged with plant life.

2. Reservoirs: These are generally larger than lakes.

3. Estuaries: Estuaries are deltas formed at the mouth ofrivers, where they join the ocean. The mixing of fresh and salt water gives estuaries

II. Flowing water Bodies

The water, which originate from the point of precipitation and flows in streams and rivers are called flowing water bodies.The flowing water carries sedimentary materials and dissolved minerals.

Physical and chemical properties of terrestrial water

Water has several unique properties.

1. At room temperature water is colorless with a tint of blue, tasteless and odourless liquid.

2. Many substances dissolve in water and is commonlyrefereed to as universal solvent.

3. Water has high specific heat, it can absorb large amount of heat energy before it begins to get hot.

4. Water in a pure state has a neutral pH. Water changes its pH (neither acidic nor basic) when

substances are dissolved in it.

5. Water conducts heat more easily than any liquid except mercury. This fact causes large bodies of liquid water like lakes and oceans to have essentially a uniform temperature profile.

6. Water molecule exists in liquid form over wide rangeof temperature 0 – 100OC.

7. Water is a universal solvent.

8. Water has high surface tension.

Environment significance

1. When CO2 dissolves in water, it reacts with water to produce carbonic acid(H2CO3).

2. Metal - carbonate ion pairing influences the effective concentration of HCO3 and hence pH gets affected.

3. Water acts as a substrate for metabolic reactions. eg: photosynthesis, hydrolytic reactions.

4. Potential of water is reduced by the addition of solutes, addition of water - binding surfaces, negative pressures and a reduction in temperature.

4.4.2 Physical and chemical properties ofmarine water

Marine water is the water found in sea (or) ocean. Onaverage marine water has a salinity of about 35%. This means that every kilogram of marine water has approximately 35 grams of dissolved salts (Na+ & Cl- ions).

Marine water is not uniformly saline throughout theworld. Where mixing occurs with fresh water runoff from river mouths or near melting glaciers, marine water can be less saline.

Physical and chemical properties of marine water vary according to latitude, depth, nearness to land and input of fresh water.

Physical and chemical properties of marine water

1. The marine water is denser than both fresh water decreases as the salt concentration increases.

2. pH of marine water is between 7.5 - 8.4.

3. The speed of sound in sea water is roughly 1500 meters per second.

Environmental significance

1. Climate change, rising atmospheric carbondioxide, excess nutrients and pollution in many forms are altering global oceanic geochemistry.

2. An increasing acidity, reduced subsurface oxygen in both near-shore and deep waters, rising coastal nitrogen levels and widespread increases in mercury and persistent organic pollutants.

Marine water is different from terrestrial water

1. Marine water contains more dissolved ions than alltype of terrestrial water.

2. Marine water contains about 2.8 time more bicarbonate than terrestrial water.

3. All these differences are only due to varying residence time of sea water solutes. Sodium and chloride have very long residence time while calcium tends to precipitate much more quickly.

4.5 WATER QUALITY PARAMETERS

The quality of water is an important parameter to be determined in order to decide the type of application or treatment required. The quality of water varies to place to place and seasons.

The followings are some important parameters of qualityof water.

1. Physical parameters.

2. Chemical parameters.

3. Biological parameters.

4.5.1 Physical Parameters

1.Colour

Colour is a shade imparted by organic or inorganic material, which change the appearance of the water.

Colour is found mostly in surface water. The colours of natural water range from pale straw through yellowish-brown to dark brown. The colour of natural waters is mainly due to the presence of dissolved or colloidal organic or inorganic materials.

Sources1. Organic sources => Algae, tannins, humic compounds

organic dyes, etc.

2. Inorganic sources => Fe and Mn compounds, chemicals and inorganic dyes from various industries.

Sanitary Significance

1. The colours and the materials which produce colourare often objectionable in which the water and the manufactured product come into contact.

Dyeing, scouring and laundering

2. Variation in colour of water from the same sourcewith atime serves s index of quality of the water.e.g.,

(a) Yellowish tinge => indicates the presence of ‘Cr’and organic matter.

(b) Yellowish red => indicates the presence of iron.

(c) Red-brown=>indicates the presence of peatymatter.

Removal of colour

Colour and colour producing materials are removed by coagulation, settling, adsorption and filtration.

2. Tastes and Odours

Disagreeable odours and tastes are objectionable for various industrial processes such as food products, beverages, textiles, paper, pulp. Most of the odours in natural waters are organic in nature, except H2S.

Sources

Organic sources: Algae and decaying vegetation, etc.

Inorganic sources: Mercaptans, amines and sulphides, etc.

The tastes and odours observed in chlorinated waters are due to chloro-organic compounds formed by the reaction between chlorine and organic matter present in the water.

Removal of Tastes and Odours

1. Organic tastes and odours may be removed by aeration (or) activated carbon treatment.

2. Inorganic tastes due to H2S (or) Iron may be removed by chemical methods like oxidation,chlorination (or) precipitation.

3. Turbidity and sediments

Turbidity is the reduction of clarity of natural water due to the presence of finely divided, insoluble impurities suspended in water.

Sources

1. Inorganic sources

Clay, silt, silica, ferric hydroxide, calcium carbonate, sulphur, etc.,

2. Organic sources

Finely divided vegetable or animal matter, oils, fats, greases, micro-organisms, etc.,

Removal of Turbidity and Sedimentsition

Turbidity of water may be removed by sedimentation followed by

1. Coagulation and filtering

2. Coagulation and settling

3. Coagulation, settling and filtering.

Sanitary significance

Tolerance of turbidity for different industries depends on the type of industry and the grade of the product being manufactured.

1. Turbidity caused by suspended silt and mud is objectionable in boilers and in cooling-water systems.

2. Turbidity caused by colloidal or dissolved organic matter will interfere with water-softening processes.

4.5.2 Chemical Parameters

1. pH

The hydrogen ion concentration is represented by the pH value, which is defined as

pH =-log10[ H+ ]pH is defined as negative logarithm of hydrogen ion concentration. The pH value ranges from 0-14 as

0 ----- 7 ------- 14Acidic -------- Neutral ------- Basic

Generally pH of natural waters lies in the neutral range. For drinking water recommended pH = 6.5 to 8.5. For irrigation recommended pH = 6.0 to 9.0. Some surface waters passing over areas rich in sodium and potassium posses alkaline pH. The rain water contaminated by the dissolved gases such as SO2 and NOx will have acidic pH.

2. AddityAcidity of water is a measure of its base-

neutralizing ability. The acidity in water is usually imparted by the dissolved carbondioxide (or) by the mineral acids.

In pure water, the decrease in pH of about 0.45 occurs as the temperature is raised by 250C.

1. Mineral acids

Sources

Mineral ores like iron pyrites (FeS2), (or) sulphur compounds.

These are oxidised to acids by bacteria in the presence of O2 and H2O

2. Carbondioxide

Industrial smoke, smoke from vehicles.


1. The mineral acids cause more environmental and health problems than the carbon dioxide acidity.

2. It is undesirable to consume.

3. When acid water contacts with stone concrete and metals, it corrodes them and solubilising several heavy metals, so the structure gets collapsed.

3. Alkalinity

Alkalinity of water is a measure of its acid-neutralising ability. Natural alkalinity in waters is imparted by the hydroxides, carbonates and bicarbonates.

Sources

Hydroxides, carbonatesand bicarbonates of alkalimetals, borates silicates, phosphates.

Industries like fertilizer,detergent, leatherand paint.


1. Very high values of alkalinity are harmful to aquatic organisms.

2. Alkalinity in boiler feed water causes caustic embrittlement of pipes.

Removal of Alkalinity

Alkalinity in water, can be removed by adding limited amount of HCl.

4. Fluoride

Fluoride is found in ground water as a result of dissolution from geologic formulations. Surface waters generally contain much smaller concentration of fluoride

Sources

Fluoride containingminerals

Fluorapatite (Ca10 F2 (PO4)6),

cryolite (Na3AlF6) and igneous rocks containing fluosilicates.

Contaminated domesticsewage, run-offfrom agricultural lands

Phosphate fertilizers.


1. Optimum fluoride concentrations, prescribed in public water supplies, are in the range of 0.7 to 1.2 mg / lit.

2. Beneficial health effects have been observed where the fluoride levels are optimum.

3. If the fluoride concentration is low in drinking water it causes dental caries in children.

4. If the fluoride concentration is high it causes fluorosis.

Removal of fluoride (Defluoridation)1. Precipitation using aluminium salts in alkaline

media.

2. Using strongly basic anion exchange resin.

3. By adsorption on activated carbon.

5. Nitrogen

Nitrogen is a inert gas, which is relatively unimportant as far as water treatment is concerned.

Sources 1. Plant materials, fertilizers.

Sanitary significance1. Since it is inert, in analysing waters, nitrogen is

practically never determined.

2. It has no corrosive effects on metals.

Removal of NitrogenNitrogen in water, can be removed by boiling the water.

6. ChloridesAlthough chlorides are not considered as harmful as such their concentrations over 250 mg/lit impart peculiar taste to water, which is unacceptable for drinking purposes.

7. Sulphates

When sulphates are present in excess amount in drinking water, they may produce a cathartic effect on the people consuming such water.

8. Nitrates

Excessive concentrations of nitrates are undesirable especially for infants. The maximum contaminant level for nitrate is 10 mg/lit.

9. Arsenic

Arsenic is a toxic heavy metal even a very small dose can result in severe poisoning. Only 0.05 mg/lit has been recommended for arsenic in drinking water.

4.5.3 Biological impurities

Micro-Organisms

Micro organisms are more abundant in surface waters,where as in deep well waters, the bacterial count is very low or even absent. The growth of these organisms in water, used for industrial purposes, may cause serious problems and hence effective measures must be taken to prevent the growth of these organisms. Organic growths in water generally take place at temperatures ranging from 100C - 350C.

Sanitary significance1. Due to the growth of this micro-organisms in pipe

lines carrying capacity gets reduced.

2. These coatings block the flow through valves, pumps, nozzles, filters and hence their efficiency gets reduced.

3. Algae, fungi and bacteria produces fouling and corrosion.

Prevention of Growth of Micro-Organisms

1. The growth of algae, mussels fungi and bacteria is controlled by chlorination.

2. Sterilizing agents such as CuSO4, Sodium pentachloro phenate are also used.

3. Iron and Manganese bacterial growths, known as Crenothrix, are prevented by removal of these metals, followed by chlorination

4.5.4. Specifications for Drinking Water

The common specifications recommended by the U.S Public Health for Drinking Water are given below.

1. Water should be clear and odourless.

2. It should be cool.

3. It should be pleasant to taste.

4. Turbidity of the water should not exceed 10 ppm.

5. pH of the water should be in the range of 7.0 - 8.5.

6. Chloride and sulphate contents should be less than 250 ppm.

7. Total hardness of the water should be less than 500 ppm.

8. Total dissolved solids should be less than 500 ppm.

9. Fluoride content of the water should be less than 1.5 ppm.

10. The water must be free from disease-producing bacteria.

11. Water should be free from objectionable dissolved gases like H2S.

12. Water should be free from objectionable minerals such as lead, chromium, manganese and arsenic salts.

4.5.5 Water Quality Standards

Water used for drinking should have certain quality. The following table 4.4 summarizes several quality criteria and their standards for drinking water.

Table 4.4 Standards for drinking water

S.No. ParameterWHO standard

in mgs/litreISI standardin mgs/litre.

1.Colour, odour and

taste.

Colourless,odourless and

tasteless

Colourless,odourless and

tasteless.

2. pH 6.9 6.9

3. Total dissolved solids 1500 -

S.No.

Parameter WHO standardin mgs/litre

ISI standardin mgs/litre.

4. Dissolved oxygen

- 3.0

5. Chloride 250 600

6. Sulphate 400 1000

7. Nitrate 45 -

8. Cyanide 0.2 0.01

9. Fluoride 1.5 3.0

10. Chromium 0.05 0.05

11. Lead 0.05 0.1

12. Arsenic 0.05 0.2

4.5 WATER POLLUTION

Definition

Water pollution may be defined as, “the alteration in physical, chemical and biological characteristics of water which may cause harmful effects on humans and aquatic life.”

The pollutants include sewage, industrial chemicals and effluents, oil and other wastes. Besides, chemicals from the air dissolved in rain water, and fertilizers, pesticides and herbicides leached from the land also pollute water.

4.6.1 Types, effects and sources (causes) of water pollution

Water pollution is any chemical, biological or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses.

1. Infectious Agents


Human and animals wastes.

Bacteria, viruses, protozoa and parasitic worms.

Effects

Variety of diseases.

2. Oxygen Demanding Wastes (Dissolved oxygen)

Organic wastes such as animal manure and plant debris that can be decomposed by aerobic(oxygen-requiring) bacteria.

This degradation consumes dissolved oxygen in water. Dissolved oxygen (DO) is the amount of oxygen dissolved in a given quantity of water at a particular pressure and temperature.

The saturated point of DO varies from 8-15 mg/lit.


Sewage, animal feedlots, paper mills, and food processing facilities.

Effects

Large populations of bacteria decomposing these wastes can degrade water quality by depleting water of dissolved oxygen. This causes fish and other forms of oxygen-consuming aquatic life to die.

3. Inorganic chemicals

Water soluble inorganic chemicals

(i) acids,

(ii) compounds of toxic metals such as lead (Pb), arsenic (As) and selenium (Se) and

(iii) salts such as NaCl in ocean water and fluorides (F-) found in some soils.


Surface runoff, industrial effluents and household cleansers.

Effects

(i) Can make fresh water unusable for drinking or irrigation.

(ii) Causes skin cancers and neck damage.

(iii) Damage the nervous system, liver and kidneys.

(iv) Harm fish and other aquatic life.

(v) Lower crop yields.

(vi) Accelerates corrosion of metals exposed to such water.

4. Organic Chemicals

Oil, gasoline, plastics, pesticides, cleaningsolvents, detergents.


Industrial effluents, household cleansers, surface runoff from farms.

Effects

(i) Can threaten human health by causing nervous system damage and some cancers.

(ii) Harm fish and wild life.

5. Plant Nutrients

Water-soluble compounds containing nitrate(NO3

- ), phosphate (PO43- ) and

ammonium(NH4+ ) ions.


Sewage, manure, and runoff of agricultural and urban fertilizers.

Effects

(i) Can cause excessive growth of algae and other aquatic plants, which die, decay, deplete dissolved oxygen in water and kill the fish.

(ii) Drinking water with excessive levels of nitrates lower the oxygen carrying capacity of the blood and can kill urban children and infants.

6. sediments

Soil, silt, etc.,


Land erosion.

Effects

(i) Can reduce photosynthesis and cloud water.

(ii) Disrupt aquatic food webs.

(iii) Carry pesticides, bacteria, and other harmful substances.

(iv) Settle out and destroy feeding and spawning rounds of fish.

(v) Clog and fill lakes, artificial reservoirs, stream channels and harbours.

7. Radioactive Materials

Radioactive isotopes of iodine, radon, uranium, cesium, and thorium.


Nuclear power plants, mining and processing of uranium and other ores, nuclear weapons production and natural sources

Effects

Genetic mutations, birth defects, and certain cancers.

8. Heat (Termal Pollution)

Excessive heat


Water cooling of electric power plants and some types of industrial plants. Almost half of all water withdrawn in United States each year is for cooling electric power plants.

Effects

1. Lowers dissolved oxygen levels and makes aquatic organisms more vulnerable to disease, parasites and toxic chemicals.

2. When a power plant first opens or shuts down for repair, fish and other organisms adapted to a particular temperature range can be killed by the abrupt change in water temperature known as thermal shock

9. Point and Non-point Sources of Water Pollution

1. Point Sources

Point sources are discharged pollutants at specific locations through pipes, ditches or sewers into bodies of surface water.

Includes factories, sewage treatment plants, abandoned underground mines and oil tankers.

2. Non-point sources

They are usually large land areas or air sheds that pollute water by runoff, subsurface flow or deposition from the atmosphere. Location of which cannot be easily identified.

Include acid deposition and runoff of chemicals into surface water from croplands, livestock feedlots, logged forests, urban street, lawn, golf courses and parking lots.

4.6.2 Characteristics (or) Testing of riverwater (waste water)

1. Dissolved oxygen (DO)

Dissolved oxygen (DO) is the amount of oxygen dissolved in a given quantity of water at a particular pressure and temperature.

Significance of DO

(i) DO is vital for the support of fish and other aquatic life in river water.

(ii) It determines whether the biological changes are brought about by aerobic or anaerobic micro-organisms.

(iii) DO determinations serve as the means of control of river pollution.

(iv) A minimum level of DO (4 mg/lit) must be maintained in rivers so as to support the aquatic life in a healthy condition. Thus, it is necessary to ensure that the treated water must have atleast 4 mg/lit of DO before its disposal into river.

2. Biochemical Oxygen Demand (BOD)

BOD is the amount of oxygen required for the biological decomposition of organic matter present in the water.

Significance of BOD

(i) It is an important indication of the amount of organic matter present in the river water.

(ii) Since complete oxidation occurs in indefinite period, the reaction period is taken as 5 days at 200C. For all practical purposes, it is written as BOD5.

(iii) The rate of oxidation and demand depends on the amount and type of organic matter present in river water.

3. Chemical Oxygen Demand (COD)

COD is the amount of oxygen required for chemical oxidation of organic matter using some oxidising agent like K2Cr2O7 and KMnO4.

Significance of COD

(i) It is carried out to determine the pollutional strength of river water.

(ii) It is rapid process and takes only 3 hours.

4.6.3 Control measures (methods) of waterpollution

1. The administration of water pollution control should be in the hands of State or Central Government.

2. Scientific techniques are necessary to be adopted for the environmental control of catchment areas of rivers, ponds or streams.

3. The industrial plants should be based on recycling operations, because it will not only stop the discharge of industrial wastes into natural water sources but by products can be extracted from the wastes.

4. Plants, trees and forests control pollution and they acts as natural air conditioners.

5. Forests in and around big cities and industrial establishments are capable of reducing the sulphur dioxide and nitric oxide pollutants to a greater extent from the atmosphere. Hence the national goal should be “Conservation of Forests” and campaign should be “Plant more trees”.

The global destruction of forests should be discouraged or atleast minimized and afforestation should be encouraged because no one on this earth will escape from the adverse effects of a balding earth.

6. It is not advisable to discharge any type of waste, either treated, partially treated or untreated, into streams, rivers, lakes, ponds and reservoirs. The industries are expected to develop close-loop water supply schemes and domestic sewage may be used for irrigation.

7. Highly qualified and experienced persons should be consulted from time to time for effective control of water pollution

8. Public awareness regarding adverse effects of water pollution is a must. So there should be propagand a for water pollution control on radios, TVs etc.,

9. Suitable laws, standards and practices should be framed to regulate the discharge of undesirable flow of water in water bodies and such regulations should be modified from time to time in order to accommodate the changing requirements and technological advancements.

10. Basic and applied research in public health engineering should be encouraged.

11. The possible reuse or recycle of treated sewage effluents and industrial wastes should be emphasized and encouraged.

4.6.4 Waste Water (or) Sewage Treatment

Objectives of waste water treatment

The main objectives of waste water treatment are

(i) to convert harmful compounds into harmless compounds.

(ii) to eliminate the offensive smell.

(iii) to remove the solid content of the sewage.

(iv) to destroy the disease producing microorganisms.

Treatment Process

The sewage (or) waste water treatment process involves the following steps.

I. Preliminary Treatment

In this treatment, coarse solids and suspended impurities are removed by passing the waste water through bar and mesh screens.

II. Primary treatment (or) Settling process

In this treatment, greater proportion of the suspended inorganic and organic solids are removed from the liquid sewage by settling. In order to facilitate quick settling coagulants like alum, ferrous sulphate are added.

These produce large gelatinous precipitates, which entrap finely divided organic matter and settle rapidly.

III. Secondary (or) Biological treatment

In this treatment, biodegradable organic impurities are removed by aerobic bacteria. It removes upto 90% of the oxygen demanding wastes. This is done by trickling filter or activated sludge process.

1. Trickling filter process

Trickling filter is a circular tank and is filled with either coarse or crushed rock. Sewage is sprayed over this bed by means of slowly rotating arms (Fig. 4.5).

When sewage starts percolating downwards, microorganisms present in the sewage grow on the surface of filtering media using organic material of the sewage as food.

After completion of aerobic oxidation the treated sewage is taken to the settling tank and the sludge is removed. This process removes about 80-85% of BOD.

Fig. 4.5 Trickling filter

2. Activated sludge process

Activated sludge is biologically active sewage and it has a large number of aerobic bacterias, which can easily oxidise the organic impurities.

The sewage effluent from primary treatment is mixed with the required amount of activated sludge. Then the mixture is aerated in the aeration tank (Fig. 4.6). Under these condition,

organic impurities of the sewage get oxidised rapidly by the micro-organisms.

After aeration, the sewage is taken to the sedimentation tank. Sludges settle down in this tank, called activated sludge, a portion of which is used for seeding fresh batch of the sewage. This process removes about 90-95% of BOD.

IV. Tertiary treatment

After the secondary treatment, the sewage effluent has a lower BOD (25 ppm), which can be removed by the tertiary treatment process.

In the tertiary treatment, the effluent is introduced into a flocculation tank, where lime is added to remove phosphates.

From the flocculation tank the effluent is led to ammonia stripping tower, where pH is maintained to 11 and the NH4 is converted to gaseous NH3.

Then the effluent is allowed to pass through activated charcoal column, where minute organic wastes are adsorbed by charcoal. Finally the effluent water is treated with disinfectant (chlorine).

V. Disposal of sludge

This is the last stage in the sewage treatment. Sludge formed from different steps can be disposed by

(i) dumping into low-lying areas.

(ii) burning of sludge (incineration),

(iii) dumping into the sea,

(iv) using it as low grade fertilizers.

The flow sheet diagram of sewage treatment

4.7 ABSORPTION OF HEAVY METALS

Heavy metals are chemical elements with a specific gravity that is at least 5 times the specific gravity of water(sp.gr. of water is 1 at 40C). Heavy metal includes most metals with an atomic number greater than 20.

4.7.1 Sources of heavy metals in theenvironment

There are a number of heavy metals in the nvironment.Some of them are toxic and the rest non-toxic.

Mining industry, chemical and leather industries and thermal power plants contribute heavy metals in the atmosphere.

Health Effect

Small amounts of the heavy metals like antimony, arsenic, bismuth, cadmium, cerium, chromium, cobalt, lead,copper, gold are necessary for good health. But large amount of any one of them may cause acute or chronic toxicity(poisoning).

4.7.2 Removal of heavy metals by absorption

Heavy metals present in water may be removed by the following absorption process.

1. Using coconut shell carbons

Coconut - based carbon was found to remove 94% of Cr (VI) solution after a 4 hrs contact time during equilibrium batch tests.

2. Using Rice - Husk carbon (RHC)

Rice hulls (or) Rice husk is a better and low cost adsorbent used in water treatment process. The activated form of rice husk adsorbent can be used for the adsorption of Cr and Zn metal ions.

3. Using Fly ash

Fly ashes like pulverized - fuel (fly) ash, combustion of powdered coal are used as an very good adsorbents in water purification. Fly ash (or) fly ash and coal fly ash blends are used for the removal of heavy metals such as copper and chromium ions from waste water.

4. Using Clay and coal - based adsorbents

(a) Fuller’s earth and calcined kaoline have been investigated for the removal of Pb and Cd from the water.

(b) China clay was used for the removal of As (III) and Zn (II) from distilled water.

4.7.3 Water treatment process

1. Zeolite (or) Permutit Process

Zeolites are naturally occurring hydrated sodium aluminosilicate. Its general formula is Na2O . Al2O3 . xSiO2. yH2O . (x = 2 - 10 , y = 2 – 6) .

Natural zeolites are green sand and non-porous. The synthetic form of zeolite is known as permutit, which is porous and possess gel structure, hence it is generally used for water softening.

Synthetic zeolite is represented by Na2Ze. The sodium ions which are loosely held in Na2Ze are replaced by Ca2+ and Mg2+ ions present in the water.

Process

When hard water is passed through a bed of sodium zeolite (Na2Ze), kept in a cylinder (Fig. 4.7), it exchanges its sodium ions with Ca2+ and Mg2+ ions present in the hard water to form calcium and magnesium zeolites. The various reactions taking place during softening process are

Fig. 4.7 Zeolite (or) Permutit process

The softened water is enriched with large amount of sodium salts, which do not cause any hardness, but cannot be used in boiler.

Regeneration

After some time zeolite gets exhausted. The exhausted zeolite is again regenerated by treating with 10% solution of NaCl.

Advantages of Zeolite process

1. Water obtained by this process will have onlyhardness of 1-2 ppm.

2. This method is cheap, because the regenerated zeolite can be used again.

3. No sludge is formed during this process.

4. The equipment used is compact and occupies a small space.

5. Its operation is easy.

Disadvantages of Zeolite process

1. Turbid water cannot be treated, because it blocks the

pores of the zeolite bed.

2. Acidic water cannot be treated, because it decomposes the structure of zeolite.

3. Water containing Fe, Mn cannot be treated, because

regeneration is very difficult.

4. This process cannot be used for softening brackish

water, because brackish water contains Na+ ions. So the ion exchange reaction will not occur.

2. Ion Exchange (or) Demineralisation process

This process removes almost all the ions (both anions and cations) present in the hard water.

The soft water, produced by lime-soda and zeolite processes, does not contain hardness producing Ca2+ and Mg2+ ions, but it will contain other ions like Na+, K+, SO4

2-, Cl- etc. On the other hand DM. (Demineralised) water does not contain both anions and cations.

Thus a soft water is not demineralised water whereas a demineralised water is soft water.

Types of ion exchange resins

This process is carried out by using ion exchange resins,which are long chain, cross linked, insoluble organic polymers with a microporous structure. The functional groups attached to the chains are responsible for the ion exchanging properties.

1. Cation exchanger

Resins containing acidic functional groups (-COOH, -SO3H) are capable of exchanging their H+ ions with other cations of hard water. Cation exchange resin is represented as RH2.

2. Anion Exchanger

Resins containing basic functional groups (-NH2, -OH) are capable of exchanging their anions with other anions of hard water. Anion exchange resin is represented as R (OH)2.

Process

The hard water first passed through a cation exchange column, (Fig. 4.8) which absorbs all the cations like Ca2+, Mg2+, Na+, K+, etc., present in the hard water.

Fig. 4.8 Ion Exchange (or) Demineralisation process

The cation free water is then passed through a anion exchange column, which absorbs all the anions like Cl-, SO4

2-, HCO3-, etc., present in the water.

The water coming out of the anion exchanger is completely free from cations and anions. This water is known as demineralised water or deionised water.

Regeneration

When the cation exchange resin is exhausted, it can be regenerated by passing a solution of dil HCl or dil H2SO4.

Similarly, when the anion exchange resin is exhausted,it can be regenerated by passing a solution of dil NaOH.

Advantages of ion-exchange process

1. Highly acidic or alkaline water can be treated by this process.

2. The water obtained by this process will have very low hardness (nearly 2 ppm).

Disadvantages of ion-exchange process

1. Water containing turbidity, Fe and Mn cannot be treated, because turbidity reduces the output and Fe, Mn form stable compound with the resin.

2. The equipment is costly and more expensive chemicals are needed.

4.8 SOIL POLLUTION

Definition

Soil pollution is defined as, “the contamination of soil by human and natural activities which may cause harmful effects on living beings.”

Table 4.5 Composition of soil

Components %

Mineral matter (inorganic)

45

Organic matter 5

Soil water 25

Soil air 25

4.8.1 Types, effects and sources (causes) ofsoil pollution

Soil pollution mainly results from the following sources

1. Industrial wastes.

2. Urban wastes.

3. Agricultural practices.

4. Radioactive pollutants.

5. Biological agents.

1. Industrial wastes

Disposal of industrial wastes is the major problem for soil pollution

Sources

The industrial pollutants are mainly discharged from the various origins such as pulp and paper mills, chemical industries, oil refineries, sugar factories, tanneries, textiles,steel, distilleries, fertilizers, pesticides, coal and mineral mining industries, drugs, glass, cement, petroleum and engineering industries etc.,

Effect

These pollutants affect and alter the chemical and biological properties of soil. As a result, hazardous chemicals can enter into human food chain from the soil or water and disturb the biochemical process and finally lead to serious effects on living organisms.

2. Urban wastes

Urban wastes comprises both commercial and domestic wastes consisting of dried sludge of sewage. All the urban solid wastes are commonly referred to as refuse.

Constituents of urban refuse

This refuse contains garbage and rubbish materials like plastics, glasses, metallic cans, fibres, paper, rubbers, street sweepings, fuel residues, leaves, containers, abandoned vehicles and other discarded manufactured products.

Urban domestic wastes though disposed off separately from the industrial wastes, can still be dangerous. This is so because they cannot be easily degraded.

3. Agricultural practices

Modern agricultural practices pollute the soil to a large extent. Today with the advancing agro-technology, huge quantities of fertilizers, pesticides, herbicides, weedicides are added to increase the crop yield. Apart from these farm wastes,manure, slurry, debris, soil erosion containing mostly inorganic chemicals are reported to cause soil pollution.

4. Radioactive pollutants

Radioactive substances resulting from explosions of nuclear dust and radioactive wastes (produced by nuclear testing laboratories and industries) penetrate the soil and accumulate there by creating land pollution.

1. Radio nuclides of radium, thorium, uranium, isotopes of potassium (K-40) and carbon (C-14) are very common in soil, rock, water and air.

2. Explosion of hydrogen weapons and cosmic radiations induce neutron, proton reactions by which nitrogen (N-15) produces C-14. This C-14 participates in the carbon metabolism of plants which is then introduced into animals and man.

3. Radioactive waste contains several radio nuclides such as Strontium-90, Iodine-129, Cesium-137 and isotopes of iron which are most injurious. Sr-90 gets deposited in bones and tissues instead of calcium.

4. Nuclear reactor produces waste containing Ruthenium-106, Iodine-131, Barium-140 and Lanthanum-140, Cesium-144 along with the primary nuclides Sr-90 and Cs-137 has a half life of 30 years while Sr-90 has 28 years. Rain water carries Sr-90 and Cs-137 to be deposited on the soil where they are held firmly with the soil particles by electrostatic forces. All these radio nuclides deposited on the soil emit gamma radiations.

5. Biological agents

Soil gets large quantities of human, animal and bird’s excreta which constitute the major source of land pollution by biological agents.

1. Heavy application of manures and digested sludges could cause serious damage to plants within a few years. Because the sludges are containing more live viruses and viable intestinal worms.

2. In addition to these excreta, faulty sanitation, municipal garbage, waste water and wrong methods of agricultural practices also induce heavy soil pollution.

Table 4.6 Major physico-chemical characteristics ofuntreated wastes of Organic chemical industries in Soil

S.No Industry Physico-chemical characteristics

1. Pulp and paper

Suspended solids, high or low pH,colour, fibres, BOD, COD, hightemperature, fibres.

2. Rubber industry

Chlorides, suspended and dissolvedsolids, variable pH and high BOD.

3. Oil refineries Acids, alkalis, phenols, resinousmaterials and petroleum oils.

4. Antibiotics Toxic organics and high acidity oralkalinity.


5. Synthetic drugs

High suspended and dissolvedorganic matter including vitamins.

6. Distillery

Very high COD, low pH, highorganic matter, high suspended anddissolved solids containing nitrogen,high potassium.

7.Organic chemicalindustry

Toxic compounds, phenols, highacidity, alkalinity.

Table 4.7 Major physico-chemical characteristics ofuntreated wastes of Inorganic chemical industries in Soil


1.Thermal PowerPlants

Heat, heavy metals, dissolved solidsand inorganic compounds.

2. Steel Mills

Acids, phenols, low pH, alkali,limestone, oils, fine suspendedsolids, cyanides, cyanates, iron salts,ores and coke.

3. Cotton Industry

Sodium, organic matter, colour, highpH and fibres.


4. Metal Plating Metallics, toxic cyanides, cadmium,chromium, zinc, copper, aluminiumand low pH.

5. Iron Foundry Coal, clay, suspended solids andiron.

6. Pesticides Aromatic compounds, acidity andhigh organic matter.

7. Acids Low pH and organic content.

8. Tanneries Calcium, chromium, high saltcontent, colour, dissolved andsuspended matter.

9. Explosives Alcohol, metals, TNT and organicacids.

4.8.2 Control measures of soil pollution

The pressure on intensification of farm activities increases for two reasons.

1. Population growth.

2. Decrease of the available farm land due to urbanization.

1. Control of Soil erosion

Soil erosion can be controlled by a variety of forestry and farm practices.

(a) Trees may be planted on barren slopes.

(b) Contour cultivation and strip cropping may be practiced instead of shifting cultivation.

(c) Terracing and building diversion channels may be undertaken.

Reducing deforestation and substituting chemical manures by animal wastes would also help to arrest soil erosion in the long term. Maintaining soil productivity is vital and essential for sustainable agriculture.

2. Proper dumping of unwanted materials

Excess of waste products by man and animals cause chronic disposal problem. Open dumping is most commonly practiced method. Recently controlled tipping is followed for solid waste disposal. The surface so obtained then can be used for housing or sports field.

3. Production of natural fertilizers

Excessive use of chemical fertilizers and insecticides should be avoided. Biopesticides should be used in place of toxic chemical pesticides.

Organic wastes contained in animals dung can be used for preparing compost manure and biogas rather than throwing them wastefully polluting the soil.

4. Proper Hygienic condition

People should be trained regarding the sanitary habits.

Lavatories should be equipped with quick and effective disposal methods.

5. Public Awareness

Informal and formal public awareness programs should be imparted to educate people on health hazards by environmental pollution.

Mass media, educational institutions and voluntary agencies can achieve this.

6. Recycling and Reuse of wastes

To minimize soil pollution, the wastes such as paper, plastics, metals, glasses, organics, petroleum products and industrial effluents etc., should be recycled and reused.

Industrial wastes should be properly treated at source. Integrated waste treatment method should be adopted.

7. Ban on Toxic Chemicals

Ban should be imposed on chemicals and pesticides like DDT, BHC etc., which are fatal to plants and animals. Nuclear explosions and the improper disposal of radioactive wastes should be banned

4.9 SOLID WASTE MANAGEMENT (OR)SOIL WASTE MANAGEMENT (OR)

WASTE SHED MANAGEMENT

Rapid population growth and urbanization in developing countries have led to the generations of enormous quantities of solid wastes and consequential environmental degradation.

An estimated 7.6 million tonnes of municipal solid waste is produced per day in developing countries.

These wastes are disposed in open dumps creating considerable nuisance and environmental problems.

These are potential risks to health and to the environment from improper management of solid wastes.

Management of solid waste is therefore, become very important in order to minimize the adverse effects of solid wastes.

4.9.1 Types and sources of solid wastes

Depending upon the nature, solid wastes can be broadly classified into three types

1. Urban (or) Municipal wastes.

2. Industrial wastes.

3. Hazardous wastes.

I. Sources of Urban (Municipal) Wastes

Urban or municipal wastes include the following wastes

1. Domestic wastes: It contains a variety of materials thrown out from the homes.

Food waste, cloth, waste paper, glass bottles, polythene bags, waste metals, etc.,

2. Commercial wastes: It includes the wastes coming out from the shops, markets, hotels, offices, institutions, etc.,

Waste paper, packing material, cans, bottle,polythene bags, etc.,

3. Construction wastes: It includes the wastes of construction materials.

Wood, concrete, debris etc.,

4. Biomedical wastes: It includes mostly the waste organic materials.

Anatomical wastes, infectious wastes, etc.,

Type and characteristics of Urban (municipal) Wastes

(a) Bio-degradable wastes: The urban solid waste materials, that can be degraded by micro organisms are called biodegradable wastes.

Food, vegetables, tea leaves, egg shells, dry leaves, etc.,

(b) Non - Biodegradable wastes: The urban solid waste materials that cannot be degraded by micro organisms are called non-biodegradable wastes.

Polythene bags, scrap metals, glass bottles, etc.,

II. Source and Characteristics of Industrial Wastes

The main sources of industrial wastes are chemical industries, metal and mineral processing industries.

1. Nuclear power plants: It generates radioactive wastes.

2. Thermal power plants: It produces fly ash in large quantities.

3. Chemical industries: It produces large quantities of hazardous and toxic materials.

4. Other industries: Other industries produce, packing materials, rubbish, organic wastes, acids, alkalis, scrap metals,rubber, plastic, paper, glass, wood, oils, paints, dyes, etc.,

III. Hazardous Wastes

Hazardous wastes are the wastes, that pose a substantial danger immediately or over a period of time to human, plant or animal life.

Sources of Hazardous wastes

Chemical manufacturing companies, petroleum refineries, paper mills, smelters, radioactive substances, biological wastes and other industries.

Types and characteristics of hazardous wastes

1. Toxic wastes: These are poisonous even in very small or traces amounts.

(a) Acute toxicity: These wastes have immediate effect on humans or animals causing death.

(b) Chronic toxicity: These wastes have long-term effect slowly causing irreparable harm to the exposed persons. It is much more difficult to determine.

2. Reactive wastes: These wastes react vigorously with air, water, heat and generate toxic gases.

Gun powder, nitroglycerine, etc.,

6. Heavy metals: Lead, mercury and arsenic are hazardous substances.

3. Corrosive wastes: These wastes destroy materials and living tissues by chemical reaction.

Acids and bases

4. Radioactive wastes: These are from nuclear power plants and persist in the environment for thousands of years.

5. Infectious wastes: It causes infection to others.

Used bandages, human tissue from surgery,hypodermic needles, etc.

4.9.2 Effect of Solid Wastes (or) Effect ofImproper Solid Waste Management

1. Due to improper disposal of municipal solid wastes on the road side and their immediate surroundings, biodegradable materials undergo decomposition. This produces foul smell and breeds various types of insects, which spoil the land value.

2. Industrial solid wastes are the sources of toxic metals and hazardous wastes, which affect the soil characteristics and productivity of soils when they are dumped on the soil.

3. Toxic substances may percolate into the ground and contaminate the ground water.

4. Burning of some of the industrial wastes (or) domestic wastes (like cans, pesticides, plastics ,radio active materials, batteries) produce furans ,dioxins and polychlorinated biphenyls, which are harmful to human beings.

4.9.3 Process of Solid Waste Management (or)Process of preventing solid waste generationin urban areas (or) Waste Shed Management

Solid waste management includes, the waste generation, mode of collection, transportation, segregation of wastes and disposal techniques.

Steps Involved in Solid Waste Management (or)Waste Shed Management

Two important steps of solid waste (waste shed) management is Reduce, reuse and recycle, before destruction and safe storage of wastes.

I Reduce, Reuse and Recycle (3R)

1. Reduce the usage of raw materials

If the usage of raw materials are reduced, the generation of waste also gets reduced.

Flow Chart

2. Reuse of waste materials

(a) The refillable containers, which are discarded after use, can be reused.

(b) Rubber rings can be made from the discarded cycle tubes, which reduces the waste generation during manufacturing of rubber bands.

3. Recycling of materials

Recycling is the reprocessing of the discarded materials into new useful products.

(a) Old aluminum cans and glass bottles are melted and recast into new cans and bottles.

(b) Preparation of cellulose insulation from paper.

(c) Preparation of fuel pellets from kitchen waste.

(d) Preparation of automobiles and construction materials from steel cans.

The above process saves money, energy ,raw materials and reduces pollution.

II Discarding wastes

For discarding solid wastes the following methods can be adopted.

Methods of disposal of Solid Waste

1. Landfill

2. Incineration

3. Composting

1. Landfill

Solid wastes are placed in sanitary landfill system in alternate layers of 80cm thick refuse, covered with selected earth fill of 20cm thickness. After two or three years, solid waste volume shrinks by 25-30% and the land is used for parks , roads and small buildings.

The most common and cheapest method of waste disposal is dumping in sanitary land-fills which is invariably employed in Indian cities. Land-fill structure is built either into the ground or on the ground into which the waste is dumped.

The method involves spreading the solid waste on the ground , compacting it and then covering it with soil at suitable intervals.

Advantages

1. It is simple and economical.

2. Segregation not required.

3. Land filled areas can be reclaimed and used for other purposes.

4. Converts low-lying, marshy waste-land into useful areas.

5. Natural resources are returned to soil and recycled.

Disadvantages

1. A large area is required.

2. Since land is available away from town, transportation cost is heavy.

3. Bad odors, if land fills are not properly managed.

4. The land filled areas will be the sources of mosquitoes and flies and hence insecticides and pesticides are to be applied at regular intervals.

5. Causes fire hazard due to the formation of methane in wet weather.

2. Incineration (or) Thermal process

It is a hygienic way of disposing solid waste. It is more suitable if the waste contains more hazardous material and organic content.

It is a thermal process and is very effective for detoxification of all combustible pathogens.

It is an expensive technology compared to land-fill and composting because incinerators are costly.

In this method the municipal solid wastes are burnt in a furnace called incinerator. The combustible substances such as rubbish, garbage, dead organisms and the noncombustible matter such as glass, porcelain, metals are separated before feeding to incinerators.

The noncombustible materials can be left out for recycling and reuse. The left out ashes and clinkers from the incinerators may be accounted for only about 10 to 20% which need further disposal either by sanatory landfill or by some other means.

The heat produced in the incinerator during the burning of refuse is used in the form of steam power for generation of electricity throughout turbines.

The municipal solid waste is generally wet but has a very high calorific value so it has to be dried up first before burning. The waste is dried in preheated from where it is taken into large incinerating furnace called destructors which can incinerate about 100 to 150 tones per hour.

The temperature normally maintained in a combustion chamber is about 7000C and may be increased to about 10000C when electricity is to be generated.

Advantages

1. The residue is only 20-25% of original weight, the clinker can be used after treatment.

2. It requires very little space.

3. Cost of transportation is not high as incinerators located within city limits.

4. Safest from hygienic point of view.

5. An incinerator plant of 300 tones per day capacity can generate 3MW of power.

Disadvantages

1. Its capital and operating cost is high.

2. Needs skilled personnel.

3. Formation of smoke, dust and ashes needs further disposal, due to which air pollution may be caused.

3. Composting

It is another popular method practiced in many cities in our country. In this method, bulk organic waste is converted into a fertilising manure by biological action.

The separated compostable waste is dumped in underground earthern trenches in layers of 1.5 m and is finally covered with earth of about 20 cm and left over for decomposition.

Sometimes certain microorganisms such as actinomycetes are introduced for active decomposition.

Within 2 to 3 days biological action starts, the organic matters are being destroyed by actinomycetes and lot of heat is liberated increasing the temperature of the compost by about 750C and finally the refuse is converted to powdery brown coloured odourless mass known as humus and has a fertilizing value which can be used for agricultural field.

The compost contains lot of nitrogen essential for plant growth apart from phosphates and other minerals.

World Health Organisation (WHO) has set up a compost plant in New Delhi in 1981 with a capacity to handle 90 to 100 tonnes of waste everyday. The prepared compost was supplied to nurseries, kitchen gardens and horticulture department. The composting technology is widely employed in developing countries.

Advantages

1. When the manure is added to soil, it increases the water retention and ion-exchange capacity of soil.

2. A number of industrial solid wastes can also be treated by this method.

3. It can (manure) be sold thereby reducing the cost of disposing of wastes.

4. Recycling - occurs.

Disadvantages

1. The non-consumables have to be disposed separately.

2. Use of compost has not yet caught up with farmers and hence no assured market.

4.9.4 Objectives (or) significance forprevention of hazardous wastes management

1. Avoid (or) reduce generation of hazardous wastes.

2. Dispose the wastes as close as possible to the place where they are generated.

3. Manage the wastes in environmentally sound and effective way.

4. Optimise environmentally sound recover of the hazardous wastes.

5. Prevent illegal international traffic in hazardous wastes.

6. Promoting and strengthening institutional capacities in hazardous waste management.

7. Promoting and strengthening international co-operations in the management.

8. Promoting the prevention and minimisation of using hazardous wastes.

9. Reduce to a minimum (or) eliminate the trans boundary movements.

4.10 MARINE POLLUTION

Definition

Marine pollution is defined as, “the discharge of wastesubstances into the sea resulting in harm to living resources,hazards to human health, hindrance to fishery and impairment of quality for use of sea water.”

Marine pollution is associated with the changes in physical, chemical and biological conditions of the sea water. This water is also unfit for human consumption and industrial purposes because of high salt content. Chemically it is a solution of 0.5 M NaCl and 0.005 M MgSO4 containing traces of all conceivable matter in the universe.

About half of the world population live nearer to coastal lines and derive many benefits from the coastal zones and oceans. The coastal zones contains rich heritage, coral reefs, wetlands and seagrass beds

Coral reefs

Coral reefs are underwater structures made from calcium carbonate secreted by corals. Corals are colonies of tiny living animals found in marine waters containing few neutrients. Most coral reefs are built from stony corals.

Benefits (or) importance of coral reefs

The coral reefs which are the most productive eco-systems offer many benefits to people.

1. Reefs support more than one millions species.

2. They provide feeding, breeding and nursery areas to fish and shell fish.

3. They offer medicines.

4. They act as buffer to ocean waves and protect coastal lines from storms and so on.

The coral reefs have been valued at 47 thousands US dollars per square meter of shoreline for their protection function alone. The coastal wetlands provide habitats for over 2000 species of fish and plants. Sea grass beds which are under water ocean grass lands support a wide variety of commercially valuable species of fish

Factors affecting coral reefs

The coral reefs are threatened by

1. The sediment from deforestation carried by the runoffs.

2. The agricultural and industrial chemicals reaching through river discharges.

3. The boat anchors and the careless divers.

4. Rising ocean temperatures, ocean acidification.

4.10.1 Sources (causes) of marine pollution

1. Dumping the Wastes

The most serious issue is dumping of untreated wastes and sewage into oceans by the coastal towns and cities and industrial units.

All that what is carried by rivers ultimately ends up in the seas. On their way to sea, rivers receive huge amounts of sewage, garbage, agricultural discharge, pesticides,including, heavy metals.

These all are added to sea. Huge quantity of plastic is being dumped in sea.

Effect

Many marine birds ingest plastic that causes gastro-intestinal disorders.

2. Oil pullution of Marine Water

The great damage to water is imposed by petroleum and its products.

Oil enters water from cracks of oil tankers,accidental spillage, cleaning of fuel tanks by merchant and warships and also from street cleaning.

Heavy petroleum products precipitate to the bottom or are adsorbed on rock, stone, and sand banks to inhibit the life of the hydrobionts. One drop of petroleum spreads over a great area to isolate the water from contact with atmospheric oxygen.

EffectsThe continuous oil films inhibit photosynthesis

and the formation of oxygen. This inhibits the growth of plankton,which is the main source of the hydrobionts inhabiting the water body.

All aquatic animals depend either directly or indirectly on plankton, which is the basis of the trophic chain.

The surface of water in contact with the shore is usually contaminated with oil, which interferes with the normal development of many hydrocarbons.

4.10.2 Effects of Marine pollution1. The presence of heavy metals and organic pollutants

cause more damage in birds as thinning of eggshell and tissue damage of egg.

2. Oil pollution cause damage to marine fauna and flora including algae, fish, birds, invertebrates. About 50,000 to 2,50,000 birds are killed every year by oil.

3. Oil spilling in sea water causes abnormally low body temperature in birds resulting in hypothermia. Nearly 150 rare species of bald eagles also became victims when they ingested oil during Exxon Valdez accident.

4. Oil films are able to retard significantly the rate of oxygen uptake by water.

5. The continuous oil films inhibit photosynthesis and formation of oxygen. This inhibits the growth of plankton, which is the main source of the hydrobionts inhabiting the water body.

6. Hydrocarbons and benzpyrene accumulate in food chain and consumption of fish by man may cause cancer. Detergents used to clean up the spill are also harmful to marine life.

4.10.3 Control Measures of Marine Pollution

The world wide fund for Nature and World Conservation Union suggested a plan for sustainable management involving six principles.

1. Plans for conserving marine biodiversity must be taken into account of human needs.

2. People should be educated about marine ecosystems and the benefits offered by them.

3. Local communities must be involved in protecting and managing their coastal resources.

4. Social and economic incentives must be offered for conserving and sustainable use of marine resources.

5. The fact that all the oceans in the world are connected must be reflected in the policies.

6. Governments must manage their own waters while extending cooperation to the neighbouring states.

Other control measures

1. The industrial units on the coastal lines should be equipped with pollution control instruments and efficient treatment facilities.

2. The urban growth near the coasts should be regulated.3. The needs of fisherman, who live on the coasts and

depend on marine resources, should be accommodated.

Methods of removal of oil

Several methods have been devised to deal with oil floating on the sea

1. Physical Methods

(i) Skimming the oil off the surface with a suction device appears to be the simplest method.

(ii) The floating oil can be absorbed using a suitable absorbing material like polyurethane foam. Chopped straw and saw dust can also be used to absorb oil from the sea water.

(iii) Chemicals can be used to coagulate the oil.

2. Chemical Methods

(i) Dispersion.

(ii) Emulsification.

(iii) Using chemical additives.

Protective measuresSome of the protective measures are

(a) Municipal and industrial wastes should be treated before being allowed to join the sea.

(b) Coastal wastes should be periodically analyzed for detecting pollution levels.

(c) Soil erosion in the coastal land should be arrested by suitable control techniques.

(d) Recreational beaches should be maintained to meet hygienic and aesthetic standard.

4.11 NOISE POLLUTION

Definition

Noise pollution is defined as, “the unwanted, unpleasant or disagreeable sound that causes discomfort for all living beings.”

Unit of Noise (Decibel)

The sound intensity is measured in decibel (dB), which is one tenth of the longest unit Bel. One dB is equal to the faintest sound, a human ear can hear.

Noise level

Normal conversation sound ranges from 35 dB to 60 dB. Impairment of hearing takes place due to exposure to noise of 80 dB or more. Noise above 140 dB becomes painful.

4.11.1 Types and sources (causes) of noise

It has been found that environmental noise is doubling every 10 years. Generally noise is described as,

1. Industrial noise.

2. Transport noise.

3. Neighbourhood noise.

1. Industrial Noise

Highly intense sound or noise pollution is caused by many machines.

There exists a long list of sources of noise pollution including different machines of numerous factories, industries and mills.

Industrial noise, particularly from mechanical saws and pneumatic drill is unbearable and is a nuisance to public.

In the steel industry, the workers near the heavy industrial blowers are exposed to 112 dB for eight hours and suffer from the occupational pollution.

Recently, it has been observed by the Institute of Oto-Rino Laryngology, Chennai that enormously increasing industrial pollution has damaged the hearing of about 20% workers.

2. Transport Noise

The main noise, comes from transport. It mainly includes road traffic noise, rail traffic noise and air craft noise. The number of road vehicles like motors, scooters, cars, motor cycles, buses, trucks and particularly the diesel engine vehicles have increased enormously in recent years.

That is why, this form of pollution is gaining importance, especially in large and over crowded towns and cities. According to experts, the noise level in most of the residential areas in metropolitan cities is already hovering on the border line because of vehicular noise pollution.

A survey conducted in metropolitan cities has shown that noise level in Delhi, Bombay and Calcutta is as high as 90 dB. Inhabitants of cities are subjected to this most annoying form of transport noise which gradually deafen them.

3. Neighbourhood Noise

This type of noise includes disturbance from household gadgets and community. Common noise makers are musical instruments, TV, VCR, radios, transistors, telephones, and loudspeakers etc., Ever since the industrial revolution, noise in environment has been doubling every ten years.

4.11.2 Effects of Noise Pollution

1. Noise Pollution affects human health, comfort and efficiency. It causes contraction of blood vessels, makes the skin pale, leads to excessive secretion of adrenalin hormone into blood stream which is responsible for high blood pressure. Blaring sounds have known to cause mental distress, heart attacks neurological problems, birth defects and abortion.

2. It causes muscles to contract leading to nervous breakdown, tension etc.,

3. These adverse reactions are coupled with a change in hormone content of blood, which in turn increase the rate of heart beat, contraction of blood vessels, and dilation of pupil of eye.

4. It affects health efficiency and behaviour. It may cause damage to heart, brain, kidneys, liver and may also produce emotional disturbances.

5. The most immediate and acute effect of noise is the impairment of hearing which diminishes by the damage of some part of auditory system. When exposed to very loud and sudden noise acute damage occurs to the ear drum. Prolonged exposure to noise of certain frequency pattern will lead to chronic damage to the hair cells in the inner ear.

6. In addition to serious loss of hearing due to excessive noise, impulsive noise also causes psychological and pathological disorders.

7. Ultrasonic sound can affect the digestive, respiratory,cardio vascular systems and semicircular canals of the internal ear. The rate of heart beat may also be affected. It may decrease or increase depending on the type of noise.

8. Brain is also adversely affected by loud and sudden noise as that of jet and aeroplane noise etc. People are subjected to Psychiatric illness.

9. Recently it has been reported that blood is also thickened by excessive noises.

10. It is quite surprising that our optical system is also a prey for noise pollution. Pupillary dilation, impairment of night vision and decrease in the rate of colour perception are some of its severe effects.

4.11.3 Control measures of noise pollution

1. Source Control

This may include source modification such as acoustic treatment to machine surface, design changes, limiting the operational timings and so on.

2. Transmission Path Intervention

This may include containing the source inside a sound insulating enclosure, construction of a noise barrier or provision of sound absorbing materials along the path.

3. Receptor control

This includes protection of the receiver by altering the work schedule or provision of personal protection devices such as ear plugs for operating noisy machinery. The measure may include dissipation and deflection methods.

4. Oiling

Proper oiling will reduce the noise from the machines.

5. Planting trees around houses can also act as effective noise barriers.

6. Different types of absorptive materials can be used to control interior noise.

4.11.4 Preventive measures

Noise can be reduced by prescribing noise limits for vehicular traffic, ban on honking of horns in certain areas and creation of silent zones near schools and hospitals and redesigning of buildings to make them noise proof.

Other measures can involve reduction of traffic density in residential areas and giving preferences to mass public transport system.

Zone Day-time Night-time

Silent zone 50 40

Residential zone 55 45

Commercial zone 65 55

Industrial zone 70 70

Table 4.8 Ambient Noise Level dB.

4.12 THERMAL POLLUTION

Definition

Thermal pollution is defined as the addition of excess of undesirable heat to water that makes it harmful to man, animal or aquatic life or otherwise causes significant departures from the normal activities of aquatic communities in water.

4.12.1 Sources (causes) of Thermal pollution

The following sources causes thermal pollution.

1. Nuclear power plants.

2. Coal-fired power plants.

3. Industrial effluents.

4. Domestic sewage.

5. Hydro-electric power.

1. Nuclear power plants

Nuclear power plants including drainage from hospitals, research institutes, nuclear experiments and explosions, discharged a lot of unutilized heat and traces of toxic radio nuclides into nearby water streams.

Emissions from nuclear reactors and processing installation are also responsible for increasing the temperature of water bodies.

The operations of power reactors and nuclear fuel processing units constitute the major contributor of heat in the aquatic environment.

Heated effluents, from power plants, are discharged at 100C, higher than the receiving water will affect the aquatic flora and fauna.

2. Coal-fired power plants

Some thermal power plants utilize coal as fuel, while a few plants use nuclear fuel. Coal-fired power plants constitute the major source of thermal pollutants.

Their condenser coils are cooled with water from nearby lake or river and discharge the hot water back to the stream increasing the temperature of nearby water to about 150C.

The heated effluents decrease the dissolved oxygen content of water. It results into killing of fish and other marine organisms.

3. Industrial effluents

Industries, generating electricity like coal powered and nuclear powered plants, require huge amounts of cooling water for heat removal.

Other industries like textile, paper and pulp as well as sugar also release heat in water but to a much lesser extent. Normally the discharged water from stream-electric power industry using turbo generators, will have a higher temperature ranging from 60C to 90C than the receiving water.

This results in the increase of stream temperature to a level at which natural dissipation of heat will be inefficient.

In modern stations, producing 100 MW, nearly one million gallons are discharged in an hour with increase in temperature of the cooling water passing by 8 to 100C.

4. Domestic Sewage

Domestic sewage is commonly discharged into rivers, lakes, canals or streams with or without waste treatment. The municipal sewage normally has a higher temperature than the receiving water.

With the increase in temperature of the receiving water, the dissolved oxygen content decreases and the demand of oxygen increases.

5. Hydroelectric Power

Generation of hydroelectric power, sometimes, results in negative thermal loading in water systems. Apart from electric power industries, various factories with cooling requirement contribute to thermal loading.

It has been reported that about 18% more heat is given to cooling waters in nuclear power plants than any other plant of equivalent size.

Hence the anaerobic condition will set up resulting in the release of foul and offensive gases in water. The marine organisms which depend on the dissolved oxygen will die out.

4.12.2 Introduction of thermal pollution intostreams by human activities

1. Industries and power plants use water to cool machinery and then discharge the warmed water into a stream.

2. Stream (water) temperature rises when trees and tall vegetation providing shades are cut down.

3. Soil erosion caused by construction.

4. Removal of stream side vegetation.

5. Poor farming practices.

4.12.3 Effects of Thermal Pollution

1. Reduction in dissolved oxygen

Concentration of dissolved oxygen (DO) decreases with increase in temperature of water.

2. Increase in Toxicity

The rising temperature increases the toxicity of thepoison present in water. A 100C rise in temperature doubles the toxic effect of potassium cyanide, while a 800C rise in temperature triples the toxic effects of O-xylene causing massive mortality of fish.

3. Interference with biological activities

Temperature is considered to be of vital significance to physiology metabolism and biochemical process in controlling respiratory rates, digestion, excretion and overall development of aquatic organisms. The temperature changes totally disrupt the entire ecosystem.

4. Interference with reproduction

In fishes, several activities like nest building, spauning, hatching, migration and reproduction etc., depend on optimum temperature.

5. Direct mortality

Unutilized heat in water is responsible for direct mortality of aquatic organisms. The increase in temperature exhausts the micro-organisms and shortens their life span. Above a particular temperature, death occurs to fish due to failure in respiratory system, nervous system process.

6. Food storage for fish

Change in temperature alters the seasonal variation in the type and abundance of lower organisms. The fish may lack the right food at the right time.

4.12.4 Control measures (or) management ofthermal pollution

The following methods can be adopted to control the high temperature caused by thermal dischargers.

1. Cooling Towers

The use of water from water systems for cooling purposes, with subsequent return to the water way after passage through the condenser, is termed as cooling process.

To make it more effective, cooling towers are designed to control the temperature of water.

Cooling towers transfer some of the heat from hot water to the surrounding atmosphere by the process of evaporation.

Cooling tower is generally used to dissipate the recovered waste heat to eliminate the problems of the thermal pollution. Cooling tower are of two types.

(a) Wet Cooling tower

Hot water, coming out from the condensor (reactor) is allowed to spray over baffles. Cool air, with high velocity, is passed from sides, which takes away the heat and cools the water.

Fig. 4.9 Wet cooling tower

(b) Dry Cooling tower

Here the hot water is allowed to flow in a long spiral pipes.

Cool air, with the help of fan, is passed over these hot pipes, which cools down the hot water.

This cool water can be recycled.

Fig. 4.10 Dry cooling tower

2. Cooling ponds

Fig. 4.11 Cooling pond

Cooling ponds are the simplest method of cooling thermal discharges.

Heated effluents on the surface of water in cooling ponds maximize dissipation of heat to the atmosphere and minimize the water area and volume. This warm water wedge acts like a cooling pond.

3. Spray Ponds

The water coming out from condensers is allowed to pass into the ponds through sprayers.

Here the water is sprayed through nozzles as fine droplets. Heat from the fine droplets gets dissipated to the atmosphere.

Fig. 4.12 Spray pond

Fig. 4.13 Artificial lake

4.13 NUCLEAR HAZARDS (POLLUTION)(Radio Active pollution)

Radiation hazard in the environment comes from ultraviolet, visible, cosmic rays and microwave radiation which produce genetic mutations in man.

Artificial lakes are man made bodies of water which offer possible alternative to once-through cooling.

The heated effluents can be discharged into the lake at one end and the water for cooling purposes may be withdrawn from the other end. The heat is eventually dissipated through evaporation.

Nuclear energy is used to produce clean electric power. The energy released in the splitting of nuclei in the atoms is used to generate electricity.

There were about 600 nuclear power rectors in developed countries upto 1985. US alone have 100 licensed nuclear plants.

About 53 power plants were cancelled between 1980 and 1984 due to enormous radiation danger.

The biggest hazard comes from X-rays which account for 95% of out radiation exposure other than cosmic rays.

The nuclear power plants are more convenient to run. Once fueled, they can operate for several months. These plants are different from conventional electricity generating plants.

In the fueled plants, fossil fuel is burnt to produce heat. But the fuel used in nuclear plants, being radioactive, is critically dangerous and the waste materials are hazardous. No power plant is perfectly contamination proof.

Leakage may occur from several points which may be chronically radioactive. The nuclear wastes released by the nuclear reactor also emit radiations, if not properly stored.

4.13.1 Sources of Nuclear Hazards

Various sources of nuclear hazards are grouped into two types

1. Natural sources.

2. Man-made (Anthropogenic) sources.

1. Natural sources

(a) The very important natural source is space, which emit cosmic rays.

(b) Soil, rocks, air, water, food, radioactive radon-222 etc., also contain one or more radioactive substances.

2. Man-made sources

Man-made sources are nuclear power plants, X-rays, nuclear accidents, nuclear bombs, diagnostic kits, etc., where radioactive substances are used.

4.13.2 Effects of Nuclear Hazards

Radiation pollution of the environment is one of the most horrible ecological crisis to which we are subjected severely.

Radioactive radiation affects the cells in the body and the function of glands and organs.

People suffer from blood cancer and bone cancer if exposed to doses around 100 to 1000 roentgens.

Unlike the other pollution, radioactive pollution can cause genetic disorders even in the subsequent generations.

Studies have shown that the health effects due to radiation are dependent on the level of dose.

2. The use of eye is vulnerable to radiation. As its cell die, they become opaque forming cataracts that impair sight.

3. Acute radiation sickness is marked by vomiting, bleeding of the gums and in severe cases, mouth ulcers.

1. Exposure of the brain and central nervous system to high doses of radiation causes delirium, convulsions and death within hours or days.

4. Internal bleeding and blood vessel damage may show up as red spots on the skin.

5. Nausea and vomiting often begin a few hours after the gastrointestinal tract is exposed. Infection of the intestinal wall can kill weeks afterwards.

6. Unborn children are vulnerable to brain damage or mental retardation, especially if irradiation occurs during formation of the central nervous system in early pregnancy.

4.13.3 Control Measures from Nuclear Hazards

1. Nuclear devices should never be exploded in air. If these activities are extremely necessary then they should be exploded underground.

2. In nuclear reactors, closed-cycle coolant system with gaseous coolants may be used to prevent extraneous activation products.

3. Containments may also be employed to decrease the radioactive emissions. It can be achieved by using tightly sealed boxes and closed cycle system.

4. Production of radioisotopes should be minimized, as once produced they cannot be rendered harmless by any means except the passage of time.

5. Minimum number of nuclear installations should be commissioned.

6. Fission reactions should be minimized as the rate of decay of radionuclides and subsequent emission of radiation are unaltered by man.

7. In nuclear and chemical industries, the use of radioisotopes may be carried under a jet of soil or water instead of powder or gaseous forms.

8. In nuclear mines, wet drilling may be employed along with underground drainage.

9. Extreme care should be exercised in the disposal of industrial wastes contaminated with radio nuclides.

11. Use of high chimneys and ventilations at the working place where radioactive contamination is high. It seems to be an effective way for dispersing radio-pollutants.

12. Disposal methods are the possible ways to distribute the radio-pollutants. These methods make the pollutant in a confined place to spread over a large space such that pollution can be weakened and its effects can be reduced.

10. Nuclear medicines and radiation therapy should be applied when absolutely necessary with minimum doses.

4.13.4 Disposal of Radioactive wastes(Nuclear Hazards)

Since nuclear wastes are extremely dangerous the way in which they are disposed is strictly controlled by international agreement.

Classification of radioactive wastes

The nuclear wastes are usually classified into three categories.

1. High level wastes (HLW)

2. Medium level wastes (MLW)

3. Low level wastes (LLW)

1. High level wastes

Spent nuclear fuel

HLW have a very high radioactivity per unit volume. They have to be cooled and stored for several decades by its producer before disposal.

Since they are too dangerous, must be contained either by converting them into inert solids (ceramics) and then buried deep into earth or stored in deep salt mines.

2. Medium level wastes

Filters, reactor components, etc.,

MLW are solidified and are mixed with concrete in steel drums before being buried in deep mines or below the sea bed in concrete chambers.

3. Low level wastes

Solids or liquids contaminated with traces of radioactivity.

LLW are disposed off in steel drums in concrete-lined trenches.

4.14 ROLE OF INDIVIDUAL IN PREVENTION POLLUTION

Environmental pollution cannot be prevented and removed. The proper implementation and especially the individual participation are the important aspects which should be given due importance and stress.

The individual participation is useful in law making processes and restraining the pollution activities and thereby the public participation plays a major role in the effective environmental management.

4.14.1 Role and responsibility of Individualparticipation in environmental protection

1. Plant more trees.

2. Help more in pollution prevention than pollution control.

A small effort made by each individual at his own place will have pronounced effect at the global level. It is aptly said “Think globally act locally”.

Each individual should change his or her life style in such a way as to reduce environmental pollution.

3. Use water, energy and other resources efficiently.

4. Purchase recyclable, recycled and environmentally safe products.

5. Use CFC free refrigerators.

6. Use natural gas than coal.

7. Reduce deforestation.

8. Increase use of renewable resources.

9. Remove NOx from motor vehicular exhaust.

10. Use office machines in well ventilated areas.

11. Use less polluting substitutes for harmful cleaning agents, paints and other products.

12. Use of eco-friendly products.

13. Don’t use polystyrene cups that have chloro fluoro carbon (CFC) molecules, which destroy ozone layer.

14. Use rechargeable batteries. Rechargeable batteries will reduce metal pollution.

Role of Women in Environmental Protection

Women play an important role in environmental protection, considering their status in social production, consumption and their influence to future generations at home. Various roles of women are

15. Use organic manure instead of commercial inorganic fertilizers.

16. Reduce garbage by recycling and reuse.

17. Slow population growth.

1. In rural areas, women plant trees and grass, grow vegetables with the drip-irrigation method in order to save water.

2. In urban areas, they go shopping using cloth bags to reduce white pollution.

3. Women refuse to use disposal products to save energy and resources

4. Women choose green products instead of poor quality that harm the environment.

5. Women reduce the amount of trash they dispose off so as to recycle natural resources.

6. Women buy non-phosphate detergents to reduce the

incidence of water pollution.

7. They refuse to eat the meat, so variety of animals are preserved.

8. They value paper and thus protect trees.

9. Women bring the concept of environmental protection into families and thus plant a green seed in the heart of children.

4.15 POLLUTION CASE STUDIES

4.15.1 Effluents Treatment at MRL, Chennai

A leading petroleum refinery, The Madras Refineries Limited (MRL) located in Chennai has taken important steps in managing the effluents discharging efficiently. The MRL has two efficient treatment plants designed to meet IS2490 quality control standards.

The Ministry of Environment and Forests has developed an industry oriented standards called MINAS (Minimum National Standards) as per the Environment Protection Act, 1986.

At the new plant, the treatment facilities consists of three streams.

1. The first is cooling water treatment.

2. The second is treating sour and merox water and

3. The third is for treating floor wash and stream waterand to remove oil.

The three efficients streams from the refinery contain the following contaminants.

2. The storm and wash water stream

Oil and grease.

3. The general purpose stream

Waste water, solids , organics and bio-organisms. The MRL has taken bold initiatives and concentrated on the water management to meet the water requirements of the factory due to decreasing sub-soil water.

1. Processes and utility stream

The contaminants are oil, grease, hydrogen sulphide, phenols, acids and alkalis.

2. Facilities for recycling to help reduce the quantum of pollutant discharge are also installed.

3. Further, MRL, went in for installation of tertiary treatment plant to treat secondary treated sewage of the city at Madras Metropolitan Water Supply and Sewage Board, to reuse the water. This facility, though costed heavily (rupees twenty five cores) and it has solved the water problem in summer. In installing this unit, it was ensured that the quality of ground in the area was not affected.

1. MRL has installed non-chromate type treatmentfacility to avoid chromium, a heavy metal, mixing with the effluent.

4.15.2 The Taj Trapezium case M.C. MehtaVs Union of India

The TajMahal is the “King Emperor” amongst world wonders. It represents the most refined aesthetic value and one of the most priceless national monuments and also a glorious reputation to the men’s achievements in architecture and engineering.

According to the petitioner, the foundries, the chemical and the hazardous industries and also the refinery at Mathura are the major sources of damage to Taj.

This has a corroding effect on the clean white marble. Industrial waste, refinery emissions, brick kilns, vehicular traffic and generator sets are primarily responsible for polluting the ambient air around the Taj Trapezium Zone (TTZ).

Both inside and outside, the marble has decayed and yellow pallor is affecting the entire monument.

The SO3, emitted by the Mathura refineries, combine with oxygen along with moisture in the atmosphere forms sulphuric acid, called acid rain.

The Taj apart from being a cultural heritage is a industry by itself bringing more than two million tourists every year and is a source of revenue for the country.

The pollution created as a consequence of development must be commensurate with the carrying capacity of our ecosystem.

The Supreme Court agreed with the petitioner and ordered many industries to close down.

Numerous other industries switched over from the use of coke/coal and obtained gas connections from the Gas Authority of India Ltd (GAIL).

The judgement vigorously applied the “Precautionary Principle” and in May 1999, the Central Government constituted the Taj Trapezium Pollution Authority.

4.15.3 The Bhopal Gas Tragedy

The world’s worst industrial accident occurred in Bhopal city, M.P. on the night of 3rd December 1984. It happened at Union Carbide India Ltd, who manufactures some carbonate pesticides, using methyl isocyanate (MIC).

The reactor got exploded, due to failure of its cooling system and 40 tons of MIC leaked into the atmosphere.

Effect

(i) Methyl-iso-cyanate is a toxic gas, lower concentrations of which affects lungs and eyes and causes irritation in the skin.

(ii) Higher amounts of MIC, remove oxygen from the lungs and can cause death.

Effects in Bhopal

The gas (MIC) spread over 40 sq. km area. About 5000 persons were killed and 65,000 people suffered from severe eye, respiratory, neuromuscular, gastrointestinal disorders. Nearly 1000 persons became blind.

4.15.4 Arsenic pollution in ground water

West Bengal, Bihar and Bangladesh are severely contaminated by the toxic heavy metal arsenic.

Effect

1. The local people, who were ingesting low doses of arsenic for 10 - 14 years, were affected from white or black spots on the skin, called melanosis.

2. Long exposures lead to bladder and lung cancer.

3. Children are more badly affected by arsenicosis.

Sources

Excessive use of lead arsenate and copper arsenite as pesticides in summer paddy and jute crop seems to be the major cause of arsenic pollution.

The states lying in the down stream side of the river Ganga are facing the problem of arsenic content. Nearly 350 million residents in Ganga basin are exposed to dangerous levels of the arsenic element in their drinking water.

4.15.5 Soft drink bottling unit (Coca-cola)

The coca-cola’s bottling unit at Plachimada, Palakkad district, Kerala, discharged large amount of sludges. These sludges are used as fertilizers by the near by farmers.

But, analysis of the sludge showed that it contains, toxic metals like cadmium and lead. The scientists warned that the level of these toxic elements would pollute the land, local water supplies and the food chain.

4.15.6 Mercury wastes

We know that the mercury is an extremely toxic metal. Thermometer manufacturing company releases very small amount of mercury (from 0.1 mg to 10 mg per 1 kg of soil sample) into the atmosphere, which contaminates the soil.

Hindustan Lever Ltd. (HLL): Hindustan Lever Ltd (HLL),Kodaikkanal, is manufacturing thermometer, disposed its mercury laden glass waste into the nearby area and created land pollution.

4.15.7 Palar River-pollution

Palar river originates in Nandidurgam of Karnataka state and flows for about 350 km through Karnataka, Andra Pradesh and Tamil Nadu.

Palar supply drinking water for several municipalities, towns and villages in Vellore district, Tamil Nadu.

By the intervention of local people and environmental groups, HLL transferred large quantities of mercury laden glass wastes from Kodaikkanal to USA.

Now the Palar is polluted by the effluent of various leather industries which intern affecting the agricultural productivity in 40,000 hectares of croplands.

Type of pollutants: Chrome tanning industries discharge large amounts of chemicals like chromium, calcium, ammonium salts, organic dyes and acids.

4.15.8 Industrial pollution (Textile and dye industries)

There are nearly 500 dying units and 195 bleaching units operating in and around Tirupur. They consume large quantity of water for processing and later discharge waste water.

The effluent from the above industries affect the surface and underground water and make the water unfit for domestic work.

The effluent also increase the pH of the soil and affect the cultivation. The rivers like Bhavani, Noyyal and Cauvery get polluted due to mixing of effluent from the above industries.

Tamil Nadu Pollution Control Board (TNPCB) has directed all textile printers and dyers of Thirupur to not allow the effluent to mix in the river systems.

4.15.9 Marine pollution

Spilled oil, breaks down the natural insulating oils and waxes, which shield the birds from water. Ultimately they loose their insulation, start shivering and freeze to death in winter.

About 30,000 birds died in Torrey canyon incident. Nearly 150 rare species of bald eagles also became victims when they ingested oil during Exxon Valdez accident.

4.15.10 Gulf war (marine pollution)

The Gulf war took place in Kuwait from January 16 to February 26, 1991 between Iraq and USA.

During the war American fighters dropped nearly a lakh of bombs, and forced the Iraqi army to withdraw from Kuwait.

During the retreat of Iraqi, they have set fire on nearly 700 oil wells of Kuwait. Since most of the oil wells are on shore of the sea, oil from the oil well spills out into the sea.

Effects

1. Nearly one million birds have been killed due to the oil slick.

2. The oil slick in the sea made the desalination plants ineffective.

The floating oil over sea water covered nearly 80 km long and 25 km wide area. The burning of oil wells continued nearly for 10 months.

The burning of oil wells released huge amounts of pollutants like CO2 and SO2 into the atmosphere.

4.15.11 The Miniamatta Epidemic (1953)(marine pollution)

Miniamatta is a small coastal village in Japan. The Chisso Chemical Company, which produces vinyl polymer plastics used organ mercurial compound.

The industry released its effluent into Miniamatta sea. The effluent containing mercury ions is converted into methyl mercury, which is highly toxic.

The marine organisms like phytoplankton and zoo-planktons easily absorb the toxic methyl mercury compound.

These organisms are consumed by small fishes and these are intern consumed by large fishes. Finally the large fishes are consumed by human beings.

Thus the poisonous chemical (methyl mercury) enter into the body of human beings through food chain.

Effect

It damages the central nervous system, which causes various disorders such as

(a) Loss of vision and hearing.

(b) Loss of muscular co-ordination and severe headache.

(c) Nervous disorders.

4.15.12 Chernobyl nuclear disaster (Nuclearpollution)

In April 26, 1986, the melt down of the Chernobyl nuclear reactor, in Russia, has leaked out the radioactive rays and radioactive materials.

Effect

1. Nearly 2000 persons have been killed by the accident.

2. People suffered due to the illness such as, degeneration of the cells, severe bleeding, anemia , skin cancer.

3. Animals, plants are also affected by nuclear radiation.

Environmental pollution may be defined as, “the unfavorable alteration of our surroundings”. It...

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