DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI

DEPARTMENT OF CIVIL ENGINEERING

GE6351 ENVIRONMENTAL SCIENCE AND ENGINEERING

Unit-II

ENVIRONMENTAL POLLUTION

Part-A

1. Give some reasons behind Global warming.[M/J-14]

The most important greenhouse gases are carbon dioxide, methane, nitrous oxide and water

vapor. While all these gases occur naturally in the atmosphere, emissions from human sources have

caused their levels to rise to a point that is no longer sustainable.

2. Define Pollution.[M/J-14]

The unfavorable alteration of our surroundings is called pollution.

3. Mention the effects ozone on plants. [N/D-14]

UV rays directly affect the aquatic systems-phyto plankton, fish. The phytoplankton

consumes large amount of carbon dioxide in the atmosphere which contributes to the global

warming.

4. List the sources of Marine pollution. [N/D-14, A/M-17]

Dumping the wastes: Huge amounts of sewage, garbage, agricultural discharge, pesticides,

heavy metals, plastics are dumped in sea. Effects: So many marine birds are affected by gastro-

intestinal disorders.

Oil pollution of Marine water: Caused by petroleum and its products. Effects: Oil films inhibit

photosynthesis & formation of oxygen. This inhibit the growth of marine plants

5. What do you mean by noise pollution? [A/M2015, N/D2015]

The unwanted, unpleasant or disagreeable sound thatcauses discomfort for all living

beings”.

6. What is acid rain? [A/M2015]

The presence of excessive acids in rain water is known as acid rain.

7. What is the role of individual in pollution prevention? [N/D2015]

Plant more trees.

Use green products.

Help more in pollution prevention than pollution control.

Proper and planned utilization of natural resources must be done by everyone.

Use water, energy and other resources efficiently and economically.

8. What is PAN? Give its detrimental effect. [M/J-16]

PAN is Peroxy Acetyl Nitrates formed by the photochemical reaction between

hydrocarbon,nitrogen oxides and light

Damage plants and art

React explosively

Plays a vaery large role in photochemical smog

9. What are the causes of thermal pollution? [M/J-16]

Sources of thermal pollution

1. Nuclear power plants

(drainage from hospitals, research institutes, nuclear experiments & explosions, emission from

nuclear reactors)

2. Coal fired power plants (some thermal power plants use coal as fuel, condenser coil are

cooled & discharge the hot water back to the nearby lake, & kills the fish & marine organisms)

3. Industrial effluents (Textile, paper, pulp, sugar industries discharge wastes)

4. Domestic sewage (Municipal sewage has higher temperature which decrease the dissolved

oxygen content & result in foul & offensive smell in water) 5. Hydro – electric power.

10. Mention the measures to control thermal pollution in the environment[N/D-16]

Cooling towers - This is used as a coolant wet cooling tower, dry cooling tower.

Cooling ponds and spray ponds.

Artificial lakes – The heated effluents can be discharged into the lake at one end and the water

for cooling purposes from the other end.

10. List any four water quality parameters and their importance[N/D-16]

Physical parameters

Temperature

Water temperature controls the rate of metabolic activities,

Turbidity

Turbidity is a measure of the cloudiness of water

Chemical parameters

pH

pH is an important limiting chemical factor for aquatic life and it ranges from 1 to 14.

Alkalinity

Alkalinity measures the amount of alkaline compounds in the water,

11. What are the characteristics of PAN?[A/M-17]

Peroxyacetyl nitrate is a peroxyacyl nitrate. It is a secondary pollutant present

in photochemical smog. It is thermally unstable and decomposes into peroxyethanoyl radicals

and nitrogen dioxide gas. It is a lachrymatory substance.

Peroxyacetyl nitrate, or PAN, is an oxidant that is more stable than ozone. Hence, it is more

capable of long-range transport than ozone. It serves as a carrier for oxides of nitrogen (NOx) into rural

regions and causes ozone formation in the global troposphere.

Part-B

1) Discuss the causes and control measures of soil pollution. [M/J-14]

Soil pollution is a result of dumping garbage, waste and other toxins making the land

contaminated or polluted. The surface of our Earth is also contaminated by poor agricultural

practices, mining and industrial waste which leads to formation of acid rain.

It may be defined as “the contamination of soil by human and natural

activitieswhich may cause harmful effects on living beings”.

SOURCES AND EFFECTS OF SOIL POLLUTION

1. Industrial wastes

Many industries produce harmful chemicals which are disposed of without being

treated.

Examples: Pulp and paper mills, chemical industries, oil refineries, sugar factories.

Effects

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, disturb the bio chemical

process and finally lead to serious effects.

2. Urban wastes

Urban wastes comprise both domestic and municipal wastes. These are also

dangerous.

Examples: plastics, glasses, metallic cans, fibers, papers, rubbers, street sweepings.

Effects

This hazardous waste contaminates soil and water resources.

3. Faulty agricultural practices

(a) Shifting cultivation

In it, the forest is burnt to use the land for cultivation. This practice exposes the soil for

soil erosion.

(b) Unskilled irrigation

Water logging may occur when the drainage system of the agricultural field is not

maintained properly.

Effects

Water logging closes the passage of air to the soil, stops the growth of soil organisms

and makes the soil barren.

(c) Injudicious use of chemical fertilizers

Use of inorganic fertilizers increases the nutrient contamination. The microbes of the

soil reduce the nitrogen to nitrite ions which enter the animal body through food or

water. It is directly absorbed in the blood stream and oxidizes the oxyhaemoglobin (the O2 carrier)

to methemoglobin, which is a poor oxygen carrier.

4. Radioactive pollutants

Improper disposal of nuclear wastes can cause radioactive substances to remain in the

soil for a long time.

Examples: Strontium-89, Strontium-90, Cesium-137 and Iodine-131.

Effects

These radioactive wastes penetrate the soil and accumulate there by creating land pollution.

Every exposure to radiation increases the risk of damage to tissues, cells, DNA and

also causes mutations.

5. Biological agents

Human excreta mixed with soil is called night soil. Open latrines in the villages and

some parts of cities are the source of this pollution.

Effects

These contain disease-causing germs which can spread the disease.

6. Acid rain

Rain becomes acidic, when the carbon dioxide (CO2) in air dissolves with rain water

and forms a weak acid.

Effects

The acid rains can change the pH of the soil making it unsuitable for cultivation.

CONTROL MEASURES OF SOIL POLLUTION

Control of soil erosion

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

Forestry and farm practices

Planned afforestation helps in preventing soil erosion.

Proper dumping of unwanted materials

Proper disposal methods must be employed. For example, composting of

biodegradable solids and incineration of non-biodegradable solids should be done.

Production of natural fertilizers

Use of bio fertilizers and natural pesticides help in minimizing usage of chemical

fertilizers and pesticides.

Proper Hygienic condition

Faulty sanitation practices must be improved.

Public awareness

Public awareness programs should be imparted to educate people regarding the

environmental pollution.

Recycling and Reuse of wastes.

The principles of three R’s, namely, Recycle, Reuse and Reduce help in minimizing

generation of solid waste.

Ban on Toxic chemicals

Any substances which are harmful to land should be banned.

Population growth

Due to the increase in population, there is an increase in soil pollution due to the

generation of heavy amount of wastes.

2) Explain one case study on waste water treatment methodology in industrial effluent.

[M/J-14, N/D-14]

Water is treated in order to make the water for beneficial purpose. It should be clear,

colorless and pleasant to taste. It should be free from excessive dissolved salts, suspended

impurities and harmful micro-organisms. The treatment of these involves the removal

ofsuspended impurities and colloidal impurities. A complete water treatment system may

consist of the application of a number of physical, chemical and biological processes.

Physical methods

Screening

Floating impurities are removed from water. The influent sewage water passes through

a bar screen to remove all large objects like cans, rags, sticks, wood pieces, leaves, plastic

packets etc., carried in the sewage stream.

Example: Wood pieces, leaves.

For removing, screens of various types are used

Example: Bar screen, Band and drum screens, micro-strainers.

Raw water is passed through the screens with holes. It retains the floating materials in

the screen and allows the water to pass.

Aeration

It is the process of mixing water with air.

Remove dissolved gases like CO2, H2S causing bad taste and odour to water. Remove

Fe and Mn salts as insoluble ferric and manganic salts.

Sedimentation

It is a process of removing relatively large particles into large reservoirs of settlement

tanks.The suspended impurities settled at the bottom of the tank due to gravitational force.

The solid particle settling depends upon flow velocity of water, particle size and shape,

particles specific gravity, temperature.

Filtration

It is the process of clarification of water by passing the water through a porous material.

It is the process of removing colloidal matter, bacteria and micro-organisms by passing the water

through filter beds.

Chemical methods

Chlorination

Chemical treatment consists of using some chemical reactions to improve the water

quality. Probably the most commonly used chemical process is chlorination.

Chlorine is the most common sterilizing agent and is capable of removing and

destroying bacteria.

Neutralisation

A chemical process commonly used in many industrial wastewater treatment operations

is neutralization.

Neutralization consists of the addition of acid or base to adjust pH levels back to

neutrality.

Coagulation

Finely divided silica, clay and organic matter do not settle down easily. These colloidal

forms of impurities are removed by coagulation and not by sedimentation.

For removing the impurities, chemicals are added. Aluminium Sulphate

[Al 2 (SO 4 ) 3 ] is the most common coagulating agent for removing clay particles.

Al 2 (SO 4 ) 3 + 6 H 2 O 2 Al(OH) 3 + 3 H2 SO4

Aluminium Sulphate Aluminium Hydroxide

Al(OH) 3 formed has enormous surface area/unit volume and it removes the finely

divided and colloidal impurities.

Examples of Coagulants

Ferric Sulphate, Alum, Ferrous Sulphate, Aluminium alum, Chlorinated Coppers,

Sodium Aluminate.

Biological treatment methods

Biological treatment methods use microorganisms, mostly bacteria, in the biochemical

decomposition of wastewaters to stable end products.

More microorganisms or sludge‟s, are formed and a portion of the waste is converted

into carbon dioxide, water and other end products.

Generally, biological treatment methods can be divided into aerobic and anaerobic

methods, based on availability of dissolved oxygen.

Trickling Filter Process

A trickling filter consists of a fixed bed of rocks, lava, coke, gravel, slag, polyurethane

foam, ceramic or plastic media over which sewage or other wastewater flows downward and

causes a layer of microbial slime (bio film) to grow, covering the bed of media. Aerobic conditions

are maintained by splashing, diffusion.

Activated Sludge Process

Activated sludge is a process for treating sewage and industrial wastewaters using air

and a biological floc composed of bacteria and protozoa.

The activated sludge process is a biological process that can be used for oxidizing

Carbonaceous biological matter

Nitrogenous matter [ammonium and Nitrogen]

3) Describe the various chemical and photochemical reactions in the atmosphere.

[N/D-14, M/J-16, A/M-17]

CHEMICAL REACTIONS IN ATMOSPHERE

The sun‟s radiation is the major source of energy that initiates chemical reactions in

the atmosphere.

The sun emits many kinds of radiation. The visible light is the radiation in which the

human eye can detect and ultraviolet light, which is higher energy radiation that cannot be

detected by the human eye.

Chemical reactions in the atmosphere can occur as gas phase collisions between molecules,

on the surfaces of solid particles or in aqueous solution. Due to the chemical reactions in the

atmosphere, ozone and hydroxyl ions are formed

a) Formation of Ozone

The oxygen molecule present in the atmosphere is decomposed to oxygen atoms.

The oxygen atoms produced can undergo a condensation reaction with O2 molecules to

form ozone.

Ozone produces the pungent smell which causes significant air pollution. Ozone

absorbs the less-energetic range of ultraviolet light, undergoing a cleavage reaction in the process

to give O2 and O in the stratosphere.

Ozone layer acts as a protective screen that absorbs ultraviolet light rays reaching the

earth‟s surface. The depletion of ozone layer takes place due to the interaction of

chlorofluorocarbons with the ozone layer.

b) Formation of Hydroxyl Ion

The water molecule present in the atmosphere is broken to form a hydrogen radical(H)

and a hydroxyl radical (HO). The hydrogen radical reacts with another water molecule to form hydrogen

and a second hydroxyl radical. The hydrogen radical can also react with an oxygen molecule (O2) to

form a second hydroxyl radical and an oxygen atom.

The new oxygen atom can then react with another water molecule to form two new

hydroxyl radicals.

PHOTO CHEMICAL REACTIONS IN ATMOSPHERE

Photochemical reaction occurs by the absorption of energy in the form of light.

The molecules get excited by absorbing energy in which the chemical and physical

properties differ from the original molecules. The newly formed molecules differ in their structure

and other properties

These new chemical species change to new structures, combine with each other or

other molecules, or transfer electrons, hydrogen atoms, protons, or their electronic excitation

energy to other molecules.

Photosynthesis

Plants prepare their food by the process called photosynthesis. The energy from the

sunlight is converted into chemical energy. This chemical energy is synthesized from atmospheric

carbon dioxide and water thus releasing molecular oxygen as a byproduct. Photosynthesis process

balances the atmospheric oxygen levels.

4) Explain the sources, effects and control measures of noise pollution. [M/J-14,N/D-14,A/M-17]

NOISE

The word „noise‟ is derived from the Latin word, nausea meaning nuisance. The term

„noise‟ may be referred as an unwanted sound at a wrong time and a wrong place. Noise pollution

is defined as, “the unwanted, unpleasant or disagreeable sound thatcauses discomfort for all living

beings”.

UNIT OF NOISE

The sound intensity is measured in decibel (dB), which is one tenth of the longest unit

Bel. One dB is equal to the fainest 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.

The allowed decibel of noise during day and night time are

Code Area Day time (dB) Nighttime (dB)

A Industrial area 75 70

B Commercial area 65 55

C Residential area 55 45

D Silence Zone 50 40

SOURCES OF NOISE POLLUTION

(i) Natural sources

Examples: Thunder, Volcanic eruptions etc.,

(ii) Manmade sources

Industrial Noise

Industrial machineries (e.g. compressors, generators, grinding mills and drilling

machines) produce noise which affects millions of people. This is known as occupational noise.

Transport Noise

Transport noise mainly includes road traffic noise, rail traffic noise and air craft noise.

Examples: Vehicles like motors, scooters, cars, motor cycles, buses and trucks, etc.,produce

noise pollution.

Neighbourhood Noise

It includes noise from loud speakers, musical instruments (e.g. drum), radio, TV,

washing machines, vacuum cleaners etc.,

EFFECTS OF NOISE POLLUTION

Physiological effects

Normal sounds of the order 70 dB can have measurable physiological effects. They

include increase of blood pressure and heart beat, head ache and peptic ulcer.

Noise in the range of 120-150 dB has effects on respiratory system causing asthma

and other physiological change resulting dizziness, nausea and vomiting.

Noise leads to auditory fatigue which is characterized by whistling and buzzing in ears.

Exposure to high level of noise of about 140 dB leads to hearing loss. (deafness)

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

It causes a change in hormone content of blood, which in turn increase the rate of heart

beat, contraction of blood vessels.

Our optical system is also a prey for noise pollution. pupillary dilation, impairment of

night vision and decrease in the rate of color perception are some of its severe effects.

Psychological effects

Noise interrupts sleep. Because sleep is important to emotional stability, noise

contributes to distress and emotional disturbances like anxiety and tension.

Loud noise reduces working efficiency, interferes with communication and causes

accidents.

Loud noise reduces mental capability and aggravates any existing psychological

conditions.

High level noise may cause mental and nervous illness.

CONTROL OF NOISE POLLUTION

Industrial workers should use ear protection aid such as soft plastic muffs, rubber ear

plugs, head phones etc.,

Sound absorbing materials like acoustic tiles or perforated plywood should be fixed on

walls, floors and ceilings of houses.

Lead shields and barriers in buildings are good for controlling noise pollution.

Use of loud speaker should be banned by law.

Low noise emitting vehicles should be designed and used.

Use of crackers in social functions should be limited.

Industries, Railway stations and Aerodromes should be far away from the residential

areas.

Plantation of trees like Neem, Aashok, Coconut, Banyan and Tamarind around schools,

hospitals, libraries and factories can reduce noise to the extent of 6-10 dB.

Noise Control Devices

(i) Mufflers or Silencers

Muffler or silencer is a pipe or duct used to suppress noise transmission from the engine.

They are broadly classified into two categories:

(ii) Dissipative silencers

A dissipative silencer, which is also known as absorptive silencer, works on the principle of

absorbing noise. They make use of absorbing materials like fiber glass, mineral wool etc.,

(iii) Reactive silencers

A reactive silencer works on the principle of reflecting sound. Here, noise is reflected back

towards the source. (Machine)

For example, automobile engine silencers work on the principles of both noise absorption

and reflection.

(iv) Ear Muffs

These are ear protection aids to be used by industrial workers. The ear muff provides a

complete cushion entirely surrounding and isolating each ear.

(v) Helmets

It is a personnel protection aid made of reinforced glass fibre. They have ability to protect the

skull and soft areas of the head against the transmission of damaging pressure waves.

5) Describe the role of individual in the prevention of pollution. [N/D-14,A/M2015]

Plant more trees.

Use green products.

Help more in pollution prevention than pollution control.

Proper and planned utilization of natural resources must be done by everyone.

Use water, energy and other resources efficiently and economically.

Purchase recyclable, recycled and environmentally safe products.

Reduce deforestation.

Soil must be conserved properly which increases the food production.

Remove NO from motor vehicular exhaust.

Use of eco-friendly products.

Overexploitation of natural resources must be banned strictly.

Use CFC free refrigerators.

Use natural gas than coal.

Use rechargeable batteries. Rechargeable batteries will reduce metal pollution.

Use organic manure instead of commercial inorganic fertilizers.

Do not put pesticides, paints, solvents, oils or other harmful chemicals into the drain or

ground water.

Use only the minimum required amount of water for various activities. This will prevent

fresh water from pollution.

6) Explain the causes, effects and control measure of air pollution. [M/J-14, A/M2015, N/D2015,

M/J-16, N/D-16, A/M-17]

GASEOUS POLLUTANTS

Among the various pollutants, the major primary pollutants which are most significant are

Oxides of Nitrogen (NOx)

Oxides of Sulphur (SOx)

Oxides of Carbon (CO)

Hydro carbons (CxHy)

Particulates

OXIDES OF NITROGEN

The oxides of nitrogen involved in air pollution, denoted by NOx are N2O, NO, NO2,

N2O3 and N2O5.

Sources of NOx Pollution

By the combustion of coal, oil, natural gas and other organic matter.

From automobile exhausts.

Fixation of nitrogen from atmosphere.

Effects of NOx pollution

(i) On plants

Higher concentrations of NOx damage the leaves of plant, retard the photosynthetic

activity and cause chlorosis, leaf spotting.

(ii) On human health

High levels of NOx cause internal bleeding, lung cancer, head ache, eye irritation, chest

pain etc.,

(iii) On materials

NOx fades away a number of textile dyes like cotton, rayon etc. and higher levels of

NOx cause 10% loss of fibre strength in cotton and rayon.

Control of NOx pollution

By chemisorptions using alkaline scrubbing solutions.

By catalytic decomposition.

OXIDES OF SULPHUR

SO2 is the second important contributor of air pollutants.(nearly29%)

SO2 in low concentration is essential for animals and plants both, but it becomes

injurious when its concentration increases.

Sources of SO2 pollution

Due to volcanic activity (67%) and other natural sources.

Manmade sources 33% due to combustion of fuels, coal-fired power stations, chemical

plants, etc.,

Reactions of SO2 in the atmosphere

SO2 undergoes several chemical reactions in air forms particulate matter and aerosols

etc., SO2 and SO3 gases are washed down from the atmosphere in the form of sulphuric acid

aerosol which gives rise to acid-rain.

SO2 + O3 → SO3 + O2

SO3 + H2O → H2SO4 → (H2SO4) n → Acid rain

Sulphuric acid aerosol

Effects of SO2

(i) On human

The lower concentration of SO2 causes irritation to eyes and respiratory tract.

Higher concentration of SO2causes throat irritation, cough and lung cancer.

(ii) On plants

It is most injurious to trees causing chlorosis and dwarfing.

It affects soil fertility.

(iii) On materials

SO2 polluted air enhance corrosion of metals.

Paper absorbs SO2 which is oxidized to H2SO4 causing the paper to brittle and fragile.

Control of SO2 pollution

SO2 can be reduced and controlled by the following important methods.

Removal of sulphur from fuel before burning.

Use of lower content sulphur fuels.

Use of natural gas.

OXIDES OF CARBON (CO)

Sources of CO emission

The natural processes which contribute to CO in atmosphere are volcanic activity,

natural gas and marsh gas emissions etc., However most of the CO in the atmosphere is due to

the human activities such as

Automobile exhausts.

Forest fire.

Agricultural activities.

Industrial operations.

Effects of CO emission

(i) On plants

It causes leaf drop, leaf curling and reduction in leaf sizes.

(ii) On humans

The haemoglobin present in the blood act as the oxygen carrier from lungs to various

tissues.CO inhibits absorption of oxygen by haemoglobin so that the capacity of blood for carrying

O2 is reduced creating problems like head ache, fatigue and coma.

CO causes difficulty in breathing, vomiting, reduced mental activity in lower

concentration (100 - 500ppm) and even death after few hours in 1000ppm of CO.

(iii) On environment

It increases globe temperature.

Control of CO emission

Minor modifications of internal combustion engines are required to control the CO

emissions formed during fuel combinations.

Fuel modification and development of substitute fuels.

HYDRO CARBONS

Sources of Hydro carbons

Hydrocarbon, especially methane is emitted into the atmosphere by natural activities

such as anaerobic decomposition of organic matter in water, soil and sediments by micro-

organisms.

Hydrocarbons are also emitted into the atmosphere by human activities such as

automobile exhausts, burning of coal, oil and wood.

Effects of Hydrocarbons

Hydrocarbons combine with NO to form photochemical smog which causes irritationof

eyes, nose throat, respiratory tract and reduced visibility.

Hydrocarbons cause yellowing of green leaves. (chlorosis)

Carcinogenic hydrocarbons like benzopyrene can react with DNA causing mutations

and cancer.

They reduce the tensile strength of polymers

Control of hydrocarbons

Hydrocarbons from auto exhaust emission can be controlled by applying techniques

like incineration, absorption and condensation etc.,

PARTICULATES

Air-borne small, solid particles and liquid droplets are commonly known as particulates.

They are present on air in excess and pose serious threat to air pollution problems.

Examples: Smoke, dust, mist, spray, fumes, fly ash etc.,

Sources of particulates

Volcanic eruption.

Blowing of dust and soil by wind, spraying of salt by seas and oceans.

Burning of wood and coal.

Fly ash emission from power plants .

Forest fire.

Effects of particulate pollutants

(i) On plants

They tend to lower the pH of the soil making it more acidic and infertile.

They reduce the rate of photosynthesis and retard the growth of plants and crop

production.

(ii) On humans

Dust causes allergy and respiratory disease. Silicosis, a chronic lung disease, is

caused by inhalation of dust containing silica.

Asbestos particles cause lung disease and cancer in the abdomen.

Smoke develops symptoms of cancer and asthma.

(iii) On materials

Particulates cause damage to buildings, sculptures, monuments and paints.

Particulates accelerate corrosion of metals and make the soil infertile. In Bhopal

disaster, the soil was coated with dust due to Methyl IsoCyanate (MIC) leakage and the

soil fertility is lost.

MITIGATION PROCEDURE (PARTICULATES AND GASEOUS EMISSIONOF AIR

POLLUTION - SO2, NO, CO, HC)

Control of NOx pollution

by chemisorptions using alkaline scrubbing solutions.

by catalytic decomposition.

Control of SO2 pollution

SO2 can be reduced and controlled by the following important methods.

Removal of sulphur from fuel before burning.

Use of lower content sulphur fuels.

Use of natural gas.

Control of CO emission

Minor modifications of internal combustion engines are needed to control the CO

emissions formed during fuel combinations.

Fuel modification and development of substitute fuels.

Control of hydrocarbons

Hydrocarbons from auto exhaust emission can be controlled by applying the

techniques like incineration, absorption, and condensation etc.,

Control of particulates and gaseous emissions

1. Source control

Use only unleaded petrol.

Use petroleum products and other fuels that have low sulphur and ash content.

Plant trees along busy streets because they remove particulates and carbon monoxide

and absorb noise.

Industries and waste disposal sites should be situated outside the city centre.

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

hydrocarbons.

2. Control measures in Industrial centres

Emission rates should be restricted to permissible levels .

The most effective method of air pollution control is by equipments. Some common

types of equipments are

Cyclonic separators.

Fabric filters. (Bag house)

Electrostatic precipitators.

Wet scrubbers.

Cyclone Separator

In cyclone separator, the gas is passed through the spiral (vortex) which produces

centrifugal force on the suspended particles. They whirled round through a tight circular vortex ore

and move upwards. The heavier particles hit the walls. They settle out and are collected at the

bottom.

Fabric Filters (bag house)

In Fabric filters, the dust-laden gases are passed through a filled fabric. The fabric

material is used in a structure called bag house, where the filters are automatically shaken and air

is blown through them in the reverse direction to clean them. The heavier particles collect at the

bottom of the bag house.

They are quite effective for particles smaller than one micron and its collection

efficiency is 99%.They are used in industries deals with rock pollutants, pigments etc.,

Electrostatic Precipitator (ESP)

The ESP is a physical process by which the particulates suspended in the gas steam

receive electrical charges and caused to migrate to a collecting surface on which an opposite

charge is maintained.

ESP consists of gas distribution plates, discharge electrodes, collector electrode plates,

a dust cleaning system and dust collection hoppers.

It is capable of removing particles as small as 1µm with an efficiency of 90% for large

particles, the removal efficiencies are 99.9%.

It is commonly used to remove fine particulates from the gas steams, particularly at

cement and thermal-power plants.

7) Explain the causes, effects and control measure of water pollution. [N/D-15, M/J-16]

Water pollution is defined as “the alteration in physical, chemical and

biologicalcharacteristics of water which may cause harmful effects on human and aquatic

life”.

EFFECTS AND SOURCES OF WATER POLLUTION

Water pollution makes the water unfit for living organisms.

1. Infectious agents

Bacteria, viruses, protozoa and parasitic worms cause water pollution.

Sources: Human and animal wastes.

Effects: Diseases.

2. Oxygen demanding wastes

Animal manure and plant that can be decomposed by aerobic bacteria. This

degradation consumes the dissolved oxygen in water. Lowers dissolved oxygen levels makes

aquatic organisms more vulnerable to disease.

Sources: Sewage, paper mills and food processing facilities.

Effects: Wastes can degrade quality by depleting water of dissolved O2.

3. Inorganic Chemicals

Compounds of toxic metals such as lead, arsenic and selenium and the salts such as

NaCl in ocean water.

Effects: Genetic mutations, birth defects and certain cancers.

4. Thermal pollution (Heat)

Source: Discharges from power station

Effects: Death of fish and other organisms.

5. Industrial effluents

The wastes containing soap, phenol, cyanides, lead, mercury and pesticides discharge

from industries is called industrial effluents.

Effect: Aquatic life.

6. Agricultural wastes

The agricultural runoff water contains residual pesticides and fertilizers which causes

water pollution.

Effect: Aquatic life.

7. Siltation

Clay, Ores and fine particles of soil on which water travels causes turbidity in

water.Effect: Aquatic life.

8. Plant Nutrients

Source: Fertilizers, animal and plant wastes.

Effect: Aquatic life.

CONTROL MEASURES OF WATER POLLUTION

Industrial plants should be based on recycling operations.

Highly qualified and experienced persons should be consulted from time to time for

effective control of water pollution.

The industries must treat the waste before the water is discharged into the rivers and

seas.

The pollutants must be treated chemically and must be converted into the non toxic

substances.

The low level of radioactive wastes in the water is removed by the oxidation of ponds.

8) Write a note on:

(1) Nuclear hazards. [A/M2015, N/D2015] (2) Thermal pollution. [N/D2015]

The contamination of water resources (river, lake, sea) with hot industrial effluents which are

harmful to aquatic life is called, thermal pollution.

The rising levels of greenhouse gases and depleting fossil fuels have provoked serious

thoughts about exploitation of nuclear energy for power generation.

Radioactive (nuclear) pollution is a special form of physical pollution related to all major

life-supporting systems – air, water and soil. Nuclear waste is the radioactive waste left over from

nuclear reactors, research projects and bomb production.

TYPES OF NUCLEAR WASTES

Based on the intensity of radioactivity they release, nuclear wastes can be categorized

into low, medium and high level wastes.

Low-level wastes

These wastes discharge a small amount of radioactivity in a large volume of material.

This level of radioactivity is supposed to be too low to cause any harmful effects in the

environment.

The primary sources of these wastes are the nuclear materials used in industrial,

medical and research procedures.

Intermediate-level wastes

These waste release a higher radioactivity compared to low-level wastes but lesser

than high-level wastes.

They cannot be directly discharged to the environment. Spent nuclear fuel from power

plants is the basic source of these wastes.

High-level radioactive wastes

These waste are generated by nuclear power plants and some institutes conducting

research on nuclear fuels.

They are a significant hazard to the environment as they discharge intense levels of

radioactivity.

These wastes may remain in the environment for several hundred years.

Their disposal is quite difficult and they have to be completely isolated and stored for a

long time before final disposal.

SOURCES OF NUCLEAR HAZARDS

The sources of radioactivity are both natural and man-made.

(i) Natural Sources

Cosmic rays from outer space.

Emissions from radioactive materials from the earth's crust.

(ii) Manmade Sources

Mining and processing of radioactive ores.

Use of radioactive material in nuclear power plant.

Use of radioactive isotopes in medical, industrial and research applications.

Use of radioactive materials in nuclear weapons.

EFFECTS OF NUCLEAR HAZARDS

Exposure at low doses of radiations (100 - 250 rads), causes fatigue, nausea, vomiting

and loss of hair.

Exposure at higher doses (400 - 500 rads), the bone marrow is affected, blood cells are

reduced, natural resistance and fighting capacity against germs is reduced, blood fails

to clot and the irradiated person soon dies of infection and bleeding.

Higher irradiation doses (10,000 rads) kill the organisms by damaging the tissues of

heart, brain, etc.,

Develop cancer of different types.

Through food chain also, radioactivity effects are experienced by man.

Exposure of the brain and central nervous system to high doses of radiation causes

delirium, convulsions and death within hours or days.

Eye is vulnerable to radiation and becomes opaque forming cataracts that impair sight.

Acute radiation sickness is marked by vomiting, bleeding of gums and in severe cases

mouth ulcers.

Nausea and vomiting often begin a few hours after the gastrointestinal tract is exposed.

Unborn children are vulnerable to brain damage or mental retardation, especially if

irradiation occurs during formation of the central nervous system in early pregnancy.

CONTROLMEASURES

Safety measures should be enforced strictly.

Waste disposal must be careful, efficient and effective.

There should be regular monitoring and quantitative analysis through frequent sampling

in the risk areas.

Appropriate steps should be taken against exposure.

Safety measures should be strengthened against nuclear accidents.

Nuclear devices should never be exploded in air.

Use of high chimneys and ventilations at the working place where radioactive

contamination is high. It seems to be an effective way for dispersing pollutants.

SOURCES OF THERMAL POLLUTION

The following sources contribute to thermal pollution,

Thermal power plants.

Hydro-electric power.

Nuclear power plants.

Industrial effluents.

Domestic sewage.

Thermal power plants

The thermal power plants are engaged in generating electricity from thermal power.

Water is heated by burning coal or nuclear fuel to produce steam. The steam rotates the turbine to

get electricity

The steam gets cooled and discharged into the nearby river or lake as hot water. The

heated effluents decrease the dissolved oxygen (DO) content of water. It results into killing of fish

and other marine organisms.

Hydro – electric power

Generation of hydro- electric power sometimes, results in negative thermal loading in

water systems. 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.

Nuclear Power Plants

Nuclear power plants including drainage from hospitals, research institute, nuclear

experiments and explosion discharge a lot of unutilized heat and traces of toxic radionuclides into

nearby water streams. It increases the temperature of water bodies which severely affect the

aquatic flora and fauna.

Domestic Sewage

Domestic sewage is commonly discharged into rivers, lakes, canals or streams with or without

water treatment. The municipal sewage normally has a higher temperature than the receiving water

As a result dissolved oxygen is reduced. Hence the anaerobic condition will set up

resulting in the release of foul and offensive gases in water. The marine organisms which depend

on DO will die.

4. Industrial Effluents

Industries like textile, paper, pulp and sugar also release heat to the water bodies,

which affect aquatic life.

EFFECTS OF THERMAL POLLUTION

Harmful effects of thermal pollutants are,

On human

Toxic pollutants like Cd, As and Cl present in heated effluents make the water

unsuitable for any purpose. Replicated human pathogens spread infectious disease in man.

Reduction in Dissolved Oxygen (DO)

Concentration of dissolved oxygen decreased with increase in temperature of water.

The reduced DO severely affect the aquatic flora and fauna.

Change in water properties

The decrease in density, viscosity and solubility of gases increases the settling speed

of suspended particles which seriously affect the food supplies of aquatic organisms.

Increase in Toxicity

The raising temperature increases toxicity of the poison present in water.

Interference with reproduction of fishes.

Change in metabolic rate of fishes.

The increase in temperature exhausts the micro-organisms and shortens their life span.

Interference with biological activities such as digestion, respiration of aquatic animals.

CONTROL OF THERMAL POLLUTION

Thermal power plants should be far away from the water resources.

Thermal pollution can be reduced by direct conversion of the heat into electricity.

Another method to reduce thermal pollution is to use the waste heat for useful purpose.

The waste heat may be used to warm homes by means of a heat pump in areas like

Ooty.

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

discharges.

(i) Cooling towers

(ii) Cooling ponds

(iii) Spray ponds

(iv) Artificial lakes

Cooling towers

Cooling towers are heat removal devices used to transfer waste heat to the atmosphere

through the cooling of a water stream to a lower temperature. They are used as an important

component in many industrial and commercial processes needing to dissipate heat.

With respect to the heat transfer mechanism employed, the main types are:

Dry cooling towers: Dry towers operate by heat transfer through a surface

thatseparates the working fluid from ambient air, such as in a tube to air heat exchanger, utilizing

convective heat transfer. They do not use evaporation.

Wet cooling towers or open circuit cooling towers: Wet towers operate on

theprinciple of evaporative cooling. The working fluid and the evaporated fluid (usually water) are

one and the same.

Cooling pond

A cooling pond is a man-made body of water primarily formed for the purpose of

supplying cooling to a nearby power plant or industrial facility such as a petroleum refinery, pulp

and paper mill, chemical plant, steel mill or smelter.

Cooling ponds are used where sufficient land is available, as an alternative to cooling

towers or discharging of heated water to a nearby river or coastal bay.

Spray pond

An arrangement for lowering the temperature of water by evaporative cooling. The

water to be cooled is sprayed by nozzles into a pond of water, cooling in the air as it falls.

The cooling effect is primarily due to the evaporation of part of the sprayed water. (The

evaporation of 1 percent of the water lowers its temperature by approximately 6° C.)

Artificial lakes

A natural or artificial pond or lake used for the storage and regulation of water.

Many lakes are artificial and are constructed for industrial or agricultural use, for hydro-

electric power generation or domestic water supply or for aesthetic or recreational purposes.

9) What is marine pollution? Explain the ill effects of marine pollution with the help of a

case study .[N/D-14, N/D-15, M/J-16, N/D-16]

Any unwanted addition of various kinds of wastes into sea is called “marine

pollution”.

Marine Pollution is also defined as "Introduction by man, directly or indirectly,

ofsubstances or energy into the marine environment resulting in such destructive effects as harm

to living resources, hazard to human health, hindrance to marine activities including fishing,

impairment of quality for use of sea-water and reduction of amenities."

Coral reefs

Coral reefs are the most diverse and beautiful of all marine habitats. The development of these

structures is aided by algae known as zooxanthellae. Coralline algae, sponges and other

organisms, also contribute to reef growth.

Benefits of Coral Reefs

Coral reefs benefit the environment and people in numerous ways. For example, they

Protect shores from the impact of waves and from storms.

Provide benefits to humans in the form of food and medicine.

Provide economic benefits to local communities from tourism.

Factors affecting Coral Reef

The coral reefs are threatened by

The sediment from deforestation carried by the runoffs.

The agricultural and industrial chemicals reaching through river discharges.

The boat anchors and the careless drivers.

Rising ocean temperature, ocean acidifications.

SOURCES OF MARINE POLLUTION

Agricultural run off

Modern agricultural methods use lot of fertilizer, pesticides and other inputs. During the

rain, unutilized chemicals are washed off from the surface and added to the sea. This results in

nutrient loading of marine water.

Waste Disposal

Hundreds of tons of inert solid wastes are dumped into the ocean from ships annually,

of these plastics and polystyrene are deadly to marine life.

Oil Spills

Large oils spills can pollute a local area, equally important is the discharge of crude oil

while cleaning ships and emptying tanks at sea.

Acid rain

Acid rain is not a natural phenomenon but a result of industrial and automobile pollution.

Poisonous gases from these sources are released in the environment which when combined with

rainwater forms acid rain. Acid rain facilitates the transfer of harmful gases to oceans.

Land based sources

About 80% of marine pollution comes from land based activities. Land based sources of marine

pollution are those types of pollution introduced into the marine environment from a variety of land

sources.

Storm water

Storm water flow contain high levels of pollutions, such as heavy metals oil residues,

nutrients, micro organisms such as viruses, bacteria and protozoa from faecal material.

Municipal and Industrial wastes

Disposal of fully or partially treated municipal and industrial wastes into rivers and/or

bays, through pipe lines, also contributing to total land based marine pollution.

Rivers

Rivers carry to the sea water containing contaminants such as nutrients and pesticides

from agricultural runoff, faecal pollution resulting from poor sanitation and industrial discharges.

EFFECTS OF MARINE POLLUTION

Oil spilling

Oil spilling causes abnormally low body temperature in birds resulting in hypothermia.

Oil films

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

Heavy metals and organic pollutants

The presence of heavy metals and organic pollutants cause more damage in birds as

thinning of eggshell and tissue damage of egg.

Organic matter

Decomposition of organic matter present in the untreated or partially treated waste

causes depletion of dissolved oxygen content of the marine water. This can cause the death of

marine plants and animals and may lead to changes in biodiversity.

Eutrophication

Disposal of effluent with more nitrogen and phosphorus causes 'eutrophication', which

may cause growth of algal blooms. These blooms can discolour the water, clog fish gills or even be

toxic.

Pathogenic micro-organisms

These cause gastric and ear-nose-throat infections, hepatitis and even cholera and

typhoid.

Toxic chemicals

Substances causing toxic effects that damage the physiological processes and

functions of reproduction, feeding and respiration.

Pesticides

Pesticides such as DDT (Dichlorodiphenyltrichloroethane) and other persistent chemicals

accumulate in the fatty tissue of animals. These chemicals can cause reproductive failure in

marine mammals and birds.

Human health

Many pollutants such as dioxins, furans, polychlorinated biphenyls (PCB's) and some

heavy metals are accumulating in the marine organisms. When humans are consuming sea foods

from the polluted areas they are affected by these pollutants.

Radioactive wastes

Any leakage or failure of radioactive waste containers, which are used to dispose low

level radioactive wastes in deep sea causes more effects.

PREVENTIONS/CONTROL OF MARINE POLLUTION

Following are some of the preventive measures of marine pollution

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

Careful handling of oil and petroleum products.

The oil can be removed by the physical and chemical methods.

(i) Physical Methods

1. Skimming of oil from the surface with a suction device.

2. The floating oil can be adsorbed using a suitable absorbing material like polyurethane

foam.

(ii) Chemical Methods

1. Dispersion

2. Emulsification

3. Ban ocean dumping of sludge and hazardous dredged materials

4. Dispose fully treated municipal and industrial wastes

5. Regulate coastal development

6. Hygienic and aesthetic maintenance of recreational beaches

7. Controlled use of pesticides and chemicals in agricultural activities in delta portions.

8. Separate sewage and storm water lines.

9. Ban on dumping of radioactive wastes.

10. Plans for conserving marine biodiversity .

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

resources.

12. Social and economic incentives must be offered for conserving and sustainable use of

marine resources.

13. Governments must manage their own water while extending cooperation to the

neighbouring states.

10) Discuss about the causes, impacts and control measures of ozone depletion in the

atmosphere. (N/D-16)

Causes

Ozone layer was attacked by chlorofluorocarbons which are released into atmosphere

by refrigerator, air conditioners, etc.,

Chlorofluorocarbons undergoes photo dissociation to release chlorine which breaks

ozone into oxygen.

CFC + hν Cl*

Cl* + O

3

ClO* + O

2

ClO* + O* Cl* + O

2

Each chlorine atom is capable of attacking several ozone molecules. Thus, a chain

reaction is set up and thousands of ozone molecules are destroyed. The depletion of ozone layer

leads to the formation of ozone hole.

Other substances responsible for ozone depletion are halons, trichloroethylene

andmethyl chloroform and carbon tetra chloride. These substances are called as ozonedepleting

substances.

Effects of Ozone depletion

Effect on Human Health

The UV rays affect the human health. It causes skin cancer, cataracts, allergies etc.,

Italso produces blisters on skin.

Higher levels of UV radiations damage immune system. Hence it causes allergies

andsome infectious diseases.

Effect on Aquatic system

UV rays directly affect the aquatic systems-phyto plankton, fish. The phytoplankton

consumes large amount of carbon dioxide in the atmosphere which contributes to the global

warming.

Effect on Materials

It reduces the life time of the materials like paints, plastics.

Effect on Climate

It also affects the climate due to increase in the average temperature of the earth

surface.

Control of Ozone Depletion

Release of CFC‟s must be controlled.

Manufacturing and using of ozone depleting substances must be controlled.

11) Write a flow sheet and explain the steps involved in Solid waste Management (A/M2015,

N/D-16)

The principal objectives of soil waste management are to control, collect, treat, utilize

and dispose of the solid wastes in an economical manner consistent with the protection of public

health.

Management of solid waste is very important in order to minimize the adverse effects of

solid wastes.

TYPES OF SOLID WASTES

1. Urban wastes

Sources

Domestic wastes

Commercial wastes

Bio medical wastes – Anatomical wastes, infectious wastes.

2. Industrial wastes

Sources

Nuclear power plants – generates radioactive wastes.

Thermal power plants – produces fly ash in large quantities.

Chemical industries – produces large quantities of hazardous and toxic materials.

METHODS OF SOIL WASTE MANAGEMENT AND DISPOSAL

Reduce, Reuse and Recycle of materials.

Reduce

The raw materials used must be reduced to decrease the waste generation.

Reuse

The materials which were discarded can be reused for various purposes.

Recycle

The waste material is again made into a useful material by the process of recycling.

The most commonly used solid waste management and disposal methods are (i)

Open dumping

(ii) Sanitary landfill

(iii) Incineration

(iv) Composting.

(i) Open dumping

In olden days, solid wastes were disposed into open lands by municipalities. The dumps

are usually in low-lying areas near a water course.

This method of solid waste disposal is unsanitary and causes problems like water pollution,

bad odours, blowing papers, fires, flies, rats etc.,

These problems were mostly reduced by burial of the waste (sanitary landfill).

(ii) Sanitary landfill

In sanitary landfill, the solid wastes are covered in the underground at the end of the

disposal of the waste every day.

The complex organic wastes are slowly decomposed by the soil microorganisms by aerobic

bacteria and fungi.

The anaerobic microorganisms decompose most of the solid waste present in the landfill

due to the absence of air .

The water soluble organic acids generated in this process enter the waste media and

diffuse through the landfill soils.

The bacteria and fungi present in the soils aerobically metabolise these organic acids into

CO2 and water.

Criteria for an ideal sanitary landfill site

It should be cheap.

It should be accessible and at least 1.5km far away from the commercial and residential

neighbouring area.

It should be reasonably leveled, clear and well drained, with a capacity of use for at least 3

years.

It should not be deleterious or offensive to the surroundings.

It should be located above the ground water table so that the underground water supplies

are not polluted.

Problems with land filling

Economic problems

The land used as landfill cannot be used in future a productive farm land.

Aesthetic problems

Poorly operated landfill operations cause bad odours, insects, blowing papers and rats in

addition to dust and noise from waste transporting vehicles and compacting operations.

Environmental problems

Liquids from the wastes contaminate the ground water because of having high organic

content, soluble salts and other constituents.

About 60% of methane gas is generated during the anaerobic decomposition of organic

matter in the landfill and which may pose a potential fire hazard.

CO2 produced from the anaerobic decomposition combines with water giving carbonic acid.

The resultant acidic medium may help in dissolution of minerals and salts of Ca, Mg present in the

waste or in the soil and increases the hardness of the water.

(ii) Incineration

The process of burning of solid wastes to a very high temperature (200 C) is called

incineration.

It is an exothermic process in which solid combustible wastes are converted into

incombustible residue (ash) and gaseous products.

Incineration is most advantageous because the bulk of solid waste can be reduced to a

small volume of ash.

The heat produced during incineration can be used to produce steam which runs the

turbines generating electricity.

The following steps are important for successful incineration process.

Handling and feeding the wastes to the incinerator.

Combustion of waste within the incinerator.

Removal of the incombustible residue to the disposal site.

Removal of gaseous and gas-born residues.

Advantages

It reduces the transportation costs for carrying the solid wastes to disposal site.

It reduces the land requirement.

The residue obtained from this process is free from degradable materials (pollution free).

Disadvantages

The capital and operating costs are very high.

The air is polluted by the residue obtained from incineration.

It can‟t be used for radioactive wastes.

(iv) Composting

Composting is the aerobic decompositions of organic matter present in the refuse by

microbes like bacteria and fungi.

The organic matter is converted into stable humus like substance which can be used as

farm manure to increase crop production.

Composting involves the following three steps:

(a) Removal of Non compostable materials

Non compostable materials like metallic cans, glass and plastics are removed and the

garbage is ground in hammer mills or wet pulpers. Then it is mixed with a nutrient source (e.g. sewage

sludge, animal manure or night soil), filler (e.g. wood chips which help aeration) and water. ( to provide

50% moisture)

(b) Digestion

The mixture is kept in long rows of small heaps for 4-6 weeks. The mixture is turned over

twice a week. The colour darkens and a musty smell develops at the completion of the process.

The material is now allowed to stabilize for another 2-3 weeks. The organic matter is

degraded by the microbes and compost is formed.

(c) Product upgradation

The products obtained from the digestion is upgraded by methods like curing, grinding,

screening, pelletizing and bagging for better marketing prospects.

12) What are the effects of heavy metals in aquatic environment? (A/M-17)

The presence of heavy metals in water results in the disturbance of enzyme activity and

metabolic disorders. The enzyme containing sulphur attract metal ions . the following metal ions

causes biochemical effects.

1. Lead

2. Mercury

3. Cadmium

4. Arsenic

5. Chromium

1. Lead

Lead was released from industries like paint, electrochemical and from anti-knocking agents enter

the water bodies. Haemoglobin is an essential content of our human body. Lead has affinity for sulphur and

inhibits the enzyme activity in the heme synthesis. Also brain damage and genetic problems will arise due

to the presence of organic lead compounds. It also leads to coma and death

2. Mercury

Mercury from various chemical industries, batteries, fungicides, pharmaceuticals and

mercury vapour lamps enters the environment and affects the aquatic life by inhibiting

the heme activities. It acts as the enzyme inhibitor due to its sulphur affinity. Mercury enters the food

chain and inhibits the active transport of sugar through membranes. Neurological disorders and brain

disorders also occurs. It damages the central nervous system of babies. It also impairs hearing and

vision. Progress of poisoning leads to death.

3. Cadmium

Cadmium from Nickel – Cadmium batteries, paint industry, fungicides released into the

aquatics acts as an enzyme inhibitor. The discharge of Cd causes heart diseases, respiratory

disorders, kidney and liver damage. It also causes kidney stone formation.

4. Arsenic

Pesticides and fertilizers release the toxic arsenic which inactivate the enzymes. The

presence of arsenic causes lung and skin cancer. It also causes brain damage. It also leads to protein

deficiency.

5. Chromium

Chromium released from glass, textile and paint industries becomes toxic and carcinogenic.

Cr6+ oxidation state is toxic and causes ulcer and irritation. Health problems caused by chromium (VI)

are skin rashes, respiratory problems, lung cancer, kidney and liver damage.

The metals may enter the body by:

Ingestion

Inhalation

Absorption through the skin or mucous membranes

They are then stored in the soft tissues of the body. The heavy metals once absorbed,

compete with other ions and bind to proteins, leading to impaired enzymatic activity resulting in

damage to many organs throughout the body.