Sunday, November 10, 2013

Disaster management in India


India, due to its geographical locations and geological formations, is a highly disaster prone country. Its long coastline, snow-clad high peaks, high mountain ranges, the perennial rivers in the north all combine to add to this problem. India, which has only two per cent the total geographical area, has to support 16 per cent of total world population. Naturally, there is a tremendous pressure on the natural resources, which directly or indirectly lead to the occurrence of disasters, namely floods, droughts, landslides, earthquakes, etc.

India has faced a number of disasters, ranging from flood, earthquakes, cyclones, tsunami, drought, landslides. A few recent disasters faced by India include Uttar Kasha earthquake in UP in 1991, Later earthquake in Maharashtra in 1993, Chama earthquake in Gujarat, super cyclone in Orissa in 1999, Buhl earthquake in Gujarat in 2001, Tsunami in 2004 and Mumbai-Gujarat flood in 2005. Besides, India has a bad experience of technology-related tragedy in the form of gas tragedy in Bhopal in 1984. India also faced the problem of Plague in Gujarat.

India has set-up a disaster management unit in the centre called the National Disaster Management Authority (NDMA - under the ministry of home affairs, where several disasters are handled by different units. The website lists a central contact for information regarding any disaster in the country.

Diasater Management Cycle


The Disaster management cycle illustrates the ongoing process by which governments, businesses, and civil society plan for and reduce the impact of disasters, react during and immediately following a disaster, and take steps to recover after a disaster has occurred. Appropriate actions at all points in the cycle lead to greater preparedness, better warnings, reduced vulnerability or the prevention of disasters during the next iteration of the cycle. The complete disaster management cycle includes the shaping of public policies and plans that either modify the causes of disasters or mitigate their effects on people, property, and infrastructure.

The disaster cycle or the disaster life cycle consists of the steps that emergency managers take in planning for and responding to disasters. Each step in the disaster cycle correlates to part of the ongoing cycle that is emergency management. This disaster cycle is used throughout the emergency management community, from the local to the national and international levels.

The first step of the disaster cycle is usually considered to be preparedness. Prior to a disaster’s occurrence, emergency manager will plan for various disasters which could strike within the area of responsibility.

The second stage in the disaster cycle is response. Imminently prior to a disaster, warnings are issued and evacuations or sheltering in place occurs and necessary equipment is placed at the ready.

After the immediate response phase of the disaster cycle has been completed, the disaster turns toward recovery, focusing on the longer term response to the disaster. During the recovery phase of the disaster cycle, officials are interested in cleanup and rebuilding. During the recovery phase, lessons learned are collected and shared within the emergency response community.

The mitigation phase of the disaster cycle is almost concurrent with the recovery phase. The goal of the mitigation phase is to prevent the same disaster-caused damages from occurring again.

Finally, using the lessons learned from the response, recovery, and mitigation phases of the disaster the emergency manager and government officials return to the preparedness phase and revise their plans and their understanding of the material and human resources needs for a particular disaster in their community.

Basic principles of disaster mitigation, disaster management and methodology



Disaster management relies heavily on the use of maps and mapping techniques for control of disasters and managing response. The maps used vary from topographic maps, land-use maps, hazard maps, geologic maps, vegetation maps, population distribution rods, seismic maps and hurricane tracking maps.

Schematic maps generated using computer graphics are used extensively to generate updated information about disaster situations as they develop. By monitoring stream flow and water level at an upstream location, the disaster manager can map the expected flood zone and predict threatened areas, extent of flooding and the areas that need to be evacuated on a priority basis. Computer-generated maps are used in risk analysis, vulnerability analysis, evacuation planning, flood monitoring, damage assessment and reconstruction planning.

Aerial photography is widely used as a tool for disaster management for both pre and post-disaster planning activities. Aerial photographs are extensively used for hazard analysis, disaster assessment, reconstruction planning and management.

Remote sensing is acquisition of information about a subject that is not in direct contact with the device. Weather RADAR, weather satellites, seismographs and sono buoys are examples of remote sensing systems.

Remote sensing data may be used for disaster management in the form of risk analysis and mapping, disaster warning, cyclone warning, drought monitoring, volcanoes, large-scale fires, etc.

Electronics communications are very important in disaster management. They are used for coordination and control, assessment, reporting, monitoring, scheduling logistics, reunification and tracing separated families.

Impact of disasters on Environment, Infrastructure and development


Disasters are now recognized as one of the major contributors to underdevelopment, and underdevelopment is one of the major contributors to disaster. It has

also been recognized that if disaster response is mishandled, many years of progress can be wiped out and the chances for further progress set back. Disasters can alter agricultural patterns, settlement patterns, patterns of migration, work habits, diets, and even basic family structures. If disaster management is well planned and development oriented, a disaster can provide opportunities for accelerating the pace of development. Constructive changes can then be made.

All disaster-related activities are divided in-to distinct time periods.

Phases Of Disaster Response (Natural Disasters)

The Preparatory Phase. Activities carried out in the preparatory phase include organization, legislation, development of procedures, inventories of resources, and establishment of response plans. These activities are broadly classified as disaster prevention, mitigation and preparedness.

Warning Phase. By monitoring events, we look for indicators that tell when, where, and what magnitude the event may be. This is known as prediction or forecasting. Warning is possible for droughts and famines, cyclones and most severe weather phenomena, volcanoes, large scale fires, and in some cases earthquakes.

Emergency Phase This phase include search-and-rescue, first aid, emergency medical assistance, and restoration of emergency communication and transportation networks. Sometimes, it also necessitates evacuation from areas still vulnerable to further disaster events and provision of temporary shelter, food, and water.

Rehabilitation (Or Transitional) Phase. In this phase, people begin to return to work, to repair infrastructure, damaged buildings and critical facilities, and to take other actions necessary to help the community to return to normal.

Emergency relief measures must be discontinued during this phase so that people can begin to regain their self-reliance.
Reconstruction Phase. During this period people reconstruct housing and other community facilities, and agriculture returns to normal. The actual time span is often very difficult to define.

Types of disasters


A disaster is a natural or man-made hazard resulting in an event of substantial extent causing significant physical damage or destruction, loss of life, or drastic change to the environment. A disaster can be defined as any tragic event stemming from events such as earthquakes, floods, catastrophic accidents, fires, or explosions. It is a phenomenon that can cause damage to life and property and destroy the economic, social and cultural life of people.

Hazards are divided into natural or human-made.

A natural disaster is a consequence when a natural hazard affects humans and/or the built environment. Various phenomena like earthquakes, landslides, volcanic eruptions, floods and cyclones are all natural hazards that kill thousands of people and destroy crores of rupees of living environment and property each year. Developing countries suffer more or less chronically by natural disasters. Asia tops the list of casualties due to natural disasters.

Man-made disasters are the consequence of technological or human hazards. Examples are stampedes, fires, transport accidents, oil and chemical spills, nuclear radiations and wars.

Saturday, November 9, 2013

Issues involved in enforcement of environmental legislation

Three issues that are especially important for environmental legislation are:

1. The precautionary principle This principle has evolved to deal with risks and
uncertainties faced by environmental management. The principle implies that an ounce of
prevention is worth a pound of cure— it does not prevent problems but may reduce their

occurrence and helps ensure contingency plans are made.

2. The polluter-pays principle In addition to-the obvious—the polluter pays for the
damaged caused by a development—this principle also implies that a polluter pays for
monitoring and policing. A problem with this approach is that fines may bankrupt small
businesses, yet be low enough for a large company to write them off as an occasional
overhead, which does little for pollution control.

3. Freedom of information: Environmental planning and management is hindered if the
public, NGOs or even official bodies are unable to get information.

A number of laws have been enforced for safeguarding the environmental quality. However, these laws and acts could not be enacted successfully in light of the following problems.
  1. Drawbacks of wildlife protection act, 1972
    1. Since this act has been enacted just as a fallout of Stockholm conference held in 1972, it has not included any locally evolved conservation measures.
    2. The ownership certificates for some animal articles (Ex: Leopard and Tiger skins) often serve as a tool for illegal trading.
    3. Jammu and Kashmir have their own wildlife acts, therefore, hunting and trading of many endangered species, prohibited in other states are allowed in Jammu and Kashmir.
    4. The offenders of this act are not subject to any harsh fines. The fine is only Rs. 25000 or imprisonment for up-to three years.
  2. Drawbacks of the Forest (conservation) Act, 1980
    1. This act only transfers the powers from state to centre to decide the conversion of reserve forests to non-forest areas.
    2. The power has been centralized at the top and local communities have been completely ignored from the decision making process regarding the nature of forest areas.
    3. Tribal people living in forests are totally dependent on forest resources. If they are stopped from exploiting forests for their livelihood, they resort to criminal activities like smuggling, killing, etc.
    4. This law is concentrated on protecting trees, birds and animals but not on protecting poor people
    5. The forest dwelling tribal communities have a rich knowledge about forest resources, their importance and conservation. However, their role and contribution is not acknowledged.
  3. Drawbacks of pollution related acts
    1. The power and authority has been given only to the central government with little power to the state government. This hinders effective implementation of the act in the states.
    2. The penalties imposed by this act are very small when compared to the damage caused by big industries due to pollution.
    3. A person cannot directly file a petition in the court.
    4. Litigation, related to the environment is expensive, since it involves technical knowledge.
    5. For small industries, it is very expensive to install an individual custom-made effluent treatment plant
    6. The position of chairman of the board of most industries is occupied by a political appointee. Hence it becomes difficult to implement the act without political interference.

Wednesday, November 6, 2013

Environment Protection Act

Acid rain - Formation, Effects and Control measures

Acid rain

Normally rain water is slightly acidic due to the fact that CO2 present in the atmosphere gets dissolved in it. Because of the presence of Oxides of Nitrogen and Sulphur (NOx and SOx) as pollutants in the atmosphere, the pH of rain water is lowered further. This type of precipitation of water is called acid rain or acid deposition.

Formation of Acid Rain
Acid rain means the presence of excessive acids in rain water. Thermal power plants, industries and vehicles release nitrous oxide and sulphur dioxide into the atmosphere by burning of coal and oil. When these gases react with water vapour in the atmosphere, they form acids and descend on Earth as "acid rain" through rain water.
SOx   +   H2O   =    H2SO4
NOx   +  H2O    =   HNO3

Due to the drifting of these gases in the atmosphere by wind, their presence is felt as far as 2000 km away. Air pollution in one nation can cause acid rain in another nation.

Effects of Acid Rain

Effect of acid rain on human beings:
  1. Acid rain has been found to be very dangerous to living organisms as it can destroy life. Human nervous system, respiratory system and digestive system are affected by acid rain.
  2. It can also cause premature death from heart and lung disorders such as asthma and bronchitis
Effect of acid rain on buildings
  1. The 'Taj Mahal' in Agra is affected from the acid fumes being emitted from 'Mathura Refinery'. Crystals of CuSO4 and MgSO4 are formed as a result of corrosion due to acid rain.
  2. Acid rain corrodes houses, monuments, statues, bridges and fences.

Ozone layer depletion

Ozone layer depletion process
Ozone is a colourless, odorless gas composed of three atoms of oxygen (O3). Ozone has the same chemical structure regardless of where it occurs and can be useful or harmful depending on where it occurs in the atmosphere. Ozone is formed naturally in the upper stratosphere when wavelengths less than 240nm are absorbed by normal oxygen molecules which dissociate to give O atoms. The O atoms in combination with other oxygen molecules produce ozone.
In the stratosphere, about 19 to 30 km above the Earth's surface, ozone is constantly being produced and destroyed naturally. This production and destruction makes stratosphere with ozone layer that filters the Ultra-Violet radiation from the Sun and protects life on Earth. Normally there is a fine balance between production and destruction of ozone thereby safeguarding life on Earth.
Man-made chemicals called Chloro Fluoro Carbons(CFCs) are used as aerosol sprays, refrigerants and coolants etc destroy ozone molecules in  the stratosphere.
The CFCs themselves do not destroy ozone molecules but they decay ozone molecules at low temperatures. A small amount of chlorine atom and chlorine mono-oxide function as catalyst in the process of destruction of ozone. The equations involved are:
Cl  +  O3  =  ClO  + O2
ClO  + O  =  Cl  +  O2
Hence, net effect:
O3  +  O  =  2O2
Chlorine atom in the above reaction functions as a catalyst and is not consumed in the reaction. Chlorine atom used in the reaction remains as chlorine atom even at the end of the reaction. Once chlorine has broken one ozone molecule, it is free to repeat the process until it is removed by another reaction in the atmosphere. Chloro-Fluoro-Carbons are very stable molecules and can live upto 100 years.

Ozone Depletion Potential (ODP)
The ozone depletion potential of a compound is defined as the measure of its ability to destroy stratospheric ozone.
It may be defined as the ratio of total amount of ozone destroyed by a particular agent to the amount  of ozone destroyed by the same mass of CFC-11.
The ODP of CFC-11 is always taken as 1.0
ODP is a relative measure with CFC-11 taken as a standard reference. Therefore, if the ODP of a compound is 0.5, it is roughly speaking half as 'bad'  as CFC-11.

Factors affecting ODP
  1. Nature of  the halogen (Bromine containing halocarbons usually have much higher ODPs than hydrocarbons. This is because Bromine is an effective ozone destruction catalyst than Chlorine)
  2. The number of chlorine or bromine atoms in a molecule.
  3. Molecular mass and
  4. Atmospheric lifetime
Dobson Unit
 Dobson Unit (DU) is the scale for measuring the total amount of ozone occupying a column overhead.
One Dobson Unit (1DU) is defined as 0.01mm at 0C and 1 atmospheric pressure.
If the ozone layer thickness when compressed to 0C and 1 atmosphere pressure is about 5mm, the average amount of ozone would be about 500 DU.

Harmful effects  of ozone layer depletion
Ozone layer protects all life forms on Earth from the Sun's harmful UV radiation. Any significant decrease in the amount of ozone in the stratosphere results in the amount of UV radiation reaching the Earth's surface leading to harmful effects on all living organisms.
Effects on human health 
  1. Reddening of skin in sun shine (Sun burn)
  2. Skin cancer
  3. Reduction in body's immunity to disease
  4. Eye disorders like cataracts and blindness
Other living organisms
  1. UV rays are particularly harmful to small plants and animals living in the sea called 'plankton'. Plankton forms the base of ocean food chain
  2. UV rays damage certain crops like rice which is the staple food for many people in the world
  3. UV radiation can damage polymers used in paint, clothing and other materials.

Global warming - Definition, Effects, Control and Remedial measures

Global warming is defined as the increase in temperature of Earth, that causes change in climate

The last few centuries have seen an increase in industrial, agricultural and other human activity resulting in release of more green house gases in the atmosphere. These gases cause the atmosphere to trap increasing amounts of heat energy in the Earth's surface making the planet warmer than usual.

The global temperature is now 1C higher than in 1900. Predictions of future climate indicate that by the middle of the next century, the Earth's global temperature may be 1C to 3C higher than what it is today.

Researchers have checked through indirect evidence (tree rings, coral growth, ice cores) and confirmed that the warmest decade in the past 1000 years was from 1990 to 1999. The warmest year of the millenium was 1998.

The International Red Cross and Red Crescent have analyzed the past 33 years of natural disasters and 90% of them were weather related. Moreover, the occurrence of these disasters has increased in the past three decades.

Effects of Global Warming
Following  are the effects of global warming:
  1. More heat waves
  2. Expansion of desert area
  3. Natural fires in forest lands
  4. More evaporation of water from oceans and water bodies
  5. Melting of Ice caps in Arctic and Antarctic regions
  6. More cloud formation in the atmosphere
  7. Shorter and warmer winters coupled with longer and hotter summers
  8. Changes in rainfall pattern
  9. Rise in sea level
  10. Flooding and submergence of low lying coastal areas
  11. Disruption in farming
  12. More drought
  13. Impact on plants, animals and humans
Control and remedial measures:
Some of the remedial and control measures of global warming are listed below: 
  1. Reduction in consumption of fossil fuels such as coal and petroleum
  2. Use of bio-gas plants
  3. Use of nuclear power plants
  4. Increasing forest cover
  5. Use of unleaded petrol in  automobiles
  6. Installation of pollution controlling devices in automobiles (catalytic converter) and industries (Electro Static Precipitators, Bag filters, Wet scrubbers etc)

Climate change - causes and effects

Climate change
Climate change refers to the sum of all statistical weather information of the atmospheric elements, with specified area over a long period of time. Climate never remains static but is a dynamic process and changes to a lesser or greater degree. Climate change is a common deviation from average as well as extreme temperatures.
The Earth's surface and lowest part of the atmosphere have warmed up to an average by almost 0.6C during the last 100 years. If the rate climate change is constant, global surface temperatures could be anywhere between 1.4 and 5.8C higher now than in 1999 by 2100. Sea level rise is projected to be between 9 and 88cm by 2100.

The United Nations Framework Convention on Climate Change (UNFCC-1992) and the Kyoto Protocol (KP-1997) represent the first steps taken by the international community to protect the climate system from man-made interferences. Several countries have agreed to reduce greenhouse gas emissions by about 5% by 2008 to 2012. In practical terms, this means
  • using resources, particularly fossil-fuel-derived energy more efficiently
  • reusing and recycling products wherever possible and
  • developing renewable forms of energy that are inexhaustible and do not pollute the environment
Causes of climate change
  1. Variation of Earth's orbital characteristics
  2. Atmospheric carbon dioxide variations 
  3. Volcanic eruptions and
  4. Variations in solar output
Effects of climate change
Climate change has pronounced effects on every part of the Earth. It affects both living and non living components of most ecosystems on the Earth.
  1. Mean Sea Level (MSL) is increased by around 1.8mm per year.
  2. Many ecosystems of the world will have to adapt rapidly to the constantly changing global temperatures.
  3. The rate of species becoming extinct will be increased.
  4. Human health, agriculture, forestry and water resources will be affected.
  5. Increasing change in surface temperatures, changing rates of evapo-transpiration and precipitation (due to climate change) will influence the hydrological cycle.
  6. Frequency and intensity of extreme weather events is increased leading to unexpected flooding and drought
  7. Societies experiencing social, economic and climatic stress will be worst affected and least able to adapt.

Envionmental ethics

Environmental ethics is defined as the analysis of the human use of Earth's limited resources.

Ethics is the branch of philosophy that primarily discusses issues dealing with human behaviour and character. Ethics attempts to establish a basis for judging right from wrong and good from bad.

Environmental ethics is the branch of ethics which analyzes human use of Earth's limited resources. A growing trend is to combine the study of both ecology and economics to help provide a basis for sustainable decisions on environmental use.

Environmental ethics attempts to answer questions of how human beings should relate to their environment regarding the usage of environmental resources and their treatment of other species (plant and animal).

A few conflicts that arise from environmental policies deal with the rights of individuals versus those of the state and rights of private property owners versus those of a community.

Population Explosion

Population Explosion
The enormous increase in population, due to low death rate (mortality) and high birth rate (natality), is termed as population explosion. Human population is not increasing at a uniform rate throughout the world.
Population increase can be better understood in terms of doubling time. Doubling time is the number of years needed for a population to double. It varies from about 25 years in developing countries to 100 years in developed nations.

Reasons for population explosion:
  1. Introduction of modern facilities reduces mortality rate and increases natality rate leading to population explosion.
  2. Increase of life expectancy also a major reason contributing to population explosion 
Effect of population explosion or Environmental and Social impacts of growing population
  1. Poverty: Infant mortality is an indicator of poverty. In 34 developing countries, more than one in ten children die before they reach the age of five. In developing countries, people opt for smaller families in the face of high mortality rate. 
  2. Population explosion leads to environmental degradation.
  3. Population explosion causes over-exploitation of natural resources leading to shortage of resources for the future generations.
  4. Many of the renewable resources like forests and grass lands are also under threat.
  5. Increase in population also increases disease, economic inequity and communal wars.
In order to combat the problem of population explosion, the Government of India introduced the Family Welfare Programme as an integral part of the overall national policy.

Objectives of Family welfare programme:
  1. Slowing down population explosion by reducing fertility and
  2. Reducing the pressure on the environment due to over-exploitation of natural resources.

Watershed management

Watershed management:
Watershed is defined as the geographic area from which water in a particular stream, lake or estuary originates.It includes entire area of land that drains into the water body. It is supported from other systems by high points in the area such as hills or slopes.
Ex: Watershed of a lake would not only include the streams entering the lake but also the land that drains those streams and eventually the lake.
Watershed management is a process aimed at protecting and restoring the habitat and water resources of a watershed, incorporating the needs of multiple stakeholders.

Impacts of human beings on a watershed:
The activities of human beings have the following impacts on a watershed:
  1. Altering water course: The water course is altered by changing the contour of the land and adding storm water systems
  2. Adding pollution sources: The type of pollutant absorbed and carried by the storm water depends on the land use. During the course of storm water impounded in a parking area might pick-up litter, road salt, motor oil and carry these pollutants to a local stream. In agricultural fields, the rainwater might wash fertilizers and soil into a stream. Melting of snow might wash fertilizers and pesticides into the lawn of suburban homes.
  3. Urbanization: Urbanization has impacted local resources in more ways than one can imagine. It has resulted in a change in the flow and constituents of water flowing into a watershed. Urbanization has changed both the surface and ground water. Urban areas have replaced trees, plants and shrubs with impervious surfaces like roads, roof tops, parking lots and other hard surfaces. These impervious surfaces prevent water to seep into the ground thereby increasing surface runoff. This leads to increased flooding after storms and reduced flow in streams and rivers during dry seasons.
  4. Scouring of channels: Erosion of stream banks and scouring of channels occurs due to increase in volume. Sediment in eroded stream banks clogs the gills of fish and light needed by aquatic plants. Sediment settles in stream channels, lakes and reservoirs thereby increasing flooding and requiring  dredging to clear streams or lakes for boating.
Goals of watershed management:
The two main goals of watershed management are listed below:
  1. Watershed management seeks to preserve the environment and
  2.  Watershed management is applied to make the most cost-effective methods to achieve the above listed goal
Controlling storm water flow
It is essential to control storm-water flow in order to reduce the impact of development of local watershed and aquifers. Storm-water flow can be controlled in both quality and quantity by minimizing the disturbances developed in the natural flow of water. By designing in alignment with nature, the impact of urbanization can be greatly reduced. Storm-water flow can be controlled in the following ways:
  1. Minimizing development of impervious surfaces
  2. Maximizing areas of dense vegetation
  3. Use of structural storm water management basins
  4. Reducing the possibility of pollution of storm-water

Water conservation

Water conservation:
Among the essential elements for the existence of life, water is rated as the most important. Water is  a universal solvent and is largely responsible for determining the structure, function and distribution of species in an ecosystem.
The original source of water is precipitation from the atmosphere. Water on earth occurs in all three phases. As a liquid, it forms the hydrosphere. Around 75% of the earths surface is covered with hydrosphere.
The total amount of water on the earth's surface is around 266 x 10E20 kg. Around 97% of water on the Earth is salt water, 2% is locked in polar ice -caps, mountains and glaciers and the remaining 1% is available as fresh water.
The production, development and efficient management of water resources for beneficial use is called water conservation. Listed below are a few techniques of water conservation.
  1. Rainwater harvesting
  2. Watershed management
  3. Construction of storage reservoirs
  4. Reuse of industrial wastewater and
  5. Better agricultural practices

Monday, November 4, 2013

Solid waste management - sources, effects and methods of disposal

Solid waste management

Rapid population growth and urbanization in developing countries has led to people generating enormous quantities of solid waste and consequent environmental degradation. The waste is normally disposed in open dumpscreating nuisance and environmental degradation. Solid wastes cause a major risk to public health and the environment. Management of solid wastes is important in order to minimize the adverse effects posed by their indiscriminate disposal.

Types of solid wastes: Depending on the nature of origin, solid wastes are classified into
Urban wastes include the following wastes:
Domestic wastes containing a variety of materials thrown out from homes
Ex: Food waste, Cloth, Waste paper, Glass bottles, Polythene bags, Waste metals, etc.
Commercial wastes: It includes wastes coming out from shops, markets, hotels, offices, institutions, etc.
Ex: Waste paper, packaging material, cans, bottle, polythene bags, etc.
Construction wastes: It includes wastes of construction materials.
Ex: Wood, Concrete, Debris, etc.
Biomedical wastes: It includes mostly waste organic materials
Ex: Anatomical wastes, Infectious wastes, etc.

Classification of urban wastes
Urban wastes are classified into:
Bio-degradable wastes - Those wastes that can be degraded by micro organisms are called bio-degradable wastes
Ex: Food, vegetables, tea leaves, dry leaves, etc.
Non-biodegradable wastes: Urban solid waste materials that cannot be degraded by micro organisms are called non-biodegradable wastes.
Ex: Polythene bags, scrap materials, glass bottles, etc.

The main source of industrial wastes are chemical industries, metal and mineral processing industries.
Nuclear plants: It generated radioactive wastes
Thermal power plants: It produces fly ash in large quantities
Chemical Industries: It produces large quantities of hazardous and toxic materials.
Other industries: Other industries produce packing materials, rubbish, organic wastes, acid, alkali, scrap metals, rubber, plastic, paper, glass, wood, oils, paints, dyes, etc.

  1. Due to improper disposal of municipal solid waste on the roads and immediate surroundings, biodegradable materials undergo decomposition producing foul smell and become a breeding ground for disease vectors.
  2. Industrial solid wastes are the source for toxic metals and hazardous wastes that affect soil characteristics and productivity of soils when they are dumped on the soil
  3. Toxic substances may percolate into the ground and contaminate the groundwater.
  4. Burning of industrial or domestic wastes (cans, pesticides, plastics, radioactive materials and batteries) produce furans, dioxins and polychlorinated biphenyls that are harmful to human beings.
Solid waste management involves waste generation, mode of collection, transportation, segregation of wastes and disposal techniques.

Two important steps involved in solid waste management are:
Reduce, Reuse and Recycle of Raw Materials
Discarding wastes

Reduce - If usage of raw materials is reduced, the generation of waste also gets reduced
Reuse  - Refillable containers that are discarded after use can be reused
               Rubber rings can be made from discarded cucle tubes and this reduces waste generation during      manufacture of rubber bands.
Recycle- Recycling is the reprocessing of discarded materials into new useful products
Ex:     Old aluminium cans and glass bottles are melted and recast into new cans and bottles
          Preparation of cellulose insulation from paper
          Preparation of automobile body and construction material from steel cans
This method (Reduce, Reuse & Recycle), i.e, 3R's help save money, energy, raw materials and reduces pollution.

The following methods are adopted for discarding wastes:
  1. Landfill
  2. Incineration and
  3. Composting
LANDFILL: Solid wastes are placed in a sanitary landfill in which alternate layers of 80 cm thick refuse is covered with selected earth-fill of 20 cm thickness. After 2-3 years solid waste volume shrinks by 25-30% and land is used for parks, roads and small buildings. This is the most common and cheapest cheapest method of waste disposal and is mostly employed in Indian cities.
It is simple and economical
Segregation of wastes is not required
Landfilled areas can be reclaimed and used for other purposes
Converts low-lying, marshy waste-land into useful areas.
Natural resources are returned to soil and recycled.
Large area is required
Land availability is away from the town, tansportation costs are high
Leads to bad odour if landfill is not properly managed.
Land filled areas will be sources of mosquitoes and flies requiring application of insecticides and pesticides at regular intervals.
Causes fire hazard due to formation of methane in wet weather.

It is a hygenic way of disposing solid waste. It is suitable if waste contains more hazardous material and organic content. It is a thermal process and very effective for detoxification of all combustible pathogens. It is expensive when compared to composting or land-filling.
In this method municipal solid wastes are burnt in a furnace called incinerator. Combustibe substances such as rubbish, garbage, dead organisms and non-combustibe matter such as glass, porcelain and metals are separated before feeding to incinerators. The non-combustible materials can be left out for recycling and reuse. The leftover ashes and clinkers may account for about 10 to 20% which need further disposal by sanitary landfill or some other means.

The heat produced in the incinerator during burning of refuse is used in the form of steam power for generation of electricity through turbines. Municipal solid waste is generally wet and has a high calorific value. Therefore, it has to be dried first before burning. Waste is dried in a preheater from where it is taken to a large incinerating furnace called "destructor" which can incinerate about 100 to 150 tonnes per hour. Temperature normally maintained in a combustion chamber is about 700 C which may be increased to 1000 C when electricity is to be generated.

Residue is only 20-25% of the original and can be used as clinker after treatment
Requires very little space
Cost of transportation is not high if the incinerator is located within city limits
Safest from hygenic point of view
An incinerator plant of 3000 tonnes per day capacity can generate 3MW of power.

Its capital and operating cost is high
Operation needs skilled personnel
Formation of smoke, dust and ashes needs further disposal and that may cause air pollution.

It is another popular method practiced in many cities in our country. In this method, bulk organic waste is converted into fertilizer by biological action.
Separated compostible waste is dumped in underground trenches in layers of 1.5m and finally covered with earth of 20cm and left for decomposition. Sometimes, actinomycetes are introduced for active decomposition. Within 2 to 3 days biological action starts. Organic matter is destroyed by actinomycetes and lot of heat is liberated increasing the temperature of compost by 75C and the refuse is finally converted into powdery brown coloured odourless mass called humus that has a fertilizing value and can be used in agriculture. Humus contains lot of Nitrogen essential for plant growth apart from phosphates and other minerals.
Manure added to soil increases water retention and ion-exchange capacity of soil.
This method can be used to treat several industrial solid wastes.
Manure can be sold thereby reducing cost of disposing wastes
Recycling can be done
Non-consumables have to be disposed separately
The technology has not caught-up with the farmers and hence does not have an assured market.

Thermal pollution - causes, effects and control measures of thermal pollution

Thermal pollution
Thermal pollution is defined as the addition of excess of undesirable heat to water thereby making it harmful to man, animal or aquatic life. Thermal pollution may also cause significant departures from nor activities of aquatic communities.

Sources of Thermal Pollution:
The following sources contribute to thermal pollution.
  1. Nuclear power plants
  2. Coal fired plants
  3. Industrial effluents
  4. Domestic sewage
  5. Hydro-electric power
  1. Nuclear power plants: Nuclear power plants including drainage from hospitals, research institutions, nuclear experiments and explosions, discharge a lot of heat that is not utilized along with traces of toxic radio nuclides into nearby water streams. Emissions from nuclear reactors and processing installations are also responsible for increasing the temperatures of water bodies. The operations of power reactors and nuclear fuel processing units constitutes the major contributor of heat in the aquatic environment. Heated effluents from power plants are discharged at 10 C higher than the receiving waters that affects the aquatic flora and fauna.
  2. Coal-fired power plants: Coal fired power plants constitute a major source of thermal pollution. The condenser coils in such plants are cooled with water from nearby lakes or rivers. The resulting heated water is discharged into streams thereby raising the water temperature by 15C.  Heated effluent decreases the dissolved content of water resulting in death of fish and other aquatic organisms. The sudden fluctuation of temperature also leads to "thermal shock" killing aquatic life that have become acclimatized to living in a steady temperature.
  3. Industrial effluents: Industries like textile, paper, pulp and sugar manufacturing release huge amounts of cooling water along with effluents into nearby natural water bodies. The waters polluted by sudden and heavy organic loads result in severe drop in levels of dissolved oxygen leading to death of several aquatic organisms.
  4. Domestic Sewage: Domestic sewage is discharged into rivers, lakes, canals or streams with minimal treatment or without any treatment. These wastes have a higher organic temperature and organic load. This leads to decrease in dissolved oxygen content in the receiving waters resulting in the set-up of anaerobic conditions causing release of foul and offensive gases in water. Eventually, this leads to development of anoxic conditions resulting in rapid death of aquatic organisms.
  5. Hydro-electric power: Generation of hydroelectric power sometimes leads to negative thermal loading in water systems. Apart from electric power industries, various factories with cooling requirement contribute to thermal loading.
Thermal pollution in streams by human activities
  1. Industries and power plants  use water to cool machinery and discharge the warm water into a stream
  2. Stream temperature rises when trees and tall vegetation providing shade are cut.
  3. Soil erosion caused due to construction also leads to thermal pollution
  4. Removal of stream side vegetation
  5. Poor farming Practices also lead to thermal polloution
Effects of Thermal pollution
  1. Reduction in dissolved oxygen: Concentration of Dissolved Oxygen (DO) decreases with increase in temperature.
  2. Increase in toxicity: The rising temperature increases the toxicity of the poison present in water. A 10C increase in temperature of water doubles the toxicity effect of potassium cyanide, while 80C rise in temperature triples the toxic effects of o-xylene causing massive mortality to fish.
  3. Interference in biological activity: Temperature is considered to be of vital significance to physiology, metabolism and biochemical processes that control respiratory rates, digestion, excretion, and overall development of aquatic organisms. Temperature changes cause total disruption to the entire ecosystem.
  4. Interference in reproduction: In fishes, several activities like nest building, spawning,hatching, migration and reproduction depend on optimum temperature.
  5. Direct mortality: Thermal pollution is directly responsible for mortality of aquatic organisms. Increase in temperature of water leads to exhaustion of microorganisms thereby shortening the life span of fish. Above a certain temperature, fish die due to failure of respiratory system and nervous system failure.
  6. Food storage for fish: Abrupt changes in temperature alters the seasonal variation in the type and abundance of lower organisms leading to shortage of right food for fish at the right time.
 Control measures for thermal pollution
The following methods can be adapted to control high temperature caused by thermal discharges:
  1. Cooling towers: Use of water from water systems for cooling systems for cooling purposes, with subsequent return to the water way after passage through a condenser, is called cooling process. Cooling towers transfer heat from hot water to the atmosphere by evaporation. Cooling towers are of two types:
    (i) Wet cooling tower: Hot water coming out from the condenser (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.
    (ii) Dry cooling tower: Here, hot water is allowed to flow in long spiral pipes. Cool air with the help of a fan is passed over these hot pipes, which cools down hot water. This cool water can be recycled. 
  2. Cooling ponds: Cooling ponds are the best way to cool thermal discharges. Heated effluents on the surface of the water in cooling ponds maximise dissipation of heat to the atmosphere and minimise the water area and volume. The warm water wedhe acts like a cooling pond.
  3. Spray ponds: The water coming out from condensers is allowed to pass into the ponds through sprayers. Here water is sprayed through nozzles as fine droplets. Heat from the fine droplets gets dissipated to the atmosphere.
  4. Artificial lakes: Artificial lakes are man made water bodies that offer once-through cooling. The heated effluents can be discharged into the lake at one end and water for cooling purposes may be withdrawn from the other end. The heat is eventually dissipated through evaporation.

Noise pollution - Causes, types, effects and control of noise pollution

Noise pollution
Noise is defined as, "the unwanted, unpleasant or disagreeable sound that causes discomfort to all living beings". Sound intensity is measured in decibels (dB), that is the tenth part of the longest unit Bel. One dB is the faintest sound that a human ear can hear.

TYPES OF NOISE: Environmental noise has been doubling every ten years. Noise is classified as:
  1. Industrial Noise
  2. Transport  Noise and
  3. Neighbourhood noise
Industrial Noise: It is sound with a high intensity sound caused by industry machines. Sources of such noise pollution is caused by machines from machines in various factories, industries and mills. Noise from mechanical saws and pneumatic drills is unbearable and a nuisance to the public.
The Indian Institute of Oto-Rino Laryngology, Chennai reported that increasing industrial pollution damages the hearing ability by atleast 20%.
Workers in steel industry, who work close to heavy industrial blowers are exposed to 112dB for eight hours suffer from occupational pollution.

Transport Noise: Transport noise mainly consists of traffic noise from road, rail and aircraft. The number of automobiles on roads like motors, scooters, cars, motor cycles, buses, trucks and diesel engine vehicles have increased enormously in the recent past further aggravating the problem of transport noise.
Noise levels in most residential areas in metropolitan cities is hovering around the border line due to increased vehicular noise pollution. This high level of noise pollution leads to deafening in the elderly.

Neighbourhood noise: This type of noise includes disturbance from household gadgets and community. Common sources being musical instruments, TV, VCR, Radios, Transistors, Telephones, and loudspeakers etc. Statistically, ever since the industrial revolution, noise in the environment has been doubling every ten years.

Effects of Noise pollution
  1. Noise pollution affects both human and animal health. It leads to:
        1. contraction of blood vessels
        2. making skin pale
        3. excessive adrenalin in the blood stream which is responsible for high blood pressure.
        4. Blaring sounds are known to cause mental distress
        5. Heart attacks, neurological problems, birth defects and abortion
  2. Muscle contraction leading to nervous breakdown, tension, etc
  3. The adverse reactions are  coupled with a change in hormone content of blood, which in-turn increases  heart beat, constriction of blood vessels, digestive spams and dilation of the pupil of the eye.
  4. Adverse affects health, work efficiency and behaviour. Noise pollution may cause damage to the heart, brain, kidneys, liver and may produce emotional disturbance.
  5. The most immediate and acute effect of noise is impairment of hearing that diminishes some part of the auditory system. Prolonged exposure to noise of certain frequency pattern leads to chronic damage to the inner ear.
  6. Impulsive noise may cause psychological and pathological disorders
  7. Ultrasonic sound can affect the digestive, respiratory, cardiovascular system and semicircular canals of the internal ear.
  8. The brain is adversely affected by loud and sudden noise by jets and airplanes. People are subjected to psychiatric illness.
  9. Recent reports suggest that blood is thickened by excessive noise.
  10. The optical system of human beings is also affected by noise pollution. Severe noise pollution causes:
    1. Pupullary dilation
    2. Impairment of night vision and
    3. Decrease in rate of colour perception
Control measures:
  1. SOURCE CONTROL: This includes source  modification such as acoustic treatment to machine surface, design changes, limiting operational timings, etc
  2. TRANSMISSION PATH INTERVENTION: This includes containing the source inside a sound insulating enclosure, constructing 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 noise from the machine.
Preventive measures:
  1. Prescribing noise limits for vehicular traffic
  2.  Ban on honking (usage of horns) in certain areas
  3. Creation of silence zones near schools and hospitals
  4. Redesigning buildings to make them noise proof
  5. Reduction of traffic density in residential areas
  6. Giving preference to mass public transport system.

Soil pollution - Types, effects, sources and control of soil pollution

Soil pollution
Soil pollution is defined as, “contamination of soil by human and natural activities which may cause harmful effect on living organisms”. Composition of soil is listed below:
Organic mineral matter 45
Organic matter 05
Soil water 25
Soil air 25

Soil pollution mainly occurs due to the following:
  1. Industrial wastes
  2. Urban wastes
  3. Agricultural practices
  4. Radioactive pollutants
  5. Biological agents

Industrial wastes – Disposal of Industrial wastes is the major problem for soil pollution
Sources: Industrial pollutants are mainly discharged from various origins such as pulp and paper mills, chemical fertilizers, 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, disturb the biochemical process and finally lead to serious effects on living organisms.

Urban wastes – Urban wastes comprise of both commercial and domestic wastes consisting of dried sludge and sewage. All the urban solid wastes are commonly referred to as refuse.
Constituents of urban refuse: This refuse consists of 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 industrial wastes, can still be dangerous. This happens because they are not easily degraded.

Agricultural practices – Modern agricultural practices pollute the soil to a large extent. With the advancing agro-technology, huge quantities of fertilizers, pesticides, herbicides and 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

Radioactive pollutants/ - Radioactive substances resulting from explosions of nuclear testing laboratories and industries giving rise to nuclear dust radioactive wastes, penetrate the soil and accumulate giving rise to land/soil pollution.
  1. Radio nuclides of Radium, Thorium, Uranium, isotopes of Potassium (K-40) and Carbon (C-14) are commonly found in soil, rock, water and air.
  2. Explosion of hydrogen weapons and cosmic radiations include neutron, proton reactions by which Nitrogen (N-15) produces C-14. This C-14 participates in Carbon metabolism of plants which is then into animals and human beings.
  3. Radioactive waste contains several radio nuclides such as Strontium90, Iodine-129, Cesium-137 and isotopes of Iron which are most injurious. Strontium get deposited in bones and tissues instead of calcium.
  4. Nuclear reactors produce waste containing Ruthenium-106, Iodine-131, Barium-140, Cesium-144 and Lanthanum-140 along with primary nuclides Sr-90 with a half life 28 years and Cs-137 with a half life 30 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 the radio nuclides deposited on the soil emit gamma radiations.
  5. Biological agents – Soil gets a large amount of human, animal and bird excreta which constitute a major source of land pollution by biological agents.
    Ex: 1. Heavy application of manures and digested sludge can cause serious damage to plants within a few years

Control measures of soil pollution:
  1. Soil erosion can be controlled by a variety of forestry and farm practices.
    Ex: Planting trees on barren slopes
      Contour cultivation and strip cropping may be practiced instead of shifting cultivation
      Terracing and building diversion channels may be undertaken.
Reducing deforestation and substituting chemical manures by animal wastes also helps arrest soil erosion in the long term.

    1. Proper dumping of unwanted materials: Excess wastes by man and animals pose a disposal problem. Open dumping is the most commonly practiced technique. Nowadays, controlled tipping is followed for solid waste disposal. The surface so obtained is used for housing or sports field.
    2. Production of natural fertilizers: Bio-pesticides should be used in place of toxic chemical pesticides. Organic fertilizers should be used in place of synthesized chemical fertilizers. Ex: Organic wastes in animal dung may be used to prepare compost manure instead of throwing them wastefully and polluting the soil.
    3. Proper hygienic condition: People should be trained regarding sanitary habits.
      Ex: Lavatories should be equipped with quick and effective disposal methods.
    4. Public awareness: Informal and formal public awareness programs should be imparted to educate people on health hazards by environmental education.
      Ex: Mass media, Educational institutions and voluntary agencies can achieve this.
    5. 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.
      Ex: Industrial wastes should be properly treated at source. Integrated waste treatment methods should be adopted.
    6. 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 improper disposal of radioactive wastes should be banned.

Water pollution - types, effects, sources and control of water pollution

Water pollution

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.”

Pollutants include:

  1. Sewage
  2. Industrial effluents and chemicals
  3. Oil and other wastes

Chemicals in air dissolve in rain water, fertilizers, pesticides and herbicides leached from land pollute water.

TYPES, EFFECTS AND SOURCES 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.

Infectious agents
Ex: Bacteria, Viruses, Protozoa, and parasitic worms.

Human sources
Human and animal wastes

Effects: Variety of diseases.

Oxygen demanding wastes (Dissolved oxygen): 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 to 15 mg/L Ex: Organic wastes such as animal manure and plant debris that can be decomposed by aerobic (oxygen-requiring) bacteria.

Human sources: 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.

Inorganic chemicals
Ex: Water soluble inorganic chemicals:
  1. Acids
  2. Compounds of toxic metals such as lead (Pb), arsenic (As) and selenium (Se)
  3. Salts such as NaCl in oceans and fluoride (F-) found in some soils

Human sources: Surface runoff, industrial effluents and household cleansers Effects: Inorganic chemicals can:
  1. Make freshwater unusable for drinking and irrigation
  2. Cause skin cancer and neck damage
  3. Damage nervous system, liver and kidneys
  4. Harm fish and other aquatic life
  5. Lower crop yields
  6. Accelerate corrosion of metals exposed to such water

Organic chemicals
Ex: Oil, Gasoline, Plastics, Pesticides, Cleaning solvents and Detergents.
Human Sources: Industrial effluents, household cleansers and surface runoff from farms.

  1. Can threaten human health by causing nervous system damage and some cancers.
  2. Harm fish and wildlife.
Plant nutrients
Ex: Water soluble compounds containing nitrate, Phosphate and Ammonium ions.
Human sources: Sewage, manure and runoff of agricultural and urban fertilizers.

  1. Can cause excessive growth of algae and other aquatic plants, which die, decay, deplete dissolved oxygen in water thereby killing fish
  2. Drinking water with excessive levels of nitrates lower the oxygen carrying capacity of the blood and can kill urban children and infants.

Ex: Soil, silt, etc.
Human Sources: Land erosion

  1. Causes cloudy water thereby reducing photosynthetic activity
  2. Disruption of aquatic food chain
  3. Carries pesticides, bacteria and other harmful substances
  4. Settles and destroys feeding and spawning grounds of fish
  5. Clogs and fills lakes, artificial reservoirs, stream channels and harbours.

Radioactive materials:
Ex: Radioactive isotopes of:
  1. Iodine
  2. Radon
  3. Uranium
  4. Cesium and
  5. Thorium
Human sources: Nuclear power plants, mining and processing of uranium and other ores, nuclear weapon production and natural sources.

Effects: Genetic mutations, birth defects and certain cancers.

Heat (Thermal pollution)
Ex: Excessive heat

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

  1. Low dissolved oxygen levels thereby making aquatic organisms more vulnerable to disease, parasites and toxic chemicals.
  2. When a power plant starts or shuts down for repair, fish and other organisms adapted to a particular temperature range, can be killed by an abrupt temperature change known as thermal shock.
Point and non-point sources of water pollution:
Point sources These are pollutants that are discharged at specific locations through pipes, ditches or sewers into bodies of surface waters.
  1. Ex: Factories, sewage treatment plants, abandoned underground mines and oil tankers.
  2. Non point sources These pollutants cannot be traced to a single point of discharge. They are large land areas or air-sheds that pollute water by runoff, subsurface flow or deposition from the atmosphere.
    Ex: Acid deposition, runoff of chemicals into surface water from croplands, livestock feedlots, logged forests, urban streets, lawns, golf courses and parking lots.

Control measures of water pollution
  1. Administration of water pollution control should be in the hands of state or central government
  2. Scientific techniques should be adopted for environmental control of catchment areas of rivers, ponds or streams
  3. Industrial plants should be based on recycling operations as it helps prevent disposal of wastes into natural waters but also extraction of products from waste.
  4. Plants, trees and forests control pollution as they act as natural air conditioners.
  5. Trees are capable of reducing sulphur dioxide and nitric oxide pollutants and hence more trees should be planted.
  6. No type of waste (treated, partially treated or untreated) should be discharged into any natural water body. Industries should develop closed loop water supply schemes and domestic sewage must be used for irrigation.
  7. Qualified and experienced people must be consulted from time to time for effective control of water pollution.
  8. Public awareness must be initiated regarding adverse effects of water pollution using the media.
  9. Laws, standards and practices should be established to prevent water pollution and these laws should be modified from time to time based on current requirements and technological advancements.
  10. Basic and applied research in public health engineering should be encouraged.

Air Pollution - causes, effects and control measures

Air pollution - Air pollution may be defined as the presence of one or more contaminants like dust, mist, smoke and colour in the atmosphere that are injurious human beings, plants and animals.
  1. Rapid industrialization
  2. Fast urbanization
  3. Rapid growth in population
  4. Growth of vehicles on the roads and
  5. Activities of human beings have disturbed the natural balance of the atmosphere.
The composition of Air is given below:
Nitrogen                                     78%
Oxygen                                      21%
Argon                                        less than 1%
Carbondioxide                           0.037%
Water vapour                            Remaining
Ozone, Helium and ammonia     Trace amount

Sources of Air pollution
Sources of  air pollution are of two types.
Natural sources and Artificial sources

Natural sources of pollution are those that are caused due to natural phenomena. Ex: Volcanic eruptions, Forest fires, Biological decay, Pollen grains, Marshes, Radioactive materials.

Artificial sources are those which are created by man. Ex: Thermal power plants, Vehicular emissions, Fossil fuel burning, agricultural activities etc.

Classification of Air Pollutants
Depending on the form of pollutants present in the environment, they are classified as:
  1. Primary pollutants and
  2. Secondary pollutants
Primary pollutants are those that are directly emitted in the atmosphere in the harmful form
Ex: CO, NO, CO2, SO2 etc.

Secondary pollutants are those that are formed by reacting with other components or some basic component of the atmosphere to form new pollutants.
Ex: Oxides of Nitrogen (NO2 or NO3) react with moisture in the atmosphere to give Nitric acid

Indoor air pollutants are primary air pollutants. The most important indoor air pollutant is Radon gas.
Sources of indoor air pollutants are:
  1.  Radon gas is emitted from building materials like bricks, concrete, tiles, etc that are derived from soil containing radium
  2. Radon is also found  in natural gas and ground water and is emitted while being used.
  3. Burning fuel in the kitchen and cigarette smoke release pollutants like CO, SO2, HCHO (Formaldehyde) and BAP (Benzo-(A) pyrene).
Carbonmonoxide: It is a colourless, odourless gas that is poisonous animals. It is formed by incomplete combustion of carbon containing fuels.
Source of carbonmonoxide is cigarette smoking and incomplete combustion of fossil fuels (more than 77% comes from motor vehicle exhaust)
Health effects include reduced ability of red blood cells to carry oxygen to body cells and tissues. This leads to headache and anemia. At high levels it causes coma, irreversible brain damage and death.

Nitrogen Dioxide: It is a reddish-brown irritating gas that causes photochemical smog. In the atmosphere, it gets converted into nitric acid (HNO3). It is caused by burning fossil fuels in industries and power plants.
Health effects include lung irritation and damage. Environmental effects involve acid deposition leading to damage of trees, lakes, soil and ancient monuments. NO2 can damage fabrics.

Sulphur Dioxide: It is a colourless and irritating gas that is formed by combustion of sulphur containing fossil fuels such as coal and oil. In the atmosphere it is converted into Sulphuric acid which is a major component of acid deposition.
Health effects involve breathing problems for healthy people.
Environmental effects involve reduced visibility and acid deposition on trees, lakes, soils and monuments leading to their deterioration and adverse effect on aquatic life.

Suspended Particulate Matter (SPM): Includes a variety of particles and droplets (aerosols) that can be suspended in atmosphere for short  to long periods.
Human sources for SPM include burning coal in power and industrial units, burning diesel and other fuels in vehicles, agriculture, unpaved roads, construction, etc.
Health effects include nose and throat irritation, ling damage, bronchitis, asthama, reproductive problems and cancer.
Environmental Effects include reduced visibility and acid deposition. Acid deposition may lead to damaged trees, soils and aquatic life in lakes.

Ozone is a highly reactive gas with an unpleasant odour occurring in the stratosphere where it protects mankind fro the harmful ultra-violet rays from the Sun. However on earth, it is a pollutant.
It occurs on earth due to reaction between Volatile Organic Compounds (VOCs) and Nitrogen Oxides. It moderates the climate

Photochemical smog is a browinsh smoke that frequently forms on clear, sunny days over large cities with significant amounts of automobile traffic.It is mainly due to chemical reactions among nitrogen oxides and hydrocarbons in the presence of sunlight.
Health effects include breathing problems, cough, eye, nose and throat irritation, heart diseases, reduced resistance to colds and pneumonia.
Environmental effects involve damage to plants and trees. Additionally, Smog reduces visibility.

Lead is a solid and highly toxic metal. Its compounds are emitted into the atmosphere as particulate matter.
Human Sources: Paint, Smelters (metal refineries), lead manufacture, storage batteries, leaded petrol, etc
Health effects: Lead accumulates in the body and brain leading to nervous system damage and mental retardation (especially in children), digestive and other health problems. Lead containing chemicals are known to cause cancer in test animals.
Environmental Effects: It can harm wildlife.

Hydrocarbons Lower haydrocarbons accumulate due to decay of vegetable matter.
Human effects: They are carcinogenic

Chromium: It is a solid toxic metal emitted into the atmosphere as particulate matter.
Human sources: Paint, Smelters,  Chromium manufacture, Chromium plating.
Health Effects: Perforation of nasal septum, chrome holes, etc.

The atmosphere has several built-in self cleaning processes such as dispersion, gravitational settling, flocculation, absorption, rain-washout, etc to cleanse the atmosphere. However, control of contaminants at their source level is a desirable and effective method through preventive or control technologies.
Source control: Some measures that can be adopted in this direction are:
  1. Using unleaded petrol
  2. Using fuels with low sulphur and ash content
  3. Encouraging people to use public transport, walk or use a cycle as opposed to private vehicles
  4. Ensure that houses, schools,  restaurants and playgrounds are not located on busy streets
  5. Plant trees along busy streets as they remove particulates, carbon dioxide and absorb noise
  6. Industries and waste disposal sites should be situated outsdide the city preferably on the downwind of the city.
  7. Catalytic converters should be used to help control emissions of carbon monoxide and hydrocarbons
Control measures in industrial centers
  1. Emission rates should be restricted to permissible levels by each and every industry
  2. Incorporation of air pollution control equipment in design of plant layout must be made mandatory
  3. Continuous monitoring of the atmosphere for pollutants should be carried out to know the emission levels.
The following equipment is used to control air pollution:

    1. Control of SPM by gravitation 
    Control of SPM by gravitation
    Equipment used: Gravitational Settling Chamber A typical gravitational chamber is shown below.

    The dust laden gas enters at the inlet and due to the sudden increase in cross-section the particulate matter settles at the bottom and can be removed from the dust hoppers as shown
    The clean gas free from particulate matter exits  from the outlet
    Simple to construct and maintain
    Efficient to remove particles of diameter greater than 50 mm from gas streams
    They are used as pre-cleaners before passing gases through high efficiency collection devices
    They rely on gravitational settling and are the simplest and oldest mechanical collectors for removal of particulates from gas streams
    Flow within the chamber must be uniform without macroscopic mixing
    Dust removal system must be sealed to prevent production of turbulence due to air from leaking into chamber
    Efficiency of the equipment increases with increased residence time of the waste gas. Hence, the equipment is operated at lowest possible gas velocity
    The size of the unit depends on:
    gas velocity which should preferably be less than 0.3 m/s
    Low capital and energy cost
    Low maintenance and operating costs
    Low pressure drop
    Equipment is not subjected to abrasion due to low gas velocity
    Equipment provides incidental cooling of gas stream
    Temperature and pressure limitations depend on material of construction
    Pollutants are collected in dry state
    Low particulate matter collection efficiency
    Unable to handle sticky materials
    Large size
    Trays in multiple tray settling chamber may warp under high temperatures.

    2.  Control of SPM by centrifugation
    Equipment used: Cyclonic separator
    Centrifugation is a process that involves the use of centrifugal force for sedimentation of a heterogeneous mixture with a centrifuge. It involves removal of particulates from air, gas or a liquid stream without use of filters with a vortex separation. When removing particulates from a gaseous stream, a gas cyclone is used while a hydrocyclone is used to remove particulates from a liquid stream. This method can also be used to separate fine droplets of liquid from a gaseous stream.
    A high speed rotating air flow is formed in a cylindrical or conical container called a cyclone.
    Air flows in a helical pattern from the top to a narrow bottom as show,

     Cyclones use the principle of inertia to remove particulate matter from a gas stream. Several cyclones operating in parallel is known as multicyclone. In a cyclone separator, dirty gas is fed into a chamber where a spiral vortex exists. The large particles hit the inside walls of the container and drop down into the collection hooper. The clean flue gas escapes from the top of the chamber. Cyclones can be used efficiently to remove particles of size 10 microns or more. High efficiency cyclones can remove particles of dimeter as small as 2.5 microns. They are the least expensive of all particulate collection devices. They are used as rough separators before the gas is passed through fine filtration systems. Their efficiency is between 50-99%. Cyclone separators work best on flue gases that contain large amount of big particulate matter.
    Cyclones are less expensive to install or maintain as they do not contain any moving parts
    It is easy to dispose particulate matter as it is collected in the dry state
    Space requirement is very less
    They are not efficient in collecting particulate matter smaller than 10 microns
    They cannnot handle sticky material

    3.   Control of SPM by filtration
    In a fabric filter system, a stream of the polluted gas is made to pass through a fabric that filters out the particulate pollutant and allows the clear gas to pass through. The particulate matter is left in the form of a thin dust mat on the insides of the bag. This dust mat acts as a filtering medium for further removal of particulates increasing the efficiency of the filter bag to sieve more sub mi­cron particles (0.5 ┬Ám).

    A typical filter is a tubular bag which is closed at the upper end and has a hopper attached at the lower end to collect the particles when they are dislodged from the fabric. Many such bags are hung in a baghouse. For efficient filtration and a longer life the filter bags must be cleaned occasionally by a mechanical shaker to prevent too many particulate layers from building up on the inside surfaces of the bag. A typical bag house filter is shown in the figure below.

    Bag filter is a high quality performance instrument to effectively control particulate emissions and its efficiency is as high as 99%
    Collection efficiency is not affected by sulphur content in fuel
    It is not sensitive to particle size distribution
    It does not require high voltage
    It can be used to collect flammable dust
    Special fiber or filter aids can be used to sub-micron level smoke and fumes
    Fabric life is reduced due to presence of highly acidic or alkaline atmospheres, especially at high temperatures
    Maximum operating temperature is 500 F
    Collection of hygroscopic materials or condensation of moisture can lead to fabric plugging, loss of cleaning efficiency and large pressure losses.
    Certain dusts may require special fabric treatments to aid in reducing leakage or to help in cake removal
    Fabric bags are prone to burning or melting at extreme temperatures.

    4.  Control of SPM by scrubbing
    A scrubber is a system used to remove harmful materials from industrial exhaust gases before they are released into the environment. The two main ways to scrub pollutants out of exhaust are:
    Dry scrubbing and
    Wet scrubbing
    In dry scrubbing, harmful components of exhausted flue gas are removed by introducing a solid substance (usually in the powdered form) in the gas stream.

    Wet scrubbing involves removal of harmful components from exhaust by spraying a liquid substance through the gas.

    Both methods work similarly and perform the same process of removing pollutants. The difference lies in the materials they use to remove the pollutant from the gas stream. By removing acidic gases from the exhaust before it is released into the atmosphere, scrubbers help in the prevent the formation of acid rain.
    Scrubbing is sometimes referred to as flue gas desulfurization.

    Scrubbing is the most effective technique for the removal of oxides of sulphur and is widely used. Scrubbers remove sulphur oxides from flue gases by passing the gases through a spray of water in a wet scrubber that contains many chemicals, mainly calcium carbonate.
    If a dry scrubber is used, the flue gas comes in contact with pulverised limestone. The chemical reaction between suphur dioxide and calcium carbonate yields calcium sulphite. The calcium sulphite either falls out of the gas stream or is removed with other particulates.
    Scrubbers are highly efficient and remove almost 98% of sulphur from flue gases. However, they are expensive to maintain and install. They are also energy intensive as the flue gas must be reheated after coming into contact with water vapour in the wet scrubber to make the gas buoyant to exit the smoke stacks.

    5.  Control of SPM by Electrostatic precipitator
    An Electrostatic precipitator is mainly used to control particulate matter. An Electrostatic precipitator uses electrostatic forces to separate dust particles from exhaust gases. A number of high-voltage, direct-current discharge electrodes are placed between grounded collecting electrodes. The contaminated gases flow through the passage formed by the discharge and collecting electrodes as shown in the figure below.

    Air borne particles receive a negative charge as they pass through the ionized field between the electrodes. These charged particles are then attracted to the oppositely charged electrode and stick to it. The collected material is then removed by rapping or vibrating the electrodes. Cleaning the electrodes is done without interrupting the air flow.
    The main components of all electrostatic precipitators are:

    • a power supply unit to supply high voltage DC power
    • ionizing section to impart a charge to the particulates in the gas stream
    • an attachment to remove the collected particulates
    • a housing to enclose the precipitator zone

    The following factors influence the collection efficiency of electrostatic precipitators:

    • Larger collection surface areas and lower gas flow rates increase efficiency of electrostatic precipitators due to increased time for the electrical activity to collect the dust particles
    • The dust particle migration velocity to the collecting electrodes can be increased by:
    • Decreasing gas velocity
    • Increasing gas temperature and
    • Increasing the voltage field

    There are two types of precipitators:

    1. Single-stage precipitators that combine an ionization and collection step also known as cottrell precipitators. It is mainly used in mineral processing operations.
    2. Low voltage, two stage precipitators that use a similar principle, but in this case, the ionization section is followed by collection plates. It is mainly used for filtration in air-conditioning systems. 

    Electrostatic precipitators may be:
    Plate precipitators in which particles are collected on flat parallel surfaces about 20 to 30 cm apart with a series of discharge electrodes spaced along the centerline of two adjacent plates. The contaminated particles pass through the passage between the plates and the particles get charged and adhere to the collection plates. The particles are eventually removed by rapping the plates and the dust is collected in the hoppers or bins placed at the base of the precipitator.
    Tubular precipitators consist of cylindrical collection electrodes with discharge electrodes located on the axis of the cylinder. The contaminated gases flow around the discharge electrode and through the inside of the cylinders. The charged particles are collected on the grounded walls of the cylinder. The collected dust is removed from the bottom of the cylinder. They are generally used for collection of mist or fog or for adhesive, sticky, radioactive or extremely toxic materials.
    Air  pollution can be reduced by adopting the following approaches.
    1. Ensuring sufficient supply of oxygen to the combustion chamber and adequate temperature so that the combustion is complete thereby eliminating much of the smoke consisting of partly burnt ashes and dust.
    2. To use mechanical devices such as scrubbers, cyclones, bag houses and electro-static precipitators in manufacturing processes. The equipment used to remove particulates from the exhaust gases of electric power and industrial plants are shown below. All methods retain hazardous materials that must be disposed safely. Wet scrubber can additionally reduce sulphur dioxide emissions.
    3. The air pollutants collected must be carefully disposed. The factory fumes are dealt with chemical treatment.