WHAT IS SOIL POLLUTION? ITS CAUSES AND EFFECTS.

• Soil pollution can be define as a land degradation which is caused by the presence of toxic substances and chemicals such as solvents, pesticides, lead, and other heavy metals etc.
• It is important to understand that If soil contains compounds that are toxic then it is very harmful for human beings and other living organisms.

      Main causes for soil pollution

1. Urban waste :

• Both the domestic and commercial wastes are considered as urban waste. All urban solid wastes are commonly termed as "Refuse" which contains garbage and rubbish material like papers, fibers, plastics, glasses, leaves, abandon vehicle parts etc.
• We are in our daily life escapes those stuffs from our house and some are from our house and some are organic debris. 

2. Industrial waste :

• Industrial waste contributes more quantity of solid and liquid waste to soil.  The industrial wastes are major source of soil pollution. 
• Industrial wastes mainly contains organic and inorganic compounds along with non-biodegradable materials.
• Most common waste from industries are effluents and their accumulation in soil promote soil pollution.

3. Agricultural waste :

• In modern agriculture, the use of pesticides are on high level to grow more copes. Pesticides are substances (or mixtures of substances) that are used to kill or inhibit the growth of pests. 
• Common types of pesticides used in agriculture include:
• Herbicides – used to kill/control weeds and other unwanted plants.
• Insecticides – used to kill insects.
• Fungicides – used to kill parasitic fungi or inhibit their growth.

4. Soil conditioner :

• The soil conditioners are used to increase fertility of soil. Generally these contains toxic metals such as arsenic, cadmium, lead and mercury.

5. Radioactive waste :

• Generally storage and disposal of radio-active waste causes penetration and accumulation of radio-active materials and causes soil pollution.

6. Biological agent :

• Soil gets large quantities of human, animal and birds excreta, which consist the major source of soil pollution by biological agent.
• The pathogenic organisms that pollute the soil may be classified into three category and these are follows.

1. Pathogenic organisms occurring in contaminated soil.
2. Pathogenic organisms excreted by humans.
3. Pathogenic organisms excreted by animals.

      Effects of soil pollution :

1.  Effect on Health of Humans:

Crops and plants are grown on polluted soil. these will absorb much of the pollution by the crops and then pass these on to human when they consume it. It can be cause for Headaches, nausea, vomiting,Coughing, pain in the chest, and Irritation of the skin and the eyes in humans.

2.  Decreased Soil Fertility:

The toxic chemicals present in the soil can decrease soil fertility and therefore decrease in the soil yield. The contaminated soil is then used to produce fruits and vegetables which lacks quality nutrients and may contain some poisonous substance to cause serious health problems in people consuming them.

3. Toxic Dust:

The emission of toxic and foul gases from landfills pollutes the environment and causes serious effects on the health of some people. The unpleasant smell causes inconvenience to other people.

4.  Effect on Growth of Plants:

Most plants are unable to adapt when the chemistry of the soil changes so radically in a short period of time. Fungi and bacteria are produced in this kind of soil which decline the growth of plants.

WHAT IS THERMAL POLLUTION? ITS SOURCES, EFFECTS AND CONTROLS.

• Thermal pollution is the degradation of water quality by any process that changes ambient water temperature. It is a rise in temperature of water bodies due to discharging of hot industrial effluents.
• A common cause of thermal pollution is the use of water as a coolant to cool their equipments by power plants and industrial manufacturers.
• The sources of thermal Pollution :   

1. Nuclear Power Plant 
2. Coal-fired power Plant 
3. Industrial Effluents 
4. Domestic Sewage
5. Hydro-electric power 
6. Thermal Power Plant

• The discharged effluents of these sources have a higher temperature than the intake water that reduces the concentration of oxygen from the water which causes the deleterious effects on the marine ecosystem.
• Other causes of thermal pollution include soil erosion, deforestation, runoff of water by pavement, natural disasters like volcano eruption and geothermal activities.

Effects of thermal pollution :

1. Decrease in DO (Dissolved Oxygen) Levels: The warm temperature reduces the levels of DO (Dissolved Oxygen) in water. The warm water holds relatively less oxygen than cold water. The decrease in DO can create suffocation for plants and animals such as fish, amphibians and copepods, which may give rise to anaerobic conditions. Warmer water allows algae to flourish on surface of water and over the long term growing algae can decrease oxygen levels in the water.

2. Increase in Toxins: With the constant flow of high temperature discharge from industries, there is a huge increase in toxins that are being regurgitated into the natural body of water. These toxins may contain chemicals or radiation that may have harsh impact on the local ecology and make them susceptible to various diseases.

3. Loss of Biodiversity: A dent in the biological activity in the water may cause significant loss of biodiversity. Changes in the environment may cause certain species of organisms to shift their base to some other place while their could be significant number of species that may shift in because of warmer waters.  Organisms that can adapt easily may have an advantage over organisms that are not used to the warmer temperatures.

4. Increases Metabolic Rate: Thermal pollution increases the metabolic rate of organisms as increasing enzyme activity occurs that causes organisms to consume more food than what is normally required, if their environment were not changed. It disrupts the stability of food chain and alter the balance of species composition.

5. Migration: The warm water can also cause particular species of organisms to migrate to suitable environment that would cater to its requirements for survival. This can result in loss for those species that depend on them for their daily food as their food chain is interrupted.

Steps to control thermal pollution :

1. Heated water from the industries can treated before discharging directly to the water bodies.

2. Heated water from the industries can be treated by the installation of cooling ponds and cooling towers.

3. Industrial treated water can be recycled for domestic use or industrial heating.

4. Through artificial lakes: In this lake Industries can discharge their used or heated water at one end and water for cooling purposes may be withdrawn from the other end. The heat is eventually dissipated through evaporation.

WHAT IS BOD AND COD? EXPLAIN IN BRIEF ABOUT IT.

• The term BOD and COD are stands for Biological oxygen demand and Chemical oxygen demand respectively. They are used in case of self purification of water from natural sources and diluted waste water. Mostly for polluted water sources having organic impurities and contaminates.

      BOD test :

• The amount of oxygen required by micro-organism to oxidize organic waste aerobically is called biological oxygen demand. 
• The BOD test is used to measure waste loads to treatment plants, determine plant efficiency (in terms of BOD removal), and control plant processes.  It is also used to determine the effects of discharges on receiving waters.  A major disadvantage of the BOD test is the amount of time (5 days) required to obtain the results.

• A sample is putting into a BOD bottle containing aerated dilution water.  At initiation, DO content is determined and recorded and the bottle is kept in the dark for five days at 20°C.  At the end of five days, the final DO content is determined and the difference between the final DOf reading and the initial DOi  reading is calculated. The decrease in DO is corrected for sample dilution, and represents the biochemical oxygen demand of the sample.
• The BOD of dilluted water sample is calculated by,                              BOD5 = DOi - DOf                                                                                    P
• Where, DOi = Dissolved oxygen in dilluted water at initial                         stage                                                                        DOf  = Dissoved oxygen in dilluted water at final                            stage                                                                        P  =  The dillution factor                                                           = Volume of undilluted sample                                              Volume of dilluted sample

            COD test :

• The amount of oxygen required for oxidize all the organics (biodegradable or non-biodegradable) in a waste water or polluted water.
• The COD test only takes a few hours to complete, giving it a major advantage over the 5-day BOD test. Wastewater treatment system personnel can use COD as an almost real-time operational adjustment parameter.
• COD can test wastewater that is too toxic for the BOD test.
• The COD test uses a chemicals (potassium dichromate in a 50% sulfuric acid solution) that oxidizes both biodegradable and non-biodegradable substances in a wastewater sample, which results in a higher COD concentration than BOD concentration for the same wastewater sample since only organic compounds are consumed during BOD testing.

• The difference between BOD and COD.                            BOD
• It is stands for biological oxygen demand.
• Demanded oxygen is supplied by the water itself.
• This method is used for biodegradable waste only.
• The value of BOD is always less than the value of COD.
• The time duration take by the BOD is 5 days.
• It is less scientific.                                                                 COD
• It is stands for chemical oxygen demand.
• Demanded oxygen is supplied by the solution of chemicals (pottasium chromate in 50% solution of sulphuric acid)
• This is used for both biodegradable and non-biodegradable waste.
• The value of COD is always higher than the value of BOD.
• The time duration take by the COD is nearly about 2 hours.
• It is more scientific.

WHAT IS THE PARAMETERS TO MEASURE THE WATER QUALITY?

The parameters which are used to identify the quality of water are called water quality parameters. Here four types of parameters are given below.

1. Physical parameter :

• Temperature
• Color
• Odour
• Taste
• Turbidity
• Total suspended solid
• Dissolve solid

2. Chemical parameter :

• Alkalinity
• Ph value
• Hardness
• Heavy metals
• Biological oxygen demand
• Chemical oxygen demand
• Oil and grease
• Dissolved oxygen : Oxygen is available in water in dissolved condition. This is called DO. The concentration of DO is depends upon the pressure, temperature and other physical , chemical and biochemical condition of water.
• Following points reveal the importance of DO as parameter.
• The DO test is basis of BOD test.
• Oxygen is an important factor in corrosion. The DO test is used to control the amount of oxygen.
• In liquid waste, DO is the factor to complete biodegradable process by organisms.
• BOD test
• COD test

3. Biological parameter :

• The presence of E-coli in water usually with the help of most probable number MPN is the example of biological parameter.

4. Radiological parameter :

• The presence of radioactive particles in water is the example of radiological parameter.

WASTEWATER TREATMENT PLANT/ SEWAGE TREATMENT PLANT

• Wastewater treatment plants is usually based on the need to reduce organic and suspended solids matters to limit pollution of the environment.To control the water pollution, a proper treatment is required for waste water before discharge it into the natural water bodies.                 
• A waste water plant have a some units namely, 

1. Screening

2. Grit chamber
3. Primary sedimentation tank
4. Secondary sedimentation tank
5. Disinfection tank or Chlorination tank
6. Thickening and sludge dewatering
7. Anaerobic digester
8. Sludge disposal 


The schematic representation of waste water treatment plant is given below.









After collecting the wastewater to treatment plant through drainage lines, Several processes occur on it which are given below.



1.Screening :

Screening is the first unit operation used at wastewater treatment plants. Screening involves the removal of large objects for example nappies, cotton buds, plastics, diapers, rags, sanitary items, nappies, face wipes, broken bottles etc. These solid wastes are removed from the wastewater and then disposed off in landfills. A separate device also use to remove dissolved pollutants from water like oil, grease etc. which is called skinning device.

2. Grit chamber :

After the screening process, the water flows from the grit chamber where it removes sand, gravel, cinder, or other heavy solid materials that are heavier (higher specific gravity) than the organic biodegradable solids in the wastewater. 


3.Primary sedimentation tank :

This process involves the separation of macrobiotic solid matter from the wastewater. Primary treatment is done by pouring the wastewater into big tanks for the solid matter to settle at the surface of the tanks. The sludge, the solid waste that settles at the surface of the tanks, is removed by large scrappers and is pushed to the center of the cylindrical tanks and later pumped out of the tanks for further treatment. The remaining water is then pumped for secondary treatment.


4. Secondary sedimentation tank :

The secondary treatment stage involves adding seed sludge to the wastewater to ensure that is broken down further. Air is first pumped into huge aeration tanks which mix the wastewater with the seed sludge which is basically small amount of sludge, which fuels the growth of bacteria that uses oxygen and the growth of other small microorganisms that consume the remaining organic matter. This process leads to the production of large particles that settle down at the bottom of the huge tanks. The wastewater passes through the large tanks for a period of 3-6 hours. It is also known as biological treatment. 

There are different type of biological units are used.

1. Activated sludge process
2. Oxidation pond
3. Rotating disc biological contractor
4. Tricking filter

5. Disinfection tank or chlorination tank

After the primary and secondary treatment stages are directed to digesters. The digesters are heated at room temperature. The solid wastes are then treated for a month where they undergo anaerobic digestion. During this process, methane gases are produced and there is a formation of nutrient rich bio-solids which are recycled and dewatered into local firms. The methane gas formed is usually used as a source of energy at the treatment plants. It can be used to produce electricity in engines or to simply drive plant equipment. This gas can also be used in boilers to generate heat for digesters.


6. Thickening and sludge dewatering :

The sludge that is produced and collected during the primary and secondary treatment processes requires concentration and thickening to enable further processing. It is put into thickening tanks that allow it to settle down and later separates from the water. This process can take up to 24 hours. The remaining water is collected and sent back to the huge aeration tanks for further treatment.


7. Anaerobic digester :

After the primary and secondary treatment stages are directed to digesters. The digesters are heated at room temperature. The solid wastes are then treated for a month where they undergo anaerobic digestion. During this process, methane gases are produced and there is a formation of nutrient rich bio-solids which are recycled and dewatered into local firms. The methane gas formed is usually used as a source of energy at the treatment plants. It can be used to produce electricity in engines or to simply drive plant equipment. This gas can also be used in boilers to generate heat for digesters.

8. Sludge disposal :

In the last stage, The sludge is treated and sent back into the environment and can be used for agricultural use or land fill.

WHAT IS WATER POLLUTION?

• Any biological or chemical change in the quality of water due to the presence of contaminants in water is called water pollution. Water pollution has affected the lives of humans and animals in all aspects. Water pollution is very hazardous to the environment.

• Sources of water pollution

1.Point sources : It includes small area outlets.

• Factory outlets
• Power plant outlets
• Underground mines
• Oil wells
• Sewage treatment plants

2.Non-point sources : It includes large area outlets.

• Soil erosion
• Agriculture land
• Acid deposition from atmosphere

• Categories of water pollution 

1. Ground water : 

• Ground water is most important natural resource on earth. It will be polluted when contaminants mixed with water on land and seep deep into ground water. Groundwater gets polluted when contaminants from pesticides and fertilizers to waste leached from landfills and septic systems make their way into an aquifer. Groundwater can also spread contamination far from the original polluting source as it seeps into streams, lakes, and oceans.

2. Surface water : 

• Surface water includes oceans, rivers lakes, ponds etc. Surface water get deteriorate due to farm waste and fertilizer runoff into river, Municipal and industrial waste discharges, algae in lake and pond etc. Also It deteriorate by Contaminants such as chemicals, nutrients, and heavy metals are carried from farms, factories, and cities by streams and rivers into our ocean.

The Most Common Types of Water Contamination :

1. Oxygen demanding wastes

2. Pathogen

3. Volatile organic compounds

4. Agricultural 

5. Thermal pollution

6. Heavy metals

1. Oxygen demanding wastes :

• Oxygen demanding wastes are substance that oxidize in the receiving body of water. These wastes are decomposed by bacteria (If they are biodegradable). During the process of degradation, the dissolved oxygen is utilize by the bacteria. Thus, the bacteria reduces the level of dissolved oxygen in the water. The dissolved oxygen is most important parameter of water, as its level drops, the life of fish and other aquatic organisms are fall under threat and in extreme case they does not survive.
• Oxygen Demanding Wastes are Comes from sewage, animal tissues, dead plants, pulp mills, runoff from farmlands, and dumping of wastes into streams. As the oxygen is demanded for the degradation of these waste so they are known as oxygen demanding waste.
• Moreover, DO level drops it creates undesirable odours, tests and color of water. which is unacceptable for domestic use.

2. Pathogen :

• The disease causing organisms, usually micro-organism that grows and propagates within the host is called the pathogen.
• The contaminate water is responsible for the spread of many disease. The natural water contains various types of living organisms. Some organisms born in water and remain in it due to its tendency. Some organisms are introduce in water by man during disposal of sewage in water.
• Some of the living organisms such as bacterias, viruses and protozoa are infections to human and they are responsible for the serious health problems. So they are known as pathogen.
• Following are the different pathogens present in water            1. Bacteria : It causes for cholera and typhoid.                  2. Algae : It causes for different type of skin disease.        3. Protozoa : It causes for amebic infections.

3. Volatile organic compound :

• Volatile organic compounds are most commonly found pollutants in ground water. They are often used as solvent in industrial processes.
• The VOCs are especially toxic and the presence in drinking water can cause for special concern.

4. Agricultural :

• The most common use of chemical in agriculture to increase crop quantity and quality is pesticides. It is used to control unwanted species of plants and animals. To prevent fungal infection, fungicide are also used.
• These pesticides and fungicides are washed off due to rainfall and irrigation system and get mixed with surface water bodies and deteriorate them.

5. Thermal effluents :

• After the introduction of industrialization, water gets more deteriorate through them. An accumulation of such contaminants in water which are produced by power plants, factories and mills and mixed with river and coastline water bodies.
• These power plants escape or discharge a large amount of heated water in the water bodies causing harmful for aquatic and marine organisms.

6. Heavy metals :

• Metals are introduced into aquatic system because of the weathering or erosion  of soil and rocks from volcanic eruption and such human activities like mining, processing etc.
• The term heavy metals has been used for those metals which have relatively higher density greater then 5.
• However, toxic matters are replaced the term heavy metals. Copper, chromium, lead, mercury, cadmium are the examples of heavy metals.

Effects of Pollution of Water :

1. It can be spread diseases in humans when they consume polluted water. It causes typhoid, cholera, hepatitis and various other diseases.
2. It can destruct aquatic ecosystem. A small change can threat many lives of organisms in water and it will be cause for collapse of entire ecosystem.
3. Chemicals in a water body, encourage the growth of algae. These algae form a layer on top of the pond or lake. Bacteria feed on this algae and this decreases the amount of oxygen in the water body which severely affecting the aquatic life.
4. It can also lead to serious disruption in food chains when toxins and pollutants in the water are consumed by aquatic animals (fish, shellfish etc) which are then consumed by humans.
5. The untreated sewage contains harmful chemicals that cause death in aquatic animals.

Measures to prevent water pollution :

1. Abstain from flushing contaminated liquids, pills, drugs, or medications down the drain. These substances contain scores of toxic materials that destroy the quality of natural water systems. Instead, use the recommended disposal methods.
2.  Ensure minimal use of bleach or detergents. During cleaning of laundry, it is vital to minimize the use of bleach and detergents. Instead, you can persist on only using phosphate-free detergents and soaps.
3. Reduce the use of herbicides, pesticides, and fertilizers. Excessive use of herbicides, pesticides, and fertilizers leads to water pollution as the chemicals contained in the products often find way into the water systems through surface runoff or infiltration into the soil. Minimizing their usage or using organic methods for pest, weed, and disease control can appreciably reduce water pollution.
4. Proper sewage treatment and management. Proper sewage treatment is required to limit the amount of toxic substances that normally end up in water systems such as lakes, rivers, and oceans. Also, individual homes that use septic tanks or cellar drains need to ensure proper management of their home sewage to avoid pollution.
5. Always conserve water. Play an active role in reducing water pollution by conserving water at all time. You can achieve this by ensuring the taps are always turned off when they are not in use. Conserving water reduces the amount of contaminated water that needs to be treated.
6. Skip the use of plastics. Plastic leftovers such as used plastic water bottles, disposable plastic plates, and plastic bags frequently end up in the oceans, lakes, streams and rivers, contaminating natural habitats and destroying aquatic life.
7. Practice organic farming. Organically grown crops reduce the quantity of herbicides and pesticides used in farming. It also promotes the use of organic fertilizer which promotes natural growth and eliminates the use of toxic chemicals found in synthetic fertilizers, which can penetrate into the ground and pollute water supplies.

WHAT IS SMOG? TYPES OF SMOG.

• Smog is a man made harmful pollutants combination. It is a mixture of smoke and fog into air. It is a mixture of various gases with water vapor.
• There are two types of smog exist.

1. Sulphurous smog or reducing smog
2. Nitrogenous smog or photo-chemical smog

1. Sulphurous smog or reducing smog :

•  It is a mixture of smoke, fog and sulphur dioxide. This smog affects the london city very badly for several years after the introduction of coal and fuel. So it is also known as London smog.
• The component of sulphurous smog:

1. Oxide of sulphur
2. Particulate matter which are coming from smoke
3. Humidity or water from fog

Formation process of sulphurous smog :

• Sulphurous smog occurs mainly in the early morning hours in winter where there is relatively high humidity in the absence of winds and stable atmospheric zone, the chemical reaction take place in the presence of sunlight in the early morning.                                                                   S + O2          -----    SO2                                                     2SO2 + O2        -----    2SO3
• The reaction takes place by oxidation and particulate matter. The SO2 combines with moisture present in fog to form sulphuric acid H2SO3. This acid is again oxidized and form sulphuric acid H2SO4 and this combines with NH3 present in smoke to form ammonium salt [(NH4)2SO4].
•                      SO2  +  H2O ---- H2SO3                                                      2H2SO3 + O2  ----  2H2SO4                                              H2SO4  +  2NH3  ---- [(NH4)2SO4]
• This type of smog are not photo-chemical in nature.
• This smog can affect the throat of human being.

2. Nitrogenous smog :

• The main component of this kind of smog is oxides of nitrogen. So it is called nitrogenous smog. It is not consists smoke and fog. During the formation of this type of smog, photo-chemical reactions are take place. So, it is known as a photo-chemical smog. This smog is first appears in los-angles. so it is also called los-angles smog.
• The main compounds present in this type of smog are :

1. Oxides of nitrogen
2. Tropospheric ozone
3. Hydrocarbon
4. Photoradiation

Formation of nitrogenous smog or photo-chemical smog

• Photo-chemical smog is an example of secondary air pollutant because it results from the interaction of nitrogen oxide and nitrogen dioxide.
• NO and NO2 both are primary pollutants. When the both interact with ultraviolet rays, the result is photo-chemical smog. The interaction among hydrocarbons, oxides of nitrogen and sunlight produces new component that are harmful for humans.
• The two most damaging king of materials formed are ozone O3 and PAN (peroxy acetyl nitrates). Ozone is harmful because it destroys chlorophyll and injures lung tissue and PAN is harmful because it causes inflammation is respiration activity and eye irritation. 

Formation of peroxy acetyl nitrate :

• NO reacts with free oxygen in atmosphere and convert in nitrogen dioxide NO2.                                                                        NO  + O2 --- NO2
•  Now this NO2 absorb energy from the sun and breaks up NO2 nitrogen dioxide and again convert it into nitric oxide and free oxygen molecule.                                                      NO2 ----  NO+ O
• The oxygen molecule are very reactive with O2 which present in air and start producing ozone O3.                                    O  +  O2 ----  O3
• The ozone reacts rapidly with NO which is produce in second equation and regenrate NO2.
• O3 and NO2 both are toxic gases. They reacts with each other in the presence of unburnt hydrocarbon in pollutant air and produce peroxy acetyl nitrate.