Water Pollution | Environment for UPSC 2024 (Pre & Mains) PDF Download

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WATER POLLUTION 
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WATER POLLUTION 
Water pollution is the addition/presence of 
undesirable substances to/in water such as 
organic, inorganic, biological, radiological, heat, 
etc which degrades the quality of water so that 
it becomes unfit for use’. 
 
Water pollution is caused by a variety of human 
activities such as industrial, agricultural and 
domestic. 
 
Natural sources of pollution of water are soil 
erosion, leaching of minerals from rocks and 
decaying of organic matter. 
 
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WATER POLLUTION 
Water pollution is the addition/presence of 
undesirable substances to/in water such as 
organic, inorganic, biological, radiological, heat, 
etc which degrades the quality of water so that 
it becomes unfit for use’. 
 
Water pollution is caused by a variety of human 
activities such as industrial, agricultural and 
domestic. 
 
Natural sources of pollution of water are soil 
erosion, leaching of minerals from rocks and 
decaying of organic matter. 
 
PUTRESCIBILITY is the process of decomposition of organic matter 
present in water by microorganisms using oxygen. 
Dissolved Oxygen (DO) – Biological Oxygen Demand (BOD) – 
Chemical oxygen demand (COD) 
DO 
Presence of organic and inorganic wastes in water decreases the 
dissolved Oxygen (DO) content of the water. 
Water having DO content below 8.0 mg/L may be considered as 
contaminated. 
 Water having DO content below. 4.0 mg/L is considered to be highly 
polluted. 
DO content of water is important for the survival of aquatic 
organisms 
 A number of factors like surface turbulence, photosynthetic activity, 
O2 consumption by organisms and decomposition of organic 
matter are the factors which determine the amount of DO present 
in water. 
The higher amounts of waste increases the rates of decomposition 
and O2 consumption, thereby decreases the DO content of water. 
 
 
 
Page 4


 
 
WATER POLLUTION 
Water pollution is the addition/presence of 
undesirable substances to/in water such as 
organic, inorganic, biological, radiological, heat, 
etc which degrades the quality of water so that 
it becomes unfit for use’. 
 
Water pollution is caused by a variety of human 
activities such as industrial, agricultural and 
domestic. 
 
Natural sources of pollution of water are soil 
erosion, leaching of minerals from rocks and 
decaying of organic matter. 
 
PUTRESCIBILITY is the process of decomposition of organic matter 
present in water by microorganisms using oxygen. 
Dissolved Oxygen (DO) – Biological Oxygen Demand (BOD) – 
Chemical oxygen demand (COD) 
DO 
Presence of organic and inorganic wastes in water decreases the 
dissolved Oxygen (DO) content of the water. 
Water having DO content below 8.0 mg/L may be considered as 
contaminated. 
 Water having DO content below. 4.0 mg/L is considered to be highly 
polluted. 
DO content of water is important for the survival of aquatic 
organisms 
 A number of factors like surface turbulence, photosynthetic activity, 
O2 consumption by organisms and decomposition of organic 
matter are the factors which determine the amount of DO present 
in water. 
The higher amounts of waste increases the rates of decomposition 
and O2 consumption, thereby decreases the DO content of water. 
 
 
 
 
BOD 
 
The demand for O2 is directly related to increasing input of 
organic wastes and is expressed as biological oxygen 
demand (BOD) of water. 
Water pollution by organic wastes is measured in terms of 
Biochemical Oxygen Demand (BOD). 
BOD is the amount of dissolved oxygen needed by bacteria 
in decomposing the organic wastes present in water.  
It is expressed in milligrams of oxygen per litre of water. 
The higher value of BOD indicates low DO content of water.  
Since BOD is limited to biodegradable materials. 
Therefore, it is not a reliable method of measuring pollution 
load in water. 
 
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WATER POLLUTION 
Water pollution is the addition/presence of 
undesirable substances to/in water such as 
organic, inorganic, biological, radiological, heat, 
etc which degrades the quality of water so that 
it becomes unfit for use’. 
 
Water pollution is caused by a variety of human 
activities such as industrial, agricultural and 
domestic. 
 
Natural sources of pollution of water are soil 
erosion, leaching of minerals from rocks and 
decaying of organic matter. 
 
PUTRESCIBILITY is the process of decomposition of organic matter 
present in water by microorganisms using oxygen. 
Dissolved Oxygen (DO) – Biological Oxygen Demand (BOD) – 
Chemical oxygen demand (COD) 
DO 
Presence of organic and inorganic wastes in water decreases the 
dissolved Oxygen (DO) content of the water. 
Water having DO content below 8.0 mg/L may be considered as 
contaminated. 
 Water having DO content below. 4.0 mg/L is considered to be highly 
polluted. 
DO content of water is important for the survival of aquatic 
organisms 
 A number of factors like surface turbulence, photosynthetic activity, 
O2 consumption by organisms and decomposition of organic 
matter are the factors which determine the amount of DO present 
in water. 
The higher amounts of waste increases the rates of decomposition 
and O2 consumption, thereby decreases the DO content of water. 
 
 
 
 
BOD 
 
The demand for O2 is directly related to increasing input of 
organic wastes and is expressed as biological oxygen 
demand (BOD) of water. 
Water pollution by organic wastes is measured in terms of 
Biochemical Oxygen Demand (BOD). 
BOD is the amount of dissolved oxygen needed by bacteria 
in decomposing the organic wastes present in water.  
It is expressed in milligrams of oxygen per litre of water. 
The higher value of BOD indicates low DO content of water.  
Since BOD is limited to biodegradable materials. 
Therefore, it is not a reliable method of measuring pollution 
load in water. 
 
 
COD 
 
Chemical oxygen demand (COD) is a slightly 
better mode used to measure pollution load 
in water. 
COD measures the amount of oxygen in parts 
per million required to oxidize organic 
(biodegradable and non-
biodegradable) and oxidizable 
inorganic compounds in the water sample.