UNIT I
WATER SCIENCE
Water, the unique component of nature plays a crucial role in the evolution of life. All the
creations of the world emerged on the bands of rivers and have been central to the growth of human
society.
It is believed that life oriented in water and is sustained by it. Now a days, the standard and
maturity of the society is indicated by the purity of its rivers.
Water is the most essential compound for all living matter on the earth. Water is not only
essential for the lives of animals and plants, but also occupies a unique position in industries. It is
widely used in drinking, bathing, sanitary, washing, irrigation, fire-fights, air-conditioning and also
production of industrial materials.
Adequate supply of safe potable water is quite essential and is the basic need of all life on
the earth. Because of unplanned industrializations, surface and ground water sources have been
contaminated; as a result, preservation of water and managing water quality has become
complicated. Conservation of water has become the need of the hour as it has a great impact on
the health of human beings.
Rivers are known as the cradlers of civilization. But regrettably this has resulted in water
pollution because for a long time, streams and rivers have been used for disposal of wastes. In
2002, UN estimates that nearby $100 billion people struggle to access clean drinking water and
2.5 billion people lack of adequate sanitation. It is estimated that by 2024, 2/4 of the population of
the world would suffer from extreme water shortage.
SOURCES OF WATER
The two important sources of water are
(1) Surface water and
(2) Underground water.
1. Surface water
The water available on the earth’s surface is called as surface water. Surface water includes
rain water, river water, lake water and sea water.
4
, The surface water from various resources evaporates, condense and precipitates as rain,
snow or both moves through various organisms and finally enters to sea, surprisingly 90% of water
which evaporates returns to the ocean after passing through the hydrological processes.
2. Underground water
Underground water is divided into well water and spring water. The ground absorbs rain
water and dissolves many soluble minerals present in the soil region. Hence underground water
is rich in minerals but contains minimum amount of organic impurities.
IMPURITIES IN WATER
Water is the most important element through which the life sustains on the earth. But man
has exploited the water resources than any other natural resources for his modern livelihood.
Pollution is the alteration of physical, chemical and biological characteristics of natural
resources mainly water, air and land caused by anthropogenic activities that is harmful to existing
or proposed use of the resources.
Generally, the pollutants of water are classified as follows
1. Suspended impurities: These impurities impart turbidity, colour and odour to water. It may
be organic or inorganic in nature.
2. Colloidal impurities: Products from organic waste, finely divided silica, clay, etc
3. Dissolved impurities: Presence of dissolved salts like carbonates, bicarbonates, chlorides
and sulphates of calcium, magnesium, potassium and sodium and dissolved gases like O2,
CO2, etc
4. Microorganisms: They include bacteria, fungi and algae.
Due to the above mentioned activities water becomes unsuitable for various uses like domestic,
industrial and agricultural purposes, mainly the anthropogenic activities such as population
explosion, rapid industrialization and over exploitation of natural resources, developmental
activity, modern consumerism and various other activities.
SOURCES OF IMPURITIES IN WATER
Surface water bodies are commonly polluted by soil erosion caused during rainy season
that carries both organic and inorganic impurities along with suspended particles.
They are also polluted by industrial effluents and chemicals /discharge of sewage, oil and
5
,other wastes.
1. Gases are picked up from the atmosphere by rain.
2. Decomposition of plant and animal matter are responsible for organic impurities in water.
3. Agricultural runoff is a major cause by the addition of fertilizers, pesticides and
herbicides.
4. Harmful microorganisms such as microbes, pathogens, viruses present in animal and
human fecal matters.
TYPES OF WATER
Water is classified into two types based on its lather forming property with soap solution.
(a) Soft Water
Soft water is one of that gives good lather readily with soap solution.
2 RCOONa + H2O RCOOH + NaOH
Soft water
b) Hard Water
Water that does not produce lather with soap readily but forms an insoluble
precipitate-like white scum is known as hard water.
2RCOONa + H2O (RCOO)2Ca + 2NaCl
Hardwater Insoluble soap
HARDNESS OF WATER
Hardness is the characteristic of water which prevents lathering of soap. This property of
water is due to the presence of carbonates, bicarbonates, sulphates and chlorides of calcium,
magnesium and heavy metals.
A sample of hard water when treated with soap does not produce lather with soap, but it
forms white sticky precipitates. This is due to the formation of insoluble soap of calcium and
magnesium stearates.
2C17H35COONa + CaCl2/MgCl2 (C17H35COO)2 Ca/Mg + 2NaCl
Soap (soluble) salts (soluble) insoluble precipitates
Based on hardness, water can be classified into two types
6
, 1) Hard water: Water which does not produce lather with soap solution readily, but produces
white precipitate (scum) is called hard water. This is due to the presence of dissolved
calcium and magnesium salts.
2) Soft water: Water, which produces lather, readily with soap solution is called soft water.
This is due to the absence of dissolved calcium and magnesium salts.
Disadvantages of hardness
1. In Domestic use:
a) Washing: When used for washing purposes, hard water does not producing lather freely
with soap. This decreases cleaning quality of soap and portion of it is wasted.
b) Bathing: Hard water does not lather freely with soap solution, but produces sticky scum on
the bath-tub and body. Thus, the cleaning quality of soap is depressed and a lot of it is
wasted.
c) Cooking: The boiling point of water is increased because of presence of salts. Hence more
fuel and time are required for cooking.
d) Drinking: Hard water causes bad effects on our digestive system. Moreover, the possibility
of forming calcium oxalate crystals in urinary tracks is increased.
2. Industrial Use:
a) Textile Industry: Hard water forms insoluble precipitates of calcium and magnesium
soaps which adhere to the fabrics and limits its usage.
b) Sugar Industry: The water which containing sulphates, nitrates, alkali carbonates are
used in sugar refining creates difficulty in the crystallization of sugar.
c) Dyeing Industry: The dissolved salts in hard water may reacts with costly dyes forming
precipitates.
d) Paper Industry: The dissolved calcium, magnesium and ferrous salts in water may affect
the quality of paper.
e) Pharmaceutical Industry: Hard water may cause formation of some undesirable
products.
7
WATER SCIENCE
Water, the unique component of nature plays a crucial role in the evolution of life. All the
creations of the world emerged on the bands of rivers and have been central to the growth of human
society.
It is believed that life oriented in water and is sustained by it. Now a days, the standard and
maturity of the society is indicated by the purity of its rivers.
Water is the most essential compound for all living matter on the earth. Water is not only
essential for the lives of animals and plants, but also occupies a unique position in industries. It is
widely used in drinking, bathing, sanitary, washing, irrigation, fire-fights, air-conditioning and also
production of industrial materials.
Adequate supply of safe potable water is quite essential and is the basic need of all life on
the earth. Because of unplanned industrializations, surface and ground water sources have been
contaminated; as a result, preservation of water and managing water quality has become
complicated. Conservation of water has become the need of the hour as it has a great impact on
the health of human beings.
Rivers are known as the cradlers of civilization. But regrettably this has resulted in water
pollution because for a long time, streams and rivers have been used for disposal of wastes. In
2002, UN estimates that nearby $100 billion people struggle to access clean drinking water and
2.5 billion people lack of adequate sanitation. It is estimated that by 2024, 2/4 of the population of
the world would suffer from extreme water shortage.
SOURCES OF WATER
The two important sources of water are
(1) Surface water and
(2) Underground water.
1. Surface water
The water available on the earth’s surface is called as surface water. Surface water includes
rain water, river water, lake water and sea water.
4
, The surface water from various resources evaporates, condense and precipitates as rain,
snow or both moves through various organisms and finally enters to sea, surprisingly 90% of water
which evaporates returns to the ocean after passing through the hydrological processes.
2. Underground water
Underground water is divided into well water and spring water. The ground absorbs rain
water and dissolves many soluble minerals present in the soil region. Hence underground water
is rich in minerals but contains minimum amount of organic impurities.
IMPURITIES IN WATER
Water is the most important element through which the life sustains on the earth. But man
has exploited the water resources than any other natural resources for his modern livelihood.
Pollution is the alteration of physical, chemical and biological characteristics of natural
resources mainly water, air and land caused by anthropogenic activities that is harmful to existing
or proposed use of the resources.
Generally, the pollutants of water are classified as follows
1. Suspended impurities: These impurities impart turbidity, colour and odour to water. It may
be organic or inorganic in nature.
2. Colloidal impurities: Products from organic waste, finely divided silica, clay, etc
3. Dissolved impurities: Presence of dissolved salts like carbonates, bicarbonates, chlorides
and sulphates of calcium, magnesium, potassium and sodium and dissolved gases like O2,
CO2, etc
4. Microorganisms: They include bacteria, fungi and algae.
Due to the above mentioned activities water becomes unsuitable for various uses like domestic,
industrial and agricultural purposes, mainly the anthropogenic activities such as population
explosion, rapid industrialization and over exploitation of natural resources, developmental
activity, modern consumerism and various other activities.
SOURCES OF IMPURITIES IN WATER
Surface water bodies are commonly polluted by soil erosion caused during rainy season
that carries both organic and inorganic impurities along with suspended particles.
They are also polluted by industrial effluents and chemicals /discharge of sewage, oil and
5
,other wastes.
1. Gases are picked up from the atmosphere by rain.
2. Decomposition of plant and animal matter are responsible for organic impurities in water.
3. Agricultural runoff is a major cause by the addition of fertilizers, pesticides and
herbicides.
4. Harmful microorganisms such as microbes, pathogens, viruses present in animal and
human fecal matters.
TYPES OF WATER
Water is classified into two types based on its lather forming property with soap solution.
(a) Soft Water
Soft water is one of that gives good lather readily with soap solution.
2 RCOONa + H2O RCOOH + NaOH
Soft water
b) Hard Water
Water that does not produce lather with soap readily but forms an insoluble
precipitate-like white scum is known as hard water.
2RCOONa + H2O (RCOO)2Ca + 2NaCl
Hardwater Insoluble soap
HARDNESS OF WATER
Hardness is the characteristic of water which prevents lathering of soap. This property of
water is due to the presence of carbonates, bicarbonates, sulphates and chlorides of calcium,
magnesium and heavy metals.
A sample of hard water when treated with soap does not produce lather with soap, but it
forms white sticky precipitates. This is due to the formation of insoluble soap of calcium and
magnesium stearates.
2C17H35COONa + CaCl2/MgCl2 (C17H35COO)2 Ca/Mg + 2NaCl
Soap (soluble) salts (soluble) insoluble precipitates
Based on hardness, water can be classified into two types
6
, 1) Hard water: Water which does not produce lather with soap solution readily, but produces
white precipitate (scum) is called hard water. This is due to the presence of dissolved
calcium and magnesium salts.
2) Soft water: Water, which produces lather, readily with soap solution is called soft water.
This is due to the absence of dissolved calcium and magnesium salts.
Disadvantages of hardness
1. In Domestic use:
a) Washing: When used for washing purposes, hard water does not producing lather freely
with soap. This decreases cleaning quality of soap and portion of it is wasted.
b) Bathing: Hard water does not lather freely with soap solution, but produces sticky scum on
the bath-tub and body. Thus, the cleaning quality of soap is depressed and a lot of it is
wasted.
c) Cooking: The boiling point of water is increased because of presence of salts. Hence more
fuel and time are required for cooking.
d) Drinking: Hard water causes bad effects on our digestive system. Moreover, the possibility
of forming calcium oxalate crystals in urinary tracks is increased.
2. Industrial Use:
a) Textile Industry: Hard water forms insoluble precipitates of calcium and magnesium
soaps which adhere to the fabrics and limits its usage.
b) Sugar Industry: The water which containing sulphates, nitrates, alkali carbonates are
used in sugar refining creates difficulty in the crystallization of sugar.
c) Dyeing Industry: The dissolved salts in hard water may reacts with costly dyes forming
precipitates.
d) Paper Industry: The dissolved calcium, magnesium and ferrous salts in water may affect
the quality of paper.
e) Pharmaceutical Industry: Hard water may cause formation of some undesirable
products.
7
