Notes On Water, Our Lifeline - CBSE Class 7 Science
Water Water is an essential element in daily life. Water is used by all living organisms on earth to perform their life processes. Contaminants are the suspended and dissolved impurities of water. Humans contaminate water by their activities. Drinking contaminated water results in the development of diseases such as cholera, typhoid and arrowhead. Polluted water can sometimes be fatal. Water should be boiled and filtered before it is used for drinking as it contains many impurities that are not visible to naked eye.  Waste water Waste water is the contaminated water which is often referred to as liquid waste. Liquid waste is mainly released from wash rooms, kitchen and other areas where sewage gets collected. Liquid wastes are usually disposed through closed drains. Components of waste water There are many components of waste water. Sewage or liquid waste makes up the main component of waste water. Human excreta in the form of faeces is the main suspended impurity in the sewage. Oil and grease float as layers or froth on the waste water. Industrial liquid wastes are the effluents contaminating water. Agricultural wastes like pesticides, fertilisers do not dissolve in water but remain in the waste water. Causes for contamination of water Human activities like bathing and washing clothes in rivers and lakes. Animals bathing in rivers and lakes. Increase in population forms the major cause for water contamination. Untreated sewage. Industrial wastes. Agricultural wastes. Water scarcity Water scarcity refers to lack of sufficient access to drinking water. Water has become so scarce that many people have to travel several kilometres to fetch drinking water. More than 1.5 billion people all over the world do not get clean drinking water. March 22nd is celebrated as World Water Day. It was on March 22, 2005, that the United Nations declared 2005-2015 as the International Decade for the Action “Water for Life”. Every house releases lot of waste water daily. Waste water should be cleaned before it is drained into water bodies. Sewage Sewage is liquid waste containing dissolved impurities called as contaminants. Contaminants are the harmful substances which can cause illness. Sewage comprises dissolved and suspended impurities. Organic and inorganic impurities: Organic impurities in sewage include animal waste, urine, oil, vegetable and fruit waste, faeces, pesticides and herbicides. Inorganic impurities include phosphates, nitrates and metals. Disease-causing bacteria: Coliform bacteria and certain Bacilli. Saprotrophic bacteria: Bacteria that feed on dead organisms. Nutrients: Sewage contains some useful nutrients, such as phosphorus and nitrogen. Other microbes: Microbes that cause typhoid, cholera, diarrhoea and dysentery are present in sewage. Types of Sewage There are various types of sewage, depending upon the colour and odour. Sullage water: Waste water released from the kitchen is called sullage water. The contaminants in sullage water are mild detergents, oils and food particles. Foul waste: Waste water released from toilets is termed as foul waste. It consists of human waste and a lot of bacteria that release gases and bad odour. It is highly infectious. Trade waste: Wastes released from industries and commercial organisations is called as trade waste. It consists of acids and strong chemicals that are toxic in nature. Agricultural waste: Rain water which runs off from agricultural field carries toxic substances into water resources. Sewerage Small and big pipes that carry waste water are called sewers. All sewers together form the sewerage. Waste water is carried from home to the point of disposal, that is, the waste water treatment plant through sewerage. After the treatment of waste water, the clean water is released into nearby water bodies. Sewerage has manholes that can be used to clear blockages. Manholes are located at every 50 to 60 metres in the sewerage. Manholes are placed at every junction of pipes forming sewerage. In the absence of sewerage facility, waste water is directly drained into nearby streams and lakes resulting in water contamination.

#### Summary

Water Water is an essential element in daily life. Water is used by all living organisms on earth to perform their life processes. Contaminants are the suspended and dissolved impurities of water. Humans contaminate water by their activities. Drinking contaminated water results in the development of diseases such as cholera, typhoid and arrowhead. Polluted water can sometimes be fatal. Water should be boiled and filtered before it is used for drinking as it contains many impurities that are not visible to naked eye.  Waste water Waste water is the contaminated water which is often referred to as liquid waste. Liquid waste is mainly released from wash rooms, kitchen and other areas where sewage gets collected. Liquid wastes are usually disposed through closed drains. Components of waste water There are many components of waste water. Sewage or liquid waste makes up the main component of waste water. Human excreta in the form of faeces is the main suspended impurity in the sewage. Oil and grease float as layers or froth on the waste water. Industrial liquid wastes are the effluents contaminating water. Agricultural wastes like pesticides, fertilisers do not dissolve in water but remain in the waste water. Causes for contamination of water Human activities like bathing and washing clothes in rivers and lakes. Animals bathing in rivers and lakes. Increase in population forms the major cause for water contamination. Untreated sewage. Industrial wastes. Agricultural wastes. Water scarcity Water scarcity refers to lack of sufficient access to drinking water. Water has become so scarce that many people have to travel several kilometres to fetch drinking water. More than 1.5 billion people all over the world do not get clean drinking water. March 22nd is celebrated as World Water Day. It was on March 22, 2005, that the United Nations declared 2005-2015 as the International Decade for the Action “Water for Life”. Every house releases lot of waste water daily. Waste water should be cleaned before it is drained into water bodies. Sewage Sewage is liquid waste containing dissolved impurities called as contaminants. Contaminants are the harmful substances which can cause illness. Sewage comprises dissolved and suspended impurities. Organic and inorganic impurities: Organic impurities in sewage include animal waste, urine, oil, vegetable and fruit waste, faeces, pesticides and herbicides. Inorganic impurities include phosphates, nitrates and metals. Disease-causing bacteria: Coliform bacteria and certain Bacilli. Saprotrophic bacteria: Bacteria that feed on dead organisms. Nutrients: Sewage contains some useful nutrients, such as phosphorus and nitrogen. Other microbes: Microbes that cause typhoid, cholera, diarrhoea and dysentery are present in sewage. Types of Sewage There are various types of sewage, depending upon the colour and odour. Sullage water: Waste water released from the kitchen is called sullage water. The contaminants in sullage water are mild detergents, oils and food particles. Foul waste: Waste water released from toilets is termed as foul waste. It consists of human waste and a lot of bacteria that release gases and bad odour. It is highly infectious. Trade waste: Wastes released from industries and commercial organisations is called as trade waste. It consists of acids and strong chemicals that are toxic in nature. Agricultural waste: Rain water which runs off from agricultural field carries toxic substances into water resources. Sewerage Small and big pipes that carry waste water are called sewers. All sewers together form the sewerage. Waste water is carried from home to the point of disposal, that is, the waste water treatment plant through sewerage. After the treatment of waste water, the clean water is released into nearby water bodies. Sewerage has manholes that can be used to clear blockages. Manholes are located at every 50 to 60 metres in the sewerage. Manholes are placed at every junction of pipes forming sewerage. In the absence of sewerage facility, waste water is directly drained into nearby streams and lakes resulting in water contamination.

#### Activities

 Activity 1 Tmwa.com has built a design to explain the efficient usage of water in different parts of our house. User has to just click on different rooms displayed at the top.Water used in that room for different purposes are highlighted. Some measures of conserving water are also discussed. This creates an awareness in student to use available water efficiently. Go to Activity Activity 2 Sawater.com has created an interactive module which allows the student to select different topics 'Waterwise tour', 'Play the game', or 'Calculate water usage at home'. Selection of waterwise tour helps in navigating through different water devices at home which we use for various purposes. User will alos be questioned and depending upon the answers he selects, water usage in gallons is calculated by the module. This makes every person conscious about conserving water. Go to Activity

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