The chapter “Safe Drinking Water” is taken from Let’s Learn and Look Around Class 4 Environmental Studies for students of JKBOSE. In my earlier post, you have read about Question Answers of Chapter 4 Safe Drinking Water. This post is about Safe Drinking Water Class 4 Chapter Notes. Let’s get started:
The chapter “Safe Drinking Water” is about different sources of water, how water gets polluted and how can we remove impurities from water and what are characteristics of drinking water.
Safe Drinking Water Class 4 Chapter Notes
Water is the most common and important substance on the earth. 70% of the earth’s surface is covered with water. Imagining life without water is impossible.
The first living organisms were found in water i.e. life started in water and it is the main constituent of the bodies of all living things. Water is found filled in the seas and lakes, flowing in rivers and on high mountains and polar regions, it exists as snow or ice. In the air, water is found in the form of vapour. As water vapour rises, it reaches cold air high in the sky. It turns back into tiny drops of water which join to make clouds. The drops fall to the ground as rain.
Water helps plants to grow. It is used for drinking, washing, cooking and bathing. For our daily use, we get water from lakes, tanks, wells or rivers. Water obtained from these sources may not be pure.
How Does Water Become Impure?
Rainwater is the main source of water for us and it is the purest form of natural water. However, when it passes through the air many harmful and poisonous gases from the atmosphere mix with it and make water impure.
Rainwater falling a little after the first shower is generally clean.
After rainwater reaches the surface of the earth, many more impurities get dissolved in it. It takes mud and sand particles with it while flowing through streams and rivers. When this water collects in lakes and ponds, the mud and sand slowly settle down at the bottom. Now the water looks clear. The soluble impurities, however, remain in the water. This water is impure due to these soluble impurities.
Water Becomes Impure Owing to Many Reasons
- People wash their cattle in ponds and rivers. The dirt and mud sticking to the bodies of cattle mix with the water.
- People wash their utensils and clothes in water. The left. overs of food from the utensils and dirt from clothes get mixed with water. When this water flows to the rivers and ponds it makes them dirty.
- Sick people take baths and wash their clothes in the reservoirs of water. As a result of this, germs mix with water.
- Some people urinate and defecate near the sources of water. Due to this germs enter the water.
- Sometimes, drainage water containing germs and poisonous chemicals from factories enters the water reservoirs and contaminates them.
- Sometimes, water is collected in small pits. This is known as stagnant water. In due course, stagnant water becomes very dirty. Insects, mainly mosquitoes breed in stagnant water and spread many diseases.
Seawater is the most impure form of water. It receives all the impurities present in river water. Dissolved salts, especially common salt, give seawater a salty taste. Seawater cannot be used for home and agriculture.
Some rainwater seeps through the soil. It passes through various layers of sand, stones, and clay and finally meets with the hard rock. The rock does not allow water to pass through it.
The reservoir of water that collects over the hard rock is called underground water.
Underground Water May be Used for Drinking and Agriculture
The underground water is usually pure because impurities are filtered out when it passes through the various layers of the earth. It may contain dissolved salts. We get this water through hand pumps and by digging wells.
The purity of hand-pump water and well water depends upon their depth. Shallow hand pumps and shallow wells are often polluted with the sewage water. Sometimes, waste matter from the ground falls into the well water and makes it dirty. The water of deep hand-pumps and deep wells may contain impurities that are present in the surrounding soil.
We cannot get pure water from natural sources. But all the impurities mixed with water are not harmful. Some salts dissolved in water are useful to us. Yet impure water contains many dangerous impurities. Such water spreads diseases. It is, therefore, essential to purify water before use.
Characteristics of Drinking Water
- It should be colourless.
- It should be odourless (without any smell). It should be free from suspended impurities.
- It should not contain germs and bacteria.
- It should contain dissolved gases like oxygen and hydrogen.
- It should contain dissolved mineral salts that make water healthy and give us a pleasant taste.
Purification of Drinking Water
Purification of water for drinking purposes involves:
- Removal of suspended or insoluble impurities.
- Destroying harmful germs and bacteria.
- Removal of Suspended or Insoluble Impurities
Insoluble impurities of water can be removed by filtration. The addition of little alum to impure water helps in settling down floating particles of mud and other impurities. This is called sedimentation. This water is then filtered to remove insoluble impurities from it.
At home, water is filtered by a ceramic water filter. Some kinds of water purifiers are also available which can be fitted with the tap. Water passes through the filter and purifier and is collected in a vessel.
On a large scale, the water of the river or lakes is filtered by passing it through layers of sand, pebbles (gravel) and char-. coal.
- Destroying Harmful Germs and Bacteria
Filtered water does not contain insoluble impurities. It looks clean. Yet it may contain harmful germs and bacteria. To destroy harmful germs and bacteria, the following methods are used:
- Chlorination: A gas called chlorine is passed through the filtered water, and harmful germs and bacteria are killed. This process is known as chlorination. The well water is purified by adding bleaching powder or potassium permanganate. These substances also kill germs.
- Aeration: The tank containing filtered water is treated with air under pressure. The organic matter reacts with the oxygen present in the air and is made harmless. This process is known as aeration. Aeration also kills harmful germs. Thus, purified water reaches the homes through the municipal water supply system. We get this water through the tap.
The tap water can be made still safer to drink by boiling. Boiling kills the germs. During the monsoon, water is generally contaminated with harmful germs. So boiled water is safe for drinking. Hence, during the monsoon, drinking water must be boiled.
If water is boiled for 20-25 minutes, all harmful germs in the water are killed and water becomes potable. But such water after boiling should be well-stored. If dirty fingers or dirty utensils are dipped in such boiled water, they will be contaminated again.
Water is precious. We must not waste it. If we do not save water, soon there will not be enough water for all of us. For avoiding wastage of water, we will take the following steps:
- While taking water for drinking, we should take only just enough water.
- We should make economical use of water while taking bath or washing clothes.
- The water tap should be closed immediately after use
Points to Remember:
Aeration: Adding air (a gas) to a liquid under pressure.
Alum: A white mineral salt.
Atmosphere: The gases envelop the surrounding the earth.
Ceramic: Made of clay.
Chlorination: Treating water with chlorine to kill harmful germs in it.
Contamination: Making impure by adding dangerous or disease-carrying substances.
Filtration: Process of filtering liquid, etc.
Impurities: Substances present in another substance. that make it of poor quality.
Odourless: Without a smell.
Purification: The process of making pure by removing dirty and harmful substances.
Reservoir: Natural or artificial lake used as a source to store water.
Sedimentation: Process of depositing undissolved matter to the bottom of a liquid.
Sewage water: Water mixed with waste matter from human bodies, factories, towns, etc.
Shallow: Not deep.
Stagnant water: Water which is not flowing and therefore dirty and of unpleasant smell.
Underground water: Water that collects over the hard rock layer.
That,s all we have about Safe Drinking Water Class 4 Chapter Notes. Hope you have got your answers. Do share your views about this post in the comment section.