Water

How to Purify Water – Water Purification Process

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How to Purify Water – Water Purification Process

Water supplied in our homes generally comes from rivers and is contaminated with suspended impurities like sand, silt, and clay; soluble impurities like salts; and also microorganisms. Water, therefore, has to be cleaned in big purification plants before it reaches our homes. The three main processes through which water undergoes during purification are sedimentation, filtration, and chlorination. Figure outlines the various processes employed in purification of water.

How to Purify Water - Water Purification Process 1
Diagrammatic representation of stages of purification of water

Impure water can be purified by various methods like filtration, distillation, and sedimentation.

Filtration: In this method, insoluble impurities are removed by passing impure water through a filter or a filter paper.
How to Purify Water - Water Purification Process 2Sedimentation and decantation: In this method, impure water is allowed to stand undisturbed in a container, which allows insoluble impurities like mud to settle at the bottom as sediments. This process is called sedimentation. Clean water can thereafter be transferred into a clean container by the process of decantation.
How to Purify Water - Water Purification Process 3Distillation: In this method, impure water is first heated to its boiling point to convert water into steam. The impurities are left behind in the container. The steam is then passed through a condenser, where it cools and changes back into liquid water.
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Purification of Water at Home

The water supplied to our homes may not be entirely free from undesirable impurities. Also, in villages and small towns water is directly taken from wells, hand pumps, and rivers. Thus, purification of water at home becomes necessary. This can be done by both physical (e.g., boiling) and chemical (e.g., chemical tablets and electric water filters) means. Let us discuss some of these.

Boiling: Boiling water is one of the easiest ways of purifying water. It is, however, very important that water is boiled at 100°C for at least 10-15 minutes to kill harmful microorganisms.

Addition of chemical tablets: Chemicals like chlorine tablets or potassium permanganate can be added to water from wells and water tanks to kill harmful microorganisms and germs.

Use of electric water filters: Electric water filters have a micro-porous filter, carbon, and a source of ultraviolet radiation. The micro-porous filter strains out physical impurities present in the water, like dust, rust, dirt, and mud. Carbon absorbs organic impurities and removes unwanted taste and odour. Ultraviolet radiation kills microorganisms.

Purification of Water Using Sunlight

Did you know, sunlight can be used to purify water?
Sunlight is already being used in many developing countries as medium to disinfect water. This method is popularly known as solar water disinfection (SODIS). Exposure to sunlight has been shown to deactivate many  disease-causing microorganisms. This is an effective method of treating water where fuels or cookers are unavailable or are very expensive. Inspite of its various advantages, this method has some limitations as well. The duration to which water is exposed to sun, strength of sunlight, bottle material, etc. determines its effectiveness.
The basic steps involved in the purification of water using sunlight are:

  1. Wash the bottle well.
  2. Fill it up with water and close the lid.
  3. Place the bottle on a corrugated iron sheet or on the roof top.

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What are the Physical Resources and Explain the Role of Air

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What are the Physical Resources and Explain the Role of Air

The materials present in natural environment & useful to living organism are called natural resources.

Natural Resources can be classified into two groups.

  1. Physical resources : E.g, Air, water, soil, minerals, coal etc.
  2. Biological resources :  E.g. Microorganisms, plants & animals.

The Breath of life : Air
Air is a mixture of gases which is odourless, tasteless & invisible. Air also holds water vapour & dust particles.

Atmosphere :
The envelop of air that surrounds the earth is called Atmosphere.

Role of atmosphere in climate control  :
Air is a bad conductor of heat. It act as a protective blanket for the living organisms to exist in the following way –

  1. Atmosphere prevent the sudden increase in temperature during the day hours. During night it slow down the escape of heat into the outer space. Thereby preventing excessive cooling during night.
  2. The ozone shield of atmosphere absorb most of the harmful UV radiations coming from the sun.  The excessive heat & sun rays are reffected back into the outer space by dust particles.

Movement of Air :
Heating of air occur due to reradiation of solar radiations by the land & water bodies. In fact, when the solar radiation fall on the earth, some are absorbed & majority of these are reflected back or reradiated by the land & water bodies. These solar radiations heat up the atmosphere from below. As a result, convection currents are set up in the air. But since the land gets heated faster than the water, the air over land also gets heated faster than the air over water bodies. Hot air on land rises upwards thereby producing an area of the low air pressure. Air from region of high pressure will move towards this region of low pressure producing breez or wind.

Rain :
The air carrying water vapour also get heated. This hot air rises up in the atmosphere carrying water vapour with it. As the air rises. it expands & cool. This cooling cause the water vapour to condense in the form of tiny droplets. Suspended particles of dust & other materials act as nuclei to facilitate the process of condensation of water around them. A collection of tiny droplets of water appear in the form of ‘clouds’. These droplets of water slowly grown bigger by the condensation of more water droplets.
When the droplets have grown big & heavy they fall down in the form of ‘rain’.

Water
Water is one of the basic necessities of life. It is an inexhaustible natural resource which is liquid between 0ºC and 100ºC. We need water for various activites such as drinking, cooking of food, bathing and washing. It is also needed for irrigation of crop in agriculature, as an essential requirement in industries, and for navigation.
Water plays a vital role in the metabolic reactions taking place within the organism’s body. It acts as a universal solvent, providing a medium for the chemical reactions to occur. In fact, all the chemical reactions that occur within body cells involve substances that are dissolved in water. Substances are also transported from one part of the body to the other in dissolved form.
97.5% of the water on the planet earth is found in seas and oceans as saline water and is not available to us for use directly. Only 2.5% of the total water resources of the world consist of fresh water. Majority of it (about 2%) is found frozen in the ice-caps at the two poles and on snow-covered mountains. Remaining (0.6% of the total) is available to support terrestrial life. Majority (90%) of this fresh water is found underground as ground water and only 10% occurs as surface water in lakes, ponds, streams, rivers etc. Limited amount of fresh water is available to us as a renewable souce through water cycle but its distribution is uneven.

Soil
The top surface layer of this exposed, solid part of crust containing weathered minerals and humus and capable of supporting plant growth is called soil.

Soil Formation
The process of soil formation is so slow that the soil is regarded as a non-renewable resource.
Pedogenesis
It is the process of formation of soil from rocky earth’s crust. It involves following two processes:
Weathering
Decomposition of organic matter and subsequent humification and mineralization.
Main factors that influence the formation of soil from the rocks are –

  1. Temperature variations due to radiactions of the sun.
  2. Rain water
  3. Winds
  4. Living organisms

What is an Abiotic Component

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What is an Abiotic Component

Abiotic Components
The word ‘abiotic’ means ‘non-living’. Light, air, water, soil, and temperature are some examples of abiotic components of the environment. Even though these components are themselves non-living, they have an effect on the living organisms, i.e., the biotic components of the environment.

Light
Plants use light to prepare their food.

Temperature
Temperature is a measure that tells us how hot or cold something is. Earth is the only known planet that has a temperature suitable for life to exist. Even on Earth, the temperature is not uniform all around. It is very hot near the equator, while places near the poles are very cold. Temperature affects the distribution of plants and animals around the planet.

Animals whose body temperature changes with the outside temperature are called cold-blooded animals. Most reptiles, insects, and amphibians are cold-blooded. Animals whose body temperature does not change with the outside temperature are called warm-blooded animals. Most mammals and birds are warm-blooded.

Warm-blooded animals can survive in areas having extreme temperatures like the desert and the Arctic region. Here, cold-blooded animals would have difficulty in surviving. Polar bear is adapted to survive in the harsh temperatures of the Arctic.

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Polar Bear

Air
Oxygen and carbon dioxide present in air are very important for the survival of organisms. Both plants and animals need oxygen for respiration. Animals and human beings release carbon dioxide during respiration, which is used by green plants for photosynthesis. Carbon dioxide is also released by burning of fuels in vehicles and factories. Plants, in turn, release oxygen into the environment. Thus, green plants play a very important role in maintaining the balance of oxygen and carbon dioxide in the environment. Moving air or wind also helps in the reproduction of plants through pollination and dispersal of certain fruits and seeds.

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The balance of oxygen and carbon dioxide in atmosphere

Water
Water is very important for living organisms. Plants absorb water through their roots, which is then transported to different plant parts. Water is essential for carrying out photosynthesis in plants.
It also plays an important role in the human body. Blood, which transports substances within the human body, is largely composed of water. In fact, 70% of the human body consists of water.
Water dissolves vital gases like oxygen and carbon dioxide. This enables living beings to survive in water.

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Water is essential for living organisms

Soil
Soil is the uppermost layer of the Earth’s crust. It has four sub-layers – topsoil, subsoil, parent material, and the bedrock. It is in the topsoil that plants grow.
Soil is very rich in minerals like magnesium, potassium, and phosphorus. Without soil, there would be no plants and thus, no food for us. Plants grow well in loosely packed soil as it allows their roots to grow deeper and also makes it easier for them to absorb water and nutrients. This is why farmers plough their fields before sowing seeds.

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Sub layers of soil

Animals like earthworm and snail also make the soil loose by turning it.

Habitat
Thus in nature, biotic and abiotic components are closely interrelated. Biotic components (organisms) interact with one another too. A group of interdependent organisms that live in the same region and interact with one anotherform a biotic community. A biotic community includes plants, animals, and microorganisms.