Water Pollution

Question 1 What is Ganga Action Plan? When and why was it launched?

Question 2 Name the pollutants which cause water pollution?

Question 3 What is water pollution?

Question 4 State few ways of controlling water pollution?

Question 5 How do industries cause water pollution?

Question 6 Why even clear, transparent and odourless water may not be safe for drinking?

Question 7 Why hot water released by power plants and industries is considered as pollutant?

Question 8 Why does the increased level of nutrients in the lake water affect the survival of aquatic organism?

Question 9 How the use of pesticides in agriculture causes water pollution?

Question 10 What is portable water?

Question 11 Name few methods to make water safe for drinking?

Question 12 State few ways by which you can conserve water at home by preventing its wastage?

Question 13 What are the different ways in which water get polluted?

 

Water Pollution

The contamination of water of rivers, lakes and ponds, etc., with unwanted and harmful substances is called water pollution.

The unwanted and harmful substances which make the water impure (or contaminated) are called water pollutants.

The major pollutants which cause water pollution are : Sewage, Fertilisers, Pesticides and Industrial wastes. All these water pollutants are harmful and dangerous to human beings, animals and plants.

Hot water from power plants and industries is also considered a pollutant. This is because when very hot water coming from power plants and industries is discharged into a river or lake, it raises the temperature of the river water (or lake water). This rise in the temperature of river water (or lake water) has an adverse effect on the animals and plants living in it.

Sources of Water Pollution

The major sources (or causes) of water pollution are :

(1) Dumping of untreated sewage into rivers causes water pollution.

(2) Use of fertilisers in agriculture causes water pollution.

(3) Use of pesticides in agriculture causes water pollution.

(4) Discharging of untreated industrial wastes into rivers and lakes causes water pollution.

 

Harmful Effects of the water Pollutants

Untreated Sewage From Homes: The waste water containing human excreta and carried in sewers (underground pipes) is called sewage.

At many places, untreated sewage from homes is dumped into rivers which pollutes the river water. Sewage contains several harmful micro-organisms such as bacteria, protozoa, fungi, viruses and parasites (worms, etc.) which cause serious diseases in humans. The drinking of  river water contaminated with sewage can cause water-borne diseases such as cholera, typhoid, diarrhoea, dysentery and jaundice.

Fertilisers Used in Agriculture: The farmers use large amounts of chemical fertilisers (like nitrates and phosphates) in the fields to increase the yield of crops. The excess fertilisers dissolve in water and run into rivers, lakes and ponds.

The fertilisers cause rapid growth of tiny green, water plants called algae in the river (lake or pond). The algae grow so well by taking fertilisers that they cover the whole surface of water like a green sheet. When the algae complete their life cycle and die, bacteria decompose the huge mass of dead algae by using the dissolved oxygen of water in the river (lake or pond).

Due to this the amount of dissolved oxygen in the water of river, lake or pond decreases too much and the fish living in this water die of oxygen starvation. The water pollution caused by fertilisers used in agriculture decreases the amount of dissolved oxygen in water bodies and leads to the death of fish and other aquatic animals.

Pesticides Used in Agriculture: The farmers use toxic chemicals called pesticides on standing crops in the fields to protect them from pests and diseases. Some of these pesticides dissolve in rain water and run into rivers, lakes and ponds and pollute their water. These poisonous pesticides kill the aquatic animals like fish. The non-biodegradable pesticides in the polluted water are absorbed by aquatic plants. These aquatic plants are then eaten by aquatic animals like fish. During this, pesticides are transferred from aquatic plants to fish. And when a person eats the fish grown in this polluted water, the pesticides present in fish enter his body and damage his health.

 

Untreated Industrial Wastes: All the industries produce toxic chemicals (poisonous chemicals) as their waste products. These are called industrial wastes. The untreated industrial wastes are discharged by the industries (or factories) into the nearby rivers or lakes. The river water or lake water gets polluted with toxic chemicals.

The toxic chemicals present in industrial wastes are the compounds of harmful metals such as mercury, lead, arsenic, nickel and cadmium. These toxic industrial wastes are released by chemical industry, textile industry, leather industry, paper mills, sugar mills, oil refineries, dyes and paint manufacturing industries. The water of rivers and lakes polluted with toxic industrial wastes can kill fish and other aquatic animals which live in this river or lake.

The toxic metal compounds present in this polluted water can enter the human body through the food chain (like eating fish grown in this polluted water). They can damage our nervous system and cause diseases such as blood poisoning and cancer.

Harmful Effects of Water Pollution

(1) Drinking of water polluted with untreated sewage can cause diseases such as cholera, typhoid, diarrhoea, dysentery and jaundice.

(2) Water of rivers and lakes polluted with fertilisers can cause the death of aquatic animals like fish.

(3) Water of rivers and lakes polluted with pesticides can kill aquatic animals (like fish) and also damage our health (through food chain).

(4) Water of rivers and lakes polluted with toxic industrial wastes kills the aquatic animals like fish, damages our nervous system and causes diseases such as blood poisoning and cancer.

 

Pollution of River Ganga

The water of river Ganga has been highly polluted because

(1) the villages, towns, and cities which are situated on the banks of this very long river throw large quantities of garbage, untreated sewage, toxic industrial wastes, infants, dead bodies and many other harmful things directly into the river.

(2) People immerse idols of gods and goddesses in the river water.

(3)They also throw ashes of dead persons, flowers and polythene bags into the river.

(4) People can be seen bathing, and washing dirty clothes and utensils in the river water.

(5) They also bathe their cattle like cows and buffaloes in the river.

(6)Some people even defecate near the river water.

All these uncontrolled human activities pollute the water of river Ganga.

At present, the pollution level in many stretches of river Ganga is so high that no aquatic animals (like fish, etc.) can survive in it.

The river is said to be ‘dead’ at those places (because it cannot support any aquatic life at those places). A recent study by World Wide Fund for Nature (WWF) has found that Ganga is one of the ten most endangered rivers in the world due to very high level of pollution.

An ambitious plan to cleanse the highly polluted river Ganga and save it was launched in 1985. It is called Ganga Action Plan. The aim of Ganga Action Plan is to reduce the pollution level in the water of river Ganga.

Controlling Water Pollution

The various ways of controlling water pollution are :

(1) Sewage should be treated properly at sewage treatment plants to make it harmless before discharging it into nearby rivers.

(2) Farmers should use correct amounts of fertilisers and pesticides in the fields so that excessive amounts of these harmful agricultural chemicals are not washed into rivers, lakes and ponds.

(3) All the industries should treat the toxic wastes produced by them suitably to make them harmless before discharging them into rivers.

(4) Water pollution prohibition laws which exist for the industries producing toxic chemical wastes should be implemented strictly by the concerned Authorities

(5) Garbage (household waste) should not be thrown into open drains, rivers, lakes or ponds. Dead bodies should not be thrown into rivers. Dead bodies should be cremated or buried properly to prevent pollution of water.

(6) People should be made aware of the harmful effects of water pollution so that they may cooperate and help in preventing it.

 

Conservation of Water

The various ways to conserve water (or save water) at home are:

(1) Turn off the tap immediately after use. Get the leaking taps repaired immediately. A leaking tap that drips even once every second wastes a few thousand litres of water every year.

(2) Brush your teeth by filling water in a mug. Leaving the tap running while brushing the teeth may waste several litres of water. Take bath by filling water in a bucket and not directly under the running tap.

(3) Wash the utensils by filling water in a basin and not under the running tap.

(4) Use water from washing rice, pulses, vegetables and fruits for watering the plants at home.

(5) Do not use the full flush from the cistern in the toilet when a half flush is sufficient.

Potable Water

The water which is safe for drinking is called potable water. The tap water which we get through pipes in our home is clean and usually without any foul smell (or odour). It is said to be safe for drinking.

The tap water which looks clean and has no foul smell may still have some disease-causing micro-organisms (which we cannot see). Drinking of such water can make a person sick. The tap water can be purified further at home to make it absolutely safe (or fit) for drinking.

 

The various methods which can be used to make water potable(or safe for drinking) are:

(1) by filtering (by using porcelain candle filter or electric water filter)

(2) by boiling, and

(3) by chlorination (by adding chlorine tablets).

A popular household water filter is a candle-type water filter (which contains one or more candles made of porcelain to filter water). In this type of water filter, the tap water is filled in a container having candles made of porcelain fixed in it. This water gets filtered thoroughly on passing through the tiny pores of porcelain candles and drops into another container kept below. The water which collects in the lower container is very safe for drinking.

In the electric water filter (like Aquaguard) resin filters are used to remove solid particles present in tap water, and ultraviolet radiations are used to kill all the harmful micro-organisms (or germs) present in tap water and make it absolutely safe for drinking. An electric water filter is attached to the tap directly.

Water can be made absolutely safe for drinking by ‘boiling’. When water is heated, it boils at a temperature of 100°C. At this high temperature, all the harmful micro-organisms (or germs) present in water are killed and it becomes absolutely safe for drinking.

Chlorination is a commonly used chemical method for purifying water. Chlorination is done by adding chlorine tablets to water. Chlorine kills all the harmful micro-organisms (or germs) present in water and makes it absolutely safe for drinking. We should, however, not use more chlorine tablets than specified. Bleaching powder can also be used for chlorination of water and make it safe.