Page 86 - ICSE Chemistry 6

POTABLE WATER

Water that is fi t for consump on is called potable water. It should have the following characteris cs.

• It should be colourless, odourless and transparent.
• It should have suffi cient amount of dissolved salts and oxygen in it.
• It should be free from harmful chemicals and microorganisms.
Generally, freshwater and groundwater are fi t for drinking. But with Waterborne Diseases
the growth in popula on and industrializa on, most of the freshwater
Infec ous diseases which spread
resources have become contaminated with pollutants. Consump on primarily through contaminated
of polluted water can have adverse eff ects on our health and we may water are called waterborne
diseases.
become suscep ble to waterborne diseases.
Diseases Caused by Contaminated Water or Waterborne Diseases

Water present in rivers, lakes, etc. should not be used for consump on directly as it may be contaminated
with industrial and agricultural wastes, and human and animal faeces which contain pathogens.
Consump on of contaminated water may lead to various waterborne diseases such as typhoid, jaundice,
dysentery, diarrhoea, gastroenteri s and cholera.

Typhoid is a waterborne disease caused by bacteria. It aff ects the intes ne leading to high fever which
lasts for a few days.
Jaundice is caused by the Hepa s A virus. It aff ects the liver of a person. The pa ents also suff er from
nausea, stomach pain and weight loss thus resul ng in liver disorders.

Dysentery is caused by amoeba or bacteria. There is secre on of mucus during the bowel movement as
these organisms infect the wall of the intes ne. The pa ents suff er from stomach pain. Anal bleeding may
also occur in severe cases.
Diarrhoea refers to a state of frequent, loose or liquid stools. During diarrhoea, water and large amount
of essen al salts and nutrients are lost from the body. This makes a person suff ering from diarrhoea very
weak and red.

Gastroenteri s is an infl amma on of the gastrointes nal tract, involving both the stomach and the small
intes ne. Certain viruses, bacteria, their toxins or parasites can cause the infec on. It results in acute
diarrhoea along with vomi ng.
Cholera is an infec on in the small intes ne caused by a bacterium. The main symptoms are excessive,
watery diarrhoea and vomi ng.

The availability of fresh and clean drinking water is necessary to reduce the spread of waterborne diseases.
Water can be purifi ed by killing germs and removing other impuri es.

PURIFICATION OF WATER

Purifi ca on of water involves removal of impuri es such as harmful bacteria, dissolved and undissolved
solid substances like par cles of mud, sand, grit and dead organisms. In other words, water purifi ca on is
the transforma on of dirty, harmful water into clean and safe water.
On a large scale, water is purifi ed in water treatment plants before it is supplied to our houses. However,
we can also purify water at home. Some commonly used methods to purify water are discussed here.

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