SESSION-18: School Students
PAPER-5: Purifying Water by Natural Biological Process
Bharath H. Aithal, Devaraj, B.M., Narendra S.S. and Rishikesh Madhev

Abstract:

Introduction

Water is a natural gift of nature.   Man pollutes this useful gift.   This is water pollution i.e. the contamination of water by sewage, toxic chemicals, oils or other substance.   It can affect such surface waters as river, (banks) lakes and oceans, as well as water beneath the earth surface, called ground water.

Water pollution can harm many species of plants and animals including man.   This pollution occurs when people put so much waste into water system that its natural cleansing processes cannot function properly.   Some contaminants such as oil, industrial acids, etc. poison aquatic plants and animals.   Other water pollutants such as phosphate detergents, chemical fertilisers etc. pollutes by supplying excess nutrients for aquatic life.   This pollution due to enhancement of organic nutrients in an waterbody is called as Eutrophication.   This process begins when large amounts of nutrients flow into a water system.   These nutrients stimulate excessive growth of algae.   Bacteria in the water use up large amounts of oxygen digesting the excess dead algae.   The oxygen level falls resulting in death of aquatic animals.

Sometime water pollution occurs when there is improper separation of sewage water and pure drinking water.   If the water is not purified, it results in diseases such as cholera, dysentery etc. This problem can be solved by the biological process based on the principle that aerobic bacteria turn waste into useful or harmless substance.

In a healthy water system, a cycle of natural processes turns wastes into useful or harmless substance.   This biological cycle begins when aerobic bacteria present in the air use the oxygen (O 2 ) dissolved in water to digest wastes.   This digestion process releases nitrates, phosphate and other nutrients (chemical substance that living things need for growth). Algae and aquatic green plants absorb these nutrients.   Microscopic animals called zooplankton eat the algae and fish eat the zooplankton.   This fish may be eaten by the larger fish.   These animals produce body wastes and die.   Bacteria break down dead animals and animal wastes, and this cycle begins again.

Conclusion:

Using aerobic bacteria present in the air the polluted water can be made useful or harmless