Purification of Water : a Study

Topics: Chlorine, Water purification, Water Pages: 9 (1697 words) Published: September 2, 2012
Chemistry Investigatory Project

To determine minimum amount of
Bleaching Powder
Required to disinfect different samples of Water.

I. Introduction
o Purification of Water
o History of Water Purification
o Bleaching Powder

II. Experiment
o Aim
o Requirements
o Theory
o Procedure
o Observations
o Result
o Precautions


98% of the Earth’s water is present in the oceans with an average salinity of 3.5%. The remainder of the Earth's water constitutes the planet's fresh water resource. Typically, fresh water is defined as water with salinity below around 0.035%. The planet's fresh water is also very unevenly distributed. About 68.7% of the freshwater is deposited in the form of ice near the poles and 30.1% of the freshwater is present in the form of Ground Water. The rest of the fresh water is known as the surface water which is present in the form of Freshwater Lakes, Rivers and Swamps. Of all these sources, only the river water is generally valuable.

An average 4 membered household uses about 90-100 gallons i.e. 400 litres of water daily. In order to fulfill such a huge demand of water, it needs to be purified and supplied in an orderly and systematic way. Most available water sources have been contaminated over the years. In order to make them useful, we need to purify and sterilize that water.

Purification of Water

There are many methods for the purification of water. Some of them are:-

← Boiling
Boiling is perhaps the most commonly used water purification technique in use today. While in normal households it is an efficient technique, it is unfeasible for industrial purposes mainly due to efficiency problems

← Filtration
Filtration is also used for removing foreign particles from water. One major drawback of this purification process is that it cannot be used for removing foreign chemicals and impurities that are miscible with water.

Since both the enlisted methods have some drawbacks, therefore we need a purification technique which can be used anytime and anywhere, does not require the use of any third party content and which is also economically feasible on both normal scale and large scale. Hence we look at the method of purification of water using the technique of treatment by bleaching powder commonly known as “Chlorination”. History of water purification in different parts of the world

In 1854 it was discovered that a cholera epidemic spread through water. The outbreak seemed less severe in areas where sand filters were installed. British scientist John Snow found that the direct cause of the outbreak was water pump contamination by sewage water. He applied chlorine to purify the water, and this paved the way for water disinfection. Since the water in the pump had tasted and smelled normal, the conclusion was finally drawn that good taste and smell alone do not guarantee safe drinking water. This discovery led to governments starting to install municipal water filters (sand filters and chlorination), and hence the first government regulation of public water.

In the 1890s America started building large sand filters to protect public health. These turned out to be a success. Instead of slow sand filtration, rapid sand filtration was now applied. Filter capacity was improved by cleaning it with powerful jet steam. Subsequently, Dr. Fuller found that rapid sand filtration worked much better when it was preceded by coagulation and sedimentation techniques. Meanwhile, such waterborne illnesses as cholera and typhoid became less and less common as water chlorination won terrain throughout the world.

But the victory obtained by the invention of chlorination did not last long. After some time the negative effects of this element were discovered. Chlorine vaporizes much faster than water, and it was linked to the aggravation and cause of various respiratory diseases....
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