Methods of Purification of Water

Table of Contents
1. Introduction ................................. 1
2. Boiling ............................................. 2
3. Filtration ......................................... 3
4. Reverse Osmosis ....................... 4
5. Water Chlorination .................... 5
6. UV Water Purification ............... 6
7. Ozone Disinfection .................... 7
8. Solar Water Disinfection ............ 8
9. Conclusion .................................. 9
Introduction
Water purification is the process of removing undesirable chemicals,
biological contaminants, suspended solids and gases from contaminated
water. The goal is to produce water fit for a specific purpose. Most water is
purified for human consumption (drinking water), but water purification may
also be designed for a variety of other purposes, including meeting the
requirements of medical, pharmacological, chemical and industrial
applications. In general, the methods used include physical processes such as
filtration, sedimentation, and distillation, biological processes such as filters
or biologically active carbon, chemical processes such as flocculation and
chlorination and the use of electromagnetic radiation such as ultraviolet light.
The purification process of water may reduce the concentration of particulate
matter including suspended particles, parasites, bacteria, algae, viruses,
fungi and a range of dissolved and particulate material derived from the
surfaces that water may have contacted after falling as rain. The standards
for drinking water quality are typically set by governments or by international
standards. These standards will typically set minimum and maximum
concentrations of contaminants for the use that is to be made of the water. It
is not possible to tell whether water is of an appropriate quality by visual
examination. Simple procedures such as boiling or the use of a household
activated filter are not sufficient for treating all the possible contaminants
that may be present in water from an unknown source. Even natural spring –
considered safe for all practical purposes in the 19th century – must now be
tested before determining what kind of treatment, if any, is needed. Chemical
and microbiological analysis, while expensive, are the only way to obtain the
information necessary for deciding on the appropriate method of purification.
According to a 2007 World Health Organization (WHO) report, 1.1 billion
people lack access to an improved drinking water supply, 88 percent of the 4
billion annual cases of diarrheal disease are attributed to unsafe water and
inadequate sanitation and hygiene, and 1.8 million people die from diarrheal
diseases each year. The WHO estimates that 94 percent of these diarrheal
cases are preventable through modifications to the environment, including
access to safe water. Simple techniques for treating water at home, such as
chlorination, filters, and solar disinfection, and storing it in safe containers
could save a huge number of lives each year. Reducing deaths from
waterborne diseases is a major public health goal in developing countries.

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Boiling
Boiling water is used as a method of making it potable by killing microbes
and viruses that may be present. The sensitivity of different micro-organisms
to heat varies, but if water is held at 100 °C (212°F) for one minute, most
micro-organisms and viruses are in activated. In places having proper water
purification system, it is recommended only as an emergency treatment
method or for obtaining potable water in the wilderness or in rural areas, as it
cannot remove chemical toxins or impurities. The traditional advice of boiling
water for ten minutes is mainly for additional safety, since microbes start
getting eliminated at temperatures greater than 60° (140°F) and bringing it
to its boiling point is also a useful indication, the water is disinfected.

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Filtration
In the water industry, clarified water is the goal of the filtering. It is primarily
used for storm water, wastewater, and drinking water applications, but it also
has uses in industrial manufacturing, power plants, food and beverage
production facilities, mining and other heavy-duty applications.

Water filtration can remove or reduce the concentration of suspended

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In order for water to be filtered, it can only pass through the filter medium if
some driving force is applied, which may be caused by
gravity, centrifugation, application of pressure on the fluid above the filter, or
other processes that use pumps, valves and pipes to produce enough
pressure to push the water through the filter.

Reverse Osmosis
Reverse Osmosis is a water purification process that uses a semi-permeable
membrane to filter out unwanted molecules and large particles such as
contaminants and sediments like chlorine, salt, and dirt from drinking water.
In reverse osmosis, an applied pressure is used to overcome the osmotic
pressure and push the water from high concentration to low concentration of
contaminants. This means it’s being forced in reverse and the contaminated
water is trying to move into the pure water, but because it must pass through
a filter first, the contaminants get trapped and only the pure water passes
through resulting in the cleanest possible drinking water reverse osmosis
differs from carbon filtration in that it can rid the water of up to 99% of all

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contaminants and sediments, or particles as small as 1 micron. It would be
best to get a reverse osmosis filtration system to safeguard that your water is
contaminant-free.

Water Chlorination
Water chlorination is the process of adding chlorine or chlorine compounds
such as sodium hypochlorite to water. This method is used to kill bacteria,
viruses and other microbes in water. In particular, chlorination is used to
prevent the spread of water borne diseases such as cholera, dysentery, and
typhoid. As a halogen, chlorine is a highly efficient disinfectant, and is added
to public water supplies to kill disease-causing pathogen, such as bacteria,
viruses and protozoans, that commonly grow in water supply reservoirs, on
the walls of water mains and in storage tank. As a strong oxidizing agent,

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chlorine kills via the oxidation of organic molecules. Chlorine and the
hydrolysis product hypochlorous acid are not charged and therefore easily
penetrate the negatively charged surface of pathogens. It is also to
disintegrate the lipids that compose the cell wall and react with intracellular
enzymes and proteins, making them non-functional. Microorganisms then
either die or are no longer able to multiply.

UV Water Purification
UV water purification systems purify water by using ultra violet rays to kill
microorganisms present in the water. UV rays completely kill water-borne
microorganisms and prevent their reproduction by disrupting their DNA. Also,
UV rays do not lead to chemical changes in the water. As such, water purified
from UV rays doesn’t contain any harmful microorganisms and retain their
original taste. Modern water purifiers use low-pressure mercury vapor lamps
which produce ultra violet radiation at a specific level. The mercury vapor
lamps are installed in such a way that they do not contact water. One of the

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biggest advantages of using a UV water purifier is instant purification of
water. UV water purification systems do not use any chemicals. UV water
purifiers are cost-effective; the mercury vapor lamp of the appliance is similar
to a standard light bulb in terms of power consumption and price. UV water
purifiers can last long, especially if you regularly maintain the appliance.

Ozone Disinfection
Ozone disinfection Ozone is an unstable molecule which readily gives up one
atom of oxygen providing a powerful oxidizing agent which is toxic to most
waterborne organisms. It is a very strong, broad spectrum disinfectant that is
widely used in Europe. It is an effective method to inactivate harmful
protozoa that form cysts. It also works well against almost all other
pathogens. Ozone is made by passing oxygen through ultraviolet light or a

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“cold” electrical discharge. To use ozone as a disinfectant, it must be created
on-site and added to the water by bubble contact. Some of the advantages of
ozone include the production of fewer dangerous by-products and the
absence of taste and odour problems (in comparison to chlorination) .
Although fewer by-products are formed by ozonation, it has been discovered
that ozone reacts with bromide ions in water to produce concentrations of the
suspected carcinogen bromated. Bromide can be found in fresh water
supplies in sufficient concentrations to produce (after ozonation) more than
10 ppb of bromate — the maximum contaminant level established by the
USEPA. Another advantage of ozone is that it leaves no residual disinfectant
in the water. Ozone has been used in drinking water plants since 1906 where
the first industrial ozonation plant was built in Nice, France. The U.S. Food
and Drug Administration has accepted ozone as being safe; and it is applied
as an anti-microbiological agent for the treatment, storage, and processing of
foods.

Solar Water Disinfection

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has found that the wild Salmonella which would reproduce quickly during
subsequent dark storage of solar-disinfected water could be controlled by the
addition of just 10 parts per million of hydrogen peroxide.

Conclusion
We can conclude from the project that there are various methods of
purification of water. Today, we know that water is present everywhere on
earth in different forms but due to human activities water is being polluted
day by day not only that about 97% of earths water is in oceans which is not
suitable for drinking or any other purpose. So, there is very small volume of
water is left, to utilise that humans are using best ways to purify it. And in
present time humans are capable to purify water and all the methods to
purify it are mentioned in the project.

SOURCE: Wikipedia(Internet)

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