Type of Water Purifier

There are five major categories of water purifiers, depending on the purification methods they use. The following figure lists these categories :

RO Water Purifiers 
RO water purifiers are the most commonly used purifiers and are based on the principle of reverse osmosis. They make use of the membrane technology to eliminate contaminants such as salts, heavy metals and germs dissolved in water. The following image shows an RO purifier membrane :

The main advantage of using an RO purifier are as shown in the following figure :

Removes impurities such as lead, arsenic, mercury and germs from water 
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Environmental friendly 
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Suitable for hard water 
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Suitable for hard water with high total dissolved salts (TDS) 
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easy to install and maintain 

There are certain disadvantages of an RO purifier such as:

• Removes essential minerals along dissolved impurities 
• Alters the taste of water 
• Wastes large quantity of wayer
• Requires electricity to purify water
• Requires special care and maintenance for it's membrane 

UF Water Purifiers 

UF water purifiers use membranes similar to an RO membrane but with large pores. They remove all germs and bacteria from water but do not remove dissolved salts or solids. They are suitable in homes where the water supplied is not very hard and less dissolved salts. The process of privation in a UF purifier is shown in the following image :

The main advantages of using a UF purifier are as shown in the following figure :

Removes impurities and germs from muddy water 

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Environmental friendly 

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Does not require electricity to purify water 

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Retains the taste and odor of water 

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Easy to install and maintain 

There are certain disadvantages of a UF purifier such as:

• Unable to remove dissolved impurities such as arsenic, lead, nitrates and fluoride 
• Ineffective as compared to an RO water purifier as it cannot block dissolved salts and solids 
• Good only for water with low TDS 

UV Water Purifiers 

UV water purifier use ultraviolet rays to kill all germs,  bacteria and microbes dissolved in water. A small mercury lamp is placed inside the purifier, which produces high frequency short wave UV radiations. When water passes through this element, it is exposed to the UV light which kills all the living organisms. 

Separate filters then remove the dead germs. 

UV purifiers are used in residences, breweries, water stores,restaurants and municipalities. 

The following image shown the working of UV water purifiers:

The main advantage of using a UV purifier are as shown in following figure :

Removes viruses, bacteria and germs from water 

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Environmental friendly 

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No chemicals added to wayer

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Retains the taste and odor of water 

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Easy to install and maintain 

There are certain disadvantages of a UV purifier such as:

• Unable to remove dissolved impurities such as arsenic, lead, nitrates and fluorides 
• Requires electricity to purify water 

Gravity Based Water Purifiers 

Gravity based water purifiers are based on the principle of gravity. The water flows from a higher compartment over the filters to a lower compartment. They do not require electricity and use either chemical based, UF based or ceramic cartridge based filters to purify water. 

The following figure shows the parts of a gravity purifier :

The main advantages of using a gravity based purifier are as shown in the following figure :

Removes impurities and germs from muddy water 

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Environmental friendly 

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Does not require electricity to purify water 

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Suitable for soft water 

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Portable and easy to install 

There are certain disadvantages of a gravity based purifier such as:

• Unable to remove dissolved impuri+ies such as arsenic, lead, nitrates and fluorides
• Ineffective as compared to an RO water purifiers as it cannot block dissolved salts and solids 
• Good only for water with low TDS

Activated Carbon Water Purifiers 

Activated carbon is carbon with a positive charge added to it. When water flows over it, the negative ions of contaminants get attracted to the surface of the activated carbon filter. 

Activated carbon water purifiers can remove volatile organic compounds, pesticides, herbicides, chlorine and other chemicals found in tap water. This makes the water safe to drink. 

The following images shows the license of purification in an activated carbon water purifier:

The main advantage of using an activated carbon purifier are as shown in the following figure:

Removes volatile organic chemicals, radon and chlorine 

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Environment friendly 

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Eliminates bad order and taste 

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Cost effective 

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Does not require electricity to purify water 

There are certain disadvantages of an activated carbon purifier such as:

• Unable to remove dissolved microbes and impurities such as arsenic, lead, nitrates and fluorides 
• Ineffective as compared to an RO water filter as it cannot block dissolved salts and solids 
• Requires frequent filter changes 

Water Purifiers

Pure, clean and safe drinking water is a necessity for human life and health. Water that is supplied in homes is contaminated with organic and inorganic particles. It becomes critical to purify the tap water to ensure it is safe for consumption and does not have any adversely effect on health. A water purifier removes contaminants such as excess salts, suspended particles and microbes dissolved in water and preserve it's necessary vitamins and minerals. 

Water Purification Process

Water purification is the process of removing contaminants from untreated or raw water to get pure water that is safe for consumption. It consists of three different processes .

Physical processes 

• Filtration, sedimentation and distillation 

Biological processes

• Slow and filters or biologically active carbon 

Chemical processes 

• Flocculation, chlorination and the use of ultraviolet light

Steps of the Purification Process 

The water purification process consists of four major steps. 

Coagulation 

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Sedimentation 

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Filtration 

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Disinfection 

Coagulation 

When the water from ground, lakes, or river enters a water treatment plant, it is coagulated by the addition of alum and other chemicals. These sticky particles also known as floc, attract dirt particles which make them heavy and they sink to the bottom. 

Sedimentation 

The water and floc pass into the sedimentation basin. The heavy floc settles down and the water is passed through filtration tanks. 

Filtration 

The filtration tanks consist of layers of gravel and sand which filter out the remaining contaminants. 

Disinfection 

The water is passed into a closed reservoir containing disinfectants such as chlorine. These disinfectants kill the bacteria or micro-organisms present in the water 

The purified water then flows through pipes to homes. 

Water Treatment Methods

Water Treatment Methods 
There are four common types of contaminants that are generally found in water.

Bacteria 
Bacteria are a group of microorganism that are found in plants, soil and water. Most of the bacteria are harmless but some of them can cause sickness and dis3ase in humans. The most common of these are vilified bacteria which are present in intestines of warm feces and can caus3 diseases such as cramps, vomiting, diarrhea and intestinal infection.

Minerals 
Minerals are inorganic substances found in rocks and similar matter in the earth. Some minerals such as calcium, magnesium and potassium are considered good for humans and some such as lead, arsenic, and aluminum we considered harmful. Water is not a table source of minerals as it contains a mix of both types of minerals. The human body cannot absorb the minerals very well. The level of minerals dissolved in water determines it's hardness.

Particulates 
Particulates are minute particles of dirt, sand, rust and sediment found in water. Particulates themselves do not adversely affect health but they are carriers of other harmful contaminants in water : organic, inorganic and microbiological .particulates are measured in microns where one micron is oneillionth of a meter.

Chemicals 
Chemicals contaminants can be natural or man-made. They enter water through pollution, industrial discharge, urban activities, agriculture and disposal of waste. These undesirable contaminants include toxic metal salts, nitrogen, bleach, pesticides, fertilizers, human and animal drugs.
The presence of these contaminants makes water treatment very important. There methods involve removal of contaminants from water to make it safe for human consumption without any risk of unfavorable effects on health.
Water treatment is done at two levels :

Community water treatment 
Public drinking water system use surface water treatment plants to provide safe drinking water to people.

Domestic water treatment 
Individuals use home treatment units such as filters, water softeners and distillation systems to remove specific contaminants, to improve the taste of water and as precaution against disease.

Water treatment methodsbuse different types of agents to make safe for drinking purpose. Water treatment agents can be divided into three categories

Water treatment 

agents 

Chemicals       Filters         Purifiers 

Chemicals 

A variety of chemicals are used in the process of water treatment for the purpose of desalination and stoppage of fouling and scaling. The three most commonly used chemicals are chlorine, chlorine dioxide and ozone. They are used as disinfectants to kill unwanted microorganism present in water and improve the taste, odor and clarity of water. 

Filters 

Filters purify water by removing impurities from it and reducing it's contamination. The filtration process consists of making water flow over some type of filter which blocks the route of the contaminants. The filter can be a physical barrier, chemical process or a biological process. There are main type of filters.

Sediment.               Carbon block 

Fiter.                             filter 

TFC/TFM                 Inline carbon 

membrane.                            filter 

Sediment Filter

Sentiment filter renmove suspended particulate matter such as send, dirt, silt and organic matter from water. Water flows from the outside to the core of the filter and the impurities are retained on the filter surface. They, however, do not remove contaminants such as chlorine, lead, mercury and other organic compounds dissolved in water. 

Carbon Block Filter 

Activated carbon block filters are used to remove contaminants such as chlorine, benzene, which enhances the surface area as well as the ability of absorption of the filter. 

TFC/TFM membrane 

TFC/TFM are semi-permeable membranes used in the reverse osmosis (RO)  water purification systems. Untreated water is forced through the membranes which act like a strainer and allow pure water to pass through leaving the dissolved contaminants be hind 

Inline Carbon Filter 

Carbon filters can also be installed in-line as apart of the reverse osmosis water purification system. They are used as pre-treatment to safeguard other water treatment units, such as TFC/TFM membranes, from any damage due to organic fouling or oxidation. 

Purifiers 

Water purifier remove contaminants such as excess salts, suspended particles and microbes dissolved in water and preserve it's necessary vitamins and minerals. 

The difference between water filters and purifiers is the type of impurities removed by each one of them. 

The following figure lists the main differences between the two:

Water filters

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Eliminate or minimize impurities such as dissolved salts and heavy metals

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Filters work like a strainer and prevent unwanted elements from entering 

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Cannot remove viruses from water 

Water purifiers

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Eliminate contaminants such as bacteria and viruses present in water 

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Kills and removes unwanted elements from water 

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Removes even essential minerals from water 

Water Treatment

Water Treatment 
Clean and safe water is critical for everyday life. Very little of the water found in nature is drinkable as it is contaminated with virus, bacteria and parasites. This water needs to be treated before it can become useful. Water treatment is the process of removing pathogenic micro-organisms which have entered water and making it fit for use.
The following figure lists the purpose of water treatment :

• To remove pathogenic microorganism which cause various diseases 
• To extract chemicals & dissolved minerals
• To remove the excessive color of the water & turbidity 
• To control unpleasant taste and appearance of particles 

Properties of Water

Water is a transparent, odorless, tasteless and colorless liquid. It's chemical name is H2O and it is made up of two hydrogen atoms and one oxygen atom joined together by covalent bonds.

The following figure lists the various properties of water :

๏ Properties of water 

• Universal solvent 
• High specific heat 
• Strong surface tension 
• Neutral pH
• High polarity 
• Lower density of ice

Universal Solvent 
Water can form hydrogen bonds and this property makes it a powerful solvent. It can dissolve a large number of different chemical distances. It is this dissolving power of water that supports life in Earth by carrying dissolved nutrients, minerals and chemicals wherever it goes.

High Specific Heat 
Water has a high specific heat capacity. Specific heat refers to the amount of heat needed to alter the temperature of a substance. Water can absorb and store a lot of heat before it gets hot. This enables it to moderate earth's temperature.

Strong Surface Tension 
Water has a high surface tension. It's high polarity makes its molecules strongly attracted to each other. It's molecules are adhesive and form a layer on its surface. High surface ten is responsible for the capillary action of water and enables it to move through plant roots and stems and even blood vessels in animals. 

Neutral pH 
Water is neither acidic nor basic; it has a neutral pH value 7.

High Polarity 
Water has a high polarity. The hydrogen and oxygen molecules join at an angle with the oxygen atoms at vertex and the hydrogen atoms at tips. The difference in the electric negativity of oxygen and hydrogen atoms makes water a strong polar compound.

Lower Density of Ice 
The density of ice is lower than the density of water. Water expands when it freezes and it's molecules from a crystalline structure which is less dense than liquid water. This enables the inventor float on water and prevent oceans, lakes and rivers from freezing, thereby allowing life to exist on Earth.

Water

Water is the most abundant compound found on Earth and is essential for the survival of all life forms. More than 70% of Earth's surface is covered with water in the form of snow, glaciers, oceans, rivers and lakes. It is the only substance on earth that exists in all three physical states, in liquid state at standard temperature and pressure, in solid state as ice and in gaseous state as water vapor.
However, very little of this water is drinkable, as 96% of the Earth's water is salt water. Around 98% of the remaining freshwater is in the from of glaciers and polar ice caps. This leaves just about 1% of the freshwater on the surface in the form of rivers and lakes. Not all of this freshwater is safe for human consumption ad it is contaminated with bacteria.
To make fresh water safe for drinking, it needs to be cleaned so that it's intake does not cause any harm. The various properties of water make it a necessity for supporting life.