Water Treatment Technologies:
Traditional Ways to purify water:

  • Boiling: - This is the most common way of getting the water filtered at homes. Boiling of water makes water microbiologically safe, it removes bacteria present in water. Even today, people are using these methods of purification.
  • Home filters (Filters in stainless steel container) : - This is another method of getting the water filtered at homes for the purpose of drinking and cooking. This method helps in removing the suspended impurities from the water.
  • Mixing alum in the water : - Alum acts as a coagulant in water, it breaks the impurities like turbidity etc. in the form of flocs & then, the water is filtered from a cloth or sieve to make it usable. It also makes the water microbiologically safe for drinking.
  • Mixing chlorine in the water : - This method helps in killing the bacteria & viruses present in water, making the water microbiologically safe for drinking. But it does not remove the other impurities present in the water.

Following is a basic description of several of the most common water treatment technologies available to produce drinking water.

Filters : Filters are water treatment systems in which suspended solids and micron particulate matters are removed through micron rating filters. The various configurations of filters are available in market and they have varying types of mechanical and chemical reduction capabilities. Most common available filters are cartridges filters of various micron rating, pressure sand filters, activated carbon filters, dual media filters, specialty filters, multi grade filters etc. The filters are most suitable for those areas where water have only suspended solids impurities. Filters can remove the suspended solids but it can not remove the biological impurities, dissolved salts and chemical impurities.

Ultra Filtration Systems : Ultra Filtration (UF) is water treatment system in which physical impurities and biological impurities are removed through UF membrane. UF systems work by using pressure to force water through a semi-permeable membrane of pore size 0.01 microns. The UF is suitable for those areas where physical and biological impurities are reported. UF can reduce the physical impurities and biological impurities but it can not remove the dissolved salts and pesticides from water.

Nano Filtration Systems : Nano Filtration (NF) is water treatment system in which physical impurities, biological impurities and hardness are removed through NF membrane. NF systems work by using pressure to force water through a semi-permeable membrane of pore size 0.001 microns. The NF is suitable for those areas where physical impurities, biological impurities and hardness are reported. NF can reduce the physical impurities, biological impurities and hardness but it can not remove the anion dissolved salts from water.

Reverse Osmosis Systems : Reverse osmosis (RO) is water treatment system in which almost all water impurities are removed through reverse osmosis membrane. Reverse osmosis systems work by using pressure to force water through a semi-permeable membrane of pore size 0.0001 microns, which is 620,000 times finer than a human hair, 10,000 smaller than a red blood cell, 2,500 times smaller than bacteria and 20 to 500 times smaller than any virus. The RO is suitable for almost all areas where water impurities are reported. RO can reduce the physical impurities, biological impurities, dissolved salts, pesticides, chemical impurities and heavy metals.

Ultraviolet Treatment Systems : Ultraviolet (UV) treatment system is water treatment system in which microorganisms are deactivated through ultraviolet light. As the efficiency of the UV system is affected by the clarity of the incoming water supply, it is important that turbid or dirty water first be treated by filtration. UV systems are most suitable for those areas where water have only biological impurities. UV systems can reduce the bacteria and viruses from water but it can not reduce the dissolved salts, heavy metals, pesticides and chemical impurities.

1 : Traditional methods for Water Treatment

Water Treatment Technology
Table 2 : Technology Used for Treatment Process

Choosing the right technology for Drinking Water Treatment
The different technologies for drinking water treatment explained above vary in their ability to handle specific types of contaminants. Some are able to remove entire impurities, while others are more useful for single tap applications.
Technology Comparison Chart

Removes Physical Impurities Removes Biological Impurities Removes Total Dissolve Salts (TDS) Removes Hardness Removes Pesticides Impurities
Filters O X X X X
Softeners O X X OO X
Ultra Filtration Systems OO O X X X
Nano Filtration Systems OO OO X OO O
Reverse Osmosis Systems OO OO OO OO OO
Distillation Systems OO OO OO OO OO
Ultraviolet Treatment Systems O OO X X X

Legend: X : No; O : Partial; OO : Yes
Reverse Osmosis (RO) is an advanced water purification technology initially used by industries located on coasts and the armed forces to purify sea water and make it drinkable. It has now been adopted for use in homes and offices to purify the increasingly polluted water in our cities. The Reverse Osmosis technology is used in areas like Healthcare and Scientific research where purity is not just important but critical. It has now been adopted for use in homes and offices to provide the same level of purity at minimal cost. 
Reverse-Osmosis (RO) was originally developed in the 1950s by the US government as an economical method of desalinating sea water. 
Reverse-Osmosis (RO) is the most efficient and effective method of water purification known to man. It uses a special, semi-permeable membrane which removes impurities as small as 0.0001 micron (i.e. 0.00000004 inches) in size, cleansing water of all biological impurities, suspended particles, dissolved solids (TDS), Salts, Metals and chemicals. Most non-RO systems can filter particles only up to 0.5-10 microns in size, leaving out almost all dissolved impurities (like bad-tasting salts) and some finer physical impurities.

How does RO Work:
When water is passed through the semi-permeable membrane under pressure, all contaminant particles larger than 0.0001 micron are captured in the layers of membrane and only the water particles, being smaller, pass through the membrane.

Filtration Stages of a common Home RO Systems : 
Filtration Stage 1 - Sediment pre-filter 5 microns that removessuspended impurities. 
Filtration Stage 2 - In Line Pre carbon pre-filter which removes chemical impurities. 
Filtration Stage 3 - In Line Sediment filter 1 micron to remove carbon particles upto 1Micron 
Filtration Stage 4 - RO membrane that removes bacteria, virus, dissolved chemicals, etc. 
Filtration Stage 5 - Post activated carbon filter and polisher that improves the taste of the water. 

What is Hard Water? 
When water is referred to as 'hard' this simply means, that it contains more minerals than ordinary water. These are especially the minerals calcium and magnesium. The degree of hardness of the water depends upon the amount of calcium and magnesium present in water. 
Hard water is water that contains invisible dissolved rock, principally calcium and magnesium minerals. Rain water begins as soft water, free of these minerals. As rain water passes over and through the earth, flowing into lakes, rivers, streams and ground water, it absorbs the hardness minerals. While some of these minerals may be harmful to your health, they do affect the properties of water and its effectiveness for washing and cleaning. Magnesium and calcium are positively charged ions. Because of their presence, other positively charged substances will dissolve less easy in hard water than in water that does not contain calcium and magnesium. This is the cause of the fact that soap doesn't really dissolve in hard water.

Hard Water Problems: 
Clothes washed in hard water often look dull and feel harsh and scratchy. The hardness minerals combine with some soils to form insoluble salts, making them difficult to remove. Soil on clothes can introduce more hardness minerals into the wash water. Continuous laundering in hard water can damage fibers and shorten the life of clothes by up to 40 percent.

Bathing with soap in hard water leaves a film of sticky soap curd on the skin. The film may prevent removal of soil and bacteria. Soap curd interferes with the return of skin to its normal, slightly acidic condition, and may lead to irritation. Soap curd on hair may make it dull, lifeless and difficult to manage.

White deposit on showers and bathroom walls
Compounds like calcium and carbonate are present in water. Carbonate works as a buffer in water and is thus a very important component.
When calcium reacts with carbonate a solid substance is formed which is called lime. This lime is what causes the white deposit on showers and bathroom walls and is commonly known as lime deposit. It can be removed by using a specially suited cleaning agent.

Problems in Water Boiler Systems and Pipe work
Hard water also contributes to inefficient and costly operation of water-using appliances. Heated hard water forms a scale of calcium and magnesium minerals (lime scale deposits) that can contribute to the inefficient operation or failure of water-using appliances. Pipes can get clogged with scale that reduces water flow and ultimately requires pipe replacement. Lime scale has been known to increase energy bills by up to 25% 
Lime scale in Solar Heating Systems 

Solar heating, often used for heating swimming pools is prone to lime scale buildup, which can reduce the efficiency of the electronic pump and therefore can lead to deterioration of the overall performance of the system. A low cost solution to this problem is to install a magnetic water conditioner before the pump which will prevent limescale to build up and over a period of time will also remove existing limescale

What is water softening?
Water softening is a technique that serves the removal of the ions that cause the water to be hard, in most cases calcium and magnesium ions. Iron ions may also be removed during softening. The best way to soften water is to use a water softener unit and connect it directly to the water supply.
Softening water is a 4-step process:

  • The body of a water softener is a tank filled with resin beads. These beads are covered with sodium ions. As hard water passes through, the resin beads act like a magnet, attracting the calcium and magnesium ions(hardness) in exchange for the sodium ions.
  • Eventually the resin beads become saturated with mineral ions and have to be “re-charged.” This process is called regeneration, and is conducted by the control valve on the top of the tank. The control valve is the brain of the system.
  • During regeneration, a strong brine solution is flushed through the resin tank,bathing the resin beads in a stream of sodium ions which replace the accumulated calcium and magnesium ions (hardness).
  • The brine solution, carrying the displaced calcium and magnesium ions, is then flushed down the drain by fresh water. The regenerated resin beads can beused again and again.

The two crucial components of a softening system are the resin tank and the control valve. Pentair softeners consist of special STRUCTURAL tanks made in their Goa factory, out of the world class fibre reinforced plastic to ensure strength and durability. FLECK automatic multiport valves ensure that the operating system is fully automated. The consumer therefore needs to add salt at a prefixed interval and the Fleck valve ensures that the resin regeneration happens automatically – a huge move-on from the manually charged home water softeners.

  • What is Reverse Osmosis?
  • Reverse Osmosis is the reversal of the natural flow of osmosis. In a water purification system, the goal is not to dilute the salt solution, but to separate the pure water from the salt and other contaminants. When the natural osmotic flow is reversed, water from the salt solution is forced through the membrane in the opposite direction by application of pressure-thus the term REVERSE OSMOSIS. Through this process, we are able to produce pure water by screening out the salts and other contaminants.
  •  How does R.O. work?
  •  What impurities are removed by RO?
  •  Does RO remove any useful minerals, if so why should I purchase RO?
  •  Does RO kills or remove bacteria & viruses present in water?
  •  How does it differ from my existing water purifier or Aquagaurd?
  •  What is the difference between your RO and other competitors?
  •  Is RO water is equivalent to distilled water?
  •  Why RO water is called mineral water?
  •  How can I know whether my requirement is RO?
  •  Why we require pressure for RO operation?
  •  Can a RO work on borewell water?
  •  Can RO work if there is lots of sand Iron in my water?
  •  Does RO system provides best of the drinking water, if yes why corporation supply is not equivalent?
  •  What does G.P.D. Stands for?
  •  Why should I go for your 75 or 50-G.P.D. RO, if my daily requirement is only 5-6 gallons?
  •  Will RO prevent scaling in my coffeepots, etc.?
  •  Do your system take care of pesticides and Arsenic, Lead etc.?
  •  How can I know my drinking water is safe after getting your system installed?
  •  For how long RO water is safe in the storage tank?
  •  What is the running cost of a RO system?
  •  What are the AMC charges for RO system?
  •  Why your RO system is costly than others?
  •  Why cartridges require replacement, can they be cleaned & refitted?
  •  What is the life of membrane & if it goes wrong prematurely, will it be replaced FOC?
  •  Other competitors are covering all consumables under warranty, why not you?
  •  For how long I can run this system?
  •  How much chlorine should be there in feed water, which will not harm membrane?
  •  What are the feed limiting conditions for RO system?
  •  What is the power consumption for RO system?
  •  How can I get water during power failure?
  •  Can I service RO system on my own?
  •  Can one RO be connected to multiple points i.e. to refrigerator, and to kitchen?
  •  How can I get service if I am transferred to any other place?
  •  What is the maximum & minimum time for complaint attending?
  •  Do you have any finance scheme for RO Systems?
  •  I have water softener installed at my residence, still I require RO?
  •  Can this system be installed to direct supply line of corporation?
  •  Why it is necessary to install RO system to overhead tank supply. We hardly get it cleaned?
  •  Can this system be installed if my storage tank is just 2 meters above the ground?
  •  How can I use the rejected water?
  •  What impurities are removed by RO?