Know Your Water Purifier
Accessibility to safe drinking water is the main challenge that the world is facing now.For those living in remote communities where the availability of improved water sources is limited, challenges can be immense and impact the quality of life in significant ways.
Water purifiers help us to ensure that the water we drink are safe and does not contain any contaminants.
Types of water Purifiers
Major cartridges and components used in water purification systems
- Pre-Sediment filter
- Anti Scalant filter
- Sediment filter
- Pre-carbon filter
- RO filter
- Ultra-filtration cartridge
- Post carbon
- Ultra Violet
- Re-mineralizer cartridges
- Nano filter (NF)
- TDS controller
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RO Water Purifiers
Reverse-osmosis( RO) is the most effective way of purifying water since it removes almost any kind of dissolved or suspended impurities.
What is osmosis
a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.
What is reverse osmosis
a process by which a solvent passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure.
- It removes dissolved impurities from water. Eg: Lead, Mercury, Arsenic, Fluoride, Chlorine etc.
- Suitable for hard water.
- All dissolved and suspended particles in water are removed.
- Low-pressure RO requires no electricity (less efficient)
- It removes essential minerals too along with impurities rendering the water tasteless.Eg: Iron, Magnesium, Calcium, Sodium etc.
- A large quantity of water is wasted to produce potable water
- The membrane is vulnerable to sediments and bacteria which can grow on its surface
- Requires electricity for high inlet pressure. (more efficient)
- Chlorine needs to be removed using activated carbon filter to enhance the life of RO membranes
- Not effective in removing Synthetic organic chemicals as well as Volatile organic chemicals. Activated carbon filtration is preferred for organic contaminants
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Gravity Based Water Purifier.
As the name indicate Gravity Based Water Purifiers filter water based on natural force of gravity i.e. the water is allowed to flow over the filters from a higher chamber to a lower chamber. Some under sink systems also uses the natural flow that occurs when a faucet is opened to draw water through the filtration system. Gravity based purifiers can be used only when TDS value is not so high and are not as effective as RO purifiers.
Few gravity purifiers available are chemical based, and few are UF based and some are ceramic cartridge based. These may work in cases like, “something is better than nothing” and can be used only for municipally supplied water.
Stages of filtration
- Sediment filter.
- Carbon filter.
- Ultrafilter(UF) or Microfilter.
- Pellets to de activate virus and bacterias.
- Low cost, can Range from Rs. 1000 – 5000.
- Do not require Electricity for filtering.
- Higher water storage capacity around 7-20 litres.
- Filters are of low cost so easy maintenance.
- Portable and easy to use.
- Can clean muddy water.
- Efficient for Soft-water.
- can only be used for low TDS
- Table mount option only
- Germ kill kits along with the purifies are not effective and uses chemical agents for disinfection
- Cannot fully remove Germs and various micro-organisms.
- Live water feeding from plumping is not available
- They cannot filter dissolved heavy metal contaminants like arsenic, mercury nitrates etc.
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In UF Water purifiers, water is filtered through an ultra-filtration membrane where suspended particles whose size is bigger than the pores of the membrane are removed. This purification technique is ideal for those places where inlet water does not contain any dissolved chemical impurities.
- Physically removes suspended particles including germs as well as their eggs(cysts).
- Does not require electricity
- Does not require periodic maintenance
- Durable and fail- safe membrane
- Does not remove dissolved solids from water
- Ineffective against the contaminants whose size is smaller than the pores of the membrane.
An interesting article about ultrafiltration based filters
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UV Water purifier
UV purification technology uses ultraviolet Rays to kill germs and viruses present in water. It does not use any chemical to disinfect microorganisms and doesn’t add any odor to the water. This is the best method to disinfect bacteria from water and make water free from viruses causing diseases like cholera, dysentery, and typhoid.
They neither remove any dissolved or suspended particles from water nor do they alters the pH value of water.
- water with very low dissolved impurity(TDS level less than 500 mg/ltr)
- Water with high amount of virus,bacteria and germs
- tap water (open source) that we receive from municipal corporation; the water which is generally pre-treated and tastes unobjectionable.
- Sediment Filter
- Activated Carbon Filter
- UV Disinfection
- Cost effective and inexpensive require less maintenance just changes UV bulb when it stops working..
- Disinfects viruses, bacteria, and germs from the water.
- No water wastage.
- The chemical composition of water is not altered.
- Purification is done instantly, thus it requires no storage.
- Simple, clean and environment-friendly technique to kill germs and viruses.
- Requires very little amount of energy to work around 40 watts of energy same as used by tube lights.
- Compatible with all kind of water purification technologies like Reverse Osmosis, Ultrafiltration, water softening.
- very effective compared to chlorination
- Requires Electricity to clean water.
- Do not remove dissolved impurities like fluoride, arsenic, lead, nitrates.
- Ultra Violet Rays only kills(disinfect) disease-causing bacteria and germs, but it does not remove their bodies from the water.
- UV purifier cannot remove hardness from water.
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Major cartridges and components used in water purification systems
Pre-sediment filters are used to get rid of large solid particles like mud and dirt. Since they require frequent cleaning and replacement of filter, they are usually placed outside the casing of the purifier unit. It can also be opened and cleaned. It is mainly used to enhance the life of cartridges placed inside the purifier unit.
Anti Scalant filter
Antiscalant is a pretreatment to water that is highly effective in preventing the membranes and other parts from scaling. Water is passed through the anti scalent filter before it enters the reverse osmosis membrane.
It has smaller pores than the pre-sediment filter. It filters even finer particles(5𝛍m) that pass through the pre-sediment filter. Sediment Filter will usually last approx. 4-6 months, depending on the micron size.
Pre-carbon filter uses blocks of carbon to remove contaminants and impurities by chemical adsorption. As water is forced through the micro pores of the carbon filter, organics in the water adhere, or “hang on” to (or molecularly bond with) the carbon. It removes organic compounds like harmful pesticides and excess chlorine from water. It also adsorbs odor producing organics and improves the taste of water.
They are placed before RO filter mainly to prevent chlorine entering into RO filter because getting chlorine deposited over RO membrane will eventually lead to membrane fouling.
RO filter is the most effective filter cartridge in the purifying system since it removes almost any kind of dissolved or suspended impurities. Most of the RO system requires electricity since the high inlet pressure is achieved using pressure-boost pumps. Pure RO purified water is demineralized making it tasteless. Minerals are usually added as a post treatment using mineral cartridges.
Ultrafiltration is a type membrane filtration in which hydrostatic pressure forces a liquid against a thin layer of semipermeable membrane similar to RO filter which helps in the removal of microorganisms, particulate and organic substances effectively from water. All substances which contribute the color, taste and odor of water can easily be removed from water using a UF membrane.
The big advantage of UF water purifiers is that it will work without electricity and completely remove all microorganisms from water including the smallest of viruses but it cannot remove dissolved solids from water.
Post carbon uses granules of activated carbon to remove contaminants and impurities, using chemical adsorption.This is the most effective filter at removing chlorine, sediment, volatile organic compounds (VOCs), bad taste and odor from water.
They are not effective at removing minerals, salts, and dissolved inorganic compounds. Many carbon filters also use secondary media such as activated nano silver to prevent bacteria growth within the filter. Post carbon is placed before UV filter to prevent the Chlorine entering into uv chamber
UV purification technology uses ultraviolet rays that are allowed to pass through water so as to kill germs and viruses present in water. It does not use any chemical to disinfect microorganisms also don’t add odour and smell to the water. This is the best method to disinfect bacteria from water and make water free from viruses causing diseases like cholera, dysentery, and typhoid. They do not remove dissolved salts that are important for the body as well they do not make water acidic in nature like RO filter.
(Antioxidant filter, Mineraliser, Ph cartridge)
The pH of water that is passed through RO system is slightly acidic in nature and might not be ideal for health. therefore an antioxidant or mineralizer or ph cartridge is added as a post treatment method.
Antioxidant filters makes water more alkaline by increasing the pH of the filtered water and gives it antioxidant properties that remove the harmful active oxygen (free radicals) which causes cancer, diabetes, hypertension etc.
It also facilitates the nutrients and mineral absorptions that makes the water taste better and reduces the size of the clusters of water molecules so that the water is more easily absorbed in the body.
But, if we are using a TDS regulator then a portion of the water is being bypassed without RO filtration so that the complete removal of minerals and the alkalinity is prevented and there is no need to have an additional Re mineraliser system.It is advised to to buy purifier with any of these cartridges if user want 100% RO purified water.
Nanofiltration is a pressure-driven, membrane-based separation process whose characteristics fall between those of ultrafiltration(UF) and reverse osmosis(RO).The filters has a pore size of approximately 0.001 micron (1 nm) and removes particles based on molecule size, weight, and charge; NF membranes are applied for the removal of natural organic matter, especially tastes, odours and colours, and in the removal of trace herbicides and residual quantities of disinfectants in drinking water.
TDS controller allows the users to adjust the TDS level of the purified water.TDS controller works by bypassing a percentage of water without RO filtration.Even though TDS controler will prevent the water running low on minerals it adds harmful toxic solids from the bypassed water along with the minerals.
This approach is mainly used in water purifiers using RO+uv or RO+UV+UF filtration technique.
In RO + UV, the bypassed water passes without any secondary filter cartridge but in RO+UV+UF the bypassed water passes through UF filter to ensure the water safe to drink.But still the particles with size less than UF pores can reaches final drinking water along with minerals.
RO+UV+UF with TDS controller
RO+UV with TDS controller