If you are looking to buy a home or domestic water purifier/filter, read on :
Our Aquaguard was very old and needed replacement. As a matter of details, on most days we used to run the Aquaguard twice a day – storing treated water in a 10 Liter stainless-steel tank with a lid. We had an arrangement whereby on switching on the Aquguard unit, the output water directly flowed into SS tank. When the tank became full we had to switch off the unit. That meant one of us had to stand near the unit, till the tank gets filled. Our source of water supply was BMC supplied water. Question arose, which purifier should we buy. On & off we had been reading that UV is not a fully satisfactory method of disinfecting water:
that it did not really kill the bacteria, it only deactivated bacteria which gets activated in a few hours in the conducive environment. If this is so, where the treated water is stored for consumption during the day, this method may not be ideal solution for getting completelysafe drinking water.
That UV does not always penetrate the hard protective shell of CYST (Egg) of diseases causing bacteria & viruses. These become activated once in the stomach, where most conducive environment is available for their growth.
that UV penetrated the flowing water stream only to some depth, and part of the water did remain untreated or unaffected.
To add to this, we were never really satisfied with the level of service for our Aquaguard. Questions to the servicing technicians, like, how are you cleaning the Quartz tube surface, how are you cleaning the scales which get formed over the years, always remained unanswered. This obviously meant that disinfection treatment our drinking water was suppose to be subjected to was partly in our mind only. Either our strong ‘Indian’ immunity or God was protecting us all these years when we were gleefully drinking our Aquaguard out-put.
A question always baffled me; what happens to all the debris of killed bacteria & viruses? Are they not harmful in any way when we keep drinking millions of them every time we take a glass of water?
Add to this, I use to find the AMC charges for our Aquaguard most unreasonable. Consider this: Tata Motors for their Nano car was offering AMC charges which was merely twice that of Aquguard!!!
With all these at the back of my mind, we started our search for a water purifier, which will meet the following requirement:
It should deliver pure drinking water free of suspended impurities, and 100 % free of bacteria, Cysts, Spores, & Viruses. If the debris can also be removed, better.
The process should not introduce any chemicals to the water in the process of purification.
The unit needed to have auto start & stop facility to avoid overflow. This was one of the major irritant in our house as often the SS tank will overflow onto Kitchen platform, & in the busy hours of early morning, we will need to clean up the mess.
Its recurring cost should be reasonable considering the cost of Parts & labour involved.
Initial cost was not so much of consideration. We were prepared to spend, of-course within reasonable limits, whatever it took to get a pure drinking water.
This article clearly stated : Most water purifiers don’t remove viruses:
Umesh Isalkar, TNNSep 17, 2010, 01.08am IST
PUNE: Despite loud promises that these gadgets suck out disease-causing bugs from drinking water, most purifiers sold across India do not completely eliminate water-borne viruses like Hepatitis E, says Pune-based National Institute of Virology.
A study by the government-funded body that conducts research on communicable diseases and viruses evaluated eight domestic water purifier brands. It found only two – one equipped with a hollow fibre membrane and the other with a gravity-fed filter – could completely remove the viruses.
Note: (Size of hepatits A Virus is 28 Nm 0.028 micron, that of Hepatitis B Virus is 40 Nm or 0.04 Micron , Hepatits C virus is 30 to 60 Nm or 0.03 to 0.06 Micron & that of Hepatits E virus is 34 Nm or 0.034 Micron).
These were amongst the first two sites we came across, and only UV based purifier almost became out of race for us.
Thus, purely UV based purifier was ruled out. Next, though we knew that Reverse Osmosis based purifier is really not required when the source of supply is Municipal Water, having ruled out pure UV based purifier, we did not see an alternative at this stage.
So, we tried to study how does RO+UV system from Kent works. We came across following water flow diagram on the website of Kent:
On inquiry, we realized that water recovery is around 25 % of total inlet water quantity. This means, to get 20 litres of drinking water, system will use more than 80 litres of water, throwing out 60 litres as rejected water. This looked a criminal waste of water, particularly when RO is not really required as our water is from Municipality
Municipal Water supply has acceptable level of dissolved solids, & these are not only acceptable level, but are most essential for health. As these are essential minerals, above system of UV + RO system tries to add some of it back into purified water.
In addition, above water flow diagram raised several questions as follows:
How a part of water is going through UF while another part is bypassing UF, going to TDS controller directly? Does this mean, that either way it is OK: if water passes thorough UF or does not pass through. How can this be OK? Either all water should pass through or none. So, this looked like some kind of gimmick alright.
How does TDS Controller work? How can it RETAIN after they have been removed? Inquiry with KENT did not produce any convincing reply. One sales Rep. stated, that it is patented process & they can not reveal how it works. Another stated that a small quantity of source water is added back at TDS controller to create proper balance of essential dissolved solids. Nobody at KENT was willing to come clean if chemicals are not added, then how essential salts & minerals are ‘ retained’ when they have been already removed? And if chemicals are added, which chemicals & how. And, how often this will have to be replenished? Entire series of conflicting answers created more questions than clarity.
At this stage, we decided to give a skip to RO based purifier, as it was really a waste of money & water as far our need was concerned.
So we started the search all over again – which is the best, most sensible (without getting taken in by advertisements & popular beliefs) & operationally economical (without compromising the ultimate goal even wee bit) Water Purifier to purchase?
On further investigation, we came across a model SMART, offered by KENT, which worked on the basis of Ultra Filtration (no sales executive of KENT was very pleased or forthcoming to talk about SMART model as it cost only fraction of UV or UV+RO model – hardly a welcome buy contributing hardly to the monthly Sales Target!!!, & cost of regular maintenance too is a small fraction of other model.
We discovered that ultra filtration actually employs a membrane based filter with Pore size of 0.01 Micron (Micro meter = 10-6 meter), & manufacturers made claims that it will filter out all known – even smallest of Bacteria & Viruses. So we embarked on to find out what is the size of Bacteria & Viruses.
(OR fear inspired from self doubts generated because of popular belief or misleading advertisement)
However, doubt persisted. What if we are missing something & we opt out of UV based purifier, & merrily drink contaminated water? So we decided to talk to Bacteriology department of Hafkin Institute. We talked to department of Bacteriology at Hafkin to find out if our thinking had a fundamental flaw. The experts at the department not only confirmed all our findings so far, but further advised that some people are indeed allergic to debris of dead Bacteria & Viruses. However, they cautioned us, that the Ultra filtration unit we buy should be based on membrane made out of Polysulfon. They further informed that BARC had developed a technology for Ultra Filtration of Water for domestic & Industrial application, & if we find a unit based on this technology, it will serve our purpose ideally.
This is a method of complete purification whereby not even bacterial debris remain in the water. This process can be compared to the natural purification process occurring in plant tissues whereby plants absorb purified water from dirty subsoil water with the aid of their natural cell membranes. On comparison, these filters prove to be the best to combat the influx of waterborne, illness causing pathogens.
This settled that nagging self doubt, & we confidently decided to go ahead & buy ploysulfon membrane based ultra filtration unit. Now the question was which company makes this?
So we visited the BARC (Bhabha Atomic Research Center) website to know more about this technology, & to find put which companies are manufacturing unit based on their technology. For benefit of general readers, we give bellow extracts of relevant part of the write-up from the website.
BARC Technology & Salient Features of Unit based on this technology:
Ultrafiltration (UF) refers to the separation of species through membranes on size exclusion principle. It differs from micro filtration with reference to the size of the species being separated. Ultrafiltration membranes are thin polymeric film having pores of the sizes 2 nm to 100nm, operate at relatively low pressure (< 5 bar) and separate the micro species based on size exclusion principle.
BARC has developed and deployed various types of membranes and membrane devices for wide range of water related applications and already transferred the know-how of online domestic water purifier based on ultrafiltration polysulfone membrane to a number of private companies who have successfully commercialised the product in market under different brand names. These domestic water purifiers are of low capacity, zero operating cost gadgets meant to satisfy the need of safe water for small families.
BARC presents the technology for producing Back-washable Spiral Ultrafiltration Membrane Element for water purification (for removal of bacterial & colloidal species) for large capacities, communities and industrial water treatment. At present single unit devices with capacity range from about 0.5 LPM to 4 LPM per unit have been demonstrated, which can be deployed in multiple units for any desired capacity.
Backwashable spiral ultrafiltration (UF) membrane element consists of Polysulphone membrane wound in spiral configuration for compactness. The unit can produce purified water with respect to microorganisms, suspended solids and colloids. The special feature is the backwashability of the UF element to restore its stabilized pure water flux. It removes bacteria and turbidity and produces crystal clear water. These units can be used for domestic as well as industrial purposes. Salient features of Back-washable spiral UF Units
Crystal clear water free from turbidity, bio-contaminants, colloidal species.
Compact and delivers stable output quality.
Ensures continuous operation with less footprint area.
Very low operating pressure of about 2-3 Bar, back washable pressure up to 2 Bar.
Cross flow mode of operation preferred for higher turbidity feed of >10 NTU.
Eco-friendly as no chemicals are used (other than for need based cleaning).
Adaptable for high turbidity industrial water (with changes in operating parameters).
We began with making inquiries at KENT to find out what was the material of construction of the Hollow Fibre for their model SMART (Ultrafiltration based water purifier from KENT).Telephonic inquiries with KENT did not produce any satisfactory replies. So we sent them emails to
Mail to their sales office bounced, while mails to service department, inspite of two reminders remained unanswered. However, we carried out our own inquiries to find out performance of KENT’s Hollow Fibre based Ultrafiltration unit.
So we decided to once again concentrate on the unit based on B A R C technology of Spiral configuration of polysulfon membrane. We finally landed on Permionics (www.permionics.com) and sent them the mail to know detail of the technology they are using and technical specifications. The company is based in Vadodara (Gujarat), and with our experience with KENT, we were not very hopeful of receiving prompt reply. To our surprise, they were not only prompt (within less than 18 hours they replied to our mail), but they replied to each of our point very patiently. And, we saw the light at the end of the tunnel. Permionics, not only manufactured purifier based on Polysulfon membrane in spiral configuration with uniform pore size of 0.01 micron, but they seemed to have been manufacturing the same for more than 10 years, and to top it all they seemed to be responsive to customer’s questions. Here, the process of Purification is as follows:
The first stage is the Filter Cartridge which removes suspended matter from feed water
The second stage is the Ultra-filtration membrane which removes all colloidal matter and disease causing micro organisms
The third stage is the Bacteriostatic Silver Impregnated Activated Carbon to prevent microbial growth at point of use, to remove colour & odour and restore the natural taste of water
It is operated through a float control valve, eliminating need to operate it on regular basis. Fresh water is replenished as soon as water level falls bellow certain level. Flushing can be done once in one to two days to ensure long life for the membranes. The company indicates that the life of the membrane will be at-least two to three years. However, inquiries with users in Mumbai show that if flushing is done regularly – preferably daily, then life of membranes can be as long as 5 to 7 years. A new membrane replacement costs Rs. 1800/-
Which means, our last criteria of reasonable maintenance cost (against exorbitant AMC charges for UV/ RO/UV+RO purifier is also satisfied.
Hazards of Purifier using Chemicals in the process of Purification:
Chemical in water purifiers harmful’
TNN Dec 24, 2010, 04.51am IST
CHENNAI: Most of the storage water purifiers sold in the country use a chemical usually used to sanitise swimming pools, according to consumer activist Bejon Misra. Misra, who is also founder of Healthy You Foundation, was releasing his book titled Safety issues concerning storage water purifiers’ here on Thursday.
Virtually none of the storage water purifiers in the country conform to international standards, he added. “Most of the storage purifiers use trichloroisocyanuric acid, a chemical used to sanitise swimming pools. It poses severe health hazards. Health and safety is compromised for commercial gains. A study by Healthy You Foundation had come out with evidence that leading storage water purifier manufacturers do not declare that they use the chemical to treat water. The government is yet to implement any standard for water purifiers in the country,” he said.
This was not so much of our concern, as we were clear from the start. We will not be buying any purifier which introduces chemicals as a part of the process.