18 May, 2007, 14:36 pm IST
Also check for lead, bacteria, pesticides etc. If water has a strong chlorine odour, check for chloroform. Here are some tips to buying the right water purifier for yourself.
You may already have a budget in mind as to how much you would like to spend. Water Purifiers can cost you as little as Rs 1,800 and as steep as Rs 45,000. Naturally the lower end is the most basic one and the higher you go, the more features you have such as display panels, rechargeable batteries, more purification stages, higher flow rate and so on.
There are two types of water purifiers available: the storage type and the direct flow type.
This requires you to fill the container and later use the water. This is very useful if you're facing water shortage.
This is the more common type found in most homes. Here you fit the purifier directly to the tap. The advantage of this is you don’t have the hassle of storing water. Disadvantage is that it may not be too useful if you have frequent water cuts.
Every purifier has a maximum flow rate which if exceeded, will allow bacteria to pass through the system, so be careful to choose a UV that is adequate for the home in which it's being installed. Look for a filter that flows at a litre per minute or more.
The weight of your water filter is important, especially if you plan on moving it from one place to other.
Check if the body of the water purifier is durable, rust proof and attractive. There are different materials available such as Aluminium and ABS Plastic available.
Different water purifiers use different methods of purification, some have three purification stages and some five or more. A higher number of purification levels ensure cleaner drinking water. Its necessary to know about what each stage does and then choose the purifier you think is the best for your home.
Few of the purification stages include:
A micron pre-filter is designed to remove silt, dust and dirt particles from the water before it enters the main filter of the unit.
There is a special multi layer micro porous candle filter to remove all suspended impurities.
The health cartridge contains special imported resin that disinfects the water from disease causing bacteria and viruses, thus making it hygienically clean. The taste cartridge contains ion exchange resin mixed with silver impregnated activated carbon, which absorbs from water, elements such as excess chlorine and impurities like pesticides, herbicides, which impart bad odour, taste and colour to the water.
Reverse osmosis separation technology is used to remove dissolved impurities from water through the use of a semi-permeable membrane. It involves the reversal of flow through a membrane from a high salinity solution to the high purity, or permeate stream on the opposite side of the membrane. Pressure is used as the driving force for the separation. This means that through the reversal flow RO removes not only impurities, it also desalinises the water. So, for those living in areas where the water is hard, a water purifier with RO is a must. It will save the expense of spending on mineral water on a daily basis.
Ultrafiltration removes dissolved solids of and above the size 0.005-0.1 microns. It is capable of removing solids, bacteria and viruses. Ultrafiltration purifier is recommended for the areas where TDS level is below 500 mg/ltr; it’s especially useful for areas having irregular electricity supply, given that it works without electricity. It requires low maintenance; and life span of its purification membranes is long. Ultrafiltrarition does not reduce TDS of water considerably. It is usually used in large water treatment plants; its presence in domestic water purification is quite limited. But ever since BARC (Bhahbha Atomic Research Centre) India developed "on-line domestic water purification device" which is based on polysulfone type of ultrafiltration membrane, and passed the know-how to different Indian firms, Ultrafiltration system is fast gaining acceptance as the preferred solution.
Nanofiltration removes dissolved solids of and above the size of 0.0009-0.007 microns. It is capable of removing solids, bacteria and viruses. Nanofiltration purifier removes around 50-60 percent of solids. So if water has high TDS (Total Dissolved Solids) levels (say more than 500 mg/Ltr) then reverse osmosis is advisable, while ultrafiltration is suitable for area having TDS (Total Dissolved Solids) level in region of 300-400 mg/Ltr as it retains 50 percent of minerals, Nanofiltration is usually used in large water plants or liquid treatment plants. Its presence in domestic water purification is limited.
Storage purifiers are affordable (around Rs 1,800) water purification solutions, as they operate without electricity, are easy to operate and low on maintenance, are easily available and don’t need running water to operate. They appear like traditional water filters, fitted with purification cartridge with multi-stage purification - pre-filter purification, activated carbon purification, bacteria disinfectant and water polisher/taste improver. Though these are mass products and available at an affordable price range, they not very effective when it comes to water with high TDS (Total Dissolved Solids) level and smelly water with high contamination. These water purifiers are suitable for areas which receive water from open source, having lesser degree of contamination and with potable water taste.