Is the water you are drinking safe? Most people would think so, especially if you have installed a special purifier. But research conducted by consumer rights organisations claim safe water is just a myth propagated by water purifier companies.

“A lot of tall claims are made by water purifier companies,” says V. Suresh Babu, co-ordinator, river pollution, Centre for Science and Environment, a nongovernmental body based in New Delhi. “It is wrong to think that water purifiers can remove all contaminants. Research conducted by us indicate that even the most advanced form of purifiers cannot completely remove harmful pesticides such as lindane, malathion, solvents and other volatile organic compounds,” says Babu.

Most purifiers, except the ones that use ceramic candle filters, remove impurities only up to a certain level, he says. Experts recommend boiling water as a viable option. “For most middle-class people, buying an expensive water purifier is a difficult proposition. Boiling water is the safest and cheapest option. Though most of these new-fangled devices tend to remove contaminants, they also remove some essential minerals,” says Dr Ramananda Biswas of the All India Institute of Hygiene and Public Health, Calcutta.

For those who want to look beyond the simple method of boiling water, a host of options exist. So how does one make the right choice? In the first place, weigh company claims carefully, warns Roopa Vajpayee, honorary editor of Consumer Voice, an online consumer awareness magazine. “One should not be swayed by the marketing pitch of a water purification technology because chances are that a salesman will try to sell a technology which carries higher commission margins for him. Instead, you should be discerning enough to opt for a technology that is tailor-made for you. Also, it is important to spare a thought for the maintenance and replacement expenses.”

According to her, it is important to first define the safe water needs by finding out the water quality in an area where one lives. If the water is hard (salty in taste), it is better to opt for a reverse osmosis (RO) system. If the source of water is the municipal corporation, an ultraviolet (UV) candle filter will work just fine.

Most water purifiers today offer two or more treatment processes such as RO, UV, filtration and disinfection technologies. A recent market study conducted by Frost and Sullivan, the US-based consultancy firm, reveals that of the Rs 1,000-crore water purification market in India, 51 per cent purifiers in India are UV-based, while 42 per cent are based on RO. The rest are made of candle and resin filters. This contrasts with the global trend where RO-based systems have just 11 per cent of market share, making UV water filters the unanimous choice of people around the world.

S.K. Palekar, senior vice- president (marketing), Eureka Forbes, says their UV purifiers remove bacteria and viruses in three stages. Ceramic candles remove the physical impurities and the carbon filament is then used to remove toxic and organic chemicals. The last stage of the purification process involves using UV rays to kill bacteria and viruses.

“Our system works fine in an area where people get surface water, which is likely to have suspended solids and bacterial contamination. Such types of water generally have a total dissolved solid (TDS) between 750 and 1500, which our system can bring down to less than 200,” he says.

A K. Sengupta, national professional officer, World Health Organisation (WHO), India, says TDS of less than 500 is not harmful to human health. “However, there are places in Rajasthan where the TDS level is around 1,000 to 1,500. Here, too, we have seen people living a perfectly healthy life. So it is difficult to pinpoint any optimum level. It depends on the region a person lives in,” he says.

Sharada Prasad, customer marketing manager, water and air, Philips Consumer Lifestyle, says their intelligent UV system of water purifiers come with a pure protect lock that guarantees high quality of dispensed water. “If the filter is not replaced on time (within 3,000 litres of consumption), the purifier will be locked so that no more water can be dispensed,” she says. This water purifier also works on battery.

The UV system, though the most popular in India, has some disadvantages, points out Babu. “The system’s efficacy depends on the resistance of an organism. If the energy dose is not high enough, an organism’s genetic material might only be damaged — and not disrupted. This means the organism would remain and can regenerate in suitable conditions. UV light is also not effective against soluble salts, pesticides, heavy metals, organic chemicals and chlorine,” he says.

The UV system has some advantages as well. It does not introduce any toxic or significant non-toxic byproducts. It does not alter the smell or taste of treated water. In fact, it actually improves the taste of water by destroying organic contaminants. It also cleanses in seconds (chemical disinfection takes several minutes).

Another popular mode of water filtration system is the RO filter. This form of filtration process uses pressure to force water through a membrane that retains the contaminants on one side and allows pure water to pass to the other side. RO purification units involve two processes. The unit consists of two filters: a carbon sediment filter and a semi-permeable membrane. The first removes large particles from the water before it passes through the semi-permeable membrane.

Babu says though marketing gimmicks have created the impression that RO systems can completely remove pesticides and volatile organic compounds, that is actually not the case. Another drawback of the RO filters is the sheer wastage of water. The rejection rate of water can go up to 60 per cent. Only 40 per cent is the actual output, he says.

Vikash Arora, regional manager, Mumbai, Kent RO system, admits that the wastage of water is more in RO purifiers, but adds, “It is better to drink good water than bad water.” He claims their purifiers now come with double protection. Besides the RO system, Kent purifiers are now fitted with an additional UV chamber which helps in removing impurities from water. He, however, says the membrane has to be changed every two years at a cost of Rs 200. Kent purifiers are priced at Rs 16,000.

“A point of concern with the RO technology is that it reduces the pH (the measure of acidity or alkalinity of a solution) levels of water. The pH level of water should ideally be between 6.5 and 8.5 (as prescribed by the Bureau of Indian Standards). However, RO purifiers are known to reduce pH by 2-3 units, depending upon the salt constitution of water. This is worrisome as low pH levels mean that water is acidic. Consumption of acidic water can cause imbalances in the body,” says Vajpayee.

Though both RO and UV systems need annual maintenance, the expense on RO is higher, ranging between Rs 1,200 and Rs 3,600 annually. In comparison, the maintenance charges for UV purifiers are around Rs 900. At the lower end of the spectrum are those which work on the principle of chlorine technology. These systems do not require running water or electricity and are priced at Rs 1,800. Though these types of purifiers do not require any maintenance, they will not work in an area where the water is hard, feel experts.

The third edition of WHO’s guidelines for drinking water quality (Geneva, October 2003), says conventional technologies such as activated carbon (positively charged carbon is used to draw molecules from dissolved contaminants) and ozonation (passing ozone through water to oxidise pollutants) are most suitable for removing pesticides and other organic chemicals. The guidelines state that activated carbon is most effective in removing pesticides. WHO has ranked water purifiers according to their complexity and economics. Activated carbon and ion exchange rank the highest, while RO treatment is deemed the most complex.

“The problem with Indian water purifiers is that you cannot measure them against any standard. The last standard was revised by the Bureau of Indian Standards almost 17 years ago,” says Sengupta.

So what technology should one opt for? An integration of technologies is the best in dealing with the complex pollutant matrix. “Some high-end purifiers use a combination of technologies to remove impurities which may be beyond the pale of either the RO, UV or candle filter purifiers. Ideally, one should opt for these products to get the maximum benefit,” he adds.