What kind of water purification system do you need? The many kinds of water filters and processes available don’t make the choice easier. And then the common question: How do modern purifiers compare with the old candle-based filter or is good old boiled water your best bet? “Expensive is not necessarily the best. And not at all in the case of water filters,” says S.K. Virmani, manager, National Consumer Helpline.
Consumer Voice, a voluntary organization that tests products to ascertain their quality for consumers, says that it is critical for buyers to first establish the water quality in their area before deciding on the filter. A recent study of nine brands of water purifiers by Consumer Voice in accredited laboratories has shown interesting results.
Out of the nine—which include both reverse osmosis (RO) and ultraviolet (UV) purifiers—most not only remove bacteria and viruses but also heavy metals, pesticides and dissolved solids.
Experts, however, say that boiling water is a viable option. “One of the selling points of RO systems is that they remove the hardness of water.
Boiling the water also solves the problem since any process just needs to remove the calcium and magnesium from it,” says R.K. Srinivasan of Centre for Science and Environment, New Delhi.
Srinivasan says that consumers need to first find out their source of water. For instance, if your water source is groundwater (own borewell, municipality-supplied groundwater), then chances are the water will be highly saline with contaminants such as nitrates, fluorides and arsenic. Such contaminants need specialized treatment.
On the other hand, if you are supplied with surface water, it is more likely to have a higher percentage of suspended solids and bacterial contamination, in which case, boiling the water or the cheaper option of candle filters will work fine.
RO and UV filters work quite differently. An RO system passes water through a specialized membrane under pressure, whereas a UV filter uses UV light to kill bacteria and germs. RO filters, however, remove most of the useful minerals from water as well.
Consumer Voice says the normal ceramic candle filters are a cheap and effective option for water filtration.
“If you are looking for a water filter that is low-maintenance and does not consume electricity, ceramic candle filters are a good buy,” says Virmani.
Even though national standards do not require candle filters to reduce pesticide content, all tested candle filters removed most common pesticides, according to the Consumer Voice report. It adds that while RO and UV filters remove pesticides up to 99%, a candle water filter’s efficiency ranges from 53% to 99%. They also remove chlorine and E. coli bacteria up to 99%.
On drawbacks, the downside of RO filters is the sheer wastage of water. “The rejection rate of water in an RO system can go up to 60%. Only 40% is the actual output,” says Srinivasan.
On the other hand, while UV filters remove most bacteria and viruses, in situations of high percentage of suspended material in water, the bacteria might not be killed. And in the case of candle filters, the rate of filtration per hour is nowhere near the national standard, adds Virmani.
A ceramic candle filter’s main task is to remove bacteria and pathogens, a task that is fulfilled by most kinds of filters. Reports suggest that the efficiency of candle filters in removing pesticides ranges from 53% to 99%. Candle filters remove chlorine and E. coli bacteria by up to 99%.
UV filters, which work online, are more effective compared with candle filters. If the hardness of water is below 120 calcium carbonate mg per litre, UV filters are a good option. Such filters, which use UV light to kill bacteria and germs, are a cheaper option to treat municipal water.
Reverse osmosis filters are meant mostly for water with high TDS. These are also popular because they remove hardness that is, the salty taste in water. Though hard water is not unhealthy as such, it creates problems in cooking and washing. An RO system, however, may be more expensive at around Rs3,000 in annual maintenance.