In many places, you can’t drink tap water in India directly and safe or pure drinking water is a big concern for most of us.
Every year 37.7 million people in India are affected by waterborne diseases due to contamination of water by bacteria (E coli, Shigella, Vibrio cholerae), viruses (Hepatitis A, polio virus, rota virus) and parasites (E. histolytica, Giardia, hook worm). Luckily, antibiotics and other medicine can treat most water-borne diseases.
What is more worrying is the presence of arsenic and other heavy metals such as cadmium, zinc and mercury. These metals cause metabolic disruptions and damage the nervous system and kidneys irreversibly. They are also known to cause cancers of colon, liver, kidney and lung. Arsenic has been found to be way above the 0.01 mg/litre WHO guideline value and 0.05 mg/litre Indian standard of arsenic in drinking water in some parts of West Bengal, Bihar, UP, Jharkhand and Chhattisgarh.  Scientists have also linked arsenic in drinking water to greater risk of H1N1 (swine flu) infection because of lowered immune response. 
Dust particles, sand, clay, rust, and dissolvable chemicals such as sodium chloride are other water impurities which fortunately are easily rectifiable.
This brings us to the question, how do we purify the water to make it safe to drink?
Drinking tap water, especially in India, is NOT an option. Although the Municipal water departments supply good potable water in many cities, there may be times when the quality of water is not up to the mark. Why take a risk? To be on the safe side, it is best to purify the water before drinking.
An easy and effective method of water purification is boiling the water.
- Filter the water if it is muddy. Use a clean cloth for filtering. If the water is clear, you need not filter it. Go directly to the next step.
- Boil the water for one minute. If you live at an altitude of 6500 feet or higher, boil the water for 3 minutes. The World Health Organization suggests you bring the water to a rolling boil for one minute, which means, boil the water rapidly with lots of bubbling.
- Allow the boiled water to cool to room temperature and do not add ice to cool it.
- Store the boiled water in clean containers.
Boiling of water for drinking purposes removes most microbes but studies show that boiling does not fully remove the potential risk of water-borne pathogens.
Moreover, boiling does not remove arsenic and other heavy metals that may be present in the water, especially groundwater wells. Even tap water may not be heavy-metal-free. For example, findings of a study conducted to test the arsenic level in Delhi water show that it was much higher than permissible limit of 0.01 ppm (parts per million).  ‘Mixing of ground water and contamination through broken or leaking channel could be the possible reason of higher arsenic level in tap water,’ reported the researchers.
Arsenic poisoning can cause a headache, nausea and chest pains, and over time it can cause various cancers, stroke and diabetes. The problem is you won’t know whether your drinking water has heavy metals until you get the water tested.
Using chemical disinfectants
Chlorine, potassium permanganate, iodine and alum are some of the common disinfectants used for purifying drinking water. These are effective in preventing all communicable water-borne diseases.The chlorine tablet, Shudhu, can help destroy biofilms found on pots and vessels as well. These biofilms are a major source of E.coli.
However, these chemicals are not effective against arsenic and other heavy metals and fluoride.
Add one Shudhu tablet in 20 litres of water, wait for 30 minutes, and your drinking water is ready. The tablet takes one or two minutes to dissolve. 
For iodine tablets, use one tablet to treat a litre of water at room temperature. However, use of iodine can have potential drawbacks. For example, iodised water can have a taste that you may find objectionable. Iodine treated water can also be unhealthy for those with thyroid problems or pregnant women.
Aluminium potassium sulphate or potash alum is used for clearing muddy water. It is generally added to large capacity storage vessels. Wait for an hour or so till the impurities settle at the bottom of the vessel. Filter the water into another container and follow it up with chemical treatment (add chlorine or iodine tablets) to kill microbes.
The World Health Organization, however, suggests, ‘This type of treatment is less likely to be performed reliably at point-of-use for household water treatment’ and is best left to be performed in the specialised central facilities by trained personnel. 
Bottled water seems like the easiest way to get safe pathogen-free pure drinking water.
When a team of scientists from Bhabha Atomic Research Centre at Trombay checked samples from 18 brands of bottled water sold by various manufacturers in Mumbai, they found that more than quarter of samples tested contained higher than WHO-permitted limits of bromates, a carcinogenic salt containing bromide that is a by-product of the disinfection.
Again, bottled water drawn from ground water may contain heavy metal that may cause metal poisoning. And that’s not all! In 2003, the Centre for Science & Environment, Delhi, showed that bottled water had pesticide residues.
So, you may be inviting water-borne diseases or metal poisoning if you use bottled water for drinking purposes on long term basis. If you don’t have a water purifier at home or when you are away from home, then bottled water may be your only option. When buying bottled water keep in mind:
- Avoid locally manufactured bottled water. They do not follow the BIS safety regulations for drinking water. Choose popular brands such as Bisleri, Kinley and Aquafina. These companies follow high standards of filtration and bottling process.
- Check the seal. Reject the bottle if you suspect the lid has been tampered with.
- Check the manufacturing date and the expiry date.
- Make sure the bottle is clean even from the outside. The water may be clean and pure, but if there are germs on the bottle, it will not serve the intended purpose.
- Follow the instructions on the label, for example, crush the bottle after use in the case of one-time use plastic bottles.
Residential water filters and purifiers
Ultimately, opting for water filters and purifiers may be the best way to get safe and pure drinking water. There are different types of water filters and purifiers.  Here’s what they do:
- Remove excess salts.
- Remove suspended particles and harmful microbes.
- Retain the essential vitamins and minerals present in the water.
Water filters and purifiers pull in raw water, filter out impurities, and then dispense clean water. The only difference between filters and purifiers is that filters can’t remove bacteria and viruses while some purifiers not only remove microbes but can also remove fluorine, arsenic and other heavy metals.
The following purification techniques are used in filters and purifiers:
Active carbon filter – filters out soluble gases such as chlorine and also pollutants such as pesticides, dead algae, dried leaves, etc. Household carbon filters usually come with a lining of activated silver that kills bacteria.
Biosand filter – removes suspended particles and pathogens; can filter 12-18 litres of water at a time.
Reverse osmosis (RO) filter – filters out harmful dissolved minerals and pathogens. It may improve the taste of water as it removes minerals. However, be aware that it may not be 100 percent safe because some bacteria can get through the filter because of a manufacturing defect or due to wear and tear.
A disadvantage with the RO filter is that it removes even the essential minerals, which in the long run may lead to a mineral deficiency in the body.
Ion exchange resins filter – softens the water by removing the salts present and de-mineralise the water.
UV filter – the ultraviolet (UV) rays penetrate harmful pathogens in the water and destroy them by attacking their DNA (gene).
Advantages of using ultraviolet purification:
- It is chemical free.
- It does not any chemical taste or odour to the drinking water.
- It destroys pathogens very effectively.
However, UV light inside UV water purifiers can get blocked when scale forms on the UV bulb, due to heat from the bulb. Also when there is no flow of water through it, slime forms on the glass around UV bulb blocking the UV rays. So, filtration becomes ineffective after some time, and you will have to change the bulb frequently.
Moreover, the UV technique does make it 100 percent pure drinking water because UV light cannot eliminate impurities such as chlorine, heavy metals and volatile organic compounds. It is also not effective in removing suspended particles, chemicals, taste, smell or colour. So, usually they are combined with reverse osmosis (RO) systems.
As a matter of fact, most water purifier brands combine filters for better results, say RO with UV, or UV sterilisation with activated carbon filter, or maybe use more than two filtration techniques.
Which water filtration technique to choose?
The type of filter you choose must depend on the quality of water in your area. The first thing you do is get the water tested from certified labs (google the lab in your area).
If you are living in big cities such as Delhi, Mumbai, etc. your tap water is generally safe with regards to total dissolved solids (TDS) and heavy metals but not from pathogens. Your best bet would be UF or RO water purifiers.
- UF water purifiers have filtration membrane similar to RO membrane but with bigger pores so they can’t filter out dissolved solids, which are not present in your water anyways. The advantage is it works without electricity. So if you are living in an area with frequent power cuts, UF water purifiers may be the solution.
- RO purifier, on the other hand, can remove dissolved solids and poisonous chemicals, and even heavy metals. So you are assured of good quality drinking water. The disadvantage is that it requires high water pressure, and a lot of water is wasted in the reject stream which carries impurities. But you can use the rejected water to water plants and for outdoor cleaning purposes.
If the water supplied to your area is contaminated with heavy metals and organic impurities (bacteria, virus) you may need to use a RO + UV water purifier. RO will remove all impurities and whatever traces of organic impurities are left will be destroyed by the ultraviolet light.
And then, if you want a drinking water that is safe, healthy, and also retains essential minerals (remember RO removes most minerals) as well, you may have to go in for high end water purifiers that are a combination of RO + UV + UF + Auto Mineral Modulator. This type of water purifier can effectively purify water from any source, be it municipal, borewell or tanker.
‘Solutions and technologies exist to provide clean, affordable drinking water anywhere in the world. These solutions will save lives, reduce financial burdens, foster peace, and relieve millions of people from worrying about their next drink of water.’ – Jewel Kilcher, American Grammy Award-nominated singer.
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- Ghosh NC. Groundwater Arsenic Contamination in India: Vulnerability and Scope for Remedy. National Institute of Hydrology, Uttarakhand, India
- Washam C. New Face of a Well-Known Hazard: Arsenic Alters H1N1 Response in Mice. Environmental Health Perspectives. 2009;117(9):A406.
- Clasen, Thomas et al. ‘Microbiological Effectiveness And Cost Of Disinfecting Water By Boiling In Semi-Urban India’. The American Journal of Tropical Medicine and Hygiene 79.3 (2008): 407-413.
- Lalwani S, Dogra TD, Bhardwaj DN, Sharma RK, Murty OP. Study on arsenic level in public water supply of Delhi using hydride generator accessory coupled with atomic absorption spectrophotometer. Indian Journal of Clinical Biochemistry. 2006;21(1):70-76. doi:10.1007/BF02913069.
- ‘Shudhu – Water Purification Tablets’. Shudhu.org.
- World Health Organisation. Managing Water In The Home. Who.int.
- The Times of India. January 28, 2015. High toxin levels found in Mumbai’s bottled water.
- Indiawaterportal.org,. ‘Residential Water Purifiers – Everything You Need To Know Before You Buy One’. Web.