Sharad and Sheetal Agarwal, a young couple living in South Bengaluru spend Rs. 500 and above on drinking water every month. They bought a water purifier from a reputed company three years ago but felt it wasn’t safe after frequent gastro problems.

“Our building receives water from tankers mainly and we aren’t really sure of the source and how effective our purifier is, so we felt buying 20 litre Bisleri bottles was a safer option,” Sheetal says. The couple plan to acquire a new water purifier but are not sure which system would give them foolproof protection against contamination and water borne diseases. Terms such as  activated carbon, reverse osmosis, ozonisation, etc., can also be confusing in this case.

Purified water? Pic: Meera K.

Like the Agarwals, several families in Bangalore wonder what to look for when buying a water purifier that is really effective against chemicals and contaminants than just going by the tall claims of manufacturers. Citizen Matters approached S Ramani of Consumer Association of India, to find out how to buy an effective water purifier for your home. We also got some inputs from India Water Portal, an initiative of Arghyam, an NGO working in the water sector.

Test Your Water

If you really want to be sure of the quality of water you are drinking and be thorough in your pre-buying research, then the first thing to do is to test the water your receive at home, says Ramani. The process isn’t difficult. You can contact water testing labs in Bangalore such as  Essen Labs in Malleswaram (080-23341230/1567) and give them two litres of water sample in any clean bottle washed with hot water. They conduct a total of 33 tests to check for chemical, bacterial contaminants and give you the report in 12 working days. The cost works out to about Rs. 993. You could also contact Ion Exchange in Indiranagar or Aqua Diagnostics in Hosur Main Road for the same.

Click here for a list of Karnataka state recognised private labs. India Water Portal has also compiled a list of water quality testing labs in the city. You can find the list here.

Ramani says concerned citizens should “keep the lab test results in mind when shopping for a purifier.” He further adds that “there are ads for a portable Water Test Kit, around Rs. 50 per test. (One such possible source is Himedia Laboratories). These kits claim quick results for chlorine, lead, nitrate, nitrite, two pesticides, pH, and total hardness. These also claim to test for bacteria but may require waiting 48 hours. This may be a good test if you are in the habit of buying large water bottles for home use.” If you find the tests expensive, Arghyam can do indicative tests for free, post which you can take the samples for lab tests if necessary.
 
Choosing the right filter

Once you get the test results, find out what is the desirable water quality. According to Arghyam, the common contaminants in Bangalore’s drinking water supply are bacteriological contaminants, nitrate and Total Dissolved Solids (TDS). Bacteria is usually found in water from Cauvery and borewell water, while nitrate is mainly found in borewell water. TDS too is found in borewell water supply.

While no bacteria is permitted in drinking water, as per the Bureau of Indian Standards (BIS) drinking water specification, the Nitrate permissible limit is 40 parts per million (PPM) and TDS is 500 PPM. According to a report in Down To Earth, a science and environment magazine , a BIS revision started in 2003 introduced limits for 18 pesticides and four disinfection byproducts. However, it is still in the draft stage.

Once you get your water tested, the next best thing is to find out the kind of technology you need to remove contaminants from water. “The water purifier needs to remove undesirable chemicals, materials, and biological contaminants from raw water and make it fit for human consumption. In general, the methods used include physical process such as filtration and sedimentation, biological processes such as slow sand filters or activated sludge, chemical process such as chlorination and the use of radiation such as ultraviolet light,” Ramani adds. What the purification process does is reduce the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses, fungi; and a range of dissolved and particulate material derived from the surfaces that water may have contacted with.

Technologies Available

Activated carbon: This is a form of carbon (usually charcoal) that has been processed to make it extremely porous providing large surface area for adsorption or chemical reactions. Activated carbon filters use granular carbon or blocks of powdered carbon that can remove pesticides, chlorine, and other chemicals found in tap water. It is a more commonly used technology and according to the third edition of WHO’s guidelines for drinking water quality, technologies such as  activated carbon and ozonation are most suitable for removing pesticides and other organic chemicals, says a report in Down To Earth.

Reverse Osmosis (RO): This is basically filtration at molecular level. Mechanical pressure is applied to an impure solution to force pure water through a semi-permeable membrane. It is reverse because under normal osmosis, pure water moves into the contaminated water without any pressure. Reverse osmosis is theoretically the most thorough method of large scale water purification available, although perfect semi-permeable membranes are difficult to create. Unless membranes are well-maintained, algae and other life forms can colonise the membranes. Secondly, this is a very slow process. RO is required in your home if the Total Dissolved Solids (TDS) exceeds the upper limit, according to the India Water portal. RO is also suggested if you live close to an industrial area and your water may possibly be contaminated with sewage, pesticides, heavy metals, industrial effluents.

Ultra Violet Purification: This method is used mainly for disinfection and to make water containing any disease causing micro-organisms safe for drinking. Passing ultra violet rays makes these micro-organisms unable to reproduce. Usage of iodine, chlorine and plain and simple boiling water also achieve similar effect, Ramani adds.

Ion-exchange filters: This is used to remove hardness in water. Ion-exchange filters can remove iron, lead, copper, barium, radium and nitrates and are usually integrated into the water purifier along with other methods.

According to Ramani, the main purification techniques are boiling, filtration, disinfection, pH adjustment and turning  hard water soft using ion exchange resins. The water purifiers available in the market usually integrate some of these techniques. Most of these mainly start with filtering to remove the dissolved solids and use Ultra Violet (UV) rays to reduce the threat of bacteria. 
 
Testing your purifier

Most manufacturers come up with tall claims about their product. How true are these? For example,  we often hear in ads that Product X has been certified by the Indian Medical  Association. How true are most of these claims?

According to an article in Down To Earth, the Centre for Science and Environment, Delhi, checked a certificate issued by the Indian Medical Association (IMA) to popular water purifier manufacturer Eureka Forbes in 2004 and found out  that the IMA does not really test the purifier before issuing the certificate.

The standards for drinking water quality are typically set by governments or by international standards, says Ramani. “These standards will typically set minimum and maximum concentrations of contaminants for the use that is to be made of the water.” he adds. The Bureau of Indian Standards (BIS) does have standards for some water purifiers such as  UV filters and candle filters.  But we understand that these standards were developed between 1979 and 1999, when it was believed that water purifiers were meant to remove only bacteriological contaminants.  Besides, these standards only apply to water that is free of chemicals and suspended matter. The sought after RO  systems are also beyond  the pale of standards. 

Addendum

INDIAN STANDARDS FOR DRINKING WATER  –  SPECIFICATION
( BIS  10500 : 1991 )