No taking it for granted
Every day we turn on our taps in order to drink, bathe, and cook, using water from public water systems. To various extents, we often take the purity/acceptability of our tap water for granted. Once in a while, a report comes our way telling us that our water may not be all that it seems, that it may even have picked up bits of sewage or drain water on its way to our homes. We fret about it, feel cheated, wonder what can be done about it, and move on. Those of us who can afford to, install RO systems/UV or some other type of water purifiers at our homes. Some use bottled water supplied by local water-purifier units. For the rest, there is no option but to depend on municipal water supply or ground water. This test report sets out to verify the water quality across locations in the capital of India, on parameters that must be met squarely for the water to be acceptable.
Before it comes out of our taps, water in most cities usually undergoes a complex treatment process, often including filtration and disinfection. As good as our municipal water systems can be, they also can fail. For example, water with strains of E. coli bacteria can cause serious illnesses if consumed in raw form. In particular, waterborne-disease outbreaks are a great threat in the rainy seasons.
Sampling and Testing
Against this backdrop, Team Voice conducted a
random sampling of domestic supplied tap water in areas across Delhi-NCR, including Ghaziabad and Faridabad. The objective was to cover all sub-regions of Delhi-NCR geographically for assessing the quality of municipal water supply there. Overall, 20 locations in Delhi, two in Ghaziabad, and one in Faridabad were covered. Team Voice did water sampling directly from taps of households during supply time and packed the same in sterilised bottles and sent to the lab on the same day for testing. The testing was carried out in collaboration with Analytical Division, Arbro Pharmaceuticals Limited, New Delhi. The Arbro lab is NABL-accredited and conducts such tests regularly.
The testing was carried out as per Indian Standard IS: 10500 and other relevant standards for key parameters listed below. The Indian Standard has two limits: acceptable limit and permissible limit in absence of alternate source. Values in excess of those mentioned under ‘acceptable’ render the water not acceptable but still may be tolerated in the absence of an alternate source, though only up to the permissible limit. If any parameter exceeds the limit, that water is considered unfit for human consumption.
The focused testing programme is based on parameters with direct bearing on safety and health aspects. These parameters are:
a) Appearance: Drinking water should be a clear,
b) Odour: The water should be free of objectionable odour.
c) pH value: The pH is of major importance in determining the corrosivity of water. In general, the lower the pH, the higher the level of corrosion. The pH of the water entering the distribution system must be controlled to minimise the corrosion of water mains and pipes in household water systems. Failure to do so can result in the contamination of drinking water and in adverse effects on its taste, odour and appearance.
As per Indian Standard, the pH value shall be between 6.5 and 8.5.
d) Total dissolved solids (mg/l): As per Indian Standard, acceptable limit for TDS is 500 mg/l and permissible limit is 2,000 mg/l.
e) Chloride (as Cl) (mg/l): As per Indian Standard, the acceptable limit is 250 maximum and the permissible limit 1,000 maximum.
f) Fluoride (F): The Indian Standard specifies the acceptable limit as 1 maximum and the permissible limit as 1.5 maximum.
g) Turbidity (NTU): Acceptable limit is 1 NTU and permissible limit is 5 NTU maximum.
h) Total residual chlorine (mg/l): Acceptable limit is 0.2 maximum and permissible limit is 1.0 maximum.
i) Total plate count (cfu/ml): IS: 10500 has not
specified the limit.
j) Escherichia coli/ 100 ml: E. coli shall not be detectable in any 100 ml sample.
k) Coliform/100ml: Coliform shall be absent in
any 100 ml sample.