COM­PAR­A­TIVE TEST

Tap Wa­ter

Consumer Voice - - Contents - A Con­sumer Voice Re­port

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 Pa­ram­e­ters

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,

colour­less liq­uid.

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.

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