According to a Bureau of Indian Standards (BIS) study, Mumbai ranks the highest in the quality of water among capital cities in states where samples of tap water were tested. In Mumbai, all 10 samples of tap water passed the BIS test. Second in the list in Hyderabad, where only one sample failed. However, at the bottom of the list is Delhi, where all 11 samples failed the BIS test — thereby reaffirming that the capital city has the poorest water quality, the BIS study put.

The Union Minister of Consumer Affairs, Food and Public Distribution, Ram Vilas Paswan, on Saturday said, "Mumbai tops the ranking released by the Bureau of Indian Standards for quality of tap water. Delhi at the bottom, with 11 out of 11 samples failing on 19 parameters."

Union Minister Ram Vilas Paswan: Mumbai tops ranking released by Bureau of Indian Standards (BIS) for quality of tap water. Delhi at the bottom, with 11 out of 11 samples failing on 19 parameters. pic.twitter.com/3nuLuXAuqw November 16, 2019

The following methodology was followed for the study —

● IS 10500:2012 prescribes 48 parameters including radioactive substance

● Radioactive substance have been excluded from this exercise

● Test reports of Virological and Biological parameters (three parameters) have been received for Delhi only. All samples tested to conform to these three parameters.

● Test reports for other 20 cities for virological and biological are awaited. Test reports of microbiological and chemical tests have been received.

● Cities have been first categorized on the number of conforming samples out of those tested.

● Cities which have the same number of conforming samples have been further categorized on the basis of individual parameters in which samples have been non-conforming.

● Free residual chlorine has been excluded from this exercise since it is applicable only when water is chlorinated and a minimum limit has been prescribed for it.

The entire list of capital cities is provided here —

Categorization Capital No of Samples Failing No of Individual Parameters in which samples failing 1 Mumbai 0/10 0 2 Hyderabad 1/10 1 Bhubaneshwar 1/10 1 3 Ranchi 1/10 4 4 Raipur 5/10 3 5 Amravati 6/10 7 6 Shimla 9/10 1 7 Chandigarh 10/10 2 8 Thiruvananthapuram 10/10 3 9 Patna 10/10 4 Bhopal 10/10 4 10 Guwahati 10/10 5 Bengaluru 10/10 5 Gandhinagar 10/10 5 11 Lucknow 10/10 6 Jammu 10/10 6 12 Jaipur 10/10 7 Dehradun 10/10 7 13 Chennai 10/10 9 14 Kolkata 9/9 10 15 Delhi 11/11 19

The BIS study was titled 'Categorization of Cities on the basis of Reports of Samples of IS 10500: 2012 (Drinking Water-Specification) Drawn from Capital of States'.