Hello,

As per the directions of IS 10500 : 2012, the permissible limit of the ions in drinking water are as follows:

The permissible limit of ( SO4 )2- ions in drinking water is 200 ppm

The permissible limit of ( NO3 )- ions in drinking water is 45 ppm

The permissible limit of ( Pb )2- ions in drinking water is 0.01 ppm

The permissible limit of ( F )- ions in drinking water is 1.0 ppm

As per the data given in above question, when we check the concentrations of ions as per IS Code, all other ions except Pb2- are under limit. Hence, only Pb2- ions make the water unsuitable for drinking.

Best Wishes.

Hi Saiharshvardhan!!

The ion that is making the water sample unfit for drinking is lead. The safe level of a lead ion that can be in drinking water is 50 ppb, sulphate ion is less than 500 ppm, fluoride ion is 1.5 ppm and nitrate ion is 50 ppb.

Hope this helps.