Correct Answer - Option 3 : Mn
The correct answer is option 3 i.e. Mn
For drinking water, the maximum recommended level of some metals,
(i) Zn = 5.0
(ii) Fe = 0.3
(iii) Mn = 0.1
(iv) Cu = 0.05
As the concentration of Mn in the given water samples is more than the recommended concentration. Thus, it makes water unsuitable for drinking.
Manganese is a mineral that naturally occurs in rocks and soil and may also be present due to underground pollution sources.
Manganese is seldom found alone in a water supply. It is frequently found in iron-bearing waters but is rarer than iron. Chemically it can be considered a close relative of iron since it occurs in much the same forms as iron.
When manganese is present in water, it is every bit as annoying as iron, perhaps even more so. In low concentrations, it produces extremely objectionable stains on everything with which it comes in contact.
Deposits collect in pipelines, and tap water may contain black sediment and turbidity due to precipitated manganese. When fabrics are washed in manganese-bearing water, dark brown or black stains are formed due to the oxidation of the manganese.
