Mineral water
The more calcium and magnesium ions that are dissolved in water, the "harder" it is said to be; water with few dissolved calcium and magnesium ions is described as being "soft". The U.S. Food and Drug Administration classifies mineral water as water containing at least 250 parts per million total dissolved solids (TDS), originating from a geologically and physically protected underground water source. No minerals may be added to this water. In the European Union, bottled water may be called mineral water when it is bottled at the source and has undergone no or minimal treatment. Permitted is the removal of iron, manganese, sulfur and arsenic through decantation, filtration or treatment with ozone-enriched air, insofar as this treatment does not alter the composition of the water as regards to the essential constituents which give it its properties. No additions are permitted except for carbon dioxide, which may be added, removed or re-introduced by exclusively physical methods. No disinfection treatment is permitted, nor is the addition of any bacteriostatic agents.
Composition
Mineral water is water from a mineral spring that contains various minerals, such as salts and sulfur compounds. In many places the term "mineral water" is colloquially used to mean any bottled carbonated water or soda water, as opposed to tap water.