The Italian Legislative Decree no.176 of 2011 defines as natural mineral waters those waters that - originating in an aquifer or an underground reservoir - come from a spring tapped at one or more natural or bore exits, have specific hygiene properties and are beneficial for health.
As far as drinking waters, the last two specifications (hygienic features and health benefits) are not required. The common drinking waters can be subjected to purification or bactericidal treatments. On the contrary, it is strictly forbidden to subject mineral waters to any chemical treatment that will alter their composition: the only derogation that is permitted is that addition of carbon dioxide to make them into carbonated waters is authorised.
The term “thermal water” instead means natural mineral water the features of which make it suitable for therapeutic use. Marotta and Sica’s classification of 1933 represents the current water classification in Italy that regulates the permission to use mineral waters. This classification includes three parameters: temperature, fixed residue and chemical composition.
CLASSIFICATION ACCORDING TO TEMPERATURE
- COLD: temperature below 20°C
- HYPOTHERMAL: temperature between 20°C and 30°C
- HOMOTHERMAL OR THERMAL: temperature between 30°C and 40°
- HYPERTHERMAL: temperature greater than 40°C
CLASSIFICATION ACCORDING TO FIXED RESIDUE
Fixed residue consists in the total amount of dissolved substances (mostly inorganic substances) contained in the water. The determination of fixed residue is one of the most important investigations which need to be carried out in order to classify a thermal water, also because fixed residue is part of the official thermal and bottled waters with healing properties classification. It is normally expressed in mg/L and measured at 180°C:
- MINIMALLY MINERALIZED WATERS: fixed residue less than 50 mg/l
- SLIGHTLY MINERALIZED WATERS: fixed residue less than 500 mg/l
- MINERAL WATERS: fixed residue between 500 and 1000 mg/l
- WATERS RICH IN MINERAL SALTS: fixed residue greater than 1500 mg/l
CLASSIFICATION ACCORDING TO CHEMICAL COMPOSITION
Based on the chemical composition of the fixed residue, thermal water takes its name from the element or group of elements from which it is composed. While determining what kind of ionic composition there is in the water, first we have to take account of the prevalent anion (or anions) and then of the cation. When a ion is greater than 20 mEq/L, this gives the water its name. According to prevalent ionic composition, minetal waters are classified in:
- BICARBONATE WATERS
- SALT WATERS OR WITH SODIUM CHLORIDE
- SULPHUROUS WATERS
- ARSENICAL FERRUGINOUS WATERS
- SULPHATED WATERS
If there is the presence of different prevalent ions at the same time, the water will be called multi-ionic mineral water.