Sodium belongs to Ia group of Periodic table of the elements and it is in group of alkali metals. The most important compounds of sodium are: sodium-chloride (NaCl), sodium-carbonate (Na2CO3), sodium-hydro carbonate (NaHCO3), sodium-hydroxide (NaOH), sodium-phosphate (Na3PO4) and borax (NaB4O7x10H2O). Sodium compounds are using in industry of paper, glass, soups, textile, naphtha, chemical and metal industry. Sodium is natural component of rough waters, but sodium concentration is enhanced with industrial pollution, like salt treatment of roads during the winter, scour with precipitation and solution of soaps and detergent.
Origin in water
Sodium is between primary prevalent elements in underground and natural waters. Between cations in waters, sodium have 1/2 from total contents all other cations. In underground waters sodium can be connecting for sedimentary rocks of marine origin, and for halite bearing. Also it can be connecting for occurs of feldsphates and feldsphatoides. In low-mineralized waters sodium ion is in concentration from several mg/l to several tenths mg/l. With mineralization increase, concentration of sodium raises.
Sodium is important element in water change between cells and intracellular liquid. It is also important in muscle work, because sodium enables contractions.
Sodium is necessary for making gastric acid. It assists in regulation of cell permeability and preserves osmotic pressure. Sodium also assists in regulation of nerve-muscles irritability. Sodium lack brings to weakness, sicknesses, muscle spasm and in some cases with crush of vitality function in organism.
Sodium in drinking water is harmful in large concentration (even below the limits of taste) at persons who suffer from cardiac, kidney sicknesses and sicknesses of vascular organ. With studies in Netherlands is proved that sodium causes increase of blood pressure.
Maximal allowable concentrations
According to recommendations of EU for fresh water, limitary value for sodium is 200 mg/l (Directive 98/83/EC). According to our rules for drinking water (Sl. list SRJ 42/98) limitary value is 150 mg/1.
In direction of European Economic Community 80/777/EEC is prescription that in case if sodium concentration in bottled natural mineral waters is bigger then 200 mg/l, that water must declare as sodium water, and if sodium content smaller then 20 mg/l low-sodium water. These criteria accept in domestic rules (Sl list SCG 53/05). Extra limits for sodium content in bottled waters do not special signify.