Les traitements applicables aux eaux minérales naturelles : avantages et inconvénients

Eligible treatments applied to natural mineral waters. Advantages and disadvantages

¹ Agence française de sécurité sanitaire des aliments, Direction de l'évaluation des risques nutritionnels et sanitaires, Unité chargée de l'évaluation des risques liés à l'eau, 27/31 Avenue du General Leclerc - 94701 Maisons-Alfort cedex

Résumé

Les eaux minerales naturelles ainsi que les eaux de source peuvent contenir naturellement certains constituants instables (fer, manganese et soufre) ou indésirables susceptible de présenter un risque pour la santé. L'antimoine, l'arsenic, le baryum, le bore, le cadmium, le chrome, les cyanures, les fluorures, le manganèse, mercure, le nickel, les nitrates et les nitrites, le plomb et le sélénium font ainsi l'objet d'une limite de qualité.

Le respect de ces objectifs de qualité implique la mise en oeuvre, sous conditions, de traitements de l'eau.

L'article passe en revue les traitements disponibles pour l'eau potable. Les avantages et leurs inconvénients sont décrits au regard des exigences sanitaires (innocuité, efficacité, absence de sous-produits de traitement) et réglementaires relatives aux eaux minérales naturelles (pas de modification de la composition de l'eau quant à leurs constituants essentiels).

Il apparait ainsi que les traitements d'adsorption sélective sur média filtrants offrent des perspectives très intéressantes notamment pour le fluor et l'arsenic et permettent d'envisager dans un avenir proche leur application aux eaux minérales naturelles et aux eaux de source.

Par contre, en l'état actuel des connaissances, il n 'existe pas pour le baryum, le bore et les nitrates, de traitements respectant les conditions requises pour les eaux minérales naturelles.

Abstract

Natural mineral waters and spring waters may contain naturally, at spring, unstable compounds (such as iron, manganese and sulphur) and/or undesirable elements. A list of constituents of natural mineral waters which may present a risk to public health has been established and concern only antimony arsenic, barium, boron, cadmium, chromium, cyanides, fluorides, manganese, mercury, nickel, nitrates, nitrites, lead and selenium. For public health purposes, theses natural mineral waters (and spring waters) can be subjected to separation treatments, under certain conditions, to comply with admissible levels defined in European regulation.

In order to satisfy to legal requirements defined in natural mineral water directives, the authors review the list of possible and eligible treatments currently used in drinking water: coagulation followed by filtration or decanting, chemical precipitation, decarbonation with lime, ion exchanges resins, membrane technologies: nanofiltration, reverse osmosis and electrodialysis.

For natural mineral waters, used treatments must not alter the composition of the water as regards to its the essential constituents ; this implies adapted treatments.

The advantages and the disadvantages of the treatments available for drinking water are described, taking into consideration safety (harmlessness, effectiveness, absence of by-products) and legal requirements.

Ozone to remove arsenic has been authorised a few years ago but is ineffective when water doesn't contain iron. Depending of water pH, by-products may appear making water unfit for consumption. In addition, use of ozone damage the image of mineral water and make it confusing with water disinfections treatment.

New treatments based on selective adsorption on activated alumina (for fluoride removal) and oxihydroxide of manganese or iron (for manganese and arsenic removal) has appeared few years ago for drinking water and are now being implemented in mineral water industry.

Advantages of selective adsorption are numerous for mineral waters treatment. This process, commonly used in drinking water treatment, is safe and selective. It does not lead to formation of residues or by-products and does not imply any addition of chemicals.

It has the same microbiological impact on the water quality as for filtration on silica sands.

Essential characteristic elements such as calcium, magnesium, potassium, sodium, chlorides, sulphates, hydrogénocarbonates are not affected by adsorption selective.

This process is suitable for all types of waters and fulfils all requirements to remove antimony, arsenic, cadmium, chromium, cyanides, fluorides, manganese, mercury, nickel, nitrites, lead and selenium from natural mineral waters.

In the state of knowledge, forbarium, boron and nitrates contained in a natural mineral water or spring water, it does not exist a treatment complying with all theses requirements.