Drinking water must meet a number of very strict norms, laid down in the amended version of the Grand-Ducal Regulation of 7 October 2002 on the quality of water intended for human consumption, which is based on European Directive 98/73/EC. The water that is supplied must meet strict criteria of cleanliness and hygiene. Water is hygienic and clean if it is collected, produced, treated, stored and/or distributed correctly and does not contain a number or concentration of micro-organisms, parasites or substances constituting a potential danger to human health. There are, for example, stringent quality norms, referring to the presence of nitrates or other diffused substances of human or natural origin.
Each municipality monitors the quality of the water it supplies to its inhabitants, even if the supply comes from a drinking water syndicate. Once a year, the municipality informs consumers about the quality of the drinking water supplied. In addition to municipal monitoring, the Water Management Authority carries out supplementary analyses of the distribution networks.
Composition of drinking water
Depending on its origin (groundwater or surface water) and where it was collected (geological context), water contains different mineral salts and other components at variable concentrations. As it passes through the rock, groundwater gathers more minerals. This means that, on average, it has a higher mineral content than surface water.
Water is an amazing solvent, and during its cycle it dissolves a considerable number of substances, including calcium and magnesium carbonates, which are better known as "lime" and "limescale". The more lime there is in water, the -"harder" it is. Consumers often have a negative image of lime dissolved in water, because of the limescale that is deposited in appliances and installations when "hard" water is heated. However, although it is harmful for installations, lime is beneficial for humans.
The excessive use of nitrogen, in the form of chemical fertilisers and above all animal slurry, contaminates groundwater, particularly when plants are not able to fix all the nitrogen added to the soil. Nitrates are not directly harmful to humans, but inside the body they are transformed into nitrites, which interact with the red blood cells that are responsible for carrying oxygen in the blood. In extreme cases, their presence may produce respiratory problems in newborn babies.
Nitrites also modify themselves, producing nitrosamines - these are classified as being capable of causing cancer. Most nitrates, however, are absorbed in food (lettuce), and nitrites are present in other types of food, such as processed and smoked meat products. In this context, the World Health Organisation has laid down a maximum concentration for water of 50 mg per litre (limit applied in the Grand Duchy) in order to avoid any negative effect on the human body.
Tap water, and indeed mineral water, is a natural, non-sterile product. This means it is important to prevent water containing even a small quantity of any of the micro-organisms that are harmful to humans. To be able to prevent diseases, analysing the microbiological quality of water is just as important as carrying out chemical analyses.