Where does tap water come from ? How is its quality ensured?

In France, opening a tap to obtain drinking water is a particularly easy daily gesture, which gives us access to water of very good microbiological quality — which can be very useful, especially with summer heat...

Yet a out of three French people in 2020 continued to drink bottled water rather than tap water, while plastic waste harms health and the environment, bottled water is more expensive… and its quality is not always impeccable.

Let's see here where tap water comes from and what makes it safe to drink.

Where does running water come from and how does it become drinkable?

two thirds of thedrinking water produced are captured in groundwater (groundwater), the remaining third comes from surface water, also called surface water (rivers, rivers, lakes, dams). Groundwater and rivers are fed by precipitation in the form of snow and rain and then by runoff and seepage.

Human activities such as agriculture and animal husbandry and their consequences such as deforestation, the destruction of wetlands or even climate change generate significant changes in this cycle, and especially in water flows transported.

Once captured, the water is sent to a drinking water treatment plant to be treated. The treatment applied depends on the initial quality of the collected water. For groundwater, in three quarters of cases, simple physical treatment (filtration and settling) and disinfection are sufficient.

For surface waters, further physical and chemical treatments are required – these being determined by depending on the quality of the water to be treated. In some cases, a refining treatment by ozonation, activated carbons and/or membrane filtration is applied in addition in order to eliminate as much as possible the remaining dissolved organic matter as well as the micropollutants (pesticides, etc).

Disinfection then always takes place during the last stage of treatment, most often by adding chlorine, which has a long-lasting disinfectant effect making it possible to maintain water of excellent quality during its storage in tanks and until its distribution.

In France, the average drinking water consumption per inhabitant is estimated at around 150 liters per day per inhabitant including 93% for hygiene (including 20% ​​for sanitary facilities) and 7% for food. This domestic use represents 20% of overall consumption: 35% of drinking water being used for industry and electricity and 45% for agriculture, although it is not necessarily necessary to use drinking water. The reuse of treated wastewater is still very limited in France due to strict regulations and remains a minority for these uses.

Highly regulated distributed water

Once treated, the water distributed must meet certain health standards defined according to the public health code and its quality is regularly monitored from the outlet of the drinking water treatment plants, at the level of the water towers allowing its storage and all along the distribution network.

In total, about sixty parameters are controlled via limits and references of bacteriological, physico-chemical, organoleptic, or even radiological qualities, making tap water themost controlled food in France.

Overall, the quality of running water in cities is excellent in France, where almost 100% of municipalities with more than 50 inhabitants and 000% of the total population consumed water from very good microbiological quality all year in 2020.

Regarding pesticides, mainly from runoff and infiltration into the soil, 94% of the French population consumed water that complied with the regulatory limits all year round in 2020. However, the excesses detected having been limited in concentration and in time, it has almost never been necessary to set up a restriction of tap water consumption.

The risk of pesticide consumption in low doses on long-term health is still poorly known but very likely, especially on the sensitive population such as children and pregnant women.

Occasional problems may appear on the side of the very small municipalities (less than 500 inhabitants); in rural areas with intensive agriculture of the monoculture or viticultural type using pesticides ; in areas close to farms, where nitrates may be present in significant amounts ; or in areas located close to some industries.

If the standards are exceeded, it is up to the person in charge of production or distribution to take the necessary corrective actions to restore water quality.

Exceptional derogations can be put in place (in the event of absence of health risk and with the obligation of rapid compliance) or strict measures can be applied very quickly if necessary by the prefect and following theopinion of the corresponding Regional Health Agency – for example a restriction of use, or even a temporary ban on consumption, as in Châteauroux in June.

The presence of a water safety management plan, indicating the measures to be taken in the event of a problem, will be mandatory by 2027 thanks to the recast of the "Drinking water" directive of December 16, 2020.

Why use tap water rather than bottled water?

France consumes a lot of bottled water, as a result of lobbying by brands that have convinced the French that bottled water was better than tap water.

It is first of all about preserving the environment, because so-called mineral water involves the use of plastic bottles and caps as containers. The majority of this waste (87%) ends up in nature and becomes plastic pollution, having in particular a significant impact on aquatic fauna and flora. Sorting this waste in appropriate centers does not solve everything since only a quarter of plastic waste is actually recycled globally. A study on the analysis of the life cycle of mineral water has shown that it has a environmental impact sometimes 1000 times greater than that of tap water.

But it is also a public health issue linked to the presence of microplastics in water. They are mainly due to degradation larger plastic objects such as bottles. Every week we ingest the equivalent of a plastic credit card, mostly via the water we drink – from the tap and bottled – but also to a lesser extent via the food consumed, in particular shellfish, or even the air we breathe (this is an average estimated worldwide and not only in France).

Reducing or even eliminating the use of plastic, in particular by no longer consuming bottled water, would reduce the presence of microplastics in the oceans.

In addition, certain highly mineralized bottled waters are to be consumed punctually and their daily use remains inadvisable. To neutralize the potentially unpleasant taste of tap water due to chlorine, which in no way affects its sanitary quality, a very simple solution is to let it breathe by leaving it in the fridge for the hours preceding its consumption. .

It is also important to point out that bottled water, taken from underground resources, also contains minute quantities of pollutants such as pesticides or drugs.

Finally, the consumption of bottled water for drinking (i.e. 1,5 liters per day and per person) is a minimum 100 times more expensive than tap water.

We are lucky in France to have quality tap water so let's drink it, whether for the planet or for our health! You can find the average quality of water in your municipality on your annual bill or the consult online at any time.

Alice Schmitt, Post-doctoral fellow in Process Engineering, European Membrane Institute, University of Montpellier et Julie Mendret, Lecturer, HDR, University of Montpellier

This article is republished from The Conversation under Creative Commons license. Read theoriginal article.