COMPOSITION OF DRINKING WATER
Drinking water is a high-quality natural product. The water suppliers obtain it by treating it as gently as possible. For this reason, near-natural drinking water depends on intact water bodies or protection zones. Today, almost two thirds of Swiss tap water can be supplied to consumers completely without chemical treatment.
Tap water is Switzerland's most frequently controlled foodstuff and is of very high quality.
Raw water and drinking water
In the following we refer to the quality of two different waters: surface water and groundwater as it occurs in nature - so-called raw water - and drinking water or tap water as it flows out of our faucets. This distinction is important and is often ignored. For both waters different limit values apply and both can show a different quality. If, for example, a stream exceeds the limit value for pesticides, this is problematic for the local ecosystem and, in the long term, for the quality of the groundwater. However, this does not mean that limit values in drinking water are exceeded.
Raw water and drinking water must comply with different limit values and hygienic guidelines.
Cleanliness of water
If one asks about the water quality, cleanliness and purity must be considered in a differentiated way. Like any natural product, we never find water in its chemically pure form. Water is enriched with valuable minerals, but also contains trace substances. This applies to tap water as well as branded water. Clean water complies with legal and hygienic regulations. Pure' water is either a tasteless distillate or a sales argument.
As natural products, neither tap water nor branded water are pure. But both are drinkable without hesitation.
Trace substances can be of very different types and occur in different concentrations depending on the location (agricultural, residential or industrial zone) and time. These include metals, drug residues, microplastics, germs, pesticides or nitrate. Trace substances can be hazardous to health above certain concentrations. Accordingly, clean water means that the concentration of trace substances is so low that there is no health hazard from lifelong consumption. The permitted limit value for trace substances in tap water is far below a value that is hazardous to health and is permanently monitored.
Drinking Water is checked 24/7 for its quality.
Water contains many valuable minerals that the body needs. Depending on its origin (spring water, ground water or lake water), tap water contains more or less minerals. It performs very well compared to branded water: Only half of the commercially available branded water contains significantly more minerals than tap water. In addition, the human body can only absorb a certain amount of minerals, most of them through solid foods. Consequently, water with a high mineral content may not bring any added value.
Comprehensive information on the quality of drinking water in Switzerland and from all the 2,500 water suppliers can be found here.
During its natural cycle, water absorbs many valuable minerals.
Over the past decades, analytical instruments have continued to evolve. These can indicate ingredients down to the nanogram. For example, a single piece of sugar cubes dissolved in Lake Constance can be detected. This is why people today know much more about the composition of water and are discovering new trace substances. However, this does not mean that the quality of the water will deteriorate. On the contrary. It is precisely because we know more and more about water that we can take the necessary steps to combat undesirable substances. This is why the quality of the water is getting better and better.
Modern analytical instruments show an increasingly detailed picture of drinking water. Knowledge of even the smallest amounts of trace substances helps to further improve quality.
How much are micro- and nanograms?
Trace substances are present in water in the form of micro- and nanograms. Data such as 100ng/l can look like a lot at first glance. However, this misleads us about the effects of such low concentrations: If you drink water with a concentration of 100 ng/l of the drug aspirin, a daily consumption of two litres would give you 700 years to absorb the dose of a single aspirin tablet.
THE ORIGINS OF SWISS DRINKING WATER
The local water supplier is responsible for the supply to the household. In Switzerland there are over 2,500 water suppliers, most of which are communally organised. Drinking water is obtained in various ways. Depending on the geographical location, one type makes more or less sense. The basic principle is to treat tap water as close to nature as possible, i.e. with as little interference as possible with its composition.
Treatment of Spring Water
Shortly before leaving the ground, the spring is captured with drainage pipes (1). It then flows via a settling basin (2) into a reservoir (3) and from there into the supply system (4). Spring water has several advantages. Firstly, it usually does not contain any micropollutants and secondly, the difference in height between the reservoir and the households naturally creates sufficient pressure, which is why only very few electricity is needed to process and distribute it. This makes spring water the most ecological and cheapest way of obtaining water.
To extract groundwater, a shaft with small crevices is constructed (1). The water flows through this shaft, is pumped into the reservoir (2) and fed into the supply system (3). In the case of groundwater, preventive treatment with UV sterilisation is usually sufficient. Besides the natural cleaning processes during infiltration, this is made possible through groundwater protection. This protection clearly regulates agricultural and industrial activities surrounding a groundwater plant. Nevertheless, new trace substances call for intensified protection.
Treatment of Lake Water
Thanks to strict guidelines for water protection, lake water is very clean even without treatment and would usually already be safe to drink. However, equally strict guidelines for drinking water require additional treatment in order to minimise even the smallest residues. Ozonation kills germs and bacteria preventively (1), quartz sand filter out larger particles (2), activated carbon breaks down biologically active substances (3) and chlorine dioxide prevents the formation of microbes in the network (4). From there the water reaches a reservoir (5) and the supply network (6). The treatment can be further optimised with the latest ion filters. These processes are relatively energy intensive, but the enormous volume of the lakes compensates for the costly treatment and makes it an attractive source.
PRESERVING WATER QUALITY
Today's drinking water quality is a product of years of investment and effort. In order to maintain this extraordinary privilege, certain measures are absolutely necessary due to current developments.
Water utilities are increasingly confronted with conflicts of use. These arise primarily from housing construction and agriculture. Problems include zoning in and out or the use of a certain area in which there is a water catchment. Re-zoning can force water suppliers to close a catchment or install chemical treatment stages.
Over the past 50 years, one in three water suppliers has had to close a water catchment. Most of them due to conflicts of use.
The current water extraction can be carried out very close to nature. Two thirds are not treated or only treated with UV.
A high-quality drinking water supply depends on intact, clean waters. Intensive use, e.g. through the use of pesticides or fertilisers, pollutes surface or groundwater and makes treatment more difficult. Many surface waters exceed prescribed limits for nitrates and pesticides. There is a risk that groundwater will also be polluted in the long term. This increases the effort required for treatment and makes drinking water less natural and more expensive.
Pesticides are a collective term for pesticides and biocides. Switzerland is one of the countries with the highest consumption of pesticides, around 2200 tonnes per year. For this reason and due to high precipitation rates, the limit value is often exceeded in water bodies: in intensively used agricultural zones, it is even exceeded at 70% of measuring points. Around one in five drinking water catchments is affected by increased pesticide concentrations. Various experts therefore rate pesticides as the greatest threat to water quality at present.
In 2013, around 53 tonnes of antibiotics were sold in the veterinary medicine sector and around 35 tonnes were used in human medicine. Due to the high use of antibiotics, resistance to these active ingredients quickly develops. Although it is currently assumed that the spread of resistance is more likely to be a long-term process, the spread of antibiotic resistance in the environment is increasingly considered a serious problem.
The main use of nitrate is in the fertilisation of plants. Nitrates occur naturally in low concentrations in groundwater. The legally prescribed maximum value is 25 mg/l for raw water. This value is exceeded in 15% of water bodies and in as much as 60% within zones of intensive agricultural use. Small water bodies are mostly affected.
The Association of Swiss Water Suppliers (SVGW) and the Association of Swiss Wastewater and Water Protection Experts (VSA) demand the following points, among others:
- Water resources and infrastructure must be protected against conflicts of use and risks within the framework of binding structure plans.
- In the absence of such plans, the supply of drinking water must be prioritised on the basis of interests.
- Water protection legislation must be implemented consistently.
- The use of pesticides and biocides must be prohibited in the two inner groundwater protection zones (protection zones around a drinking water intake).
- As measures at source, problematic wastewater must be pre-treated at the source, alternative plant protection methods promoted, particularly hazardous substances and the use of pesticides banned by untrained users, and the approval procedure improved.
- The water supply must be further professionalised, on the one hand through well-trained personnel, but also through an economic and optimised water supply structure.
The use of pesticides is currently permitted in protection zones S2 and S3. It is a requirement of the SVGW to prohibit this.
In its Agricultural Policy 2022 (AP22), the Confederation prescribes various measures to counteract water pollution. Unfortunately, this package does not sufficiently cover any of these requirements. At present, there seems to be no interest in integrating these measures retrospectively. This development is worrying and we are obliged to give the safe and high-quality drinking water supply the status and protection it deserves.