Natural Swimming Pools: development in Europe

March 4, 2021.

The history of the development of swimming and bathing pools and natural pools in Europe.

Over 20 years ago, pioneers in this field built systems, at their own risk, which basically worked and which are still in operation today. They thus set off an avalanche which has still not come to a halt. There are many ambitious companies and planners who approach this matter after carefully researching the literature and who achieve considerable success. But the devil is in the detail. There is always a danger of making a mistake by incorrectly estimating individual factors. The advice and assistance of a professional is the only real security.

Historically, when thinking about this situation, it can safely be assumed that bathing in ponds, or in relatively small areas of water, is possible. Village ponds and fire-fighting pools existed long before bathing pools became fashionable and it is certain that people bathed in these artificially created lakes.

The limiting factor that determines whether a small area of water is suitable for bathing is the available free area of water that allows people to bathe without stirring up mud: In those times, the suitability of a pool for bathing was judged by the depth to which one could see. People do not like swimming in cloudy water. Natural waters are good for bathing if it is possible to reach deeper areas past the solid ground in the flat areas near the shores. Bathing areas in the Alpine lakes with gravel shores meet these requirements. Experts have agreed for around 100 years on the precise natural self-cleaning processes of our lakes and rivers. Once it had been recognized that the breakdown of pollutants in water is carried out with bacteria and is not, as had been previously assumed, due to chemical processes, the march to victory of fully biological plant purification systems began. The experience gained in this connection, together with new technologies, provided us with tools for creating small lakes and pools which function exactly in the same way as the Alpine lakes that were created over 20,000 years ago.

If we can succeed in creating enclosed habitats that meet all the preconditions for the living beings that are involved in natural self-cleaning to feel good, we are on the right track. Experts talk about suitable abiotic conditions, which are essential for life to continue.

The limiting factor that determines whether an artificially created lake is suitable for bathing is its stability - the stability that is created when plant and animal activity is in balance. This balance is destroyed, for example, by people, who create a disturbance by diving into the pond, which is a relatively small, enclosed ecosystem in terms of content: a disturbance, not in the form of "stirring up the mud", but through the direct incorporation of nutrients from human excreta. This disturbance triggers defence strategies in the water, which have a certain delayed effect.

Nutrients introduced from animal or human excreta are processed immediately if the conditions for growth are favourable. Processing is carried out through incorporation in a process that is the foundation of all life. Heat, light, carbon dioxide and nutrients such as nitrogen and phosphor set a process going which we call photosynthesis. In nature, production continues without interruption for as long as warmth and light allow it. The limiting factor is whether the basic nutrient substance is available in sufficient quantities. Following this production of vegetable biomass, oxygen is produced.

We are continuously confronted with this problem if, for example, sewage is introduced into standing water. Life in the water changes. The more sewage we add, the more nutrients are produced. The consequence is increased animal and plant growth. The water eutrophies. It is only a question of the water content and of time until the water can no longer cope with the burden. If the capacity of the water to purify itself naturally is exceeded, the introduction of any further sewage will cause a disaster.

As soon as there is no longer enough oxygen available in the overall balance, the animal life starts to die. Because of a lack of oxygen, all the bacteria that work without odour end their work. Their place is taken by other species that decompose without needing oxygen. The products of decomposition are then the well-known foul gases such as methane and sulphur hydroxide, rather than odourless carbon dioxide. These fears run deep.

The pioneers mentioned above took a major risk in those days. They were sure that natural self-purification would work because they had observed nature. The concept of digging out a pit, sealing it and building the excavated material back in again was basically correct. After the water had been filled in, the development of life could be observed very quickly. Water and marsh plants made the development more attractive.

The idea of the bathing pool had already been born when people started considering separating the planted area from the area set aside for swimming. Even then, people made use of separation techniques which are still in use today. One of the first ideas was to pile up larger stones above the seal, behind which the pond floor was built in. The profile was then shaped in such a way that an embankment was left. Wooden beams were also used at an early stage.

It started in the 1970s with garden ponds. Any decently designed garden had to include the element of water. Following this trend, large companies such as Oase and Heissner specialized exclusively in meeting the needs of this market.

The real pioneers came from Austria (Grad. Eng. Gammerit 1985, Prof. Roidinger, 1980). They build Local authorityical bathing ponds.

Probably the first to convert an existing swimming pool into a bathing pool was Mr. Schwedke from Hamburg (Germany).

It is now about 15 years since efforts were first made to market this product professionally. One of the first to deserve a mention was Peter Petrich, a graduate engineer from Klosterneuburg, Austria. He introduced the progressive separation of flat water/bathing area using concrete walls. Other developers such as Gerhard Brandlmaier, Wels, Austria, also introduced other swimming pool technologies at the same time.

The move towards swimming pools in a pond was becoming clear. Skilful PR work helped the young product to spread quickly. Following this, other inventive entrepreneurs began to be active, and developments were introduced thick and fast.

It is undisputed that the march to victory of the bathing pools started in Austria. The very oldest public pools were also commissioned by Austrian local authorities and hotels (at the moment there are about 30 public facilities in Austria).

The target group for "bathing pools" as a product was, initially, pure nature fans who were brave enough to take a risk. However, over time, bathing pools have become a real alternative to the traditional chemically cleaned swimming pools.

In recent years, the market has developed in two directions. Some potential pool owners want just absolutely pure nature, and reject the idea of pond technology totally.

The requirement for another group is that, in extreme cases, a pure pool with external, fully biological water purification is required – this technology is also used in the local authority sector. Both extremes are possible; the necessary technology is available. Within these two extremes, there is, of course, a range of combinations.