Swimming pond

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Swimming pond

A swimming or bathing pond is mostly artificially created still water , often as a foil pond , which is well suited for swimming or bathing and whose water is biologically cleaned primarily by plankton . In addition, the terms swimming pond, bathing pond, bio pond, biological pool, natural pool and other registered trademarks are used. Newer regulations use the designation outdoor pool with biological water treatment . This aspect distinguishes swimming ponds from other artificial bathing facilities.

A distinction must be made between swimming ponds for public use and biological pools for private use. Swimming ponds without pumping stations behave like stagnant water (with adapted biocenosis ), swimming ponds with water circulation to filters are similar in biocenosis to flowing water (see also flowing water types ).

For outdoor pools with biological water treatment, all pool-relevant safety requirements such as DIN standards and DGfdB guidelines apply in Germany. There you are no bathing water or natural pools in the sense of the relevant rules, for which lower requirements apply to the traffic safety obligation.

history

The (now entrepreneurially no longer active) swimming pond builder, biology teacher and multiple an author Richard Weixler built in 1975 along with Werner Gamerith in Waldhausen, Strudengau ( Upper Austria ) the first swimming pond. He subsequently became an entrepreneur and "swimming pond pioneer" and wrote 4 books about it. He was elected President of the Austrian and International Swimming Pond Association and was a court expert for swimming ponds.

The first swimming ponds were stagnant bodies of water with around 50% regeneration area. With the spread and further development of the idea in the emerging industry, pool-like systems were developed that only use filters for water purification instead of water and marsh plants. The development went from very natural-looking ponds to rigid swimming ponds with very small processing zones to pure pool facilities. A cleaning zone is attached to a pool; this can be located directly at the pool or connected by pipes at another location in the garden. If the regeneration zone is connected directly to the pool, a light swimming pond character is created. The first swimming ponds with a strong pool character were built in 2000 and a suitable name for these "modern swimming ponds" was sought. It was then that the term natural pool was found. The first facility of this type was built in Switzerland in 2000 with the Biberstein swimming pool . The currently largest natural pool in Switzerland is located in the Geiselweid swimming pool .

Working principle

The pond is always divided into two zones:

  • The swimming zone or the usage area is used for swimming and bathing.
  • The filter, treatment or regeneration zone is planted with marsh or aquatic plants and serves to purify the water. An exchange of water between the two areas must be possible or artificially created using water pump technology.

The minimum size for a swimming pond system depends on the type of construction chosen; such natural pools are possible with water areas of "8 square meters" or more. The German regulations of the Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau eV (FLL) for manufacturers of such systems from 2006 differentiate between five types of swimming ponds:

  1. Pond type I “pure nature” swimming pond without technology
  2. Pond type II “natural” swimming pond with surface cleaning
  3. Pond type III swimming pond with slowly flowing substrate filter
  4. Pond type IV “natural pool” with a rapidly flowing substrate filter
  5. Pond type V “natural pool” with technical unit flowing through it

The "FLL set of rules for private swimming and bathing pond systems" are guidelines for the construction of public, commercial and not exclusively privately used pools "Treatment of swimming and bathing pool water" is treated and not for natural swimming pools (e.g. river or inland lake pools). The guidelines are not law escharakter, but could in cases of damage as standard are used. The minimum depth also depends on the type.

In general, marsh and aquatic plants, algae , bacteria and zooplankton do the water purification, the less space is allowed for this purification system, the more filters, technology and energy are required. There are also swimming ponds that can do without any higher plants .

Nutrients come in many ways concluded: Exposure to bathers (eg faeces residues, urine residues, sweat , dander , hair , saliva , nasal secretions , food particles , dirt on the feet, etc.) but also by pollen , spores , dust, parts abgeblühter flowers, Fruits and seeds, discarded leaves, bird droppings (see excrement ), flooding of rainwater and topped up drinking water . The germ reduction , the germ reduction (not spoken in a biological system of disinfection , since no disinfectants such as chlorine or ozone are added) works biologically by metabolic processes of bacteria in the root system of the plants and in biofilms on all water-covered surfaces (stones , Foil, plant parts), as well as by in-situ disinfection in open water. In simple terms, "good" microorganisms eat "bad" microorganisms. A stable balance of various types of bacteria, depending on water temperature, solar radiation, pH value and plant growth, is crucial . The biological cleaning can be supplemented by mechanical filters. In spite of the ongoing cleaning, the water can be contaminated with undesirable germs in too high a concentration at any time (the water does not become sterile ).

So that there is no concentration of nutrients after nutrient inputs, they should be removed from the pond ecosystem . This usually happens by fishing out or filtering of filamentous algae Watten , floating algae and abgesunkenem sludge or "harvesting" of higher plants . Since algae generally and also at low temperatures show better growth and a higher rate of reproduction than vascular plants , the water can be cleaned most quickly and efficiently with algae and subsequent removal of the algae.

In order to prevent the water from seeping into the ground, a seal against the subsurface is usually necessary, as is the case with a garden pond . Special pond liners (made of PVC , PE , PP , EPDM or bentonite foils) and (bentonite) nonwovens ), GRP , sprayed "polyurea" ( polyurethane , "liquid foil"), concrete, clay or combinations are usually used as building materials. Due to its cost and ease of processing, the most common use of foil.

Water treatment

The pool water treatment takes place in situ through biological-mechanical processes. All water areas are connected to one another in a closed circuit. Aquatic plants ( phyto- and zooplankton ), a circulation of the water via plant filter basins (regeneration areas) and regular maintenance measures ensure the water quality is guaranteed .

Compared with a treatment plant , the entire oxygen-bearing body as acts aeration tank , the pelvic floor and the surfaces of Kieseinschüttungen act both as a seat faces for biofilms and on the other hand as a settling surfaces as in a settling tank , where sludge can settle, and the "inside" of not flowed through pebble beds ( with biofilms on the surfaces of the stones) can act as an anaerobic denitrification filter. Flow-through gravel filters with biofilms of other aerobic microbes can also be used for aerobic nitrification , provided they are constantly supplied with oxygen-rich water. (Go by, standing and swimming in shallow water or pressurized water rinses) stirred up can sludge in the pond water re suspended are.

If, for example, 20% of the total water area is available in the form of gravel, deep water or a filter trench as a sedimentation area, then, if the cloudy water gets there, 20% of the sedimentable suspended matter can be deposited there without being whirled up again (and when the remaining 80% again a fifth, etc.). This leads to an impoverishment in the swirling area and an accumulation in the sedimentation area. By suctioning off deposited sludge (through suction openings on the pool floor or with the help of pond sludge vacuums or pool cleaning robots (see service robots )), the nutrients bound therein can be effectively extracted from the pond . This should be done before the sludge is microbially broken down again and the bound nutrients go into solution again. Sucked off soil sludge is usually fed to the surface composting as mulch (when composting the sludge, it should be noted that the plasticizers and other additives ( bisphenol A , tributyltin ) released from foils (especially PVC foil) are slightly water-soluble and are adsorbed by solids and therefore occur in higher amounts in the mud than in the water). To remove sludge from large ponds, calcium peroxide is sometimes applied to the pond floor, which only slowly decomposes in water and releases oxygen, which in turn microorganisms need to break down the sludge biomass.

yoke algae floating in the pond water

Floating Jochalgenwatten be on the surface using skimmers sucked or manually abge keschert , floating algae can only kill using UV lamps (to entangle after which the algae and agglomerate) and fine filter technology be removed.

A small regeneration area at the edge of the pool

In contrast to conventional outdoor pools, in which the water is disinfected by chlorination , ozonization or other processes, the risk of disease transmission in a swimming pond is minimized through dilution . This is why the applicable regulations of the Research Association for Landscape Development Landscaping (FLL), in accordance with the requirements of the Federal Environment Agency's bathing water commission , require 10 m³ of water to be kept per visitor. A regular exchange of water with added water as well as treatment zones with corresponding aquatic plants can increase the capacity of daily bathers. The water temperature 30 cm below the water surface should not exceed 23 ° C, since at higher temperatures there is a risk of the increased multiplication of pathogens.

In the above-mentioned FLL regulations, it is recommended to equip the small children's area ( paddling pool ) with a classic pool water treatment system due to the increased risk of infection, otherwise a water suction system and pond water supply to be installed there to ensure constant "fresh water" replenishment. The Federal Environment Agency has issued appropriate building, operating and water quality regulations for public swimming ponds. In Austria there is the ÖNORM M 6235 planning, execution, operation, maintenance, monitoring and rehabilitation of small bathing ponds (in revision).

Alleged "limescale deposits" in swimming ponds or swimming pools usually consist of homogeneous mixtures of calcium carbonate , mixed carbonates, apatite , silicon dioxide and silicates and are therefore difficult to dissolve even with acids. The process of formation of these minerals in water is described in detail under water hardness # lime-carbonic acid balance . These mat-shaped hard deposits take place on plants, pool wall foils, concrete cladding and through sedimentation on the floor.

Algae growth is an indicator of an excess of nutrients in the water. These nutrients are required by all plants for growth, whereby algae have an advantage because they thrive even at low temperatures and float freely in water. Algae are eaten by zooplankton or fish or die from a lack of nutrients (because all nutrients have been bound by the "algae soup") and sink to the bottom of the pond. With the sinking of dead (floating) algae after a lack of nutrients, the pond water suddenly becomes clear. The nutrients bound in the algae can get back into the water in the natural cycle through microbial degradation of the dead algae and the cycle "algae growth - algae death - algae decomposition" begins again. By fishing and filtering off algae and removing them from the pond (cycle), the nutrients in the pond water are also reduced, so that fewer algae can be expected in the next cycle. As a result, the water "lean" in nutrients and remains clear longer. From late spring onwards, higher plants also intensify the metabolism and incorporate nutrients. By harvesting the perennial stalks in early autumn, the nutrients they have bound can be removed from the cycle.

Phosphate is a main nutrient for all plants, including algae. That is why efforts are made to lower the phosphate content in the water below a minimum content. Various methods are used, see also phosphorus elimination and phosphate trap .

Algae problem

Algae are omnipresent, they travel in the wet plumage of water birds or carried by the wind (and certain species then colonize facades). Algae are a natural component of phytoplankton and a basic food source for zooplankton , for example from water birds , fish or in the sea of krill , on which many marine animals feed. As producers, algae are part of the food chain and the biological community in the pond biotope , actually of all ecosystems .

That is why every swimming pond (but also swimming pools with chemical disinfection ) contains algae. Usually they appear in the form of agglomerations ("fluff" or thread algae ) of green algae or blue algae in sudden mass reproduction (the so-called algae bloom ) or as microscopic floating algae that cloud the water .

Algae take nutrients from the water and build them into their cells. In the water with which swimming ponds are filled, there is usually an oversupply of nutrients, so that after a new filling or refilling, there is inevitably a mass increase in algae. This continues with exponential growth until there are no more nutrients available. Then the algae inevitably die (and sink to the bottom) or survive "starving". At such a time, the water suddenly becomes clear, almost overnight, with a view to the ground. Dead algae are broken down by destructors and the nutrients get back into the water. The first algal bloom is followed by a second and so on.

Because there are so many ways to influence the water quality and the nutrient input, no two swimming ponds can be compared with each other and comparisons can easily lead to incorrect assessments. Often chance decides (for example because the fill water in this area was poor in nutrients, the nearest gravel works produced lime-poor quartz stone gravel or exclusively limestone gravel, phosphate-containing rock slabs were installed, there was little bathing weather during the year or the pond had little visitors, many or a few water birds pooed up) and thus little or there was a lot of nutrient input, whether a pond (system) is struggling with algae problems or whether it was, is and remains "always clear".

The aim of a swimming pond is to bathe in clear (colloquially "clean") water. This is why nutrients that have been introduced must be removed from the system. If the algae are netted or filtered off, the desired depletion of these nutrients in the pond occurs, subsequent algal blooms decrease and the pond remains clear longer. Aquatic plants and marsh plants used in the pond can also bind nutrients, but these plant parts must also be harvested regularly. A depletion of nutrients in the water leads to poor growth of these plants. If these are fertilized, nutrients get back into the pond ...

Sometimes details of the specialist knowledge or tricks are enough to keep a pond low in algae. For example, if water evaporation in summer and the falling water level are accepted and fresh water (which can contain new nutrients in excess) is let in again at longer intervals or only in autumn. The construction method (covering the foil on slopes or other type of foil ) must be coordinated with this "mode of operation" , because a falling water level can bring unprotected foil to sunlight, which in turn (with PVC foils) leads to embrittlement and breakage of the foil can. As an alternative, the algae nutrient phosphate could already be filtered out of the inflowing supplementary water or from the pond water.

Natural pool

Natural pool of the "Troase" swimming pool in Trossingen

Public bathing and swimming facilities that have biological water treatment through microbiological processes like in a swimming pond, but are shaped like a pool, are referred to as natural pools or, more often than not, natural pools . This technology was made possible by the continuous further development of the biomechanical cleaning of swimming ponds.

Energy generation

There have been attempts to obtain stored solar or geothermal heat in winter from swimming ponds using a heat pump .

For this purpose, absorber lines were laid on the (deep) pond floor. The disadvantage was that an ice jacket formed around the absorber lines. Because ice has a lower density than water, the (static) buoyancy of the ice tore the lines from the pond floor, which then floated loosely after the ice melted. Setting in concrete at the bottom of the pond or laying the lines under the foil prevents the desired rapid flow of heat, as is desired in geothermal projects. In addition, the cold resistance of the pond liner used must be observed. Normally fish overwinter on the ice-free pond floor, if this also freezes, the fish will not survive the winter.

literature

  • German Society for the Bathing Industry V .: DGfdB R 94.05 - Obligation to maintain safety and supervision in public swimming pools while swimming is open. Eat.
  • Hygienic requirements for small swimming ponds (artificial swimming and bathing pond systems). Recommendation of the Federal Environment Agency. In: Bundesgesundheitsbl - Health Research - Health Protection . Volume 46, No. 6, June 2003, pp. 527-529, doi: 10.1007 / s00103-003-0627-0 .
  • Tanja Büttner, Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau eV (Ed.): Recommendations for planning, building and maintaining private swimming and bathing ponds. From the work of the RWA "Private Swimming / Bathing Ponds" in coordination with the Working Group "Private Swimming / Bathing Ponds". FLL, Bonn 2006, ISBN 3-934484-97-2 .
  • Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau eV (Ed.): Guidelines for the planning, construction, maintenance and operation of outdoor swimming pools with biological water treatment (swimming and bathing ponds). FLL, Bonn 2011, ISBN 978-3-940122-28-5 .
  • German Society for Bathing Society: DGfdB R 65.09 - Checking the hydraulic function of treatment systems for outdoor pools with biological water treatment. Eat.
  • M. Schmalwieser, I. Zweimüller: Key figures on swimming ponds and natural pools - characterization of artificial bathing water using simple parameters. German Society for Limnology (DGL) -Ew. Summing up of the annual conference 2015 (Essen), 2016, pp. 143–147.
  • I. Zweimüller, M. Schmalwieser: Characterization of highly engineered swimming ponds with regard to nutrient concentrations: Dependence on fill water quality and surrounding area. German Society for Limnology (DGL) -Ew. Summing up of the annual conference 2016 (Vienna), 2017, pp. 172–177.

Web links

Individual evidence

  1. ↑ Richard Weixler's company is closed! ; at weixler.at
  2. ↑ mothering ; PDF file ; Publication by sos-regenwald.at; 2011
  3. ↑ Richard Weixler: garden and swimming ponds: construction - planting - care ; Stocker Verlag, 2008
  4. ↑ a b c d e types of swimming ponds with a precise description and their characteristics; at dgfnb.de
  5. ↑ FLL - 10 good reasons to ensure quality for the green sector ; at dgfnb.de
  6. ↑ Tanja Büttner: The new FLL “guidelines for planning, construction, maintenance and operation of outdoor pools with biological water treatment (swimming and bathing ponds)” are available as white print. , at fll.de
  7. ↑ a b c P.Pfluger, B. Wasserrab, E. O'Brien, A.Prietz, P. Spengler, C.Schneider, A. Heussner, T.Schmid, B.Knörzer, JWMetzger, DRDietrich: Development and validation of in vitro test systems for the detection of endocrine disrupting foreign substances: chemical-analytical examination and biological proof of potentially endocrine disrupting substances in sewage treatment plant outlets or receiving waters ; Environment and its safety as a basis for life (BWPLUS); at pudi.lubw.de (State Agency for the Environment Baden-Württemberg); (PDF file) ;
  8. ^ Robert Sattelberger, Marianne Heinrich, Gundi Lorbeer, Sigrid Scharf: Organotin compounds in the aquatic environment ; Publication of the Federal Environment Agency Vienna, 2002, ISBN 3-85457-661-7 ; (PDF file)
  9. ↑ Recommendations of the Federal Environment Agency (PDF; 164 kB)

See also