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Cleaning water with plants

Constructed wetlands provide simple and ecological ways to recycle greywater and wastewater. The cleaned water can be used for irrigating home gardens or flushing toilets. The teaching unit «Cleaning water with plants» provides insights into principles of eco-engineering and gives pupils the opportunity for hands-on experience by constructing their own wetland model.

  • Introduction into the water cycle: The amount of water on the earth is constant. Water neither gets lost to space, nor is it replenished from outside the planet. It runs in a continuous cycle that is driven by the sun. If water travels, it must also get very dirty on the way. Why is it then, that we can always find clean water? This experiment will provide the answers.
  • Water distribution and use: Pictures taken from space show the earth as a blue planet. Two thirds of the earth's surface is covered with water. The amount of water on our planet is estimated to be around 1.46 billion km³. However, the greatest part of that (97%) is saltwater in the oceans. This experiment illustrate how much of the total water on the planet can be used a drinking water.
  • Wastewater analysis: The experiments demonstrated here can either be conducted as an individual lesson or, once established, as routine analysis for measuring the performance of the constructed wetland model, which has to be maintained and periodically fed with «artificial wastewater». This lesson aims to explain the concepts of «clean water» and «water quality guidelines» and supports to understand the principles of water analysis.
  • Create a mini sewage evapotranspiration plant: Willow wastewater treatment plants provide the opportunity for wastewater treatment without any water discharge into the environment by evaporating the wastewater that comes to the system to the atmosphere. These systems are widely used at places with stringent water effluent standards and where soil infiltration discharge opportunities are limited. This experiment shows the potential use of different plant species and the effect of three different environmental conditions on the evaporation process.
  • Constructing a wetland model: A constructed wetland is a nature-orientated technology to treat wastewater. The following construction manual allows pupils to build their own treatment plant. Pupils get an understanding of the set-up of a constructed wetland and the way it works. They realize that constructed wetlands are a modern ecological technology, where principles of nature are used to clean wastewater. They conduct experiments to follow up the «cleaning capacity» of their treatment plant.