A continuous pond, sealed on the bottom, is equipped with 'shore zones', porous enough for the water to pass through. The shore zones are planted with wetland plants, ideally deficient in nutrients so the plants will absorb nutrients and increase microbial action by their root activities. The plants will be continuously harvested, to remove the nutrients they have absorbed from the water system and return it to agricultural land as compost fertilizer.
The water flows from the the right, through the first, second and third shore zone until it is taken out from the reception well with a small wind pump and continually pumped back to the inlet tank. By this, the water will recycle through the system several times, thus increasing the system's capacity to take up nutrients.
The size of the system is calculated from the water use of the connected population, the rainfall and estimated evapotranspiration. The designer makes such calculations.
Effects on the ecosystem
The new vegetation together with the water will make a new refuge for wildlife animals, insects and plants. They will all participate in the water purification in some way. By this, the fulfillment of a human need (clean water) will also enhance the ecosystem., a requirement for a sustainable relationship with the rest of the nature.
Price of construction
This system was constructed with a rather large contribution of the owner's own work. The cost for construction therefore amounted to less than SEK 25,000 ($ 3200 or EUR 2800). The price of the source-separating toilet system is less than SEK 15,000, so they are stll well below the connection fee to the grid, which in Sweden averages to SEK 60,000 ($ 7700 or EUR 6700)
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