The double-cycle water purification system

the combined wetpark and living wall in Ljugarn, Gotland, Sweden

In order to get a water purification system that

the double cycle grey water purification system was designed.

The double cycle system is a combination of a living wall (or folkewall) system and a wetpark system. It builds on the principle that the water is not polluted more than necessary, i.e. urine and faeces are taken care of separately, with a source-separating toilet

The first cycle goes between the folkewall and a two or three-chamber well.

Click on numbers and other items on the figure to see pictures of the details!

  1. The flow between the house and the first chamber of the three-chambered concrete well. The rain water on the roof is also added in this pipe.
  2. The flow from the first chamber of the three-chambered well to the top of the wall. About 30 litres per hour is needed here.
  3. The flow from the wall to the second chamber of the three-chambered well.
  4. The overflow from the three-chambered well to the wetpark system
  5. The flow from the collection chamber in the wetpark system to the house. It is estimated to less than 300 litres per day, or about 0.2 l/min.
The house-wall-well cycle

The second cycle goes between a small wetpark and a collection chamber. The water is pumped from the end of the wetpark back to a collection chamber placed before the first shore-zone of the wetpark. Most of the water that is pumped back returns for another flow through the wetpark, but some is taken back to the house, utilized as greywater and sent back into the first cycle.

You can read about the principles of the wetpark system here.

4 and 5, see above

6. Return flow from the second pond to the collection chamber.

7. Back flow from the collection chamber to the first pond.

Click on numbers and other items on the figure to see pictures of the details!

The double cycle

Thus, the living wall and the wetpark are combined to form two connected cycles, one fast in the folkewall (currently about 20 turnovers for the water before it leaves the living wall part to the wetpark part), and one slow, in the wetpark.

In the wetpark, the current return pumping gives a water turnover of about two monthts.

Calculated on the use of water however, the turnover based on the flow rate and the volume of the system is about one year.


The living wall system is adapted to a dry climate with mild winters. Used on places with cold winters, it is necessary to put it in a greenhouse or the like, for winter function, which is a product of heat and light.

The wetpark system is designed to endure cold, dark winters, because its slow turnover time (about one year) allow all water put into it to enjoy a summer in the system. However, in a very dry climate, the extra water taken into the system from the roof may not compensate for  the evaporation losses. In that case, a system base entirely on the living wall would be advantageous, because all the water that evaporates from that system will be from the plants, and thus productive.

If you want me to make a similar system at your place, please contact me !
More about this:

The building process

The linchpin: The source separating toilet

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