This wall was made by Carl von Wovern in Addis Ababa. The tires are filled with charcoal and gravel to make a Terra Preta-like mixture.
The water is brought to percolate in a zigzag pattern by the insertion of plastic sheets in the growth medium.
The charcoal works like a 'bank' for the nutrients, but will not be overfilled an loose its adsorption capacity due to the continous uptake of nutrients by the plants.
Hence, the actual 'purification' of the wastewater system is when the plants are harvested.
After the passage of the wall, the water is collected and pumped back for another passage.
This is the double-sided version of the wall, intended for free-standing use.
The top of the tires is cut-out on each side to give place for the plants.
Note the drainage hole at the arrow, on each side of the bottom of the tire, to the next level !
The bottom, under the wall, is a scrap metal sheet formed to collect the water draining from the bottom level tires.
In order to carry the weigth of the wall, also the bottom layer is filled with the charcoal-soil mixture.
The mixture of charcoal and gravel is 1:1 per volume.
The gravel is porous, of volcanic origin.
The the bottom row of the decks are placed on the soil mixture in the tray.
To avoid loss of the substrate, some stones are placed in the front.
After that, the tires are filled with the soil substrate to a plane slanting at both sides.
The plane is covered with some strong plastic (of about the same grade as a fertilizer bag), to lead the water from the middle to the sides, where the plants will grow.
After the insertion of the plastic in the substrate, the tires are filled up with soil to the top.
Then, new layers of tires are placed alternate to the bottom layer, to create pockets for the plant growth .
On the top of the wall is a distribution channel placed at level, to distribute the incoming water as enenly as posible over the tires.
The channel can be made from an ordinary rain gutter, overfilled with gravel over each deck, making the water spill over on the centre of the tire.
If the distribution channel is covered, unnecessary evporation might be avoided.
The grey water fro the house (A) is collected in a barrel
Then, it is pumped up and distributed over he wall (B).
This can be done automatically if a solar driven pump is used.
After just one passage through the wall, the water is remarkably pure.
The circulation system is however intended to let the water circulate several times.
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