Folkewall
Encyclopedia
The Folkewall is a construction with the dual functions of growing plants and purifying waste water. It was designed by Folke Günther in Sweden. Inspired by the "Sanitas wall" at Dr Gösta Nilsson's Sanitas farm project in Botswana
, this technique makes an efficient use of space by fulfilling two essential functions: vertical plant growing and purification
of greywater
. This system is also known as a living wall or green wall.
, LECA-pebbles ("light expanded clay aggregate"), perlite
or vermiculite
. It is designed let the water trickle
over the longest possible treatment path along the length of the wall among the pebbles.
The water is brought in at the top, and percolates following a zig-zag pattern inside the wall. As it does so the plant roots grow among the inert material and extract nutrients from the water. A film of beneficial bacteria
grows over the pebbles, releasing the nutrients in the percolating greywater. At the bottom of the wall a container collects the purified water, which can then be used for non-potable household use, for watering the garden, or it can be returned to the top of the wall.
Greywater: The water feeding the plants in the wall must be free of heavy metals
and/or unsafe pollutants, notably human waste
. This requires using source-separating toilets.
Botswana
Botswana, officially the Republic of Botswana , is a landlocked country located in Southern Africa. The citizens are referred to as "Batswana" . Formerly the British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966...
, this technique makes an efficient use of space by fulfilling two essential functions: vertical plant growing and purification
Water purification
Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...
of greywater
Greywater
Greywater is wastewater generated from domestic activities such as laundry, dishwashing, and bathing, which can be recycled on-site for uses such as landscape irrigation and constructed wetlands...
. This system is also known as a living wall or green wall.
Design
The basic design is a wall of hollow concrete slabs with compartments opening on one or both sides of the wall. The hollows are filled with inert material like gravelGravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
, LECA-pebbles ("light expanded clay aggregate"), perlite
Perlite
Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently...
or vermiculite
Vermiculite
Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite...
. It is designed let the water trickle
Trickling filter
A trickling filter consists of a fixed bed of rocks, lava, coke, gravel, slag, polyurethane foam, sphagnum peat moss, ceramic, or plastic media over which sewage or other wastewater flows downward and causes a layer of microbial slime to grow, covering the bed of media...
over the longest possible treatment path along the length of the wall among the pebbles.
The water is brought in at the top, and percolates following a zig-zag pattern inside the wall. As it does so the plant roots grow among the inert material and extract nutrients from the water. A film of beneficial bacteria
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...
grows over the pebbles, releasing the nutrients in the percolating greywater. At the bottom of the wall a container collects the purified water, which can then be used for non-potable household use, for watering the garden, or it can be returned to the top of the wall.
Other considerations
Plants used: since the harvesting of the plants is a part of the purification process, fast growing, herbaceous crops are particularly suited for the Folkewall. Annual food crops are suitable, perennials like trees and shrubs should be avoided.Greywater: The water feeding the plants in the wall must be free of heavy metals
Heavy metals
A heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight,...
and/or unsafe pollutants, notably human waste
Human waste
Human waste is a waste type usually used to refer to byproducts of digestion, such as feces and urine. Human waste is most often transported as sewage in waste water through sewerage systems...
. This requires using source-separating toilets.
Advantages
- Better use of greywater: most of the evaporation happens through the plant's leaves, which makes the method especially useful in arid climates. It is this aspect the Folkewall makes use of.
- More efficient use of the area, for example in greenhouses or other glazed areas where a wall is used as a greywater purification device, it also works as a heat exchanger and buffer.
- Purification of the percolating water, so greywater can be used as irrigation water.
- In warm climates, the wall can be used on the sunny side to cool the building.
- Low-cost housing: the combined use of Folkewalls and source-separating toilets would reduce the infrastructure cost by about 30%.