PLUVALOR-System in der Stadt
TRAISELECT-System in der StadtEAUTARCIE in EntwicklungsländerEAUTARCIE in nordischen KlimasDiese Seiten werden zur Zeit von Freiwilligen ins Deutsche übersetzt, die nicht muttersprachler sind. Unseres Ziel ist es, nützliche Informationen dem deutschsprachigen Publikum zur Verfügung zu stellen.
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The EAUTARCIE concept is one of the possible forms of ecological sanitation, with a distinct feature: instead of doing an inventory of the problems, it rather goes to the source of these problems and proposes efficient, simple and inexpensive solutions. Its other main feature is its holistic approach, which takes into account various environmental impact issues.
The considerations developed within these pages have not yet been field-tested. The technical proposals have been extrapolated from our experiments and experience on single-home set-ups. Pilot projects are needed to help determine proper sizing of the various system components. Such experiments have, up to now, not been authorized in Belgium.
To see examples of EAUTARCIE homes that are self-sufficient and self-contained in terms of water consumption, click here.
It is interesting to read a testimonial from Andalusia (Spain) on EAUTARCIE’s benefits in dry regions.
To visualize the general schematic of a PLUVALOR system, click here
.
To visualize the general schematic of a Complete TRAISELECT system,
click here.
The text within this page was first published in French on www.eautarcie.com:
in January 2007
The original text has since been adapted and first published in English on this page at www.eautarcie.org: 2009-06-15
Last update : 2010-06-24
PLUVALOR-System in der Stadt
Sustainable water management involves resorting to various water sources to feed the population. In cities where mains city water is of poor quality, rainwater reuse presents interesting possibilities as part of decentralized high quality potable water production. In reality, water that can be recovered from city roofs is substantial, although insufficient to cover whole-house needs.
Need we repeat that in a polluted world where good-quality water is becoming scarce, you need to adapt water quality to its end-uses. We only need potable water for drink (water, coffee, tea, etc.) and food preparation. And even for cooking, you don't need to have water that complies rigorously with bacterial standards for potable water.
For non-food uses, we could use safe inoffensive water that is not «potable» in the legal sense, and which's accidental absorption would not pose a health risk. This new vision on water quality provides a more pragmatic framework for water management, with substantial cost savings.
When we will cease considering water as a commodity, water distribution corporations will have no interest in pushing for increased water consumption to increase their revenues and by «detaxing» water, municipal authorities will (and must) no longer be able to expect fiscal revenues on water consumption. From that point on, we can effectively enter the realm of sustainable development.
For example, consider a city that is fully equipped with a PLUVALOR system. The sum capacity of such a city's cisterns (capacity of 150 litres per m² of roof area) represents a storage capacity equivalent to a colossal stormwater basin. Stormwater runoff is controlled and stored instead of being fully discharged into a watercourse via sewers. It is then gradually released with household use. This is an important factor in regulating the soil moisture regime.
When designing a new apartment building, the roof surface will ideally be separated in as many sectors as there are apartments [1]. Each sector will dispose of its own roof drain and cistern.
In spite of the potential economy of scale, we advise against the installation of a common collective cistern to service many apartments. Individual cistern management greatly varies from one household to the next, and represents a source of conflict. When a shared collective cistern goes dry, the fault will always be attributed to the other cistern users.
The cistern's capacity (in litres) will be calculated by multiplying the roof catchment area (m²) by 140. For example, an apartment that is serviced by a 15 m² roof area will have a cistern of 15 x 140 = 2100 litres, or slightly greater than 2 m³.
The cisterns can be placed in the basement, or underground next to the building. In a basement mechanical room, you would install a set of small well pump systems for each apartment, and also a microfiltration system to make the rainwater potable. Small section pipes would then feed each apartment kitchen with purified drinking water. An alternative solution would be to replace the microfiltration system by a primary 10-micron filtering system. A ½-inch pipe would feed a valve under each apartment's kitchen sink where a reverse osmosis unit would complete the filtering to provide drinking water to one or two faucets within the home. Purified rainwater would be used for food and drink while lesser quality city water would be reserved for other uses. Rainwater that is purified in this way is comparable to the best bottled mineral water on the market, at much lesser cost.
In cities where mains city water becomes brackish due to grave water supply problems (e.g. drawing water from polluted rivers and lakes), such mediocre city water could be regarded simply as safe inoffensive water to be reserved solely for non food needs (You should not even consider nano-filtration [2] as a option.) In such cases, subsidies could be offered towards the installation of individual rainwater filtration set-ups.
Nano-filtration is a technique used to transform badly polluted water into potable water, usually by the means of salt. The cost of such treated water is about 10 € per m³. To use such expensive water for toilet flushes is totally unreasonable.
I often hear assertions that rainwater harvesting is not really useful within cities because of greater city air pollution and reduced available roof area per inhabitant.
City Pollution
In reality, pollution of rainfall depends mainly on the wind regime. Heavily polluted rainfall can occur in areas that have no local industrial or urban pollution. Rainwater quality in cities is not fundamentally worse that elsewhere. During winter in large cities, we find a light hydrocarbon content in rainwater due to smoke from oil heating. In regions close to dust-generating industries, neighbouring domestic rainwater catchment systems tend to accumulate more sludge in their cisterns, which tends to clog the filters more quickly.
Reduced Available Roof Area
It is true that the required 30 m² of roof area per capita [3] for whole house rainwater reuse (excluding flush toilets) is rarely attained in cities. However, rainfall captured on city roofs remains a precious and important resource.
In fact, a person's daily drinking water requirements
rarely exceed 3 to 5 litres. To harvest this quantity, a roof area of 2 to 3 m² is sufficient, with a storage capacity of 300 to 400 litres.
Thus, if an apartment's roof doesn't exceed 3 m2 per person, rainwater is reserved for food and drink. When the roof area is greater, you can go even further in rainwater reuse to obtain water that is naturally mild, for personal hygiene and laundry. This means connecting the hot-water tank, clothes washing machine and even the dishwasher to the rainwater feed, while maintaining the city connection as back-up in case of dry spells.
To continue reading, go to chapter on the TRAISELECT system in an urban setting.