At the time of the Universal Exhibition in Milan, entirely dedicated to the theme "feeding the planet" the attention is turned to the nourishment of man and earth. The issue of energy efficiency and environmental needs, more and more, also pass through saving in raw materials, which are essential but steadily decreasing. Water is a vital element and for the mankind has been a perennial challenge. Today, as in the past, ensuring water for the entire world population is the main problem, not only in the areas where, for climate conditions, water always lacks, but also in the less arid and more developed territories where the risk, wrongly, seems less contingent. In fact, the total quantity of water on earth is finite, estimated as 1,386 million cubic kilometres, the 97.5% is salt water and the 2.5% is fresh water, of which only 0.4% is available in surface, and is therefore directly available for use . It has been estimated that by 2025, 1.8 billion people will experience a total scarcity of water and two-thirds of the world population could be under conditions of water stress. Systems to save water and collect rainwater or wastewater for new uses exist and are largely a cultural legacy from the past. But, if the technological development has provided more efficient systems for the collection, storage and reuse of water, these are still very rarely used because of the lack of sensitivity on this issue. If we look to the past, when man had to solve the same problem of water supply without the modern technologies and sewerage system, we realize how much this approach can become strategic for future environmental sustainability. The first real example of hydraulic engineering consists in the birth of the oases, man artificially created settlements, in arid areas and in the absence of surface water. Oases were created by subtracting large areas to the desert, which became cultivable, thanks to major hydraulic structures called Qanat, These allow to carry, drain, collect and store water from the source through tunnels dug in the sand for kilometres, and use it even at great distances (Figure 1). Much later and further, Venetian wells have played for centuries an equally important role. It is estimated that have been constructed more than six thousand wells, for the constant need of sourcing and collection of fresh water in the city. The rainwater was conveyed from roofs or from special platforms, in deep wells dug in the ground, by the so-called pilelle, stone slabs perforated with multiple holes, located at the corners of the floor around the tank. The pit was covered with waterproof clay and a round slab of stone was put in the centre, on which rested the barrel of the circular cistern. The pit was filled with sand, the spongia, which was used as a filter to keep the water always pure. A layer of clay surrounded the pit making it impervious to infiltration of brackish water, which could put at risk the entire collection system (Figure 2). At the building scale, the Pantelleria Dammuso and the Roman Domus are interesting and even current examples. The Pantelleria symbol has its origin in the tenth Century A.D.. The name comes from the Arabic word dammus, the extrados vault, a term that in the Dammuso is extended to indicate the entire building. The installation of the blocks of volcanic rock, called Pantellerite, is strictly dry and it does not provide for the use of binders for the junction, which would have required an excessive use of water. The extradoses of the adjacent domes, together with the raised edges of the roofs, operate as gutters within which rainwater can scroll to the underground tank, the kanallata. The cistern was introduced during the Punic period (from the ninth Century B.C. to the Roman period) and it represents the basic source of water of the island, which has no significant natural sources (Figure 3). The Roman Domus was designed, as the dammuso, to catch, collect and store as much water as possible and to provide a water resource for periods of increased scarcity. Water was intercepted by the impluvium, decanted in a pool at the centre of the atrium and stored in the underground cistern. An overflow system allowed the water in excess to flow into the street or in a sewer (Figure 4). These ancient systems were important to lay the basis of development of the modern devices for the collection and reuse of water, and must still be considered a good example of environmental sustainability in construction.
In vaste aree del mondo, sin da quando l’uomo ha iniziato a costruire le proprie abitazioni ha dovuto confrontarsi con il tema della raccolta e del riuso dell’acqua piovana, per affrontare i lunghi periodi di siccità o le condizioni climatiche avverse. Lo sviluppo tecnologico dei moderni sistemi di raccolta e riuso dell’acqua affonda le proprie radici nelle brillanti soluzioni trovate nel passato.
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|Titolo:||Acqua: riuso e conservazione. Lezioni del passato per la progettazione di oggi/Water re-use and collection. Past lessons for today design|
|Data di pubblicazione:||2015|
|Appare nelle tipologie:||03.1 Articolo su rivista|