The Mediterranean - Water supply
Water scarcity and water stress
978-3-14-100890-6 | Page 106 | Ill. 1
Overview
Water supply is the exploitation and distribution of drinking and process water. This is done via pipes and pumps mainly by public utilities and commercial organisations. This map focusses on the water supply in the Mediterranean, which is connected with the water consumption and management in the Mediterranean and exemplified by agriculture and tourism in Spain (see 106.4, 106.5, 107.3, 107.6).
Desalination technologies
Since the Mediterranean region is affected by water scarcity and water stress, desalination technologies play a major role in generating drinking and process water. Three of them stay in focus: the multi-stage flash evaporation (MSF), the membrane distillation (MD), and the reverse osmosis technology (RO).
All of the countries shown in map 1 make use of the latter technology. Only in Italy is falls short in comparison to the other two with only a capacity of 100,000 m3. Reverse osmosis is not only the most energy efficient way of purifying sea water, but also the most advanced and eco-friendly one. In the process sea water is forced through a semipermeable membrane by adding pressure. On the other side of the membrane salt-free water is obtained. The remaining brine water is then diluted before being returned to the open sea. In doing so the marine ecosystem is not harmed.
The membrane distillation is second on the list of technologies used for desalinating sea water. In Libya and Italy, it is even the most commonly used process, whereas it is only of minor importance in Cyprus and Malta. This technology is a thermally driven separation process, in which a temperature difference is created. This triggers a partial vapor pressure, which drives the whole sequence. Since the system makes use of a hydrophobic membrane only free water molecules can pass, thus water vapor. Hence, the membrane acts as a barrier for liquid water molecules.
The multi-stage flash distillation plays the least important role in desalination processes among the Mediterranean states with the exception of Italy, Egypt, and Libya. In comparison to the other technologies, it is rather energy consuming. This thermal process is carried out in a series of closed tanks, in which pre-heated sea water undergoes rapid boiling creating water vapor. This water vapor is then condensed into fresh water which is later collected. This process is repeated with the remaining sea water.
Desalination processes make it possible to grant people access to water, where this resource is actually a scarce commodity. The varying water supply through rainfall in particular (as shown in the graphs of 106.2) make desalination processes necessary to ensure the permanent availability of water. Hence, this technology will advance and progress even more in the future. Nevertheless, the Mediterranean region can still make use of groundwater aquifers to supply water.
