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Imad Lekouch

Production of drinking water by passive condensation of atmospheric humidity (dew)

Published on 23 February 2010
Thesis presented February 23, 2010

The work of thesis has for objective to estimate exactly the quantity of water potentially produced by dew in the village of Mirleft in the South of Agadir (Morocco), to compare it with the other alternative resources of water collection (fog, rain) and estimate its quality. The implementation at Mirleft of a meteorological station, 4 condensers and a net with fog allowed obtaining data concerning the period between 05/01/2007 and the 04/31/2008. Very numerous events of dew were observed, with rare events of fog. The dew water represents 40% of the annual contribution of rain and thus appears as an essential component in the whole water balance. A mathematical approach to modeling the dew has ben used to estimate dew yield over a dozen sites scattered throughout the territory. A spatio-temporal analysis allowed a better understanding of the phenomenon of condensation across Morocco. The average pH of the dew and the rain are respectively equal at 7.40 (± 0.28) and 6.85 (± 0.21) with an average conductivity of 727.25 μS/cm (± 678.64) and 316 μS/cm (± 306.07), representing a total mineralization of 560 mg L-1 and 230 mg L-1. In this study, the ratio TA/TC, lower than 1, indicates the alkaline nature of these waters. The analysis of the major ions showed that the concentration of Cl- and Na+ are raised with regard to that of the other elements. An analysis in main constituent (ACP) was realized on the data to identify the possible origin of the ions. To estimate the contribution marine or not marine of these ions, the fraction of the salt resulting from the sea (SSF) was calculated. The weak percentages of the SSF of the dew suggested a considerable contribution of not marine origin for constituents such as Ca2+, K+, SO42- and NO3- Cl- , Na+ and Mg2+. On the other hand in the rainwater, the values of the NSSF (No Sea Salt Fraction) indicate that only Ca2+ and NO3- are not influenced by the sea. The study of the neutralization factor revealed the decreasing order of the cations in the water of both sources NFCa2+ > NFMg2+ > NFK+. We noticed the influence of the climate on the chemistry of the dew and consequently the temporal variations where the seasons of transition and sandbanks are more concentrated in elements than the wet season characterized by high rates in dew water. The quantities of ions measured and biological analysis agrees with the World Health Organization requirements for potable water. The results in terms of yields associated with chemical analysis of dew and the successful demonstration of the condenser in different areas where our team has done this research led us to equip successful collection systems to Idousskssou (8 km SE of Mirleft).

dew formation, radiative condenser, hydrometeorology, dew and rain chemistry, temporal variation, sources of ions, factor of neutralization, climatic areas

On-line thesis.