University of Tolima1
In Colombia, the frequency and intensity of rainy seasons have been changing mainly due to El NiÃ±o events which have been observed in 2002--03, 2004--05, 2006--07 and 2009--10. During 2013 precipitations were recorded only during a period (between April to June) and total annual precipitation was 50% less than average annual values, therefore rainy season in 2013 had not a bimodal behavior as usually occurs. This situation decreased the amount of natural freshwater runoff, specifically in the Andean Zone. In this zone, natural freshwater runoff is usually a natural source of supply for agricultural production systems and ecosystems. Actually, the interest to reuse groundwater and seawater in zones with water supply problems has been increasing, but these water sources contain high levels of salt and minerals such as S, Zn, and K. Thereby, chemical treatments of seawater and groundwater are necessary for domestic and agricultural water consumption (Karagiannis & Soldatos, 2008). The goal of this study was to design a desalination plant for groundwater and seawater by using an evaporation-condensation system with solar cells, in order to supply water in those zones with water deficit.
The design included an electric motor which works with kinetic generators through finite magnetic fields, a system of pools to store both salinized water (mass input) and desalinated water (mass output), a system of heat cells to condensate the salinized water, and two gutters to decant and extract salt, similar methods have been used by Khawaji & Kutubkhanah (2008). The operation scheme is briefly described as follows: 1) The water is stored in a receiver tank. 2) The water is conducted to condensation cells which generate heat coming from kinetic power plant. 3) The evaporated water (without salt) is transported toward a storage tank where water is agitated to increase its level of oxygen. 4) The salt coming from condensation cells is conducted to receiver tank of salt. This desalination plant was designed to treat a total uptake flow of 0.24 m3 s-1, driving average flows of 0.0171 m3 s-1 in each condensation cell. Likewise, the desalination plant is designed to operate at longitudinal slopes about 0.75%, with a runlength of 20 m.
A scale model of the desalination plant was constructed in the Laboratory of Hydraulics located in the University of Tolima, Colombia, in June 2014. In order to conduct a performance testing and adjust the plant design, 20 liters of groundwater with a salinity of 2.8 dS m -1 were treated by using the desalination plant in July 2014. The salinity of groundwater was 1.7 dS m -1 after treatment with the plant.
The result of this study suggests that it is feasible to build a second scale model to treat 1 m3 water. Furthermore, this result suggests that the desalination plant could be a supply option for sites with low rainfall and high evaporative demand. The design of this desalination plant also includes a water distribution and collection system to provide to the consumers a closed water supply system and thus, promote water reuse. References: Karagiannis, I. C., & Soldatos, P. G. (2008). Water desalination cost literature: review and assessment. Desalination, 223(1), 448-456. Khawaji, A. D., Kutubkhanah, I. K., & Wie, J. M. (2008). Advances in seawater desalination technologies. Desalination, 221(1), 47-69.