A comparative assessment of the feasibility of adopting small-scale solar-powered brackish desalination units : the case of Beirut city.

Abstract

Population growth, weak water governance, and poor water resources management in Lebanon have all led to the overexploitation of groundwater resources and the intensification of saltwater intrusion. This study assesses the feasibility of implementing brackish water desalination technologies at the building level as a mean to supplement the limited public water supply within the context of Beirut. As such, a comparative assessment was conducted to evaluate the feasibility of adopting Electrodialysis Reversal (EDR) technique instead of the more commonly used Reverse Osmosis (RO) technology. The two technologies were assessed in terms of their economic, environmental, and technical requirements. The outcome revealed that the EDR units were superior to their RO counterparts when the feed water salinity ranged between 2,000 ppm and 5,000 ppm. At these low salinities, EDR had a lower energy consumption and a higher recovery ratio. RO units became more advantageous when salinity levels exceeded the 5,000 ppm threshold. Furthermore, both desalination technologies were found to be more economical as compared to purchasing water through water tankers. This study also explored the viability of using photovoltaic (PV) units installed on building rooftops to power the energy-intensive desalination systems. The results showed that the costs of producing desalinated water through the use of rooftop PV-powered EDR and RO units ranged between 0.44-0.89 $-m³ and 0.6-1.37 $-m³ respectively. Both costs were slightly higher than the cost associated with using power from the electricity grid (0.43-0.85 $-m³ and 0.58-1.35 $-m³ for grid powered EDR and RO respectively) when the current subsidized kWh price set by EDL (0.096 $-kWh) was used. When the electricity process was made to reflect the costs related to the use of private diesel-power generators (0.22 $-kWh), linking the desalination units with rooftop PV became economically feasible.