Desalination for water shortage in the Greater Beirut area : a cost benefit comparative assessment with economy of scale and environmental externalities -

Abstract

The competition over available water resources is a critical global issue associated with population growth and development. Along coastal areas, population clusters are overexploiting groundwater aquifers in an attempt to meet increased water demands. Over-pumping along with the impacts of climate change is promoting seawater intrusion and consequently deteriorating the quality of these resources. Desalination of brackish or seawater is an increasingly popular mitigation-adaptation for coastal population. In this study, the adoption of brackish and-or seawater reverse osmosis (RO) was assessed at three different scales namely, at the building, community and city level. Each system was studied with regards to its financial viability, taking into account the salinity levels of the feed water, the associated environmental externalities, and the economies of scale. Brackish RO systems operating at the building level were found to be problematic; as they are hard to regulate and are associated with high environmental costs. Centralized seawater RO systems proved to present a more sustainable option given their economy of scale, smaller environmental footprint, and ability to regulate. On average a household with a building level brackish water RO unit could save 1 $-m³ if their water was generated from a centralized seawater RO. When compared with a planned inter-basin water diversion project, RO proved to be a more costly option if environmental costs were excluded.