Abstract:
A huge geothermal aquifer is located in the northern Algerian Sahara, with brackish water
free from toxic inorganic compounds and organic matter. Therefore, this water is appropriate
for good quality potable water production after partial desalination. This paper deals with the
basic desalination plant design considerations in the context of overall optimal aquifer
exploitation. The main types of criteria for such optimization are economic and
environmental. Implementing the concept of “blending” reservoir water (at appropriate
proportion) with desalinated water, allows cost-effective and environmentally attractive
resource exploitation; the latter would be achieved by re-injecting the retentate (after
desalination) free from any chemicals that may degrade the reservoir water quality by
accumulation over the years. Results are summarized of a typical case study based on low
pressure reverse osmosis membrane desalination. Key RO membrane performance data from
a pilot unit are employed in support of this study. The results highlight the main features and
the constraints in plant design and desalinated water recovery; constraints are mainly imposed
by the need to avoid membrane scaling with no use of undesirable synthetic anti-scalants. The
proposed cost-effective plant configuration and operating mode are in accord with the overall
optimum resource exploitation. A cost analysis is also performed for a typical potable-water
production plant. Finally, possibilities are outlined of integrated exploitation of this
geothermal reservoir, whereby energy is extracted in addition to potable water production.
