Water desalination cost literature: review and assessment

As water resources are rapidly being exhausted, more and more interest is paid to the desalination of seawater and brackish water concentrations. Today, current desalination methods require large amounts of energy which is costly both in environmental pollution and in money terms. Many studies of water desalination costs appear regularly in water desalination and renewable energy related publications. Cost estimates seem to be very much site specific and the cost per cubic metre ranges from installation to installation. This variability exists because the water cost depends upon many factors, unique in each case, most important of which are the desalination method, the level of feed water salinity, the energy source, the capacity of the desalting plant, and other site related factors. This paper attempts the taxonomy of a large number of related publications, classified in a systematic method and format, in order to allow meaningful comparisons and facilitate the derivation of useful conclusions.

Desalination cost has decreased over the last years due to technical improvements and learning in a world of increasing fossil fuel prices. For conventional systems the cost for seawater ranges from 0.4h/m3 to more than 3h/m3, while for brackish water desalination the cost is almost half. When renewable energy sources are used the cost is much higher, and in some cases can reach even 15h/m3, due to most expensive energy supply systems. However, this cost is counterbalanced by the environmental benefits. The choice of desalination method affects significantly the water desalination cost. Thermal methods are used mainly in medium and large size systems, while membrane methods, mainly RO, are used by medium and low capacity systems. Yet, during the last years, RO is the optimal choice in even larger units. RO methods, which are dominant in the desalination of brackish water, have the lowest cost, mainly due to much lower energy consumption and the recent technological advances that have been achieved in membranes. Under special conditions hybrid systems can offer increased and more stable production of fresh water.