Kerry Howe

Bruce Thomson

Abstract

           Communities in the southwestern US are considering alternative sources of supply to meet their increasing water needs.  These sources include treated wastewater, brackish ground water, and water produced from extraction of fossil fuels or minerals.  These sources often are of very poor quality and require advanced treatment before they can be used for public water supply.  Water utilities’ increased willingness to pay for advanced treatment coupled with the decreasing costs of desalination technologies has led many communities to consider desalination of poor quality water as a means of augmenting their public supply.

           While seawater desalination has been successfully practiced for several decades in coastal communities, there are important differences between seawater desalination and desalination of brackish ground waters that are not clearly recognized by water resource managers.  These include: 1) important differences in process performance related to membrane fouling when treating waters with high hardness, silica, organics and other constituents, 2) impacts on water resources associated with the necessity to reject 25 to 30% or greater of the feed water, 3) disposal of brines and other process residuals, and 4) energy requirements of desalination processes in an economic climate of rapidly rising energy costs.

            This paper will compare and contrast the challenges associated with desalination of brackish ground waters at inland locations with those for seawater desalination.  Emphasis is placed on applications of these processes for treating poor quality ground water used to augment potable supplies in arid climates.