New Mexico Geological Society Annual Spring Meeting — Abstracts

The Holocene climate of the southwestern United States is characterized by periods of moderate to severe drought. Maintaining economic activity and quality of life in prolonged drought periods will demand use of non-traditional water resources including saline ground water. Current options for desalination of water include “reverse” osmosis (RO) techniques that reject dissolved salts at, while allowing water to pass through, the surface of a semipermeable membrane. Salts can accumulate over time on the membrane surface, resulting in clogging and decreased efficiency of the RO process. Common clogging salts include CaCO₃, CaSO₄•2H₂O, and amorphous SiO₂. Clogging salts are collectively referred to as scale deposits. The suitability of saline water for RO treatment is governed, in part, by the tendency of input water to form scale deposits during the RO process. Geochemical modeling that simulates the evaporation of water can be used to determine the tendency of saline waters to form scale deposits during RO.

Simulated evaporation was performed using published U.S. Geological Survey analyses of saline water from selected aquifers in New Mexico. Properties characteristic of selected aquifers include the relatively strong tendency of saline water from the Yeso aquifer to form CaSO₄•2H₂O scale deposits and the relatively strong tendency of saline water from the Rio Grande alluvial aquifer to form amorphous SiO₂ scale deposits. Scale-forming tendencies can have a relatively uniform spatial distribution, as exemplified in a limited number of samples of saline water from the basin-fill aquifer of the Estancia Basin and from the San Andres Limestone aquifer in the southeastern part of the State. However, larger spatial variations in scale-forming tendencies, such as those of saline water from the aquifers in the undifferentiated rocks of Cretaceous age in northwestern New Mexico and the aquifers in the rocks of the Dockum Group of southeastern New Mexico, appear to be more common.