Energy Requirements for Desalinating Brackish Groundwater in the United States

Abstract

Water shortages have motivated growing interest in desalinating brackish groundwater to meet fresh water requirements. Since the 1960s, only one national assessment of groundwater resource distribution and availability has been conducted in the United States, and no national assessment has been conducted on the energy costs required to make brackish groundwater potable. Yet, various organizations have collected more hydrological and chemical data from the increasing number of wells. Groundwater’s far more complex and diverse chemical composition, compared to that of seawater, makes a large-scale analysis of the resource especially valuable. This paper uses chemical and physical data from groundwater samples, compiled by U.S. Geological Survey in August 2016 from 17 sources for over 100,000 groundwater wells across the United States, to conduct a national assessment on groundwater composition and desalination energy costs. First, the paper investigates the geographic distribution of groundwater composition and reveals that composition varies largely throughout the U.S. Then, a thermodynamic analysis of the least work of separation is developed. This analysis is used to evaluate the site-specific least work of separation required for desalination, which serves as a baseline for groundwater desalination energy costs in the U.S. As with composition, least work of separation varies considerably across the nation. Lastly, areas with both low least work of separation and high water stress are determined in order to highlight regions that hold potential for desalination to reduce the gap between high water demand and low water supply.