Inland brackish groundwater desalination has the potential to expand water supplies in water-scarce areas, but adoption is constrained by the high costs and environmental impacts of concentrate (brine) disposal. Brine valorization—selectively extracting marketable products from desalination brines—offers a pathway to offset disposal costs, reduce environmental impacts, and improve economic feasibility. The challenge is that market potential depends both on technical recoverability of constituents and the ability of local or regional markets to absorb them.
To combat this challenge, a team of NAWI researchers, led by Alison Fritz at the National Energy Technology Laboratory (NETL), along with Alexander Dudchenko (SLAC), Casey De Finnda (UC Davis), and Meagan Mauter (Stanford), focused on two objectives. First, to develop a geospatially resolved market assessment that identified existing and potential markets for bulk constituents by pairing brine composition and expected volumes with market data on building materials, fertilizer, road salts, and chemicals, including caustic soda and hydrochloric acid. Second, to conceptualize and develop process models for brackish groundwater treatment and valorization and perform an economic and life cycle assessment of the proposed treatment.
To achieve the first goal, the project team used the U.S. Geological Survey brackish water databases to quantify volume and composition of groundwater sources across the United States. By pairing this volume and composition data with regional market demand for building materials, fertilizers, road salts, and industrial chemicals, the team conducted mass balances to determine how much recovered material local markets could realistically absorb. Next, to model the performance and costs of these prospective systems, they used NAWI’s WaterTAP platform to construct a digital reference treatment train. They then built a superstructure optimization model capable of evaluating the costs of thousands of candidate process configurations for treatment and valorization.
The preliminary optimization results indicate that in most scenarios, byproduct valorization is not the economically optimal configuration. The costs of the extraction schemes can outweigh the low market value of the recovered commodities. However, for certain water chemistries it can be valuable. For example, in highly saline scenarios, generating sodium chloride for road salt and hydrochloric acid and sodium hydroxide yielded outcomes that reduced net water treatment costs. The project also learned through stakeholder engagement that adaptable technologies that allow valorization decisions to follow market trends can improve the economics in volatile product markets.
Read the project brief and check out the project poster to learn more. To learn more about WaterTAP, register for NAWI’s upcoming webinar.