Injection of desalination brine into the saline part of the coastal aquifer; environmental and hydrological implications. (1st December 2021)

• Record Type: Journal Article
• Authors: Stein, Shaked; Michael, Holly A.; Dugan, Brandon
• Is Part Of: Water research. Volume 207(2021)
• Publication Date: 2021-12-01
• Subjects: Desalination -- Brine injection -- Coastal aquifers -- Saline groundwater -- Seawater intrusion; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2021.117820
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Desalination brine injection into the saline part of the coastal aquifer was tested. Groundwater flow and solute transport model was used to test injection scenarios. Brine injection pushes the fresh-saline water interface salinizing the aquifer. Pumping saline water simultaneously with brine injection negates injection effects. Aquifer recovery after injection stop would take more than 100 years. Abstract: Seawater desalination, specifically reverse osmosis (RO), has become an important water resource, especially in arid and semi-arid regions. The desalination process generates a brine solution that is usually discharged to the nearshore environment, negatively impacting the marine ecosystem. A different method of disposing of the brine solution is needed to restore and maintain the marine environment. One such method is injecting the desalination brine into the saline part of the coastal aquifer. This study aims to investigate the hydrological and environmental impacts of such injection using groundwater flow and solute transport numerical models, showing the fresh-saline water interface (FSI) response at different injection rates, depths, and distances from shore. Moreover, this study investigates the recovery evolution of the aquifer after injection stops. We also analyze the hydrological response when pumping saline groundwater (SGW) (for desalination) or freshwater (for water supply) simultaneously with brine injection. Results show that brine injection creates a high salinity plume that pushes the FSI landward and salinizes the aquifer. After 20 years of injecting 5 million m 3 y −1, 17 million m 3 of freshwater are lost due to salt contamination. It is also shown that by injecting further offshore and in shallower depths, the impact on the FSI and the aquifer is reduced. Furthermore, pumping SGW simultaneously with brine injection negates the brine plume effect on the FSI and results in a more stable interface. It is noted that aquifer recovery is a long process and even after 100 years of recovery, the aquifer is not fully rehabilitated. This paper shows for the first time the hydrological implications of brine injection into the saline part of the coastal aquifer and demonstrates its potential utility for desalination plants in protecting the environment. Graphical Abstract: Image, graphical abstract