Addressing concerns about desalination: A way forward

In response to climate change and social conflict over water resources, mining companies and other water users in Chile are intensifying their collaboration with local communities and investing in desalination to use seawater in their operations. While mines in the Atacama Desert have always operated under arid conditions, the Central Region has faced new water restrictions due to an unprecedented "mega drought" since 2010. This problem has been exacerbated by increased water demand driven by population growth and economic development.

As desalination is considered the best solution in response to the growing water scarcity problem in various regions of the country, the Chilean government has implemented new policies to encourage the use of desalinated water in urban, mining, and agricultural sectors. Chile has the largest desalination system in South America, with facilities using membrane technology, which reduces waste and employs energy recovery, although brine discharge into the sea remains a significant concern.

This solution path has several detractors among communities whose concerns can be summarised as follows:

Environmental impact: Concern about the high salinity of the brine, which, without control and monitoring, could affect marine life and ecosystems, potentially harming benthic organisms that do not adapt to excess salt in the area of influence near the discharge point of the outfalls.

Chemical elements: The effluents may contain chemicals used for membrane cleaning, which, if not neutralized before discharge, could be harmful to marine environments.

Oxygen depletion: In cases of processes that, along with desalination, increase the water temperature (which is not common in desalination plants in Chile), the hot brine can reduce oxygen levels in the water, affecting marine organisms.

While these concerns are legitimate, there is also evidence the expected impacts are not as severe as expressed:

Dilution and dispersion: Well-designed discharge systems can dilute and disperse the brine, minimising its impact on marine environments.

Advanced technologies: New desalination technologies, such as zero liquid discharge (ZLD), aim to minimize brine production and its environmental impact.

Regulations and standards: International standards for wastewater treatment and the use of eco-friendly chemicals help mitigate the negative effects of brine discharge.

Proposed solutions for desalination

1. To address these concerns, it is crucial to inform communities during the design of desalination plants and implement robust joint monitoring strategies for brine effects, both during construction and operations.
2. For this, it is key to validate saline plume dispersion and plankton uptake models during the project's operational phase. The goal is to corroborate the values obtained in modeling with empirical data collected during operation.
3. For environmental monitoring plans, it is essential to have a clear definition of the topics to be monitored, the number of monitoring stations, key variables, and frequency. Additionally, key parameters must have a clear measurement methodology and be supported by reputable laboratories.
4. Success requires cooperation within and between the various communities affected by the desalination plant, including inland and coastal regions. By fostering cooperation and integration between the private, public, and academic sectors, Chile can develop sustainable desalination practices that meet the growing water demand while protecting the environment and addressing community concerns.

Addressing community concerns: A success story

A perfect example of how to address community concerns is the collaboration between Aguas Pacífico and the Bahía Narau Fishermen's Federation, who established a technical committee to monitor sea salinity. This includes long-term participatory monitoring, with a special emphasis on salinity. The agreement resulted in a five-year bay monitoring program (2024-2028), with six measurement points and two annual campaigns (summer and winter). Together, Aguas Pacífico and the Bahía Narau Federation selected renowned academics and a laboratory as the technical body responsible for sample collection and analysis.