Brine Discharge from Desalination Plants: Environmental Contaminants, Pollution Control Processes and Mitigation Strategies

1. Introduction

Freshwater poverty is a major global problem today, particularly in arid and semi-arid regions where demand for water resources far exceeds supply. Desalination is now considered a strategic solution to ensure water security, as is the case in the MENA (Middle East and North Africa) region, where over 50% of drinking water is supplied using desalination technology [1,2].

However, this technology still poses significant environmental, health, and economic challenges. Freshwater production through reverse osmosis or thermal processes is often accompanied by highly saline discharges, called brines, and the frequent addition of chemicals such as chlorine, biocides, and anti-scalants [3,4]. These discharges disrupt saline and thermal stratification, causing biodiversity loss, deterioration of seagrass beds such as Posidonia oceanica in the Mediterranean, and the death of sensitive benthic organisms [5,6].

On the other hand, desalinated water can contain chemical byproducts such as boron and bromate, which pose significant health risks. Desalination plant workers are also exposed to hazardous chemicals on a daily basis, increasing their risk of developing occupational diseases [7,8]. In addition to these environmental and health risks, there are other energy and economic aspects: the production of desalinated water consumes a lot of energy (3-4 kWh/m³ for reverse osmosis and approximately 15 kWh/m³ for thermal processes), resulting in significant costs and a significant carbon footprint [9,10,11].

To address these challenges, an integrated approach must be developed, combining hypersaline plume modeling, health risk assessment, and energy and economic analysis, with the goal of sustainable water desalination.

Figure 1 provides the conceptual framework for this work, illustrating the main stages of the desalination process: freshwater production (blue pathway), saltwater discharge (red pathway), and their associated impacts on the environment and public health. It provides a synthetic view of the interactions studied and constitutes the basis of the methodology developed in the subsequent stages of the study.

2. Materials and Methods

2.1. General Approach

This study adopts the principle of a systematic and critical review of international scientific literature published between 2015 and 2026 in high-impact journals. The methodological objective of the work is to reassess the potential impacts of desalination plants from a health, environmental, and economic perspective, drawing on:

• Experimental data,

• Quantitative analyses,

• Documented regional case studies.

2.2. Source Selection Criteria

Throughout this study, all sources were selected based on specific inclusion and exclusion criteria, ensuring the validity and relevance of the analyzed data (Table 1).

2.3. Literature Search Strategy and Inclusion/Exclusion Criteria

Using the PRISMA methodology, 612 articles were identified in the Scopus, Web of Science, and ScienceDirect databases (2015–2026). After screening, 45 studies were selected for the final analysis. A closer examination of eight major studies, selected for their geographical and methodological diversity, shows a convergence of results regarding the impact of brine discharges (Table 2).

This review highlights the need for minimal dilution and appropriate regulation, as well as improved diffuser systems with continuous monitoring and brine recovery.

2.4. Data Analysis Methods

2.4.1. Energy Analysis

The energy analysis aims to compare the specific energy consumption of different technologies to measure their sustainability (as shown in Figure 2). These analyses show that the wide variation in energy consumption rates is due to the type of technology used. Reverse osmosis (RO) consumes an average of 3 to 4 kWh/m³, while multi-stage distillation (MSF) consumes up to 12 kWh/m³ [20,21].

Specific energy consumption (SEC) can be calculated based on the following relationship:

Where:

• Etot = total energy consumed (kWh),

• Vwater = volume of desalinated water (m³).

To compare the energy efficiency of different desalination technologies, Table 3 presents a set of specific energy consumption (SEC) values reported in some recent studies.

To better illustrate the performance gaps, Figure 2 provides a comparison of specific energy consumption (kWh/m³) between the different desalination technologies currently in use.

Thermal technologies remain energy-intensive, which limits their sustainability in energy transitions.

2.4.2. Economic Analysis

The economic analysis is based on the Levelized Cost of Water (LCOW) study, which provides a regional comparison (Figure 3). The levelized cost of desalinated water was estimated in dollars/m³ according to the International Energy Agency [24].

Where:

• Ct = total annual costs (investment, operation, maintenance),

• Vt = volume of water produced,

• r = discount rate,

• n = lifetime of the facility.

Table 4 presents the levelized costs of desalinated water (LCOW), by main production areas.

As shown in the figure below (Figure 3), there is significant variation in the cost of desalinated water by region, for a number of reasons, reflecting significant differences in energy availability, technology used and available support policies.

2.4.3. Environmental Analysis

Based on the environmental analysis, we focus on the volumes and salinity of brine discharges.

The discharged brine volumes were calculated according to:

$${\displaystyle \frac{{\mathrm{V}}_{\mathrm{b}\mathrm{r}\mathrm{i}\mathrm{n}\mathrm{e}}}{{\mathrm{V}}_{\mathrm{w}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r}}}}=(1-\mathrm{R})$$

Where:

R = recovery rate (40–50% in RO, 25–35% in MED/MSF).

MED = Multi-Effect Distillation.

MSF = Multi-Stage Flash Distillation.

Table 5 gives the average brine discharge volumes and associated salinities for various major desalination technologies.

Figure 4 highlights that membrane processes have a better ratio between produced water and discharged brine compared to thermal processes, which is better in terms of environmental sustainability.

2.4.4. Health Analysis

The health analysis is based on the epidemiological and toxicological literature on chemical by-products and nanoparticles. A set of epidemiological and toxicological data was collected on:

• Presence of chemical by-products: chlorine, bromates, and trihalomethanes (THMs).

• Toxicity of nanoparticles from membranes.

• Effects of concentrated brine on marine organisms.

3. Results

The main objective of this study is to illustrate the potential and multidimensional impact of desalination plants in terms of public health, the environment, and the economy.

3.1. Discharge Volumes and Salinities

• Desalination plant output varies on average by 1.5 liters of saline solution for every liter of freshwater [22,27].

• In the MENA region, discharges could exceed 55 Mm³/day, or about half of the total global discharge [22].

• Salinity measured in plumes ranges from 45 to 70 g/L, with maximum salinity levels above 75 g/L recorded in the Arabian Gulf [27,28].

3.2. Plume Dilution and Extension

• According to hydrodynamic models (CORMIX, Delft3D, MIKE 21), the minimum acceptable dilution ranges from 20:1 to 50:1, depending on local hydrodynamics [12].

• In the Algerian Mediterranean (Ténès, Tipaza), hypersaline plumes can extend over a distance of 100 to 300 meters from the discharge point under slow current conditions (< 0.05 m/s) [3,29]. Desalination brine discharges may cause ecological disturbances in marine ecosystems exposed to high salinity conditions [29].

Figure 5 shows the dilution and extension of brine plumes as a function of distance from the discharge point. In the Algerian Mediterranean (Ténès, Tipaza), the extension of hypersaline plumes extends up to 100 and 300 meters under weak current conditions, while in the Arabian Gulf, the salinity anomaly remains above 3 g/L beyond 300 meters. In Chile, however, it drops to less than 1 g/L from the first 100 meters. On the Chilean coast, exposed to strong currents, the dilution is less than 50 meters [15]. Hypersaline brine discharges can significantly affect marine benthic diatom diversity and coastal microbial ecosystems [19].

3.3. Comparative Ecological Impacts

• The salinity of Posidonia oceanica meadows exceeds a critical threshold of > 1 g/L above ambient levels [30].

• A significant decrease in benthic communities exceeding +2 g/L [14,31].

• Due to cumulative discharges into the Arabian Gulf waters, this has led to an increase in coastal salinity of 2 to 3 g/L, with a lasting impact on macrofauna [28].

3.4. Trends 2015–2026

• Overall increase: According to recent estimates, global brine production is expected to increase from 95 Mm³/day in 2015 to over 110 Mm³/day in 2025 [27,32].

Figure 6 shows the global increase in desalination-related brine discharges recorded through 2025. It highlights a continued upward trend, driven by the increased use of desalination technologies, particularly in arid and semi-arid regions [22].

• Diversity of methods, with a significant increase in geographic information systems (GIS) and multivariate statistical methods for spatiotemporal assessment [13,21].

• Towards recovery: Several studies have recommended the recovery of minerals (lithium and magnesium) as an alternative to simple dilution [33,34].

3.5. Synthetic Regional Comparison

Table 6 summarizes the observed regional variations in brine discharges, taking into account volumes, salinity, dilution, and environmental impacts. The Arabian Gulf tops the list, with brine discharge rates exceeding 35 Mm³/d and salinity levels reaching 75 g/L. The 20:1 ratio remains elusive, resulting in a serious impact on benthic organisms [35].

However, the Algerian (2-3 Mm³/d) and Moroccan (1-2 Mm³/d) coasts are the least affected but still at risk, particularly for Posidonia oceanica meadows. Chile and Australia, meanwhile, record moderate discharge levels (≤1 Mm³/d), with rapid mitigation and limited impacts, highlighting the urgent need for unified international standards.

Figure 7 compares the volumes and salinity of saltwater discharges by region. The highest levels are in the Persian Gulf, with over 35 Mm³/day, followed by the Mediterranean coast of Algeria and Morocco, with around 1 to 3 Mm³/day. In contrast, Chile and Australia record low levels of brine, with rapid dilution. With global production exceeding 110 Mm³/day, this illustrates the scale of the problem.

3.6. Brine Production and Impacts on the Marine Ecosystem

The amount of brine discharged by desalination plants is 1.5 liters for every liter of freshwater produced, resulting in high salinity in the presence of high concentrations of chlorine, copper, and antiscalants [28,32].

The following formula gives the ratio of produced water to infiltrated brine:

$$R={\displaystyle \frac{Q_{water}}{Q_{brine}}}$$

Where:

• Qwater = volume of water produced (m³/day)

• Qbrine = volume of brine discharged (m³/day).

Table 7 shows the ratios between produced water and brine discharged for several technologies, highlighting the low efficiency of thermal processes compared to reverse osmosis.

These discharges cause local oxygen shortages, high mortality rates among marine animals, and a significant decline in biodiversity [36].

3.7. Impacts on Public Health

Halogenated disinfection by-products formed during chlorination and chloramination of desalinated water may pose significant toxicological risks [37]. Desalinated water generally meets all drinking water standards, but the presence of residual by-products can pose serious health risks if not managed properly.

• In the Gulf region, bromate (BrO₃⁻) formation during ozonation depletion has been detected at levels up to 25 µg/L, exceeding the World Health Organization's recommended limit of 10 µg/L.

• The residual boron concentration in reverse osmosis-treated water ranges from 1.5 to 2.5 mg/L, which is very high compared to the WHO maximum limit (0.5 mg/L), which can have negative effects on reproductive health [38].

• Epidemiological studies conducted in the Kingdom of Saudi Arabia and occupied Palestine have shown a significant increase in the prevalence of kidney disease, between 12 and 18%, among the population using desalinated water compared to those using groundwater [8,39].

Table 8 summarizes the main contaminants detected in desalinated water, their average concentrations and possible exceedances of WHO standards, as well as the associated health risks.

3.7.1. Evolution of Cancer Diseases Following the Proliferation of Desalination Plants

The widespread use of desalination plants has contributed to water security in arid regions, but it has also raised health concerns, particularly regarding cancer. Although no direct link has yet been established between the use of desalinated water and increased cancer cases, several studies have shown the presence of disinfection by-products (DBPs), such as bromates and nitrosamines (NDMA), which are produced following oxidative treatments of bromide-rich seawater (chlorination and ozonation) [29,40]. As in Kuwait, high bromate levels are associated with a cancer risk of up to 3.9 x 10⁻⁴, which exceeds international limits [1]. In contrast, a study conducted in the occupied territories did not show a significant increase in colorectal cancer but recommended long-term monitoring [41]. Therefore, the association of desalination and cancer risk still requires further study and monitoring. This requires improved treatment processes, strict monitoring at all stages of desalination, and the establishment of stricter standards to mitigate potential health risks [29,42].

Table 9 shows the concentrations and presence of disinfection by-products (DBPs) in several locations around the world.

In some Gulf countries, some plants exceed the maximum bromate limit set by the World Health Organization, increasing the risk of cancer. In the occupied territories, NDMA levels remain low but require strict monitoring. In Spain and Australia, concentrations remain below guideline values.

Figure 8 illustrates the formation of disinfection by-products (DBPs) in desalination plant water, including bromates, trihalomethanes (THMs), and nitrosamines (NDMA) resulting from reactions between oxidants (chlorine, ozone, chloramine) and bromide ions. Their direct discharge into the sea leads to ecosystem degradation and negatively affects biodiversity, with potential public health risks throughout the food chain.

3.7.2. Impact on the Health of Desalination Plant Workers and Technicians

Desalination plant workers and technicians are exposed to significant chemical risks (bromates, trihalomethanes, boron, acids, and bases) that can lead to respiratory diseases, cancer, skin irritation, and poisoning. Physical stress (heat, humidity, and noise >85 dB)s can also lead to dehydration, cardiovascular and musculoskeletal disorders, and hearing impairment. Close monitoring and preventive measures are therefore necessary.

Table 10 summarizes the main chemical agents present in desalination plants, their exposure routes, and their effects on worker health.

Figure 9 shows the various occupational hazards to which desalination plant workers are exposed, which are mainly due to chemical factors and poor working conditions.

The figure shows that worker exposure to chemicals (chlorine, antiscalants, boron, and bromate) and saline aerosols constitute the most significant risks, surpassing noise and heat stress.

3.8. Case Study: Numerical Modeling of Brine Dispersion — Tenes (Western Mediterranean)

3.8.1. Objectives

To enrich this review with an innovative quantitative dimension, a numerical model of the dispersion of brine discharged from a hypothetical reverse osmosis plant on the Algerian coast (Ténès) was developed. Its objectives are as follows:

- Measurement of the spatial dimension of hypersaline plumes under different hydrodynamic conditions;

- Compliance with environmental salinity thresholds by estimating the minimum dilution required;

- Development of a set of technical recommendations adapted to the Mediterranean context.

3.8.2. Simulation Methodology

The approach combines:

1. Near-field: Estimation of initial mixing using a semi-empirical model (CorJet/CORMIX).

2. Far-field: Simulation of coastal dispersion using the three-dimensional Delft3D model, integrating various elements such as tides, winds, and currents.

3. Post-processing: Development of isosalinity maps and vertical profiles to quantify the affected area (ΔS = +1 and +2 g/L).

This methodology is consistent with recent studies conducted in the Mediterranean region [12,13,46].

3.8.3. Input Parameters

Table 11 presents the parameters adopted for the numerical simulation of brine dispersion.

3.8.4. Calculation of Minimum Dilution

The required dilution is given by:

Example: for Ssw=38 g/L, Sbr​=76 g/L, et ΔSmax=2 g/L, we ge :

$$D_{min}={\displaystyle \frac{76-38}{2}}=19$$

Initial dilution ≥ 19:1, consistent with the results from Tipaza (Ténès) [12,13].

3.8.5. Simulated Scenarios

• Scenario A (medium): current 0.15 m/s.

• Scenario B (worst case): low current 0.02 m/s.

• Scenario C (high energy): current 0.30 m/s.

• Scenario D (attenuation): optimized diffuser + deep discharge.

3.8.6. Main Results

• Under average conditions, the plume (+2 g/L) extends over 150 m.

Figure 10 reveals the dispersion process of the hypersaline plume under intermediate conditions (scenario A), with iso-salinities ΔS = +1 g/L and +2 g/L at t = 24 h.

• In weak currents, the plume remains dense and confined, extending over more than 400 m, as shown by [12] through their simulations.

Figure 11 also provides a vertical section of the dense plume from scenario B, highlighting its tight confinement to the seabed and the accumulation of salinity > +2 g/L over more than 400 m.

• In strong currents, dispersion is very rapid (< 100 m).

• Optimizing the diffuser (scenario D) reduces the surface area affected by ΔS > 2 g/L by 35%.

Table 12 presents the surface area affected by increased salinity under the different simulated scenarios.

3.8.7. Discussion and Recent References

The results obtained confirm local studies conducted in Algeria and elsewhere [12,13,47]. The recommendations for the Maghreb region are part of the regional discussion for the Middle East and North Africa regarding the brine discharge process [16].

Figure 12 shows the evolution of the surface area affected by increased salinity (ΔS > 2 g/L) as a function of current velocity. A significant decrease in the surface area of ​​the affected zone is observed when the velocity increases from 0.02 to 0.30 m/s.

4. Discussion

The results obtained highlight the importance of the multidimensional impacts of desalination, in addition to highlighting additional elements compared to previous international studies. The discussion of this study is structured around five axes: comparison with major international studies, examination of impacts on health and the environment, energy and the economy, regional case studies, and conclusion on the implications for governance and sustainability.

4.1. Comparison with Major International Studies

The results highlight significant brine discharges, ranging from 40 to 75 g/L, with hypersaline plumes reaching 100 to 300 m in the Algerian Mediterranean Sea (Amokrane et al., 2021), our study relies on local modeling (CORMIX, Delft3D) to develop tailored recommendations. The critical limits retained (+1 g/L for Posidonia oceanica, +2 g/L for benthos) are consistent with the research of [4], and show the increased vulnerability associated with weak currents and thermal stratification. This study also includes a health component, showing exceedances of the WHO limit values for bromate and boron, potentially establishing a new link between chemical discharges and public health.

4.2. Health and Environmental Impacts

4.2.1. Health Impacts

Desalinated water generally meets drinking water standards, but it contains hazardous chemicals such as boron, bromate, and trihalomethanes (THMs) [37,38].

• Boron has negative effects on fertility and fetal development [34,38].

• Bromate, which is formed during the ozonation process, has been identified as a carcinogen by the Environmental Protection Agency [40,48].

• Recent studies have shown a link between respiratory and kidney disease in workers exposed to chemical cleaning products and saline sprays [43,49].

4.2.2. Impacts on Aquatic Life

Discharges of highly saline waters laden with chemicals (chlorine, biocides, and anti-scalants) alter salt layers, posing a threat to benthic biodiversity [32,50].

Figure 13 illustrates the range of environmental impacts of brine discharges: habitat destruction, plankton/larval capture, and the spread of hypersaline and chemical clouds.

• In the Mediterranean region, this phenomenon leads to an increase in the mortality rate of Posidonia oceanica and other sensitive species [6,51,52].

• In the Red Sea, increased salinity causes rapid deterioration of coral reefs [28].

• Suction systems installed in stations result in the destruction of large quantities of plankton and fish larvae, causing an imbalance in food webs [50,52].

Our numerical simulations show that under low-current conditions (<0.05 m/s), the area affected by ΔS > 2 g/L can reach 300 m wide, while in areas with strong hydrodynamics, the dilution can be less than 50 m.

4.3. Energy and Economic Considerations

Seawater reverse osmosis (SWRO) remains the most efficient technology, with an energy consumption of 3–4 kWh/m³, compared to 10–15 kWh/m³ for thermal processes (MSF, MED) [8,10].

The levelized cost of desalinated water is relatively high, between USD 0.6 and USD 1.5 per cubic meter, which constitutes a barrier to widespread adoption of this technology, particularly in countries that rely heavily on fossil fuels to power desalination plants. However, relying on the latest technological developments and integrating renewable energies (notably photovoltaic and wind), as well as the use of new generation pressure exchangers, makes it possible to reduce the total energy consumption of the stations by around 30 to 40%, which reduces the carbon footprint and strengthens environmental and economic sustainability [52].

4.4. Regional Case Studies

The inclusion of case studies is essential to illustrate specific challenges and the solutions adopted:

• Algerian Mediterranean: adoption of multi-jet diffusers to protect Posidonia oceanica meadows.

• Arabian Gulf: major degradation of coral reefs with discharge salinity reaching 70–80 g/L; regional programs integrating nanostructured membranes and renewable energy [10,35].

• Australia: Perth SWRO plant powered by a wind farm, reducing energy consumption by 35% thanks to energy recovery [53].

• Morocco (Chtouka): solar-reverse osmosis combination producing 275,000 m³/day, reducing costs and emissions.

• Chile: Implementation of brine mining, valorizing brine by extracting lithium and magnesium [54].

4.5. Implications for Sustainability and Governance

To assess the sustainability of desalination, this study presents a comprehensive framework that combines environmental, health, and economic dimensions [54]. This report highlights the need for integrated regional governance, inspired by the European Water Framework, to standardize the management of transboundary discharges and plumes [16]. Efforts to integrate emerging technologies such as artificial intelligence and remote sensing can improve real-time monitoring and adaptive discharge management, helping to address the gaps identified by [4,22].

4.6. Novelty and Scientific Contribution

This study combines all of the following elements in its integrated approach:

• Hydrodynamic modeling using (CORMIX, Delft3D) for plume dispersion.

• Conduct health analyses based on recent epidemiological data [8].

• Economic and energy assessment (LCOW, SEC).

• Innovation prospects through brine valorization.

Unlike traditional reviews, this study provides a detailed regional view of North Africa and addresses a gap identified in the scientific literature [55].

While the results demonstrate the importance of desalination for water security, it must evolve towards sustainable models that integrate:

• Work to reduce environmental impacts through strict standards and improved technologies [51].

• Work to reduce health risks associated with chemical by-products.

• Work toward integrating renewable energy in an effort to reduce the carbon footprint.

• Work toward regional cooperation and organizational harmony.

This comprehensive approach paves the way for sustainable desalination technology, combining water security, public health, and biodiversity conservation.

4.7. Recommendations and Outlook

This study presents an integrated approach to health, environmental, economic, and energy factors, clarifying their interactions. This approach aims to guide research and policy toward sustainable desalination, based on innovation, governance, and multidisciplinary assessments of brine discharges.

1. High-resolution environmental monitoring: Numerical models must be complemented by the deployment of independent sensors for salinity, temperature, and dissolved oxygen to ensure uncertainty reduction and validate simulations in real time [12,13].

2. Remote sensing and GIS: GIS tools, combined with satellite imagery, enable continuous monitoring and mapping of hypersaline plume dynamics [15].

3. Artificial Intelligence and Predictive Modeling: Integrating machine learning and neural networks into hydrodynamic models can improve plume prediction under extreme conditions, enhancing desalination potential [56].

4. Life Cycle Assessment (LCA): Future research should use life cycle assessment to assess the overall impact of desalination, including the energy, climate, and environmental impacts of brine discharge [28].

5. Brine Valorization: Invest in research to extract brine solutions to benefit from salts, magnesium, or lithium, to convert waste into resources and reduce discharge concentrations [55].

6. A comprehensive, integrated approach: Global scientific and institutional cooperation is essential to ensure the development of common strategies and rational management of desalination impacts through shared research and databases [56].

Finally, desalination should not be viewed as a simple technical solution, but rather as a transitional technology that combines innovation, sustainability, and social justice to preserve health, biodiversity, and the economy.

5. Conclusions

The massive expansion of desalination capacity is an inevitable response to the worsening global water scarcity crisis. However, this study systematically demonstrates that this solution requires several multidimensional trade-offs in terms of biodiversity conservation, public health, sustainability, and economics. Using the PRISMA methodology to synthesize 45 studies, we reveal that brine discharges, characterized by hypersalinity (40-75 g/L) and the presence of chemical residues, pose a significant threat to diverse marine ecosystems, including sensitive benthic communities and Posidonia oceanica meadows. Regarding public health, the presence of pollutants such as boron and bromate in drinking water, whose concentrations can exceed the World Health Organization's permitted limits in many regions, poses a health risk to consumers and can even lead to cancer. Furthermore, factory workers are exposed to significant occupational and health risks. The originality of our systematic review lies in its integrated assessment framework, which simultaneously analyzes potential risks across health, environmental, energy, and economic dimensions—a comprehensive approach that is perhaps under-addressed and often fragmented in the existing literature. Furthermore, the inclusion of a regional case study using advanced hydrodynamic modeling (CORMIX, Delft3D) for the Algerian coast provides a tangible and quantitative illustration of brine dispersion dynamics. Simulation results performed on Ténès show that under low-current conditions (<0.05 m/s), a minimum initial dilution ratio of 19:1 is necessary to contain the increase in salinity below the critical threshold of +2 g/L, above which significant environmental damage is caused. This modeling process not only validates the results of other regional studies but also provides a systematic method that can be replicated in other regions to predict and mitigate impacts. The results of this study also conclusively demonstrate that the future of sustainable desalination cannot rely solely on water production using various technologies; rather, it requires a qualitative shift toward integrated governance and innovation. This includes rigorous and science-based regulation, technology-driven mitigation, and the valorization of brine as a strategic imperative.