The rapid expansion of desalination capacity in arid and semi‑arid regions has generated an urgent need to find sustainable uses for the concentrated brine by‑product produced by seawater and brackish water desalination plants. Traditionally, brine has been treated as a waste stream, often discharged into the sea or terrestrial environments with little or no value recovery. Because most desalination technologies, especially reverse osmosis, produce brine with salinities significantly higher than natural seawater, improper disposal of this stream can lead to negative environmental impacts, including increased salinity in coastal zones, benthic ecosystem disruption, and changes in water column chemistry. However, over the past two decades, researchers, governments, and private innovators have increasingly recognized that brine can be repurposed, not as a waste, but as a resource for productive systems, particularly in aquaculture [1,2].
The fundamental concept underlying brine‑based aquaculture is the exploitation of the salinity tolerance of specific aquatic species, enabling them to grow healthily in elevated salinity environments, while simultaneously reducing the environmental footprint of brine disposal [3].
Historically, aquaculture has relied on freshwater or marine environments with natural salinities suitable for the target species. The controlled use of desalination brine represents a significant departure from these traditional approaches. Early studies explored the physiological limits of various species to determine which organisms could thrive in salinities exceeding those of standard seawater (≈35 g/L). Euryhaline fish species, which can osmoregulate across a wide range of salinities, emerged as primary candidates. Of these, Nile tilapia (Oreochromis niloticus), Mozambique tilapia (Oreochromis mossambicus), and blue tilapia (Oreochromis aureus) have been the most extensively studied because of their remarkable ability to tolerate salinity levels well beyond normal seawater [2,4].
Research has shown that certain tilapia strains can survive in salinities up to 60–120 g/L, although optimal growth rates are usually achieved between 10–20 g/L [2]. The tilapia’s euryhalinity, rapid growth, and widespread aquaculture use make it a central species for brine aquaculture systems [3].
Several pilot projects and controlled experiments have demonstrated that brine from reverse osmosis desalination plants can be used directly or after targeted dilution to support tilapia production. In these systems, brine is first monitored and, if necessary, adjusted for parameters such as pH, calcium concentration, and residual chemicals [5].
Some studies report that tilapia raised in brine‑augmented systems exhibit survival rates above 95%, with harvest weights approaching those seen in conventional aquaculture systems under optimal conditions [5]. For example, research conducted with Mozambique tilapia in a brine‑supplemented aquaculture system recorded a mean final weight of approximately 0.45 kg and survival rates above 97% [5]. These results indicate that brine usage, when managed correctly, does not inherently compromise fish growth or health.
Beyond tilapia, several other euryhaline marine and estuarine species have been investigated for brine aquaculture suitability. The European seabass (Dicentrarchus labrax) is widely cultivated across the Mediterranean and Atlantic coasts due to its adaptability and market demand [4]. Experiments with this species raised in waters reflecting compositions similar to desalination brine have shown promising results, with growth performance and feed conversion ratios comparable to conventional marine aquaculture systems [4]. Similarly, gilthead seabream (Sparus aurata), another key Mediterranean aquaculture species, has demonstrated tolerance to elevated salinities in controlled brine environments, although its optimum performance is typically achieved with careful salinity management rather than full‑strength brine [6].
Other species evaluated include the red drum (Sciaenops ocellatus), native to the western Atlantic, which has high commercial value and a broad salinity tolerance, making it a suitable candidate for brine systems [10]. Mugilidae family mullets, such as the flathead grey mullet (Mugil cephalus), have also been explored because of their life history in estuarine and coastal environments [4]. These fish can efficiently utilize organic matter and tolerate a wide salinity range, which is advantageous in integrated systems where nutrient recycling is critical [4,7].
Crustaceans, particularly the Pacific white shrimp (Litopenaeus vannamei), present additional opportunities for brine aquaculture. Shrimp farming has long been a major pillar of global aquaculture, and L. vannamei is notable for its adaptability to varying salinities, from near freshwater to full‑strength seawater [7]. Studies focusing on shrimp production with brine supplementation or partial brine use have recorded acceptable survival and growth rates, especially when salinity is maintained within species‑appropriate thresholds [7]. Integrating shrimp culture with brine use can be particularly beneficial when combined with biofloc technology or multi‑trophic approaches that harness microbial communities to stabilize water quality and increase productivity [8,9].
A key innovation in brine aquaculture is the integration of polyculture and integrated multi‑trophic aquaculture (IMTA) systems, which combine multiple species at different trophic levels to enhance resource efficiency. In these systems, finfish like tilapia or seabass coexist with mollusks, microalgae, or halophytic plants, each contributing to nutrient recycling. Microalgae such as Tetraselmis spp., Nannochloropsis spp., or Dunaliella spp. can grow in high‑salinity waters and serve dual roles as fish feed and biological filters [9]. Halophytic plants such as Salicornia spp. can be irrigated with nutrient‑rich effluents from aquaculture tanks, enabling additional biomass production while reducing nutrient loads before final disposal [8,9]. These synergistic arrangements improve overall system sustainability and reduce environmental impacts [8].
An emerging approach that has shown promise is the controlled mixing of desalination brine with treated municipal wastewater to simultaneously supply salinity and nutrients such as nitrogen, phosphorus, and organic carbon that are often limited in clean seawater or conventional aquaculture systems [11]. Treated wastewater effluents, after appropriate disinfection and removal of harmful pathogens and contaminants, provide a source of nutrients that stimulate microbial growth and enhance the natural food web within the aquaculture system [11]. When combined with brine, this enriched water can improve feed conversion efficiency and reduce the dependency on external protein feeds, which are costly and often constitute the largest operational expense in aquaculture [11]. Controlled trials mixing treated wastewater with desalination brine have demonstrated increased biomass production of tilapia and shrimp, improved water quality stability, and higher overall yield when compared to brine-only or freshwater systems alone [11].
One of the most concrete examples of brine aquaculture development is found in the United Arab Emirates (UAE), where research institutions and private partners have collaborated to use desalination brine for commercial aquaculture modular units [5,11]. In these projects, brine from seawater reverse osmosis plants feeds aquaculture tanks producing tilapia at densities as high as 30 kg/m³, significantly above typical densities in conventional freshwater systems [5,11].
Pilot studies conducted in collaboration with municipal wastewater treatment facilities have also shown that mixing treated municipal effluents with brine can significantly enhance microalgae growth, which in turn supports higher trophic levels of organisms such as tilapia and shrimp [11]. The effluent from these tanks, rich in nitrogen and phosphorus, can then be used to irrigate halophytic crops, creating a circular system that generates food, biomass, and potentially fodder for livestock [8,9,11]. These real‑world applications provide compelling evidence that brine aquaculture, especially when integrated with treated wastewater, is not merely theoretical but scalable under appropriate economic and environmental conditions [11].
Despite the promising results, several challenges must be addressed before brine aquaculture can become widely adopted. The chemical composition of desalination brine varies depending on source water and treatment processes; brine may contain residual antiscalants, cleaning chemicals, or other additives used in desalination pretreatment [6]. These compounds can influence fish health and water quality if not properly managed [6]. Similarly, treated wastewater must be carefully processed to remove heavy metals, endocrine disruptors, and pathogens that can negatively affect fish health [11].
Co‑treatment systems combining brine and treated wastewater require advanced monitoring and control systems to ensure that salinity, nutrient concentrations, and contaminants remain within safe thresholds for aquatic organisms [11]. In addition, the deposition of scale‑forming minerals such as calcium carbonate in intensive systems can impair equipment and necessitate regular maintenance [6]. Technological solutions for brine conditioning and wastewater polishing, including selective ion adjustment, aeration, or biological treatment, are areas of active research [6,8].
Economic viability also remains a critical factor. While using brine and treated wastewater can reduce freshwater demand and associated costs, the capital investment in brine‑ and wastewater‑tolerant aquaculture infrastructure, water quality monitoring and treatment systems, and specialized feed may offset initial savings [12]. The profitability of such integrated systems depends on market access, operational efficiencies, regulatory frameworks, and species selection tailored to local demand [12].
For regions where freshwater scarcity, high feed costs, and limited agricultural land constrain conventional food production, the trade‑offs may favor brine‑ and wastewater‑based systems [12]. For instance, in North Africa and the Middle East, where desalination and wastewater reuse are integral to municipal water supply, coupling brine aquaculture with renewable energy and agriculture could form a nexus solution that addresses water, food, and energy security simultaneously [12].
Researchers continue to refine brine and treated wastewater aquaculture models to improve both ecological and economic outcomes. Advanced modeling of salinity effects on fish osmoregulation, nutrient cycling within IMTA, and life‑cycle analysis of resource flows inform system design [8,9]. Recent work has also explored the potential for offshore brine aquaculture, where controlled cages or floating systems use diluted brine streams in coastal waters, minimizing on‑land infrastructure and dispersing salinity gradients [10]. However, offshore approaches must carefully evaluate ecological interactions with local ecosystems and regulatory frameworks for marine aquaculture [10].
The potential for integrated brine and treated wastewater aquaculture in Africa is particularly compelling. Algeria, for example, has invested heavily in desalination infrastructure to augment water supplies [12]. As desalination capacity grows, so does the volume of brine, creating both a waste processing challenge and an opportunity [12]. Integrating desalination brine aquaculture with treated municipal wastewater reuse could support domestic fish production, reduce reliance on imported seafood, and create employment in rural coastal areas [11,12]. Likewise, countries such as Tunisia, and Egypt, where desalination, wastewater recycling, and aquaculture are growing sectors, could benefit from integrated systems that valorize multiple waste streams, reduce environmental impacts, and promote local food systems [11,12].
Conclusion
Aquaculture systems that use desalination brine and treated wastewater represent a paradigm shift in how we view and manage water and nutrient waste streams. Far from being wastes to be disposed of, brine and treated wastewater can be transformed into productive inputs for sustainable food production when matched with the right species and system designs. Species such as tilapia, European seabass, gilthead seabream, mullets, red drum, and Pacific white shrimp, combined with microalgae and halophytic plants, provide a robust portfolio for integrated aquaculture [1–11].
While technical and economic challenges remain, the growing body of research and real-world pilots demonstrates that integrated brine and wastewater aquaculture is feasible and holds promise as part of a circular water-food nexus [11,12]. With the continued expansion of desalination worldwide, especially in water‑stressed regions, such integrated systems could play a significant role in sustainable protein and biomass production in the twenty-first century [1–12].
References
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