Valuable and rare materials in seawater brine are often discarded during desalination. However, there is an increasing focus on recovering these resources, due to the economic and environmental opportunities it can bring. Despite this shift, current Sustainability Assessments (SA) in desalination overlook the brine handling and social dimensions, and brine treatment assessments remain centered on techno-economic dimensions. This work proposes a comprehensive framework for the SA of integrated desalination and resource recovery options, focusing on recovering valuable materials from brine. The framework not only evaluates pre-defined systems but supports the identification of system features of interest, such as products to assess and technologies to include, as well as the transparent selection of indicators, considering specific contexts. To develop this framework, a review of the literature on SA in desalination and brine treatment systems was conducted. Looking at the identified gaps, we synthesized the findings and key messages and proposed the integration of Multi-Criteria Analysis and Value-Sensitive Design in the decision-making process. This allows stakeholders to be involved and incorporates their values at different stages of the assessment, making it distinct from traditional SA methods. This framework offers structured guidance to stakeholders on how to carry out qualitative and quantitative assessments while ensuring transparency in the assessment process.@en

Water treatment facilities are bound to incorporate resource recovery in the near future, necessitating novel economic assessments that capture the full economic potential of these systems. This study evaluates three cost calculation methods—Non-allocation, Economic allocation, and Dual allocation— to improve the accuracy of the Levelized Cost for multi-product desalination and brine treatment plants. The methods were tested across three technical scenarios: Sc1) maximum water recovery, Sc2) integrated desalination with brine treatment for resource recovery and Sc3) electricity-based desalination for chemical recovery. Results reveal that the traditional Non-allocation method tends to overestimate production costs by uniformly applying fixed costs across products, leading to inflated levelized costs. The Economic allocation approach reduces the levelized costs of water and other recovered products by up to 81 %, enhancing competitiveness with conventional production methods. The Dual allocation approach is most effective for recovered salts and chemicals, ensuring fair cost distribution and fostering competitiveness with linear systems. Sc2 is the most economically feasible under both novel approaches due to its balanced mix of high-value products and moderate operational costs. These findings suggest that cost calculation methods should align with plant objectives: Economic allocation for scenarios prioritizing water recovery and Dual allocation for maximizing the value of salts and chemicals. This study provides a foundation for tailored economic assessments and guides plant design and investment decisions.

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Water scarcity in arid regions has driven the spread of desalination. These systems contribute to water access but come at an intensive energy cost, and lead to brine discharge and associated environmental impacts. This work aims to investigate emerging societal issues and tensions when developing and implementing a thermal desalination system to produce irrigation water in the South of Spain. This has been done in a demonstration system for solar desalination able to recover water and salts from desalination brine. For this purpose, a context-sensitive design exercise has been implemented. First, tensions between social values expressed by diverse stakeholders have been identified. Then, a set of technical scenarios for the full-scale implementation of the system were designed and evaluated, comparing them to conventional membrane desalination. The analysis indicates high economic and energy costs to avoid the environmental impacts of increasing water production.

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The transition to seawater desalination integrated with resource recovery, particularly in water- and energy-scarce regions, requires innovative approaches that consider societal benefits and costs. This study goes beyond traditional techno-economic evaluations by employing a Value-Sensitive Design (VSD) approach, which guides the selection of performance indicators and informs the design of technical scenarios for integrated seawater desalination and brine treatment systems. VSD ensures that the scenarios are socially relevant by directly incorporating stakeholder values into the design and assessment process. Four technical scenarios (Sc) were used to evaluate the VSD approach: Sc1) maximum water recovery, Sc2) and Sc3) integrated desalination with brine treatment for maximum resource recovery (using different configurations) and Sc4) electricity-based desalination for chemical recovery. Techno-economic models are implemented using Python to analyse the feasibility and performance of these scenarios. The modelling results indicate that all scenarios achieve zero brine production. However, the trade-offs between resource recovery and greenhouse gas emissions are evident. Increased salt recovery leads to higher CO2 emissions (locally) due to electricity consumption. Scenario 1 minimized electrical energy consumption and emissions while maximizing water production. Scenarios 2 and 3 performed best in water and high-quality salt production. Despite its higher CO2 emissions, Scenario 4 proved most profitable due to the production of chemicals. These findings highlight the importance of tailoring plant designs to regional needs. By providing a comprehensive understanding of trade-offs, the VSD approach fosters stakeholder dialogue and serves as a valuable decision-making tool for designing sustainable desalination systems.@en

Minimum Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) schemes have been widely proposed in the recent scientific literature not only as a possible solution to brine disposal but also as a non-conventional sustainable source of raw materials. Nevertheless, very few works have pushed the idea towards a real demonstration activity, and this somehow limits the reliability that such schemes have with respect to the real implementation potential at the industrial scale. In this work, for the first time in the literature, an integrated treatment chain for the sustainable production of freshwater and minerals has been demonstrated at a pre-industrial scale, in the island of Lampedusa (Italy). The treatment chain included a Nanofiltration (NF) step to separate monovalent and bivalent ions, followed by a Multi-Effect Distillation (MED) unit, powered by waste heat from a Thermal Power plant, generating high-quality water (<30 μS/cm) and an ultra-concentrated brine. The latter was treated in Evaporation Ponds (EPs) to generate high purity NaCl (>99 %). On the other side, the NF retentate was treated to selectively recover magnesium and calcium hydroxides (Mg(OH)₂ purity up to 98 %) in a novel Multiple Feed-Plug Flow Reactor (MF-PFR). The resulting brine fed an ElectroDialysis with Bipolar Membranes unit (EDBM), generating in-situ alkaline and acidic solutions: chemicals needed for internal usage in the plant. All units were successfully tested, reaching satisfactory performance indicators. Furthermore, the stability of each unit during the daily operational run was assessed and successfully achieved, demonstrating not only the technical feasibility of the proposed demo plant, but also the feasibility of MLD as a sustainable alternative for minerals recovery.

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This work explores resource recovery coupled to seawater desalination in small islands. As small islands depend on seawater desalination for water access, they make an excellent ground for exploring the trade-offs associated to resource recovery, like potential economic gains, energy use, and environmental impacts. Here, we investigated these tensions in the context of Lampedusa, in Italy. We then developed and evaluated scenarios for the recovery of additional water, Mg, and other resources from brines, to identify if and how resource recovery is an interesting approach for the island vis-à-vis these tensions. We have found that the potential to increase water production with water recovery from brine is an interesting alternative for small islands, especially when harnessing waste heat. However, while some technologies offer possibilities for recovering additional resources, in places like small islands the potential benefits from additional recovery do not seem to justify the costs to the local system.

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European policy encourages the adoption of sustainable systems that promote the efficient use and recovery of minerals and chemicals. In this respect, desalination brines do contain a dramatic amount of valuable minerals and can be valorized through appropriate treatments rather than releasing them into the environment. This paper proposes an innovative brine recovery system for obtaining high purity chemicals through the integration of Eutectic Freeze Crystallization (EFC) and Electrodialysis with Bipolar Membrane (EDBM) technologies. Two separate laboratory-scale experimental campaigns were carried out to validate the potential integration of the two processes. Mirabilite (Na₂SO₄∙10H₂O) has been recovered with a purity of 99.9% using the EFC, and a feed rich in NaCl with low impurities has been further processed in an EDBM unit. EDBM tests with feed solutions simulating EFC effluents have shown that it is possible to produce acidic and basic solutions with high purity (>99%), despite the presence of impurities in the feed. Interestingly, the low EDBM specific consumptions of 0.9–1.1 kWh kg⁻¹_NaOH at 100 A m⁻² and 1.3–1.6 kWh kg⁻¹_NaOH at 300 A m⁻² were comparable with and without impurities. In the context of the circular economy strategy promoted by the EU-H2020 Water Mining project, the current study demonstrates that this integrated system effectively minimizes waste, promoting sustainability while providing a potential economic return.

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