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

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.

@en

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.

@en

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.

@en

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.

@en