The authors regret that an inconsistency was identified between the results presented in Fig. 6 and the inventory data reported in Tables S.11 and S.12 of the Supplementary Information. This discrepancy arose because an additional scenario from a previous version of the manuscript was inadvertently retained in the Supplementary Information, although it was not included in the final published article. As a result, the scenario numbering in the Supplementary Information did not correspond to the scenarios discussed in the main text, leading to apparent inconsistencies for Climate change and Marine ecotoxicity results for Scenario 3. The Supplementary Information has now been corrected by removing the tables related to the excluded scenario and aligning the remaining scenario numbering with the final version of the article. The results presented in the main article remain unchanged. The authors would like to apologise for any inconvenience caused.

Due to the poor solubility of iron (III) and strong regional differences in terrestrial, riverine or airborne input, iron is a limiting micronutrient in much of the world ocean. Because of increasing living standards and climate change, rainfall is becoming more intermittent, which exacerbates drought conditions. As a result, seawater desalination has a vital and growing role in providing drinking water in many hot and arid regions of the world. Most seawater desalination plants use ferric or ferrate salts as flocculants for removing phyto- and bacterioplankton and suspended organic matter prior to the actual desalination process. Consequently, such seawater desalination plants release large amounts of suspended iron in conjunction with organic matter into coastal waters, with potentially significant consequences for the availability of this micronutrient in coastal marine ecosystems. This review paper provides important background information about the role of iron as a micronutrient in marine ecosystems, its role in the inorganic biochemistry of marine life, as well as key features of its use in seawater desalination, before providing a perspective by exploring potential implications for the physiology and biochemistry of marine life and marine ecosystem functioning.

Benthic diatoms are sensitive indicators of environmental conditions at the seabed. In this study, benthic diatom communities at two brine outfall sites of reverse osmosis (RO) seawater desalination plants in Larnaca and Dhekelia, Cyprus, were investigated using a classical, microscopy-based approach and environmental DNA metabarcoding. In general, the diversity of diatoms measured by both methods (microscopy and eDNA metabarcoding), increased by distance from the brine discharge. Increased TOC and nutrient enrichment at brine outfalls contributed to decreased diatom diversity at the Larnaca outfalls, but the diatom diversity at Dhekelia was not driven by abiotic factors. The diatom communities at the outfalls were shown to be distinct and showed temporal variation across the sampling seasons with eDNA metabarcoding, but this was the case only for Dhekelia with microscopy. The results highlight the effect of local biogeography and different brine mixing methods on diatom diversity. The results revealed that conventional morphological methods and eDNA metabarcoding rarely leads to similar conclusions. However, the complementary results emphasise that more information can be derived when combining the methods for biodiversity impact assessments.

The availability of water is still one of the most important factors affecting the sustainable growth of a country. Although many countries have free access to an inexhaustible source of water, the sea, this source cannot be used for human purposes as it is. To face this problem, desalination has been proposed for freshwater production but the generation of a waste brine effluent poses some issues of actual sustainability. In this work, the operation results of a Multiple Effect Distillation (MED) demo plant, designed for stable operation at high brine concentrations and operated as a brine concentrator, are presented. To this purpose, the integration with NanoFiltration (NF) has been implemented to minimize scaling risks, by removing bivalent ions from the feed stream. The 2-effects MED pilot unit, with a capacity of 1.7 m³/h, has been installed as part of the treatment chain of the WATER-MINING project, within the premises of the power station of the island of Lampedusa (Sicily, Italy) and is fully powered by waste heat at 70–80 °C from diesel engines. A vapor temperature of 40–50 °C allowed a perfect coupling with the low temperature waste heat source, demonstrating the possibility to produce distilled water with a conductivity between 15 and 25 μs/cm. Among the several operating conditions investigated, a recovery ratio above 80 % has been achieved and an effluent brine conductivity of 240 mS/cm was produced, very close to saturation in NaCl, thus being excellent for food-grade sea salt production in evaporative ponds. For the first time, it has been demonstrated on a pilot scale how a MED unit, supplied with waste heat, can be used efficiently as a brine concentrator, obtaining a brine concentration 8 times higher than the input concentration without any scaling problem.

The desalination sector adopts Minimal Liquid Discharge (MLD) systems to become more circular, reduce brine discharge and enhance water recovery, which transforms them to multifunctional systems. This multifunctionality requires a methodologically consistent and goal-aligned approach to environmental impact assessment that recognises how different modelling choices are connected with specific decision contexts. A criterion LCA-based framework aligned with the ISO 14044 hierarchy and tailored specifically to desalination has been developed. It guides the selection of allocation approaches based on system characteristics, integration level, and assessment objectives and is applied to assess an MLD system which co-produces desalinated water, sodium chloride, magnesium hydroxide, calcium hydroxide, sodium sulphate and hydrochloric acid. Multifunctionality was handled with system expansion and partitioning (physical and economic) approaches, resulting in different functional units. For physical and economic partitioning, the MLD system is modelled from a process and system perspective. The results indicate that the MLD system has larger environmental benefits than the reference system with system expansion. When physical and economic partitioning under different perspectives are applied, they result in different environmental burdens per co-product. The MLD system performs better than the reference system (0.005 kg CO₂/kg desalinated water) only when process economic partitioning (0.003 kg CO₂/kg desalinated water) is applied. Whereas, the rest co-products perform better than reference products for all partitioning approaches applied. Our results highlight the potential of brine as a secondary source of products. This study underscores the importance of selecting appropriate allocation approaches, contributing to sustainable practices in the desalination sector.

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.

As water research and industry shift towards resource recovery plants, comprehensive assessment methods are needed to capture environmental trade-offs. Existing life cycle assessments (LCA) on desalination often neglect key methodological challenges in multi-product zero-liquid-discharge (ZLD) systems, risking misleading conclusions. This study applies LCA to conventional desalination and with three resource recovery scenarios (integrated desalination and brine treatment) in Cyprus: Sc1) maximum water recovery using waste heat (WH), Sc2) integrated desalination plant with brine treatment using WH, Sc3) electricity-based desalination with chemicals recovery, to assess how key methodological decisions influence the results and decisions. Five impact categories were analysed: climate change, human toxicity, marine ecotoxicity, water depletion, and fossil depletion. Without product substitution, multi-product ZLD systems show higher absolute impacts than SWRO due to increased energy and chemical demands. However, when credits for recovered salts and chemicals are considered, Scenarios 2 and 3 achieve large net reductions compared to conventional production, highlighting the sustainability potential of resource recovery. Results proved highly sensitive to methodological choices: functional unit selection (increase up to 59 %), allocation methods (variation from 54 % to 90 %), while excluding WH altered impacts by up to 89 %, emphasizing the need for transparent reporting to support robust decision-making in desalination design. Sensitivity analysis showed that integrating renewable energy could cut climate change and fossil depletion impacts by up to 99 %, though with trade-offs in marine ecotoxicity and water depletion. Rather than proposing new methods, this work provides critical guidance on applying standardized LCA options to complex systems, offering directly relevant insights for practitioners and policy-makers in sustainable desalination design.

Circular economy has become a popular subject, attracting attention from academics, practitioners, and policy-makers alike. However, despite the excitement surrounding it, the concept of circular economy has been criticized for being vague and having multiple interpretations from different fields. As a result, there is a lack of evidence and guidance for practitioners, making it difficult to put into practice. Our goal is to fill this gap by bridging the design and implementation of circular economy solutions in the water sector. Through an exploratory study of two case studies, we have shown the significance of what we call as “circular water value” in the context of coal mining. This value is strongly influenced by the chemistry, concentration levels and purity of these effluents. We compared the circular value of the two cases (ranging from 2.5 to 6 euros per cubic meter) to the cost of the novel treatment system, developed by the authors through the EU-funded project ZERO BRINE, to capture this value. This allowed us to evaluate the potential for circular economy implementation. We suggest that this circular transition can offer significant opportunities to coal mining regions in enabling a just transition implementation. This is a topic that is increasingly gaining interest among academic and practitioner communities, further triggered by the recently adopted Just Transition Mechanism. This mechanism secures targeted support of 55 billion euro for the period 2021–2027 for the most affected regions within Europe. The concept of “circular water value” introduced in this article can serve as a tool for exploring the creation of emerging circular value chains from coal mines, as well as for other wastewater treatment and resource recovery projects in general.

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.

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.

A new species of the amphipod genus Pontocrates (Boeck 1871), family Oedicerotidae, is described from Cyprus in the south-eastern Mediterranean Sea. It is a sister taxon to Pontocrates moorei (Myers & Ashelby 2022), currently recorded solely from the British Isles. It is the third species of Pontocrates now known to occur in the Mediterranean Sea.

This work proposes an innovative integration of Membrane Distillation (MD) and photo-oxidation for a continuous recovery of water from arsenic (As) contaminated solutions coupled with the oxidation of arsenite (As(III)) into arsenate (As(V)). Polyvinylidene fluoride (PVDF) mixed matrix membranes (MMMs) containing titanium dioxide nanoparticles (TiO₂ NPs) as photocatalyst were developed. A systematic study elucidated the effect of TiO₂ NPs on membranes’ morphology prepared via non-solvent-induced phase separation (NIPS) using triethyl phosphate (TEP) as a green solvent for PVDF solubilization. Vacuum membrane distillation (VMD) tests carried out by irradiating the MMMs with ultraviolet (UV) radiation demonstrated the possibility of recovering up to 80 % of the water from As-contaminated synthetic and real multi-ions aqueous solutions from Sila Massif (Italy). The distillate was recovered at a rate of 6.9–7.2 kg·m⁻²·h⁻¹ (feed inlet temperature of 60 °C), while the presence of 7 wt% of TiO₂ in PVDF membranes enabled the photo-oxidation of 95 % of the As(III) to As(V) at a first order kinetic constant of 0.0106 min⁻¹. After 5 cycles of As-remediation experiments, post-hoc mechanical testing on the membrane suggested the emergence of polymer embrittlement induced by UV radiation (total irradiation time of 7.5 h), highlighting the urgent need for developing photocatalytic membranes with long-term stability. Overall, this study elucidates at laboratory scale the performance of a coupled and continuous Membrane Distillation (MD) and photo-oxidation system for arsenic (As) remediation, employing microporous hydrophobic green membranes doped with a photocatalyst.

Industrial wastewater often has high levels of salt, either due to seawater or e.g. sodium chloride (NaCl) usage in the processing. Previous work indicated that aerobic granular sludge (AGS) is differently affected by seawater or saline water at similar osmotic strength. Here we investigate in more detail the impact of NaCl concentrations and seawater on the granulation and conversion processes for AGS wastewater treatment. Glycerol was used as the carbon source since it is regularly present in industrial wastewaters, and to allow the evaluation of microbial interactions that better reflect real conditions. Long-term experiments were performed to evaluate and compare the effect of salinity on granulation, anaerobic conversions, phosphate removal, and the microbial community. Smooth and stable granules as well as enhanced biological phosphorus removal (EBPR) were achieved up to 20 g/L NaCl or when using seawater. However, at NaCl levels comparable to seawater strength (30 g/L) incomplete anaerobic glycerol uptake and aerobic phosphate uptake were observed, the effluent turbidity increased, and filamentous granules began to appear. The latter is likely due to the direct aerobic growth on the leftover substrate after the anaerobic feeding period. In all reactor conditions, except the reactor with 30 g/L NaCl, Ca. Accumulibacter was the dominant microorganism. In the reactor with 30 g/L NaCl, the relative abundance of Ca. Accumulibacter decreased to ≤1 % and an increase in the genus Zoogloea was observed. Throughout all reactor conditions, Tessaracoccus and Micropruina, both actinobacteria, were present which were likely responsible for the anaerobic conversion of glycerol into volatile fatty acids. None of the glycerol metabolizing proteins were detected in Ca. Accumulibacter which supports previous findings that glycerol can not be directly utilized by Ca. Accumulibacter. The proteome profile of the dominant taxa was analysed and the results are further discussed. The exposure of salt-adapted biomass to hypo-osmotic conditions led to significant trehalose and PO₄³⁻-P release which can be related to the osmoregulation of the cells. Overall, this study provides insights into the effect of salt on the operation and stability of the EBPR and AGS processes. The findings suggest that maintaining a balanced cation ratio is likely to be more important for the operational stability of EBPR and AGS systems than absolute salt concentrations.

The sustainable supply of water is crucial, especially on islands where water is scarce. Our study applied the social life cycle assessment (S-LCA), under the organizational approach, to assess industrial water production on the island of Lampedusa, Italy. A novel plant for industrial water production considering a circular concept was compared with the existing linear production plant based on reverse osmosis. An online survey, brief literature review and generic analysis were conducted to prioritize impact subcategories selection for site-specific analysis that regarded six organizations in the system boundaries. These subcategories were Local employment, Access to material resources, Promoting social responsibility, End-of-life responsibility, Health and safety (Workers), and Public commitment to sustainability issues. The social performance of organizations involved was assessed based on equal weighting and weighting with cost values. The generic analysis showed that wastewater treatment in Italy is underdeveloped, and water scarcity can become a serious problem in the future. The site-specific analysis based on equal weighting showed that the novel water plant results in improving social performance for all considered impact subcategories by 88 % to 91 % due to co-production when compared with the existing plant. Even increasing impacts allocation to industrial water production social benefits are still expected due to co-production. The type of weighting based on cost values showed that two organizations are the main contributors to the social performance of the novel system, and improving their corporate conduct can result in improving impacts up to 25 %, such as Public commitment to sustainability issues. To conclude, the novel plan does provide social benefits but mainly due to co-production, thus, it should be investigated more how to apply the S-LCA to linear production systems as they become more circular.

Enhanced biological phosphate removal and aerobic sludge granulation are commonly studied with fatty acids as substrate. Fermentative substrates such as glucose have received limited attention. In this work, glucose conversion by aerobic granular sludge and its impact on phosphate removal was studied. Long-term stable phosphate removal and successful granulation were achieved. Glucose was rapidly taken up (273 mg/gVSS/h) at the start of the anaerobic phase, while phosphate was released during the full anaerobic phase. Some lactate was produced during glucose consumption, which was anaerobically consumed once glucose was depleted. The phosphate release appeared to be directly proportional to the uptake of lactate. The ratio of phosphorus released to glucose carbon taken up over the full anaerobic phase was 0.25 Pmol/Cmol. Along with glucose and lactate uptake in the anaerobic phase, poly‑hydroxy-alkanoates and glycogen storage were observed. There was a linear correlation between glucose consumption and lactate formation. While lactate accounted for approximately 89 % of the observed products in the bulk liquid, minor quantities of formate (5 %), propionate (4 %), and acetate (3 %) were also detected (mass fraction). Formate was not consumed anaerobically. Quantitative fluorescence in-situ hybridization (qFISH) revealed that polyphosphate accumulating organisms (PAO) accounted for 61 ± 15 % of the total biovolume. Metagenome evaluation of the biomass indicated a high abundance of Micropruina and Ca. Accumulibacter in the system, which was in accordance with the microscopic observations and the protein mass fraction from metaproteome analysis. Anaerobic conversions were evaluated based on theoretical ATP balances to provide the substrate distribution amongst the dominant genera. This research shows that aerobic granular sludge technology can be applied to glucose-containing effluents and that glucose is a suitable substrate for achieving phosphate removal. The results also show that for fermentable substrates a microbial community consisting of fermentative organisms and PAO develop.