Chronic effects of brine discharge form large-scale seawater reverse osmosis desalination facilities on benthic bacteria

Non-target screening and prioritization of organic contaminants in seawater desalination and their ecological risk assessment

The impact of desalination brine on the marine environment is a global concern. Regarding this, salinity is generally accepted as the major environmental factor in desalination concentrate. However, recent studies have shown that the influence of organic contaminants in brine cannot be ignored. Therefore, a non-targeted screening method based on comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS) was developed for identifying organic contaminants in the desalination brine. A total of 404 compounds were tentatively identified from four seawater desalination plants (three reverse osmosis plants and one multiple effect distillation plant) in China. The identified compounds were prioritized based on their persistence, bioaccumulation, ecotoxicity, usage, and detection frequency. Twenty-one (21) compounds (seven phthalates, ten pesticides, four trihalomethanes) were then selected for further quantitative analysis and ecological risk assessment, including compounds from the priority list along with substances from the same chemical classes. Ecologically risky substances in brine include diisobutylphthalate and bis(2-Ethylhexyl) phthalate, atrazine and acetochlor, and bromoform. Most of the contaminants come from raw seawater, and no high risk contaminants introduced by the desalination process have been found except for disinfection by-products. In brine discharge management, people believed that all pollution in raw seawater was concentrated by desalination process. This study shows that not all pollutants are concentrated during the desalination process. In this study, the total concentration of pesticide in the brine increased by 58.42%. The concentration of ∑PAEs decreased by 13.65% in reverse osmosis desalination plants and increased by 10.96% in the multi-effect distillation plant. The concentration of trihalomethane increased significantly in the desalination concentrate. The change in the concentration of pollutants in the desalination concentrate was related to the pretreatment method and the chemical characteristics of the contaminants. The method and results given in this study hinted a new idea to identify and control the environmental impact factors of brine.

Commercial reverse osmosis point-of-use systems in Egypt failed to purify tap water

This study addresses the heightened global reliance on point-of-use (PoU) systems driven by water quality concerns, ageing infrastructure, and urbanization. While widely used in Egypt, there is a lack of comprehensive evaluation of these systems. We assessed 10 reverse osmosis point-of-use systems, examining physicochemical, bacteriological, and protozoological aspects of tap water (inlets) and filtered water (outlets), adhering to standard methods for the examination of water and wastewater. Results showed significant reductions in total dissolved solids across most systems, with a decrease from 210 ± 23.6 mg/L in tap water to 21 ± 2.8 mg/L in filtered water for PoU-10. Ammonia nitrogen levels in tap water decreased from 0.05 ± 0.04 to 2.28 ± 1.47 mg/L to 0.02 ± 0.04 to 0.69 ± 0.64 mg/L in filtered water. Despite this, bacterial indicators showed no significant changes, with some systems even increasing coliform levels. Protozoological analysis identified prevalent Acanthamoeba (42.5%), less frequent Naegleria (2.5%), Vermamoeba vermiformis (5%), and potentially pathogenic Acanthamoeba genotypes. Elevated bacterial indicators in filtered water of point-of-use systems, combined with essential mineral removal, indicate non-compliance with water quality standards, posing a public health concern. Further research on the long-term health implications of these filtration systems is essential.

Impacts of Desalination Brine Discharge on Benthic Ecosystems

Seawater reverse osmosis (SWRO) desalination facilities produce freshwater and, at the same time, discharge hypersaline brine that often includes various chemical additives such as antiscalants and coagulants. This dense brine can sink to the sea bottom and creep over the seabed, reaching up to 5 km from the discharge point. Previous reviews have discussed the effects of SWRO desalination brine on various marine ecosystems, yet little attention has been paid to the impacts on benthic habitats. This review comprehensibly discusses the effects of SWRO brine discharge on marine benthic fauna and flora. We review previous studies that indicated a suite of impacts by SWRO brine on benthic organisms, including bacteria, seagrasses, polychaetes, and corals. The effects within the discharge mixing zones range from impaired activities and morphological deformations to changes in the community composition. Recent modeling work demonstrated that brine could spread over the seabed, beyond the mixing zone, for up to several tens of kilometers and impair nutrient fluxes from the sediment to the water column. We also provide a possible perspective on brine's impact on the biogeochemical process within the mixing zone subsurface. Desalination brine can infiltrate into the sandy bottom around the discharge area due to gravity currents. Accumulation of brine and associated chemical additives, such as polyphosphonate-based antiscalants and ferric-based coagulants in the porewater, may change the redox zones and, hence, impact biogeochemical processes in sediments. With the demand for drinking water escalating worldwide, the volumes of brine discharge are predicted to triple during the current century. Future efforts should focus on the development and operation of viable technologies to minimize the volumes of brine discharged into marine environments, along with a change to environmentally friendly additives. However, the application of these technologies should be partly subsidized by governmental stakeholders to safeguard coastal ecosystems around desalination facilities.

Ecocriminological analysis of brine in aquatic ecosystems: impacts on Posidonia oceanica and the search for restorative justice solutions

The consumption of fresh water has generated additional problems in certain territories, along with the consequences of global warming. This has meant that in the most vulnerable areas, such as the Balearic archipelago in the Mediterranean, alternative water supply systems have been established: desalination plants. However, the ecological impact of these infrastructures is great, mainly affecting aquatic ecosystems. In light of the above, this paper addresses the ecological harm caused by desalination and brine discharges on a protected and priority species, P. Oceanica. Taking as ethico-legal foundation the theory of ecological justice, a multilevel analysis was carried out from an ecocriminology perspective on the impacts of this authorized practice on P. Oceanica and other species. Finally, a restorative justice view will allow us to understand and envision possible solutions to this ecological harm.

Strength, porosity and life cycle analysis of geopolymer and hybrid cement mortars for sustainable construction

Owing to the application of industrial wastes, geopolymers are generally regarded as a sustainable alternative to traditional construction materials. However, their lack of adoption on the industrial scale demands detailed investigations. This study conducts a comparative analysis of the compressive strength of different geopolymer and hybrid cement mortars with varying proportions of sodium hydroxide (from 5 to 25 wt%) and ordinary Portland cement (OPC) (from 15 to 35 wt%), respectively. The porosity of all designed mixtures was also analyzed using X-ray computed tomography (XCT) and water absorption tests. ReCiPe 2016 Midpoint (H) method was used for the Life cycle analysis of the geopolymer and hybrid cement mortars. Multi-criteria decision making (MCDM) approach was used to assess the sustainability potential of the designed mixtures based on compressive strength, porosity and overall environmental impact. Experimental results revealed that the increase in sodium hydroxide in geopolymer mortars up to 15 wt% offered its maximum compressive strength. Superior compressive strength was obtained at 35 wt% of OPC in hybrid cement mortars due to the formation of more C-S-H, C-A-S-H and N-A-S-H gels which fill up the voids and pores. Analysis of the macro and micro-porosity revealed that hybrid cement mortars yield denser structure than geopolymer mortars. Life cycle analysis based on 8 distinct impact categories showed that hybrid cement mortars outperform the geopolymers in all impact categories except 'mineral resource scarcity'. However, the overall environmental impact assessment using the 'coefficient of performance' depicts that hybrid cement mortars offer a significantly lower environmental burden than geopolymers. MCDM analysis shows that hybrid cement mortar with 5 wt% of sodium hydroxide and 35 wt% of OPC is the best choice for construction applications. This idea of sustainable hybrid cement mortar will be helpful for the construction industry to limit the environmental impact without compromising their structural performance.

Challenges and Solutions for Global Water Scarcity

Climate change, global population growth, and rising standards of living have put immense strain on natural resources, resulting in the unsecured availability of water as an existential resource. Access to high-quality drinking water is crucial for daily life, food production, industry, and nature. However, the demand for freshwater resources exceeds the available supply, making it essential to utilize all alternative water resources such as the desalination of brackish water, seawater, and wastewater. Reverse osmosis desalination is a highly efficient method to increase water supplies and make clean, affordable water accessible to millions of people. However, to ensure universal access to water, various measures need to be implemented, including centralized governance, educational campaigns, improvements in water catchment and harvesting technologies, infrastructure development, irrigation and agricultural practices, pollution control, investments in novel water technologies, and transboundary water cooperation. This paper provides a comprehensive overview of measures for utilizing alternative water sources, with particular emphasis on seawater desalination and wastewater reclamation techniques. In particular, membrane-based technologies are critically reviewed, with a focus on their energy consumption, costs, and environmental impacts.

Sediment Microbiota as a Proxy of Environmental Health: Discovering Inter- and Intrakingdom Dynamics along the Eastern Mediterranean Continental Shelf

Sedimentary marine habitats are the largest ecosystem on our planet in terms of area. Marine sediment microbiota govern most of the benthic biological processes and therefore are responsible for much of the global biogeochemical activity. Sediment microbiota respond, even rapidly, to natural change in environmental conditions as well as disturbances of anthropogenic sources. The latter greatly impact the continental shelf. Characterization and monitoring of the sediment microbiota may serve as an important tool for assessing environmental health and indicate changes in the marine ecosystem. This study examined the suitability of marine sediment microbiota as a bioindicator for environmental health in the eastern Mediterranean Sea. Integration of information from Bacteria, Archaea, and Eukaryota enabled robust assessment of environmental factors controlling sediment microbiota composition: seafloor-depth (here representing sediment grain size and total organic carbon), core depth, and season (11%, 4.2%, and 2.5% of the variance, respectively). Furthermore, inter- and intrakingdom cooccurrence patterns indicate that ecological filtration as well as stochastic processes may control sediment microbiota assembly. The results show that the sediment microbiota was robust over 3 years of sampling, in terms of both representation of region (outside the model sites) and robustness of microbial markers. Furthermore, anthropogenic disturbance was reflected by significant transformations in sediment microbiota. We therefore propose sediment microbiota analysis as a sensitive approach to detect disturbances, which is applicable for long-term monitoring of marine environmental health. IMPORTANCE Analysis of data, curated over 3 years of sediment sampling, improves our understanding of microbiota assembly in marine sediment. Furthermore, we demonstrate the importance of cross-kingdom integration of information in the study of microbial community ecology. Finally, the urgent need to propose an applicable approach for environmental health monitoring is addressed here by establishment of sediment microbiota as a robust and sensitive model.

Advances in understanding multilevel responses of seagrasses to hypersalinity

Human- and nature-induced hypersaline conditions in coastal systems can lead to profound alterations of the structure and vitality of seagrass meadows and their socio-ecological benefits. In the last two decades, recent research efforts (>50 publications) have contributed significantly to unravel the physiological basis underlying the seagrass-hypersalinity interactions, although most (∼70%) are limited to few species (e.g. Posidonia oceanica, Zostera marina, Thalassia testudinum, Cymodocea nodosa). Variables related to photosynthesis and carbon metabolism are among the most prevalent in the literature, although other key metabolic processes such as plant water relations and responses at molecular (i.e. gene expression) and ultrastructure level are attracting attention. This review emphasises all these latest insights, offering an integrative perspective on the interplay among biological responses across different functional levels (from molecular to clonal structure), and their interaction with biotic/abiotic factors including those related to climate change. Other issues such as the role of salinity in driving the evolutionary trajectory of seagrasses, their acclimation mechanisms to withstand salinity increases or even the adaptive properties of populations that have historically lived under hypersaline conditions are also included. The pivotal role of the costs and limits of phenotypic plasticity in the successful acclimation of marine plants to hypersalinity is also discussed. Finally, some lines of research are proposed to fill the remaining knowledge gaps.

Water Harvesting Strategies through Solar Steam Generator Systems

Solar steam generator (SSG) systems have attracted increasing attention, owing to its simple manufacturing, material abundance, cost-effectiveness, and environmentally friendly freshwater production. This system relies on photothermic materials and water absorbing substrates for a clean continuous distillation process. To optimize this process, there are factors that are needed to be considered such as selection of solar absorber and water absorbent materials, followed by micro/macro-structural system design for efficient water evaporation, floating, and filtration capability. In this contribution, we highlight the general interfacial SSG concept, review and compare recent progresses of different SSG systems, as well as discuss important factors on performance optimization. Furthermore, unaddressed challenges such as SSG's cost to performance ratio, filtration of untreatable micropollutants/microorganisms, and the need of standardization testing will be discussed to further advance future SSG studies.

Discharge of Polyphosphonate-Based Antiscalants via Desalination Brine: Impact on Seabed Nutrient Flux and Microbial Activity

Desalination brine is a hypersaline byproduct that contains various operational chemicals such as polyphosphonate-based antiscalants. Brine often sinks and flows over the seabed by density currents; therefore, it may affect sediment-water nutrient fluxes and thus microbial activity. We quantified these parameters in brine plumes around two large-scale desalination facilities located in the P-limited Southeastern Mediterranean Sea. The benthic nutrient fluxes and microbial activity were determined using ex-situ core benthocosms, to which we added brine from the dispersion area in excess salinities of ∼3% and 5% above natural levels. A higher influx of dissolved organic phosphorus (∼6-fold) and an efflux of dissolved organic carbon (∼1.7-fold) were measured in the brine-amended cores relative to the controls. This was accompanied by increased oxygen consumption (15%) and increased microbial activity (∼1.5-6.5-fold). Field observations support the results from experimental manipulations, yielding ∼4.5-fold higher microbial activity rates around the brine plume compared to uninfluenced locations. Our results imply that desalination brine can alter sedimentary processes affecting benthic nutrients inventories. Moreover, we show that brine acts as a vector of anthropogenic P, stimulating microbial activity in the sediment-water interface.

Antiscalants Used in Seawater Desalination: Biodegradability and Effects on Microbial Diversity

Antiscalants are organic polymers widely used for scale inhibition in seawater desalination. While they are susceptible to biodegradation, they provide nutrients for bacterial cell growth and energy for the microbes that assimilate and degrade them. This paper shows the biodegradability of three commercial antiscalants (polyacrylate—CA, polyphosphonate—PP, and carboxylated dendrimers—DN) applied in seawater reverse osmosis desalination (SWRO) as well as analyzing the antiscalant’s effects on microbial diversity using microbial cultures grown in seawater, under semi-continuous batch conditions. Nutritional uptake and contribution of the antiscalants to microbial growth were investigated by measuring DOC, TDN, NO₃⁻, NO₂⁻, PO₄⁻, NH₄⁺, and TP of the filtered samples of the incubated batch, twice a month, for twelve months. The microbial community was estimated by 16S rRNA sequencing. The main changes in the microbial communities were determined by the incubation period. However, bacterial orders of the antiscalant treatments differed significantly from the control treatment, namely Planctomycetales, Clostridiales, Sphingobacteriales, Rhodobacterales, and Flavobacteriales, and other unclassified bacterial orders, which were found in various relative abundances dependent on incubation times. The results showed the PP antiscalant to be the least biodegradable and to have the least effect on the bacterial community composition compared to the control. This result emphasizes the need to reassess the suitability criteria of antiscalants, and to further monitor their long-term environmental effects.

The impact assessment of desalination plant discharges on heavy metal pollution in the coastal sediments of the Persian Gulf

In recent decades the development of desalination plants (DPs) for desalination of seawater has increased dramatically, while little attention has been paid to the effects of this activity on the accumulation of heavy metals (HMs) in the sediments of affected ecosystems. The present study was implemented to evaluate (1) heavy metal accumulation in sediments impacted by DPs discharges, (2) spatial and temporal changes of HMs and the contamination degree by different types of pollution indexes (single and integrated indices), and (3) ecological risk assessment of cadmium (Cd), lead (Pb), zinc (Zn) and copper (Cu) in sediments affected by DPs discharges. A total of 288 sediment samples were collected seasonally at 24 stations from November 2019 to October 2020. Analysis of HMs concentrations in sediments near the desalination plant discharge provided evidence of local contamination. Maximum concentration of Cu and Pb elements were found in sediments near the desalination plant discharge point. Hierarchical cluster analysis revealed clear segregation of stations impacted by desalination plant discharges and away from discharges. The values of PLI index in sediments of all sampling stations were < 1, indicating that there was no metal pollution by this index. The potential ecological risk index (PERI) ranged from 5.33 ± 0.51 to 11.81 ± 4.98 in sampling sediments and were classified as "low potential ecological risk". These results demonstrate that the DPs discharge increased HMs concentrations in the sediments in close proximity to outlets. The necessary and practical regulations and policies regarding the rejection of the DPs discharge and disposal of chemical compounds must be implemented and enforced.

A Novel Hybrid Reactor of Pressure-Retarded Osmosis Coupling with Activated Sludge Process for Simultaneously Treating Concentrated Seawater Brine and Wastewater and Recovering Energy

As an attractive way to deal with fresh water shortage, membrane-based desalination technologies are receiving increased interest. However, concentrated seawater brine, in needing further treatment, remains a main obstacle for desalination via membrane technology. Here, a hybrid technology integrating pressure-retarded osmosis with activated sludge process (PRO-MBR) was applied for simultaneously treating concentrated seawater brine and municipal wastewater. Performance of the PRO-MBR, including water flux, power density, contaminants removal, and membrane fouling was evaluated and compared at two different membrane orientations (i.e., active layer facing feed solution (AL-FS) mode and active layer facing draw solution (AL-DS) mode). During the PRO-MBR process, the municipal wastewater was completely treated regardless of the membrane orientation, which means that there was no concentrated sewage needing further treatment, owing to the biodegradation of microorganisms in the bioreactor. In the meantime, the concentrated brine of seawater desalination was diluted into the salinity level of seawater, which met the standard of seawater discharge. Owing to the high rejection of forward osmosis (FO) membrane, the removal efficiency of total organic carbon (TOC), total phosphorus (TP), ammonia nitrogen (NH4+-N), and total nitrogen (TN) was higher than 90% at both modes in the PRO-MBR. In addition, the PRO-MBR can simultaneously recover the existing osmotic energy between the municipal wastewater and the seawater brine at both modes. Compared with the AL-DS mode, the AL-FS mode took a shorter time and achieved a bigger power density to reach the same terminal point of the PRO-MBR owing to a better water flux performance. Furthermore, the membrane fouling was much more severe in the AL-DS mode. In conclusion, the current study demonstrated that the PRO-MBR at the AL-FS mode can be a promising and sustainable brine concentrate and municipal wastewater treatment technology for its simultaneous energy and water recovery.

Valuing improved water services and negative environmental externalities from seawater desalination technology: A choice experiment from the Galápagos

While seawater desalination technologies can improve drinking water supply, they can also generate significant environmental externalities. A choice experiment was implemented to investigate household preferences for potential trade-offs between improved water services and environmental impacts from seawater desalination in the Galápagos Islands. Our results indicate that households are willing to pay for water quality improvements, and for protection of coastal ecosystems and marine organisms. In contrast, households seem indifferent regarding water availability and potential impacts on air quality. Our findings also suggest that respondents who consistently reject the proposed desalination project tend to be less affluent and have stronger environmental preferences than those who support it. It is concluded that stated-preference studies on improved water services should also elicit preferences for potential environmental effects of the proposed water technology.

Injection of desalination brine into the saline part of the coastal aquifer; environmental and hydrological implications

Seawater desalination, specifically reverse osmosis (RO), has become an important water resource, especially in arid and semi-arid regions. The desalination process generates a brine solution that is usually discharged to the nearshore environment, negatively impacting the marine ecosystem. A different method of disposing of the brine solution is needed to restore and maintain the marine environment. One such method is injecting the desalination brine into the saline part of the coastal aquifer. This study aims to investigate the hydrological and environmental impacts of such injection using groundwater flow and solute transport numerical models, showing the fresh-saline water interface (FSI) response at different injection rates, depths, and distances from shore. Moreover, this study investigates the recovery evolution of the aquifer after injection stops. We also analyze the hydrological response when pumping saline groundwater (SGW) (for desalination) or freshwater (for water supply) simultaneously with brine injection. Results show that brine injection creates a high salinity plume that pushes the FSI landward and salinizes the aquifer. After 20 years of injecting 5 million m³ y^-1, 17 million m³ of freshwater are lost due to salt contamination. It is also shown that by injecting further offshore and in shallower depths, the impact on the FSI and the aquifer is reduced. Furthermore, pumping SGW simultaneously with brine injection negates the brine plume effect on the FSI and results in a more stable interface. It is noted that aquifer recovery is a long process and even after 100 years of recovery, the aquifer is not fully rehabilitated. This paper shows for the first time the hydrological implications of brine injection into the saline part of the coastal aquifer and demonstrates its potential utility for desalination plants in protecting the environment.

Desalination and environment: A critical analysis of impacts, mitigation strategies, and greener desalination technologies

The desalination of seawater is perceived as one of the most viable processes to fulfill the mounting demand for freshwater. Despite enormous economic, social, and health benefits offered by desalination, there are several concerns regarding its prospective environmental impacts (EIs). The objective of this work is to critically evaluate the potential EIs of seawater desalination, and assess the prospects of greener desalination. The EIs of desalination on marine environment, land, groundwater, and air quality was systematically reviewed. An attempt has been made to analyze the actuality of these so-called impacts with reference to evidence from real desalination plants. The mitigative measures to counterbalance these unfavorable impacts are critically appraised. Furthermore, the brine management technologies for the disposal of reject stream, the recovery of precious materials and water, and the production of useful chemicals are also reviewed. Current challenges to minimize the adverse impacts of desalination and prospects of sustainable greener desalination to overwhelm global water scarcities are also discussed. The current desalination approaches have moderate and minor negative EIs. However, with proper mitigation and utilization of modern technologies, these impacts can be lessened. Furthermore, by employing various modern techniques, reject brine can be utilized for several useful applications while reducing its adverse impacts simultaneously. Recent advancements in desalination technologies have also offered many alternative approaches that provide a roadmap towards greener desalination. This review article will be beneficial for all the stakeholders in the desalination industry.

Exploring Avoided Environmental Impacts as Well as Energy and Resource Recovery from Microbial Desalination Cell Treatment of Brine

Seawater represents a potential resource to ensure sustainable availability of water for population and irrigation purposes, especially in some areas of the world. Desalination processes allow the production of fresh water, but they generate also brine as waste product. Sustainable brine management should be identified to ensure proper disposal and potentially resource recovery. This experimental study showed that emerging technologies such as Microbial Desalination Cells (MDCs) may provide a valuable contribution to the sustainability of the seawater desalination sector. In this paper, we report results on lab-scale desalination brine treatments applying MDCs, which allow energy savings, resource recovery, environmental impact minimization, and reduction of the organic load in municipal wastewater. Our results showed that MDCs’ treatment allows the removal of approximately 33 g of salts (62% of the total)—including chlorides, bromides, and sulphates—from 20 mL of brine within 96 h. The MDCs, according to the source of energy and the presence of mature biofilm at the anode, spent 7.2 J, 7.9 J, and 9.6 J in the desalination process, with the higher amount of energy required by the abiotic system and the lesser by the MDCs fed with just wastewater. Our approach also showed environmental and energy reductions because of potential metal recovery instead of returning them into marine environment. We quantified the avoided life cycle of human and marine eco-toxicity impacts as well as the reduction of cumulative energy demand of recovered metals. The main benefit in terms of avoided toxicity would arise from the mercury and copper recovery, while potential economic advantages would derive from the recovered cobalt that represents a strategic resource for many products such as battery storage systems.

Marine health of the Arabian Gulf: Drivers of pollution and assessment approaches focusing on desalination activities

The Arabian Gulf is one of the most adversely affected marine environments worldwide, which results from combined pollution drivers including climate change, oil and gas activities, and coastal anthropogenic disturbances. Desalination activities are one of the major marine pollution drivers regionally and internationally. Arabian Gulf countries represent a hotspot of desalination activities as they are responsible for nearly 50% of the global desalination capacity. Building desalination plants, up-taking seawater, and discharging untreated brine back into the sea adversely affects the biodiversity of the marine ecosystems. The present review attempted to reveal the potential negative effects of desalination plants on the Gulf's marine environments. We emphasised different conventional and innovative assessment tools used to assess the health of marine environments and evaluate the damage exerted by desalination activity in the Gulf. Finally, we suggested effective management approaches to tackle the issue including the significance of national regulations and regional cooperation.

Environmental impact of desalination technologies: A review

Due to the limited availability of freshwater supplies, desalination has become an increasingly reliable process for water supply worldwide, with proved technical and economic feasibility and advantages. Recently, desalination capacity significantly increased from approximately 35 million m³ daily (MCM/day) in 2005 to about 95 MCM/day in 2018. Seawater desalination accounts for about 61% of global desalination capacity, while brackish water desalination accounts for 30%. Membrane desalination, mainly using reverse osmosis (RO), accounts for ¾ of global desalination capacity, with the rest mostly used for thermal desalination using multi-stage flash distillation (MSF), and multi-effect distillation (MED). Despite the undeniable role of desalination for securing water supply in areas where natural freshwater supplies are scarce, desalination impacts the natural environment at different aspects. Environmental impacts (EIs) of the desalination process are different and vary significantly according to the nature of the utilized feedwater, the desalination technology in use, and the management of waste brine generated. In this work, the EIs of each desalination technology were thoroughly investigated, with careful consideration given to different feedwater qualities, and various brine management techniques. Although the different aspects of desalination EIs have been extensively studied in the literature, the literature lacks comprehensive reviews and summaries of all the associated EIs. This article compiles the different EIs associated with the whole desalination process in one-hub, applying an intake-to-outfall approach. The leading desalination technologies of RO, MSF, and MED were analyzed, along with different feedwaters. This article provides a mapping of the different technologies involving feedwater and brine management techniques and a detailed description of their impact on the environment. Finally, recommendations and conclusions were given to minimize the negative impacts of desalination on both the local and global environments.

Sustainable desalination: Long-term monitoring of brine discharge in the marine environment

The environmental impact of desalination is the most important concern related to its sustainable development. We present the results of a long-term environmental plan to monitor brine discharge (BD) from a desalination plant located in a high environmental value area in Spain. Generalized additive models were used to analyze the biological parameters of biological communities. Results of 17 years of BD monitoring show how its environmental impact can be minimized through well-planned decision-making between scientists and industry. The brine dilution prior to its discharge into an artificial channel of low ecological value significantly reduced the brine influence area. P. oceanica shoot production and echinoderms abundances were relatively stable across historical series and similar values in control and impacts locations were observed. Conversely, there was a higher abundance and species richness of fishes in the BD area. The important findings reported here should be considered for future applications in similar projects.

Environmental impacts of desalination and brine treatment - Challenges and mitigation measures

Desalination is perceived as an effective and reliable process for obtaining freshwater from aqueous saline solutions such as brackish water, seawater and brine. This can be clarified by the fact that >300 million people worldwide rely on desalinated water for their daily needs. Although the desalination process offers many advantages, there are rising concerns about possible adverse environmental impacts. Generally, environmental impacts can be generated both in the construction and operation of desalination plants. A major issue of desalination is the co-produced waste called 'brine' or 'reject' which has a high salinity along with chemical residuals and is discharged into the marine environment. In addition to brine, other main issues are the high energy consumption of the desalination and brine treatment technologies as well as the air pollution due to emissions of greenhouse gasses (GHGs) and air pollutants. Other issues include entrainment and entrapment of marine species, and heavy use of chemicals. The purpose of this review is to analyze the potential impacts of desalination and brine treatment on the environment and suggest mitigation measures.

Surface functionalization of reverse osmosis membranes with sulfonic groups for simultaneous mitigation of silica scaling and organic fouling

Organic fouling and inorganic scaling are the main hurdles for efficient operation of reverse osmosis (RO) technology in a wide range of applications. This study demonstrates dual-functionality surface modification of thin-film composite (TFC) RO membranes to simultaneously impart anti-scaling and anti-fouling properties. Two different grafting approaches were adapted to functionalize the membrane surface with sulfonic groups: (i) non-specific grafting of vinyl sulfonic acid (VSA) via redox radical initiation polymerization and (ii) covalent bonding of hydroxylamide-O-sulfonic acid (HOSA) to the native carboxylic groups of the polyamide layer via carbodiimide mediated reaction. Both approaches to graft sulfonic groups were effective in increasing surface wettability and negative charge density of the TFC-RO membranes without significant alteration of water and salt permeabilities. Importantly, we verified through surface elemental analysis that covalently bound HOSA effectively covers the native carboxylic groups of the PA layer. Both the VSA and HOSA membranes exhibited lower flux decline during silica scaling and organic (alginate) fouling relative to the control unmodified membrane, demonstrating the unique versatility of sulfonic groups to endow the TFC-RO membranes with dual functionality to resist scaling and fouling. In particular, the HOSA membrane showed excellent physical cleaning efficiencies with water flux recoveries of 92.5 ± 1.0% and 88.4 ± 6.4% for silica scaling and alginate fouling, respectively. Additional results from silica nucleation experiments and atomic force measurements provided insights into the mechanisms of improved resistance to silica scaling and organic fouling imparted by the surface-functionalized sulfonic groups. Our study highlights the promise of controlled functionalization of sulfonic groups on the polyamide layer of TFC membranes to enhance the applications of RO technology in treatment and reuse of waters with high scaling and fouling potential.

Revisiting Mean Flow and Mixing Properties of Negatively Round Buoyant Jets Using the Escaping Mass Approach (EMA)

The flow formed by the discharge of inclined turbulent negatively round buoyant jets is common in environmental flow phenomena, especially in the case of brine disposal. The prediction of the mean flow and mixing properties of such flows is based on integral models, experimental results and, recently, on numerical modeling. This paper presents the results of mean flow and mixing characteristics using the escaping mass approach (EMA), a Gaussian model that simulates the escaping masses from the main buoyant jet flow. The EMA model was applied for dense discharge at a quiescent ambient of uniform density for initial discharge inclinations from 15° to 75°, with respect to the horizontal plane. The variations of the dimensionless terminal centerline and the external edge’s height, the horizontal location of the centerline terminal height, the horizontal location of centerline and the external edge’s return point as a function of initial inclination angle are estimated via the EMA model, and compared to available experimental data and other integral or numerical models. Additionally, the same procedure was followed for axial dilutions at the centerline terminal height and return point. The performance of EMA is acceptable for research purposes, and the simplicity and speed of calculations makes it competitive for design and environmental assessment studies.

Modelling the distributions of desalination brines from multiple sources along the Mediterranean coast of Israel

We use numerical simulations to study the possible spatiotemporal effects of brine release from five desalination plants, located along the Israeli Mediterranean coastline. It is commonly believed that salinity anomalies, associated with brine discharge from desalination plants, causes effects which are confined to an area of several hundreds of meters from the discharge outfall. We show that discharging brine using diffusers produces small but robust salinity anomalies that propagate tens of kilometers as density currents (DCs). In contrast, premixing the brine with power plant cooling water compensates the negative buoyancy and prevents their generation. The propagating DCs can impact coastal water dynamics by increasing the velocities and transports in alongshore and downslope directions. The spreading and trajectories of the DCs was strongly influenced by seasonal stratification. In winter, due to a mixed water column, the DCs were relatively focused and propagate downslope. While in the summer they are confined to a narrow band along the coastline. Our model results highlight the possibility that brine discharge might have a large scale, non-negligible effect on shelf circulation than previously considered. Further studies are needed to assess the environmental, dynamical and ecological effects of desalination brine propagation, especially in the far field.

The effect of long-term brine discharge from desalination plants on benthic foraminifera

Desalination plants along the Mediterranean Israeli coastline currently provide ~587 million m³ drinking water/year, and their production is planned to increase gradually. Production of drinking water is accompanied by a nearly equivalent volume of brine discharge with a salinity of ~80 that is twice the normal, which can potentially impact marine ecosystems. The goal of this study was to examine whether benthic foraminifera, a known sensitive marine bio-indicator, are affected by this brine-discharge. For that, we investigated the seasonal and cumulative effect of brine discharges of three operating desalination facilities along the Israeli coast. Those facilities are located in Ashkelon, Hadera, and Sorek. The brine-discharge in the first two desalination plants is associated with thermal pollution, while the Sorek facility entails increased salinity but no thermal pollution. In four seasonal cruises during one year, we collected surface sediment samples in triplicates by grabs from the outfall (near the discharge site), and from a non-impacted control station adjacent to each study site. Our results highlight that the most robust responses were observed at two out of three desalination shallow sites (Ashkelon and Hadera), where the brine was discharged directly from a coastal outfall and was accompanied with thermal pollution from the nearby power plants. The total foraminiferal abundance and diversity were, generally, lower near the outfalls, and increased towards the control stations. Moreover, changes in the relative abundances of selected species indicate their sensitivity to the brine discharge. The most noticeable response to exclusively elevated salinity was detected at Sorek discharge site, where we observed a sharp decline in organic-cemented agglutinated benthic foraminifera, suggesting that these are particularly sensitive to elevated salinity. The herein study contribute new insights into the effect of brine discharge from desalination plants, on benthic foraminifera, and propose a scientifically-based ecological monitoring tool that can help stakeholders.

Phytoplankton response to N-rich well amelioration brines: A mesocosm study from the southeastern Mediterranean Sea

Human-induced eutrophication of coastal water may be a major threat to aquatic life. Here, we investigated the effects of N-rich well amelioration brines (WAB) on coastal phytoplankton population's habitat in the surface oligotrophic waters of the southeastern Mediterranean Sea (SEM). To this end, we added WAB (2 concentrations) to mesocosms (1-m³ bags) to surface SEM water during summer and winter, where changes in phytoplankton biomass, activity and diversity was monitored daily for 8 days. Our results demonstrate that WAB addition triggered a phytoplankton bloom, resulting in elevated algal biomass (maximal +780%), increased primary production rates (maximal +675%) and a decrease in eukaryotic algal α-diversity (ca. -20%). Among the species that bloomed following WAB amendments, we found the potentially toxic dinoflagellate Karlodinium venificum. This study adds valuable perspective to the effect of nutrients discharged into nutrient limited SEM coastal waters, and in particular of N-derived WAB.