Desalination brine disposal methods and treatment technologies - A review

Evaluation of enhanced nanofiltration membranes for improving magnesium recovery schemes from seawater/brine: Integrating experimental performing data with a techno-economic assessment

The global demand for valuable metals and minerals necessitates the exploration of alternative, sustainable approaches to mineral recovery. Seawater mining has emerged as a promising option, offering a vast reserve of minerals and an environmentally friendly alternative to land-based mining. Among the various techniques, Nanofiltration (NF) has gained significant attention as a preliminary treatment step in Minimum Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) schemes. This study focused on the potential of two underexplored commercial polyamide based NF membranes, Synder NFX and Vontron VNF1, with enhanced divalent over monovalent separation factors, in optimizing the extraction of magnesium hydroxide (Mg(OH)2) from seawater and seawater reverse osmosis (SWRO) brines. The research encompassed a thorough characterization of the membranes utilizing advanced physic-chemical analytical techniques, followed by rigorous experimental assessments using synthetic seawater and SWRO brine in concentration configuration. The findings highlighted the superior selectivity of NFX for magnesium recovery from SWRO brine and the promising concentration factors of VNF1 for seawater treatment. Cross-validation of experimental data with a mathematical model demonstrated the model's reliability as a process design tool in predicting membrane performance. A comprehensive techno-economic evaluation demonstrates the potential of NFX, operating optimally at 23 bar pressure and 70% permeate recovery rate, to yield an estimated annual revenue of 5.683 M€/yr through Mg(OH)2 production from SWRO brine for a plant with a nominal capacity of 0.8 Mm3/y. This research shed light on the promising role of NF membranes in enhancing mineral recovery taking benefit of their separation factors and emphasizes the economic viability of leveraging NF technology for maximizing magnesium recovery from seawater and SWRO brines.

Desalination RO reject brine as a novel-based porous geopolymer for phosphorus removal from contaminated media

Desalination reverse osmosis reject brine-based porous geopolymer (RO/GP) was produced and investigated as an improved adsorbent for phosphorus (P) removal from tainted seawater, brackish water, river water, and municipal wastewater effluent. The RO reject brine/geopolymer was produced by reacting metakaolin and fly ash with a Na-alkali activator and anhydrous RO brine as a sacrificial template. The influence of RO reject brine content on water absorption, porosity, mechanical, and structural properties were examined. The developed RO-based geopolymers exhibited the greatest porosity (58.3-84.2 % vol%), a significant ratio of open porosity to total porosity (67.7-92.1 %), and outstanding compression strength (3.6-10.4 MPa). The produced RO/GP structure has an adsorption capacity of 92.4 mg-P/g. The sequestration reaction of phosphorus by RO/GP is of pseudo-second-order kinetic behavior via Chi-squared (χ2), RMSE, and determination coefficient (R2) values. Regarding their agreement with Langmuir behavior, the phosphorus adsorption uptakes occur in homogeneous and monolayer states. The reaction is exothermic, spontaneous, and favorable. The RO/GP exhibits significant affinity for phosphorus co-existing with Cl-, Na+, SO42-, K+, HCO3-, and Ca2+. The RO/GP shows high safety during the adsorption investigation, with a total cost of 0.32 $/kg-P.

Data-Monitoring Solution for Desalination Processes: Cooling Tower and Mechanical Vapor Compression Hybrid System

The advancement of novel water treatment technologies requires the implementation of both accurate data measurement and recording processes. These procedures are essential for acquiring results and conducting thorough analyses to enhance operational efficiency. In addition, accurate sensor data facilitate precise control over chemical treatment dosages, ensuring optimal water quality and corrosion inhibition while minimizing chemical usage and associated costs. Under this framework, this paper describes the sensoring and monitoring solution for a hybrid system based on a cooling tower (CT) connected to mechanical vapor compression (MVC) equipment for desalination and brine concentration purposes. Sensors connected to the data commercial logger solution, Almemo 2890-9, are also discussed in detail such as temperature, relative humidity, pressure, flow rate, etc. The monitoring system allows remote control of the MVC based on a server, GateManager, and TightVNC. In this way, the proposed solution provides remote access to the hybrid system, being able to visualize gathered data in real time. A case study located in Cartagena (Spain) is used to assess the proposed solution. Collected data from temperature transmitters, pneumatic valves, level sensors, and power demand are included and discussed in the paper. These variables allow a subsequent forecasting process to estimate brine concentration values. Different sample times are included in this paper to minimize the collected data from the hybrid system within suitable operation conditions. This solution is suitable to be applied to other desalination processes and locations.

A comprehensive assessment of the economic and technical viability of a zero liquid discharge (ZLD) hybrid desalination system for water and salt recovery

Brine, a by-product of desalination and industrial facilities, is becoming more and more of an environmental issue. This comprehensive techno-economic assessment (TEA), focusing on the technical and economic aspects, investigates the performance and viability of a novel hybrid desalination brine treatment system known as zero liquid discharge (ZLD). Notably, this research represents the first instance of evaluating the feasibility and effectiveness of integrating three distinct desalination processes, namely brine concentrator (BC), high-pressure reverse osmosis (HPRO), and membrane-promoted crystallization (MPC), within a ZLD framework. The findings of this study demonstrate an exceptional water recovery rate of 97.04%, while the energy requirements stand at a reasonable level of 17.53 kWh/m3. Financially, the ZLD system proves to be at least 3.28 times more cost-effective than conventional evaporation ponds and offers comparable cost efficiency to alternatives such as land application and deep-well injection. Moreover, the ZLD system exhibits profitability potential by marketing both drinking water and solid salt or solely desalinated water. The daily profit from the sale of generated water varies from US$194.08 to US$281.41, with Greece and Cyprus attaining the lowest and highest profit, respectively. When considering the sale of both salt and water, the profit rises by 8% across all locations.

A life cycle assessment of early-stage enzyme manufacturing simulations from sustainable feedstocks

Enzyme-catalyzed reactions have relatively small environmental footprints. However, enzyme manufacturing significantly impacts the environment through dependence on traditional feedstocks. With the objective of determining the environmental impacts of enzyme production, the sustainability potential of six cradle-to-gate enzyme manufacturing systems focusing on glucose, sea lettuce, acetate, straw, and phototrophic growth, was thoroughly evaluated. Human and ecosystem toxicity categories dominated the overall impacts. Sea lettuce, straw, or phototrophic growth reduces fermentation-based emissions by 51.0, 63.7, and 79.7%, respectively. Substituting glucose-rich media demonstrated great potential to reduce marine eutrophication, land use, and ozone depletion. Replacing organic nitrogen sources with inorganic ones could further lower these impacts. Location-specific differences in electricity result in a 14% and a 27% reduction in the carbon footprint for operation in Denmark compared to the US and China. Low-impact feedstocks can be competitive if they manage to achieve substrate utilization rates and productivity levels of conventional enzyme production processes.

Environmentally Friendly Photothermal Membranes for Halite Recovery from Reverse Osmosis Brine via Solar-Driven Membrane Crystallization

Modern society and industrial development rely heavily on the availability of freshwater and minerals. Seawater reverse osmosis (SWRO) has been widely adopted for freshwater supply, although many questions have arisen about its environmental sustainability owing to the disposal of hypersaline rejected solutions (brine). This scenario has accelerated significant developments towards the hybridization of SWRO with membrane distillation-crystallization (MD-MCr), which can extract water and minerals from spent brine. Nevertheless, the substantial specific energy consumption associated with MD-MCr remains a significant limitation. In this work, energy harvesting was secured from renewables by hotspots embodied in the membranes, implementing the revolutionary approach of brine mining via photothermal membrane crystallization (PhMCr). This method employs self-heating nanostructured interfaces under solar radiation to enhance water evaporation, creating a carefully controlled supersaturated environment responsible for the extraction of minerals. Photothermal mixed matrix photothermal membranes (MMMs) were developed by incorporating graphene oxide (GO) or carbon black (CB) into polyvinylidene fluoride (PVDF) solubilized in an eco-friendly solvent (i.e., triethyl phosphate (TEP)). MMMs were prepared using non-solvent-induced phase separation (NIPS). The effect of GO or GB on the morphology of MMMs and the photothermal behavior was examined. Light-to-heat conversion was used in PhMCr experiments to facilitate the evaporation of water from the SWRO brine to supersaturation, leading to sodium chloride (NaCl) nucleation and crystallization. Overall, the results indicate exciting perspectives of PhMCr in brine valorization for a sustainable desalination industry.

A numerical modelling approach to investigate the fate of brine reject of farm scale desalination plants on groundwater aquifers in arid environments

Farm-scale desalination units are gaining popularity for agricultural irrigation in arid countries, such as Kuwait to meet freshwater demands. However, less attention has been given to the management of environmentally hazardous brine reject water they produce. In this study we investigated the fate of brine water produced by the inland desalination units on the underlying aquifers using numerical modelling and field investigations. The methodology involved developing groundwater flow and solute transport models using Flex VMF-SEAWAT to simulate the movement of reject brine. The field investigations included collecting 150 water samples and conducting pumping tests on newly drilled wells. This numerical simulation considered advection, dispersion, and adsorption processes with variable groundwater density following rigorous validation and calibration of the developed numerical models. The results show that the RO reject brine will significantly increase groundwater salinity, exceeding 10,000 mg/L when accounting for advection, dispersion, and adsorption processes. The sustainable yield of the aquifer, with a salinity of <10,000 mg/L, averages 500 Mm3 but is expected to be depleted within 16 years with the current extraction rate. The resulting hydraulic properties are favourable with K about 100 m/d, T > 1000 m2/day, and Sy just >0.1. The adopted values for dispersivity and adsorption coefficients for chloride and sulphate salts in the aquifer were 10 m and 1 × 10-7 [mg/L]-1 respectively. Chemical and numerical analyses indicate a mixing ratio between the reject brine and groundwater in the study area of approximately 10 %. Uncontrolled groundwater extraction, combined with the surface disposal of RO reject brine, has led to a significant decline in groundwater levels and an increase in the salinity. The adsorption ratio of simulated brine plume was 13 %. The authors recommend to dispose the RO reject water in a safe location or transfer it to the nearest wastewater treatment plant for proper treatment and reuse.

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.

Coupling redox flow desalination with lithium recovery from spent lithium-ion batteries

Electrochemical redox flow desalination is an emerging method to obtain freshwater; however, the costly requirement for continuously supplying and regenerating redox species limits their practical applications. Recycling of spent lithium-ion batteries is a growing challenge for their sustainable utilization. Existing battery recycling methods often involve massive secondary pollution. Here, we demonstrate a redox flow system to couple redox flow desalination with lithium recovery from spent lithium-ion batteries. The spontaneous reaction between a battery cathode material (LiFePO4) and ferricyanide enables the continuous regeneration of the redox species required for desalination. Several critical operating parameters are optimized, including current density, the concentrations of redox species, salt concentrations of brine, and the amounts of added LiFePO4. With the addition of 0.5920 g of spent LiFePO4 in five consecutive batches, the system can operate over 24 h, achieving 70.46 % lithium recovery in the form of LiCl aqueous solution at the concentration of 6.716 g·L-1. Simultaneously, the brine (25 mL, 10000 ppm NaCl) was desalinated to freshwater. Detailed cost analysis shows that this redox flow system could generate a revenue of ¥ 13.66 per kg of processed spent lithium-ion batteries with low energy consumption (0.77 MJ kg-1) and few greenhouse gas emissions indicating excellent economic and environmental benefits over existing lithium-ion battery recycling technologies, such as pyrometallurgical and hydrometallurgical methods. This work opens a new approach to holistically addressing water and energy challenges to achieve sustainable development.

Nutrient recovery from wastewater for hydroponic systems: A comparative analysis of fertilizer demand, recovery products, and supply potential of WWTPs

Nutrient recovery from wastewater treatment plants (WWTPs) for hydroponic cultivation holds promise for closing the nutrient loop and meeting rising food demands. However, most studies focus on solid products for soil-based agriculture, thus raising questions about their suitability for hydroponics. In this study, we address these questions by performing the first in-depth assessment of the extent to which state-of-the-art nutrient recovery processes can generate useful products for hydroponic application. Our results indicate that less than 11.5% of the required nutrients for crops grown hydroponically can currently be recovered. Potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), and magnesium sulfate (MgSO4), constituting over 75% of the total nutrient demand for hydroponics, cannot be recovered in appropriate form due to their high solubility, hindering their separated recovery from wastewater. To overcome this challenge, we outline a novel nutrient recovery approach that emphasizes the generation of multi-nutrient concentrates specifically designed to meet the requirements of hydroponic cultivation. Based on a theoretical assessment of nutrient and contaminant flows in a typical municipal WWTP, utilizing a steady-state model, we estimated that this novel approach could potentially supply up to 56% of the nutrient requirements of hydroponic systems. Finally, we outline fundamental design requirements for nutrient recovery systems based on this new approach. Achieving these nutrient recovery potentials could be technically feasible through a combination of activated sludge processes for nitrification, membrane-based desalination processes, and selective removal of interfering NaCl. However, given the limited investigation into such treatment trains, further research is essential to explore viable system designs for effective nutrient recovery for hydroponics.

Numerical modeling of geological sequestration of brine wastewater due to coal mining in the Ordos Basin, China

The coal resources play an indispensable role in the development of heavy industry in China, and coal mining activity leads to brine wastewater drainage, causing major risks for the aquatic environmental system. Thus, the effective and economic treatment of coal mine wastewater is vital to mitigate the environmental burdens, and geological sequestration by deep-well injection is a promising treatment technique. This study elucidates the physical and geochemical processes of coal mine wastewater transport in deep reservoirs and proposes an optimized injection scheme to satisfy environmental and economic benefits simultaneously in the Ordos Basin, China. First, a variable density and variable parameter groundwater reactive transport model is constructed to simulate the long-term process of deep-well injection for coal mine wastewater treatment. Then, the environmental metrics, i.e., the percentage of permeability reduction, the total mass and spatial second moment of the wastewater plume, and the economic metric defined as achieving a higher concentration at a higher injection rate are proposed to evaluate the performance of the injection scheme. The simulation results show that the secondary mineral anhydrite dominates the reduction of reservoir permeability due to the precipitation reactions with SO42- in the brine wastewater, and the permeability in the reaction zone decreases by 0.66 % ~ 1.26 % after 10 years in the basic scenario. Moreover, higher concentrations negatively affect reservoir permeability and increase total dissolved solids, while higher injection rates decrease reservoir permeability and increase the brine wastewater plume. The study also identifies promising schemes that can achieve an optimal trade-off between the conflicting metrics. Based on the economic and environmental benefits demanded in this study, an injection scenario with a concentration of C4 and an injection volume of 800 m3/d is recommended to maximize environmental benefits. Overall, this numerical study offers significant implications for designing an economically and environmentally sustainable treatment injection scheme for coal mining wastewater drainage.

Ideal conductor/dielectric model (ICDM): A generalized technique to correct for finite-size effects in molecular simulations of hindered ion transport

Molecular simulations serve as indispensable tools for investigating the kinetics and elucidating the mechanism of hindered ion transport across nanoporous membranes. In particular, recent advancements in advanced sampling techniques have made it possible to access translocation timescales spanning several orders of magnitude. In our prior study [Shoemaker et al., J. Chem. Theory Comput. 18, 7142 (2022)], we identified significant finite size artifacts in simulations of pressure-driven hindered ion transport through nanoporous graphitic membranes. We introduced the ideal conductor model, which effectively corrects for such artifacts by assuming the feed to be an ideal conductor. In the present work, we introduce the ideal conductor dielectric model (Icdm), a generalization of our earlier model, which accounts for the dielectric properties of both the membrane and the filtrate. Using the Icdm model substantially enhances the agreement among corrected free energy profiles obtained from systems of varying sizes, with notable improvements observed in regions proximate to the pore exit. Moreover, the model has the capability to consider secondary ion passage events, including the transport of a co-ion subsequent to the traversal of a counter-ion, a feature that is absent in our original model. We also investigate the sensitivity of the new model to various implementation details. The Icdm model offers a universally applicable framework for addressing finite size artifacts in molecular simulations of ion transport. It stands as a significant advancement in our quest to use molecular simulations to comprehensively understand and manipulate ion transport processes through nanoporous membranes.

The Future of Municipal Wastewater Reuse Concentrate Management: Drivers, Challenges, and Opportunities

Water reuse is rapidly becoming an integral feature of resilient water systems, where municipal wastewater undergoes advanced treatment, typically involving a sequence of ultrafiltration (UF), reverse osmosis (RO), and an advanced oxidation process (AOP). When RO is used, a concentrated waste stream is produced that is elevated in not only total dissolved solids but also metals, nutrients, and micropollutants that have passed through conventional wastewater treatment. Management of this RO concentrate─dubbed municipal wastewater reuse concentrate (MWRC)─will be critical to address, especially as water reuse practices become more widespread. Building on existing brine management practices, this review explores MWRC management options by identifying infrastructural needs and opportunities for multi-beneficial disposal. To safeguard environmental systems from the potential hazards of MWRC, disposal, monitoring, and regulatory techniques are discussed to promote the safety and affordability of implementing MWRC management. Furthermore, opportunities for resource recovery and valorization are differentiated, while economic techniques to revamp cost-benefit analysis for MWRC management are examined. The goal of this critical review is to create a common foundation for researchers, practitioners, and regulators by providing an interdisciplinary set of tools and frameworks to address the impending challenges and emerging opportunities of MWRC management.

Salinity impacts on humidification dehumidification (HDH) desalination systems: review

The use of humidification-dehumidification water desalination technology has been shown to be a practical means of meeting the demand for freshwater. The aim of this review is to investigate the impact of salinity on HDH techniques that have various benefits in terms of both economics and the environment, including the capacity to operate at low temperatures, utilize sustainable energy sources, the need for low maintenance, and straightforward construction requirements. Also, in this review, it is observed that the HDH system's components are strong and capable of treating severely salinized water. It can treat water in an appropriate way than other desalination technologies. This technology has recently been commercialized to treat highly salinized generated water. However, more research is needed to determine how salinity affects HDH productivity. According to several research investigations, while the specific thermal energy consumption increased considerably and the productivity of water per unit of time decreased significantly as the salt mass percentage grew, the purity of clean water did not suffer. The rejected brine must be reduced by increasing the total water recovery ratio in the HDH system. Through this review, it was found that brine control is becoming increasingly important in the water processing industry. ZLD systems, which aim to recover both freshwater and solid salts, can be a viable replacement for disposal methods. Finally, through this reviewer, it was concluded that HDH desalination systems may operate with extremely saline water while increasing salinity has a significant influence on system performance.

Innovative method for the brine treatment by electrokinetic principles integrated with solar photovoltaic plants

With the growing world population and industrial production, the demand for water has been continuously increasing. By 2030, it was estimated that 60.0 % of the world population will not have access to freshwater, which is about 2.50 % of the total global water. For this, a total of over 17,000 operational desalination plants have been constructed worldwide. However, the key barriers to expansion of the desalination treatments are the brine production and energy consumption. In fact, the brine production is 50.0 % higher than the freshwater, and its treatments could account for 5.0-33.0 % of total desalination cost. Here, a new theoretical approach for brine treatments integrated to solar photovoltaic plants (PVs) to supply renewable energy to the whole system has been proposed. This approach consists in combining electrokinetic and electrochemical phenomena to dilute the brine, by using an alkaline clay with high buffering power. This method substantially desalinates the brine to produce new treated seawater, using clean energy, optimizing energetic and management costs. Some hypotheses and secondary effects should validate the model, e.g., relatively high Ca2+ promotes the electro-migration; the Cl2 production reduces the Cl- concentrations; and the production of H2 can be used to store energy. A practical example for PVPs design is shown.

Prioritizing the Best Potential Regions for Brine Concentration Systems in the USA Using GIS and Multicriteria Decision Analysis

We propose a methodology for identifying and prioritizing the best potential locations for brine concentration facilities in the contiguous United States. The methodology uses a geographic information system and multicriteria decision analysis (GIS-MCDA) to prioritize the potential locations for brine concentration facilities based on thermodynamic, economic, environmental, and social criteria. By integrating geospatial data with a computational simulation of a real brine concentration system, an objective weighting method identifies the weights for 13 subcriteria associated with the main criteria. When considering multiple dimensions for decision making, brine concentration facilities centered in Florida were consistently selected as the best location, due to the high second-law efficiency, low transportation cost, and high capacity for supplying municipal water needs to nearby populations. For inland locations, Southeast Texas outperforms all other locations for thermodynamic, economic, and environmental priority cases. A sensitivity analysis evaluates the consistency of the results as the priority of a main criterion varies relative to other decision-making criteria. Focusing on a single subcriterion misleads decision making when identifying the best location for brine concentration systems, identifying the importance of the multicriteria methodology.

Difference of high-salinity-induced inhibition of ammonia-oxidising bacteria and nitrite-oxidising bacteria and its applications

The difficulty in achieving stable partial nitritation (PN) is a challenge that limits the application of mainstream anaerobic ammonium oxidation (anammox). This study proposes high-salinity treatment as a novel strategy for inactivating nitrite-oxidising bacteria (NOB). The study indicated that NOB are more sensitive to high salinity than ammonia-oxidising bacteria (AOB). The inhibitory effect on the nitrifier gradually increased with increasing salinity from 0 to 100 g NaCl/L. After 24 h and 35 g NaCl/L inhibition, the AOB and NOB activities were 36.65% and 7.15% of their original activities, respectively. After one high-salinity treatment, nitrite accumulation rate (NAR) was above 33% during nitrification. Moreover, the sludge characteristics remained almost unchanged after suppression. A novel process for achieving mainstream PN was proposed and evaluated based on the results. An energy consumption analysis showed that mainstream PN/anammox based on the ex situ high-salinity treatment can achieve higher energy self-sufficiency compared with activated sludge.

Emerging materials and technologies for electrocatalytic seawater splitting

The limited availability of freshwater in renewable energy-rich areas has led to the exploration of seawater electrolysis for green hydrogen production. However, the complex composition of seawater presents substantial challenges such as electrode corrosion and electrolyzer failure, calling into question the technological and economic feasibility of direct seawater splitting. Despite many efforts, a comprehensive overview and analysis of seawater electrolysis, including electrochemical fundamentals, materials, and technologies of recent breakthroughs, is still lacking. In this review, we systematically examine recent advances in electrocatalytic seawater splitting and critically evaluate the obstacles to optimizing water supply, materials, and devices for stable hydrogen production from seawater. We demonstrate that robust materials and innovative technologies, especially selective catalysts and high-performance devices, are critical for efficient seawater electrolysis. We then outline and discuss future directions that could advance the techno-economic feasibility of this emerging field, providing a roadmap toward the design and commercialization of materials that can enable efficient, cost-effective, and sustainable seawater electrolysis.

Integrating reverse osmosis and forward osmosis (RO-FO) for printing and dyeing wastewater treatment: impact of FO on water recovery

Reverse osmosis (RO) alone has low water recovery efficiency because of membrane fouling and limited operating pressure. In this study, a combined reverse osmosis-forward osmosis (RO-FO) process was used for the first time to improve the water recovery efficiency of secondary effluent in printing and dyeing wastewater. The effects of operating pressure and pH on water recovery and removal efficiency of RO-FO were investigated. The results showed that the optimum conditions were an operating pressure of 1.5 MPa and a feed solution pH of 9.0. Under optimal operating conditions, most of the organic and inorganic substances in the wastewater can be removed, and the rejection of total organic carbon (TOC), Sb, Ca, and K were 98.7, 99.3, 97.0, and 92.7%, respectively. Fluorescence excitation-emission matrices coupled with parallel factor (EEM-PARAFAC) analysis indicated that two components (tryptophan and tyrosine) in the influent were effectively rejected by the hybrid process. The maximum water recovery (Rw, max) could reach 95%, which was higher than the current single RO process (75%). This research provided a feasible strategy to effectively recover water from printing and dyeing wastewater.

Numerical solutions for the treatment brine by diffusive and migration flux using new brine-clay-seawater system

With the growing world population and industrial production, the demand for water has been continuously increasing. By 2030, 60.0% of the world population will not have access to freshwater, which is ∼2.50% of the total global water. For this, a total of over 17,000 operational desalination plants have been constructed worldwide. However, the key barrier to desalination expansion is brine production, which is 50.0% higher than the freshwater, generating 5.0-33.0% of total desalination cost. In this paper, a new theoretical approach for brine treatments has been proposed. It consists in combining electrokinetic and electrochemical mechanisms by using an alkaline clay with high buffering power. Advanced numerical model has been carried out to estimate the ions concentrations in the brine-clay-seawater system. Analytical analyses have been also carried out to estimate the global system efficiency. Results show the feasibility of the theoretical system, its size, and usability of the clay. This model not only should clean the brine to produce new treated seawater but also it should recover useful minerals thank to the electrolysis and precipitations effects.

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.

Multivariate optimization of characteristic parameters of continuous-flow system with a front buffer tank for industrial reverse osmosis concentrate treatment

Industrial reverse osmosis concentrate (ROC) was electrochemically oxidized using a continuous-flow system (CFS) with a front buffer tank. Multivariate optimization including Plackett-Burman (PBD) and central composite design based on response surface method (CCD-RSM) was implemented to investigate the effects of characteristic (e.g., recirculation ratio (R value), ratio of buffer tank and electrolytic zone (R_V value)) and routine (e.g., current density (i), inflow linear velocity (v) and electrode spacing (d)) parameters. R, v values and current density significantly influenced chemical oxygen demand (COD) and NH₄⁺-N removal and effluent active chlorine species (ACS) level, while electrode spacing and R_V value had negligible effects. High chloride content of industrial ROC facilitated the generation of ACS and subsequent mass transfer, low hydraulic retention time (HRT) of electrolytic cell improved the mass transfer efficiency, and high HRT of buffer tank prolonged the reaction between the pollutants and oxidants. The significance levels of COD removal, energy efficiency, effluent ACS level and toxic byproduct level CCD-RSM models were validated by statistical test results, including higher F value than critical effect value, lower P value than 0.05, low deviation between predicted and observed values, and normal distribution of calculated residuals. The highest pollutant removal was achieved at a high R value, a high current density and a low v value; the highest energy efficiency was achieved at a high R, a low current density and a high v value; the lowest effluent ACS and toxic byproduct levels were achieved at a low R value, a low current density and a high v value. Following the multivariate optimization, the optimum parameters were decided to be v = 1.2 cm h^-1, i ≥ 8 mA cm^-2, d ≥ 4, R_V = 10-20 and R = 1 to achieve better effluent quality (i.e., lower effluent pollutant, ACS and toxic byproduct levels).

Utilization of calcium-rich groundwater desalination concentrate in aquaculture

Global production of desalinated water increased greatly over the past three decades. Brackish water desalination is energetically favorable compared with seawater desalination, but high treatment costs and negative environmental impact of the concentrate byproduct hinders its development in semi-arid regions. The present study assessed key considerations associated with potential commercial aquaculture in high-flowrate calcium-rich groundwater desalination concentrate. European seabass (Dicentrarchus labrax) fingerlings, weighing 20-40 g were cultivated in brackish water (control), raw concentrate, and partially softened concentrate under flow-through conditions. Aside from two disease-related mortality events, fish survival exceeded 92% during 70 days of cultivation in all water types. The highest average growth rate of 0.26 g d^-1 was obtained in the partially softened concentrate, which was 27% and 83% higher than in the raw concentrate and in the control, respectively. Substantial mineral precipitation on equipment and minor gill damage were observed in fish tanks receiving raw concentrate, projecting serious operational issues under commercial application. Preliminary aeration-softening of the concentrate relieved CO₂ supersaturation and prevented precipitation issues. Several implementation options in a case study fish farm predict commercial and environmental feasibility in specific locations.

Hydrophobic Modified Ceramic Aeration Membrane for Effective Treatment of Brine Wastewater

A novel approach to evaporate brine wastewater using a ceramic aeration membrane was proposed. A high-porosity ceramic membrane was selected as the aeration membrane and was modified with hydrophobic modifiers to avoid undesired surface wetting. The water contact angle of the ceramic aeration membrane reached 130° after hydrophobic modification. The hydrophobic ceramic aeration membrane showed excellent operational stability (up to 100 h), high salinity (25 wt.%) tolerance, and excellent regeneration performance. The evaporative rate reached 98 kg m^-2 h^-1, which could be restored by ultrasonic cleaning after the membrane fouling occurred. Furthermore, this novel approach shows great promise for practical applications toward a low cost of only 66 kW·h·m^-3.

The Minus Approach Can Redefine the Standard of Practice of Drinking Water Treatment

Chlorine-based disinfection for drinking water treatment (DWT) was one of the 20th century's great public health achievements, as it substantially reduced the risk of acute microbial waterborne disease. However, today's chlorinated drinking water is not unambiguously safe; trace levels of regulated and unregulated disinfection byproducts (DBPs), and other known, unknown, and emerging contaminants (KUECs), present chronic risks that make them essential removal targets. Because conventional chemical-based DWT processes do little to remove DBPs or KUECs, alternative approaches are needed to minimize risks by removing DBP precursors and KUECs that are ubiquitous in water supplies. We present the "Minus Approach" as a toolbox of practices and technologies to mitigate KUECs and DBPs without compromising microbiological safety. The Minus Approach reduces problem-causing chemical addition treatment (i.e., the conventional "Plus Approach") by producing biologically stable water containing pathogens at levels having negligible human health risk and substantially lower concentrations of KUECs and DBPs. Aside from ozonation, the Minus Approach avoids primary chemical-based coagulants, disinfectants, and advanced oxidation processes. The Minus Approach focuses on bank filtration, biofiltration, adsorption, and membranes to biologically and physically remove DBP precursors, KUECs, and pathogens; consequently, water purveyors can use ultraviolet light at key locations in conjunction with smaller dosages of secondary chemical disinfectants to minimize microbial regrowth in distribution systems. We describe how the Minus Approach contrasts with the conventional Plus Approach, integrates with artificial intelligence, and can ultimately improve the sustainability performance of water treatment. Finally, we consider barriers to adoption of the Minus Approach.

EfectroH2O: Development and evaluation of a novel treatment technology for high-brine industrial wastewater

Textile production is one of the main sources of freshwater consumption by industries worldwide. In addition, according to the world bank, 20 % of the wastewater generated globally is caused by textile wet-processing. Textile wet-processing includes the processes in textile production where garments are dyed or given the final functions like water-repellency. Several thousand chemicals were used in this process, some of which are highly toxic. Discharging untreated or insufficiently treated wastewater in water bodies results in high pollution levels, severely impacting the environment and human health. Especially in textile-producing countries like India, environmental pollution and water consumption from textile wet-processing have severe impacts. Next to the high volume of chemicals used in textile production, the high salt concentration in textile wastewater also poses a challenge and is critical for freshwater systems. Moreover, textile wastewater is one of the most difficult to treat wastewater. Currently, used treatment technologies do not meet the requirements to treat textile wastewater. Therefore, the further development of efficient treatment technologies for textile wastewater is critically important. Hence, in the interdisciplinary project, effect-based monitoring demonstrates the efficiency of electrically-driven water treatment processes to remove salts and micropollutants from process water (EfectroH₂O), a low-energy Zero Liquid Discharge (ZLD) textile wastewater treatment technology is being developed consisting of a combination of capacitive deionization (CDI) and advanced oxidation processes (AOP). In addition to treatment technology development, methods for evaluating the efficiency of treatment technologies also need to be improved. Currently, mainly physicochemical parameters such as pH, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) are tested worldwide to check water quality. However, these methods are insufficient to make a statement about the toxic potential of such complex mixtures as textile wastewater. Therefore, also next to chemical analyses, effect-based methods (EBM) are used to verify the treated wastewater.

Effect of thermal characteristics on the chemical quality of real-brine treatment through hydrophilic fiber-based low-grade heat-powered humidification-dehumidification process

Considering the increasing demand for desalination plants and their byproduct brine, this study investigated a humidification-dehumidification (HDH) system for treating membrane distillation-generated real high-salinity brine using low-grade heat (45-70 ℃) to explore its feasibility for sustainable energy-efficient minimal liquid discharge. A novel super-hydrophilic fabric was adopted for accelerated humidification, and its impact on brine droplet miscarriage characteristics was evaluated. The influence of the operating fluid thermal properties (cycle 1: air preheating; cycle 2: air and brine dual-fluid preheating; and cycle 3: air post-heating after humidification) on the brine treatment efficiency, energy consumption, and chemical quality of freshwater produced was analyzed in detail to establish their characteristic nexus. It was identified that, during humidification, increasing the brine temperature (up to 55 ℃) influenced its ionic mobility, thereby promoting efficient separation of the salts/minerals and contributing to achieving better freshwater quality. Furthermore, although cycle 3 exhibited improved system thermal efficiency (gained output ratio equal to 1.77), its non-preheated air contributed to a negative effect of the reduced humidity ratio (∼17 g/kg), leading to a lower freshwater productivity of 67% than that of cycle 2 (29 g/kg and 70%). The present study also illustrates a novel effect of evaporative deposition occurring due to air-water interaction on the fabric humidifier surface, with an exploration of its effect on reducing freshwater chemical quality. The freshwater generated from optimum thermal cycle 2 exhibited reduced pH (by ∼63%), sodium (99.9%), chloride (99.9%), toxic boron (99.7%), and other chemical contaminants, thereby satisfying the major international water reuse standards.

Impacts of desalination discharges on phytoplankton and zooplankton: Perspectives on current knowledge

Large-scale application of desalination technology can result in impacts to the marine biota, such as phytoplankton and zooplankton, basal components of marine trophic webs. In this context, our perspective aimed to summarize the impacts of effluent discharges from desalination plants on phytoplankton and zooplankton in order to identify the main gaps and challenges in this theme, propose solutions, and provide recommendations for future work. We identified two main approaches to assess the desalination impacts: laboratory experiments and field studies. Most of these studies were conducted in areas impacted by effluent discharges using the BACI (before, after, and control-impact) approach. They primarily aimed to set out the impacts of hypersaline brine on the surrounding environment and, to a lesser extent, the high-temperature effluents and contaminants from desalination plants. Moreover, phytoplankton was more sensitive to effluent discharges than zooplankton. The main changes observed were a decrease in primary productivity, a loss in diversity, and a change in the community structure of planktonic populations due to the dominance of saline-tolerant groups, which highlights the importance improving treatment or dilution of effluent discharges to minimize the impacts over whole neritic trophic webs, which depend on phytoplankton. From the impacts related to effluent discharges analyzed herein, RO technology was related to most cases of negative impact related to salinity modifications. However, coagulants were related to negative effects in all study cases. Future work should focus on escalate the impacts of such effluents on other trophic levels that could be directly or indirectly impacted as well as on how to improve the quality of effluent discharges. Also, we highlight the importance of further baseline and long-term monitoring studies to investigate desalination-induced changes and community resilience to these impacts, as well as studies to provide alternatives to the use of toxic chemicals in the pre-treatment phases.

Electrodialysis with Bipolar Membranes for the Sustainable Production of Chemicals from Seawater Brines at Pilot Plant Scale

Environmental concerns regarding the disposal of seawater reverse osmosis brines require the development of new valorization strategies. Electrodialysis with bipolar membrane (EDBM) technology enables the production of acid and base from a salty waste stream. In this study, an EDBM pilot plant with a membrane area of 19.2 m² was tested. This total membrane area results much larger (i.e., more than 16 times larger) than those reported in the literature so far for the production of HCl and NaOH aqueous solutions, starting from NaCl brines. The pilot unit was tested both in continuous and discontinuous operation modes, at different current densities (200-500 A m^-2). Particularly, three different process configurations were evaluated, namely, closed-loop, feed and bleed, and fed-batch. At lower applied current density (200 A m^-2), the closed-loop had a lower specific energy consumption (SEC) (1.4 kWh kg^-1) and a higher current efficiency (CE) (80%). When the current density was increased (300-500 A m^-2), the feed and bleed mode was more appropriate due to its low values of SEC (1.9-2.6 kWh kg^-1) as well as high values of specific production (SP) (0.82-1.3 ton year^-1 m^-2) and current efficiency (63-67%). These results showed the effect of various process configurations on the performance of the EDBM, thereby guiding the selection of the most suitable process configuration when varying the operating conditions and representing a first important step toward the implementation of this technology at industrial scale.

Performance of Hypersaline Brine Desalination Using Spiral Wound Membrane: A Parametric Study

Desalination of hypersaline brine is known as one of the methods to cope with the rising global concern on brine disposal in high-salinity water treatment. However, the main problem of hypersaline brine desalination is the high energy usage resulting from the high operating pressure. In this work, we carried out a parametric analysis on a spiral wound membrane (SWM) module to predict the performance of hypersaline brine desalination, in terms of mass transfer and specific energy consumption (SEC). Our analysis shows that at a low inlet pressure of 65 bar, a significantly higher SEC is observed for high feed concentration of brine water compared with seawater (i.e., 0.08 vs. 0.035) due to the very low process recovery ratio (i.e., 1%). Hence, an inlet pressure of at least 75 bar is recommended to minimise energy consumption. A higher feed velocity is also preferred due to its larger productivity when compared with a slightly higher energy requirement. This study found that the SEC reduction is greatly affected by the pressure recovery and the pump efficiencies for brine desalination using SWM, and employing them with high efficiencies (η_R ≥ 95% and η_pump ≥ 50%) can reduce SEC by at least 33% while showing a comparable SEC with SWRO desalination (<5.5 kWh/m³).

Interpenetrating polymer networks for desalination and water remediation: a comprehensive review of research trends and prospects

Interpenetrating polymer network (IPN) architectures have gained a lot of interest in recent decades, mainly due to their wide range of applications including water treatment and environmental remediation. IPNs are composed of two or more crosslinked polymeric matrices that are physically entangled but not chemically connected. In polymer science, the interpenetrating network structure with its high polymer chain entanglement is commonly used to generate materials with many functional properties, such as mechanical robustness and adaptable structure. In order to remove a targeted pollutant from contaminated water, it is feasible to modify the network architectures to increase the selectivity by choosing the monomer appropriately. This review aims to give a critical overview of the recent design concepts of IPNs and their applications in desalination and water treatment and their future prospects. This article also discusses the inclusion of inorganic nanoparticles into traditional polymeric membrane networks and its advantages. In the first part, the current scenario for desalination, water pollution and conventional desalination technologies along with their challenges is discussed. Subsequently, the main strategies for the synthesis of semi-IPNs and full-IPNs, and their relevant properties in water remediation are presented based on the nature of the networks and mechanism, with an emphasis on the IPN membrane. This review article has thoroughly investigated and critically assessed published works that describe the latest study on developing IPN membranes, hydrogels and composite materials in water purification and desalination. The goal of this critical analysis is to elicit fresh perspectives regarding the application and advantages of IPNs in desalination and water treatment. This article will also provide a glimpse into future areas of research to address the challenges relating to advanced water treatment as well as its emerging sustainable approaches. The study has put forward a convincing justification and establishes the relevance of IPNs being one of the most intriguing and important areas for achieving a sustainable generation of advanced materials that could benefit mankind.

Freeze desalination: Current research development and future prospects

Desalination is the solution for water security in regions with insufficient resources. This comes at high energy cost and hence improving desalination technologies translate into huge saving. Freeze desalination (FD) is emerging as an attractive low energy and less corrosion alternative to provide the needed fresh water. The maturity of the heat driven cooling technology and solar cooling have given freeze desalination an additional momentum. This paper summarizes the latest research progress done on FD that continues to push this technology towards deployment. It gives an overview of the FD configurations and highlighting its pros and cons, presents the recent experimental work that investigate the physics of the technology, and reviews the latest high-fidelity numerical modeling of brine freezing and salt diffusion away from crystal lattice which taps on the advanced development in computational power and multiphysics integration. This enables one to identify the challenges facing FD technology and stating the prospect and foreseeable research. The finding suggests that direct and indirect FD have been evolved well while the indirect is becoming the mainstream method for risk avoidance, while vacuum freezing and eutectic freezing are still facing large obstacles in their application. For direct FD, gas hydrate combined with liquefied natural gas (LNG) regasification has been popular topics to reduce their desalination cost. Simulation and modeling development in indirect FD continue to improve the knowledge of the mechanism of ice growth and salt entrapment which are key problems that need further experimental and numerical investigations. Nonetheless, the current successful application of LNG cold energy in freeze desalination, the hybridization of FD with conventional desalination technologies, as well as ultrasound assisted freezing are promising directions for FD commercialization.

Distributed desalination using solar energy: A technoeconomic framework to decarbonize nontraditional water treatment

Desalination using renewable energy offers a route to transform our incumbent linear consumption model to a circular one. This transition will also shift desalination from large-scale centralized coastal facilities toward modular distributed inland plants. This new scale of desalination can be satisfied using solar energy to decarbonize water production, but additional considerations, such as storage and inland brine management, become important. Here, we evaluate the levelized cost of water for 16 solar desalination system configurations at 2 different salinities. For fossil fuel-driven plants, we find that zero-liquid discharge is economically favorable to inland brine disposal. For renewable desalination, we discover that solar-thermal energy is superior to photovoltaics due to low thermal storage cost and that energy storage, despite being expensive, outperforms water storage as the latter has a low utilization factor. The analysis also yields a promising outlook for solar desalination by 2030 as solar generation and storage costs decrease.

Multistage Surface-Heated Vacuum Membrane Distillation Process Enables High Water Recovery and Excellent Heat Utilization: A Modeling Study

Surface-heated membrane distillation (MD) enhances the energy efficiency of desalination by mitigating temperature polarization (TP). However, systematic investigations of larger scale, multistage, surface-heated MD system with high water recovery and heat recycling are limited. Here, we explore the design and performance of a multistage surface-heated vacuum MD (SHVMD) with heat recovery through a comprehensive finite difference model. In this process, the latent heat of condensation is recovered through an internal heat exchanger (HX) using the retentate from one stage as the condensing fluid for the next stage and an external HX using the feed as the condensing fluid. Model results show that surface heating enhances the performance compared to conventional vacuum MD (VMD). Specifically, in a six-stage SHVMD process, 54.44% water recovery and a gained output ratio (GOR) of 3.28 are achieved with a surface heat density of 2000 W m^-2, whereas a similar six-stage VMD process only reaches 18.19% water recovery and a GOR of 2.15. Mass and energy balances suggest that by mitigating TP, surface heating increases the latent heat trapped in vapor. The internal and external HXs capture and reuse the additional heat, which enhances the GOR values. We show for SHVMD that the hybrid internal/external heat recovery design can have GOR value 1.44 times higher than that of systems with only internal or external heat recovery. Furthermore, by only increasing six stages to eight stages, a GOR value as high as 4.35 is achieved. The results further show that surface heating can reduce the energy consumption of MD for brine concentration. The multistage SHVMD technology exhibits a promising potential for the management of brine from industrial plants.

Comparative Economic and Life Cycle Analysis of Future Water Supply Mix Scenarios for Hong Kong - A Water Scarce City

Increasing urbanization and changes in climate have placed increasing stress on urban water supply systems. Policy makers have increasingly adopted alternative water supply sources, such as desalination and water reclamation to meet this challenge, however these technologies may increase the negative environmental impacts of the water supply system. These alternative sources are energy intensive, and more expensive to produce, which raises questions about their sustainability. In this study, a Life Cycle Assessment (LCA) and a economic portfolio choice model were used to determine the impacts of Hong Kong's long term water policy. The results of our study show that the current water policy will increase the carbon emissions of producing 1 m³ of freshwater by 11% to 1.65 kg CO2-Eq due to the addition of desalination. However, a fit-for-purpose water policy approach only increases emission by 4%, to 1.54 kg CO2-Eq, by instead relying on water reclamation to offset freshwater consumption. Impacts from increased energy consumption were mitigated by improved wastewater treatment, which reduced CH₄ emissions. Although, ozone layer impacts increased due to higher NOx and N₂O emissions, highlighting the need to consider emissions from wastewater treatment processes when evaluating water reclamation processes. Impacts to water prices were also minimized when reclaimed water was chosen over desalination, due to its lower unit production cost. By considering both cost and environmental impacts of such system level changes, decision makers can more accurately evaluate different water supply approaches for data-driven policymaking.

WILL WE BE ABLE TO USE RECYCLED PLASTICS OR SHALL WE DECIDE FOR PACKAGING FREE PRODUKCTION?

Recycled plastic and its use are imperative for preserving the environment, including proper plastic wash-out. Will we ever be able to push the Czech population and firms to use recycled material? Or is it happening spontaneously? A questionnaire created on Google Forms involves ten legislative and motivational questions comprising relevant data on the amount of plastic in municipal waste between 2010 and 2020 from the Czech Statistical Office. We found that the population understands the importance of using recycled material and recycled plastic without the government's impulse. Despite the high capital intensity, the state should impose taxes to protect the sustainable environment. We suggest a comprehensive and in-depth survey to acquire more accurate data.

Decarbonized and circular brine management/valorization for water & valuable resource recovery via minimal/zero liquid discharge (MLD/ZLD) strategies

Brine (saline wastewater/water) from desalination, salt lakes, and industrial activities (e.g., pharmaceutical industries, oil & gas industries) has received a lot of attention around the world due to its adverse impact on the environment. Currently, several disposal methods have been applied; however, these methods are nowadays unsustainable. To tackle this problem, brine treatment and valorization is considered a promising strategy to eliminate brine discharge and recover valuable resources such as water, minerals, salts, metals, and energy. Brine valorization and resource recovery can be achieved via minimal and zero liquid discharge (MLD & ZLD) desalination systems. Commercially successful technologies such as reverse osmosis (RO) and distillation cannot be adopted as standalone technologies due to restrictions (e.g., osmotic pressure, high-energy/corrosion). Nonetheless, novel technologies such as forward osmosis (FO), membrane distillation (MD) can treat brine of high salinity and present high recovery rates. The extraction of several ions from brines is technically feasible. The minerals/salts composed of major ions (i.e., Na⁺, Cl^-, Mg²⁺, Ca²⁺) can be useful in a variety of sectors, and their sale prices are reasonable. On the other hand, the extraction of scarce metals such as lithium, rubidium, and cesium can be extremely profitable as their sale prices are extremely higher compared to the sale prices of common salts. Nonetheless, the extraction of such precious metals is currently restricted to a laboratory scale. The MLD/ZLD systems have high energy consumption and thus are associated with high GHGs emissions as fossil fuels are commonly burned to produce the required energy. To make the MLD/ZLD systems more eco-friendly and carbon-neutral, the authors suggest integrating renewable energy sources such as solar energy, wind energy, geothermal energy, etc. Besides water, minerals, salts, metals, and energy can be harvested from brine. In particular, salinity gradient power can be generated. Salinity gradient power technologies have shown great potential in several bench-scale and pilot-scale implementations. Nonetheless, several improvements are required to promote their large-scale feasibility and viability. To establish a CO₂-free and circular global economy, intensive research and development efforts should continue to be directed toward brine valorization and resource recovery using MLD/ZLD systems.

Hybrid Membrane Technology for Acid Recovery from Wastewater in Coated Steel Wire Production: A Pilot Scale Study

In the present study, the problem of sulfuric acid recycling from spent copper plating solution was solved using a hybrid membrane technology, including diffusion dialysis and electrodialysis. A real solution from the production of copper-coated steel wire, containing 1.45 mol/L of sulfuric acid, 0.67 mol/L of ferrous sulfate and 0.176 mol/L of copper sulfate, was processed. Diffusion dialysis with anion-exchange membranes was used to separate sulfuric acid and salts of heavy metals. Then, purified dilute sulfuric acid was concentrated by electrodialysis. The energy consumption for sulfuric acid electrodialysis concentration at a current density of 400 A/m² was 162 W·h/mol, with a current efficiency of 16%. After processing according to the hybrid membrane scheme, the solution contained 1.13 mol/L sulfuric acid, 0.077 mol/L ferrous sulfate and 0.022 mol/L copper sulfate. According to established requirements, the solution of a copper plating bath had to contain from 0.75 to 1.25 M sulfuric acid, 0.16-0.18 M of copper sulfate and ferrous sulfate not more than 0.15 M. The resulting acid solution with a small amount of ferrous sulfate and copper sulfate could be used to prepare a copper plating bath solution.

Treating reverse osmosis concentrate to address scaling and fouling problems in zero-liquid discharge systems: A scientometric review of global trends

Currently, reverse osmosis concentrate (ROC) treatment is one of the most promising techniques for its disposal because it produces freshwater with high recovery and valuable materials such as salts and reduces waste volume and environmental pollution. Public attention to the severe consequences of water pollution and strict environmental regulations on wastewater discharge has pushed water-polluting industries toward zero-liquid discharge (ZLD). However, scaling and fouling problems increase energy consumption and limit permeate flux at high salt concentrations, mainly due to calcium, magnesium, and silica precipitation, ultimately decreasing ZLD performance. Therefore, this study discusses drivers and ROC pretreatment technologies to improve ZLD efficiency and presents a scientometric review of global trends. The advantages, disadvantages, and economic and environmental aspects of conventional and emerging pre-treatment technologies were studied. Traditional treatment of chemical processes combined with precipitation removes a large amount of scaling ions; however, high operation and maintenance costs and limited full-scale plant experience are the main drawbacks. Softening and coagulation are most commonly applied to treat large volumes at a moderate cost; however, substantial sludge production and increased conductivity are major operational issues. Moreover, emerging technologies efficiently remove scale-forming ions with high capital and operating costs. New variations in standard reverse osmosis technologies have improved ZLD efficiency; nonetheless, scaling and fouling are of concern. Therefore, this review presents the studies on ROC pre-treatment technologies for removing scaling ions to enhance ZLD efficiency, which can help in future research.

Influence of Operational Strategies for the Recovery of Magnesium Hydroxide from Brines at a Pilot Scale

The continuous depletion of minerals caused by land mining and the increase in their demand have pushed the development of novel sustainable technological processes for mineral recovery from unconventional sources. In this context, magnesium (Mg) has gained considerable attention for its peculiar properties and high relevance of its compounds, such as magnesium hydroxide, Mg(OH)₂. In the present work, the influence of several operating conditions on the Mg(OH)₂ precipitation process was thoroughly investigated by adopting a novel multiple feed-plug flow reactor. The influence of (i) initial Mg²⁺ concentrations in the feed stream; (ii) brine and alkaline flow rates; and (iii) the product recycling strategy (seeded crystallization) was considered. The results marked the possibility of improving sedimentation and filterability properties of Mg(OH)₂ suspensions by adopting the recycling strategy to overcome industrial issues associated with the production of Mg(OH)₂ suspensions using NaOH solutions.

Compositing of MOFs with ceramic and nanoparticles for efficient and rapid adsorptive desalination of artificial seawater or NaCl solution

Poor water availability with the fast-growing population creates crucial issues for universal water security, and efficient approaches ought to be accomplished to balance the demand and supply. One of the most energy- and cost-effective methods for removing NaCl is adsorption desalination. Metal-organic frameworks with ceramic and nanoparticles are a comparatively new research route that increases the desalination capacity. The synthesized composites were examined for efficient and rapid removal of NaCl from NaCl solution or artificial seawater. The adsorption desalination properties were analyzed based on adsorption isotherm, adsorption kinetics, contact time, NaCl, and adsorbent dosage. The adsorptive desalination rate of ZnO@MIL88A(Fe)@α-cordierite composite was only decreased by 4% as the maximum loss after 5 consecutive cycles.

A review on role of solar photovoltaic (PV) modules in enhancing sustainable water production capacity of solar distillation units

Sustainable production of potable water is one of the United Nations sustainable development goals set for 2030. Among available renewable energy resources, solar energy is abundantly available in most of the fresh water scarce rural and remote locations. Moreover, solar distillation units and solar photovoltaic (PV) modules have been acknowledged as suitable candidates for addressing rising fresh water and electricity demands in these regions. In recent years, researchers have proposed a number of novel hybrid solar distillation units where the solar PV modules are integrated with solar thermal distillation units in different ways to harvest both electric power and potable water. In this work, a detailed review highlighting the classification, working principle, performance and features of these novel hybrid units have been carried out. In most of these hybrid units, integration is highly beneficial for solar thermal distillation units rather than for PV modules. Direct utilization of PV module as absorber, condenser and reflector in solar stills has few drawbacks. However, indirect utilization like utilizing electric power and waste heat energy recovered from PV module in distillation units has posed significant distillate yield enhancement up to 300.0%. In some cases, the integrated PV module has even generated sufficient power for carrying out essential domestic activities. Integrated PV module's performance has also improved significantly in few studies but the magnitude of improvement has not been disclosed clearly in most of the studies as more focus has been given to distillation units rather than PV modules. However, these novel hybrid configurations have not been fully explored & optimized and their techno-enviro-economic aspects have not yet been disclosed in these available precious literatures and they are still available as a potential research gap.

Resources recovery-Separation and recovery of copper from desalination brine through Lewatit TP 207 resin

Because of freshwater scarcity caused by extreme climate change, desalination technique has been developed in many countries to acquire freshwater. However, desalination plants worldwide not only produce freshwater but also generate large amounts of high salinity wastewater (brine). Brine discharge will decrease the concentration of dissolved oxygen in seawater and affect the organism's habitat. The only merit of the brine is that the concentrations of valuable metals in brine are higher than in seawater. Therefore, it is an opportunity to recover metals from brine and solve the environmental problem simultaneously. This study then aims to recover copper from brine through the ion exchange method. The research could be divided into three parts. To begin with, the saturated adsorption capacity of copper through Lewatit TP 207 resin was 30.58 mg/g, and the adsorption behavior was in accord with the Langmuir model. The optimal parameters of copper adsorption through the resin would be surveyed in the second part. The results demonstrated that 16.1 mg/l of copper could be adsorbed from brine under contacting period of 16 min, pH 14, L/S ratio of 2000, and temperature at 328 K. In addition, the thermodynamic parameters would also be explored to realize how the adsorption reaction was processed. Lastly, different agents and desorption parameters would be investigated to separate the copper from the resin. The copper compound and the resin could be obtained and regenerated after desorption. PRACTITIONER POINTS: Reusing desalination brine could reduce its amount of discharge and increase its value. A 16.1 mg/l of copper could be adsorbed from desalination brine through the Lewatit TP 207 system. The optimal parameters are contacting period of 16 min, pH 14, L/S ratio of 2000, and temperature at 328 K. After adsorbing, copper could be desorbed by HCl, and copper chloride could be acquired by vacuum drying the solutions. This is a method with the goal of laboratory-safe, low-cost, and high-energy efficiency.