Desalination brine disposal methods and treatment technologies - A review

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.

Societal values, tensions and uncertainties in resource recovery from wastewaters

The recovery of resources, including water reuse, has been presented as a solution to overcome scarcity, and improve the economic and environmental performance of water provision and treatment. However, its implementation faces non-technical challenges, including the need to collaborate with new stakeholders and face societal acceptance issues. Looking at the prominence of the circular economy in current policy developments and the challenges to resource recovery, exploring these issues is urgently needed. In this work, we reviewed a broad range of literature to identify societal values relevant to the recovery of water and other resources from wastewaters, particularly urban and industrial wastewater and desalination brines. We discuss tensions and uncertainties around these values, such as the tension between socio-economic expectations of resource recovery and potential long-term sustainability impacts, as well as uncertainties regarding safety and regulations. For addressing these tensions and uncertainties, we suggest aligning common methods in engineering and the natural sciences with Responsible Innovation approaches, such as Value Sensitive Design and Safe-by-Design. To complement Responsible Innovation, social learning with a Sustainability Transitions or Adaptive Governance perspective is suggested.

Reviewing wood-based solar-driven interfacial evaporators for desalination

Solar‒driven interfacial water evaporation is a convenient and efficient strategy for harvesting solar energy and desalinating seawater. However, the design and fabrication of solar evaporators still challenge reliable evaporation and practical applications. Wood-based solar-driven interfacial water evaporation emerge as a promising and environmentally friendly approach for water desalinating as it provides renewable and porous structures. In recent years, surface modifications and innovative structural designs to prepare high performance wood-based evaporators is widely explored. In this review, we firstly describe the superiority of wood for the fabrication of wood-based solar evaporators, including the pore structure, chemical structure and thermal insulation. Secondly, we summarize the recent developments in wood-based evaporators from surface carbonization, decoration with photothermal materials, bulk modification and structural design, and discuss from the aspects of water transportation capacity, thermal conductivity and photothermal efficiency. Finally, based on these previous results and analysis, we highlight the remaining challenges and potential future directions, including the selection of high-efficient photothermal materials, heat and mass transfer mechanism in wood-based evaporators including large-scale production at a low cost.

A Zero-Brine Discharge Seawater Desalination Using a Pilot-Scale Membrane Distillation System Integrated with Crystallizer

The management of brines generated from reverse osmosis operation remains a critical challenge requiring new approaches and processes to limit the impact of brine discharge onto ecosystems and to enhance both water and valuable resource recovery. The treatment of real seawater reverse osmosis (SWRO) brines (45,000 ppm TDS) obtained from a local Singaporean desalination plant with a crystallizer integrated pilot-scale membrane distillation unit (MDC) was studied. Commercial STOMATE® hollow fiber membranes were used in vacuum membrane distillation (VMD) configuration, leading to an average flux of around 3.7 L/m2-h at a permeate vacuum of 80 kPa and an average feed temperature of 65 °C. Consistent separation operations were achieved for the treatment of real SWRO brine over a period of 280 h; this led to a water recovery of >95% and to the collection of salt slurries, containing up to ~10−20 wt% of moisture, from the crystallizer. This approach demonstrates the potential of MDC systems to achieve zero brine discharge efficiently from seawater desalination systems, providing an environmentally friendly alternative to manage brines by increasing water recovery and generating salt slurries of economic value.

Membrane Water Treatment for Drinking Water Production from an Industrial Effluent Used in the Manufacturing of Food Additives

An integrated membrane process for treatment of effluents from food additive manufacturing was designed and evaluated on a laboratory scale. The principal focus was water recovery with the possibility of its reuse as potable water. The industrial effluent presented high content of dyes and salts. It was red in color and presented brine characteristics. The whole effluent was fed into the integrated process in continuous flow. The steps of the process are as follows: sedimentation (S), adsorption by activated carbon (AC), ion exchange using resins (IEXR), and reverse osmosis (RO) (S–AC–IEXR–RO). The effect of previous operations was evaluated by stress-rupture curves in packaged columns of AC and IEXR, membrane flux, and fouling dominance in RO. Fouling was evaluated by way of the Silt Density Index and membrane resistance examination during effluent treatment. The integrated membrane process provided reclaimed water with sufficiently high standards of quality for reuse as potable water. AC showed a high efficiency for color elimination, reaching its rupture point at 20 h and after 5L of effluent treatment. IEXR showed capacity for salt removal, providing 2.2–2.5 L of effluent treatment, reaching its rupture point at 11–15 h. As a result of these previous operations and operating conditions, the fouling of the RO membrane was alleviated, displaying high flux of water: 20–18 L/h/m² and maintaining reversible fouling dominance at a feed flow rate of 0.5–0.7 L/h. The characteristics of the reclaimed water showed drinking water standards

Renewable Energy Desalination for Island Communities: Status and Future Prospects in Greece

Energy and water are two of the most important components required to ensure prosperity and sustainable development to societies. This paper aims to review the status of renewable energy desalination for Greek islandic communities, deployed in two axes. The first one reviews the desalination systems state of the art technological solutions, their energy needs, how renewable energy may be employed and finally the cost of renewable energy desalination is investigated. The second axis focuses on Greek islands per se, where the current situation is investigated, potential solutions for meeting the water needs are evaluated, all leading to the proposal of a methodology towards designing an appropriate and applicable approach in addressing the water needs. Finally, a discussion takes place on how such options might be further deployed, particularly regarding the impacts they may produce for the livelihood and the future prosperity of the pertinent communities, and at the same time supporting the energy transition towards the EU Green Deal goals.

Optimization of convection-enhanced evaporation (CEE) using generalized cost ratios

Brine is a byproduct of desalination plants and several industrial processes which can have an adverse impact on the environment if not managed properly. Conventional brine management technologies are energy intensive and costly which limit their adoption. This study presents the first cost optimization of convection-enhanced evaporation (CEE) system to achieve a modular, cost-effective brine management and on-site treatment option for decentralized desalination plants and small-volume industries. CEE involves evaporating water from saline liquid films, released on evaporation surfaces, by the difference in vapor pressure created by forced air convection. The optimization identifies the optimal operating settings (brine flow rates, brine temperatures, and air speeds) and enables comprehensive investigation of the effect of various operational decisions on operating (energy) cost, capital cost, and footprint area. The objective functions are formulated using two cost ratios that relate material, thermal, and electrical energy costs, effectively generalizing the optimization results to be independent of location-specific cost parameters. The optimization reveals two distinct operation modes, "all-electric mode" and "heating mode". The "all-electric mode" corresponds to a lower total specific cost, ranging from $1.4 to $5 per m³, and higher footprint area, ranging from 0.5 to 1.8 m² per m³ of evaporated volume. The "heating mode" corresponds to a higher total specific cost, up to $6.5 per m³; at low energy cost ratios, a compact footprint area ranging from 0.072 to 0.5 m² per m³ of evaporated volume is achieved. Proposed designs were found to have lower costs than technologies available in the literature.

Produced Water Treatment and Valorization: A Techno-Economical Review

In recent years, environmental concerns have urged companies in the energy sector to modify their industrial activities to facilitate greater environmental stewardship. For example, the practice of unconventional oil and gas extraction has drawn the ire of regulators and various environmental groups due to its reliance on millions of barrels of fresh water—which is generally drawn from natural sources and public water supplies—for hydraulic fracturing well stimulation. Additionally, this process generates two substantial waste streams, which are collectively characterized as flowback and produced water. Whereas flowback water is comprised of various chemical additives that are used during hydraulic fracturing; produced water is a complex mixture of microbiota, inorganic and organic constituents derived from the petroliferous strata. This review will discuss the obstacles of managing and treating flowback and produced waters, concentrating on the hardest constituents to remove by current technologies and their effect on the environment if left untreated. Additionally, this work will address the opportunities associated with repurposing produced water for various applications as an alternative to subsurface injection, which has a number of environmental concerns. This review also uses lithium to evaluate the feasibility of extracting valuable metals from produced water using commercially available technologies.

Review: Brine Solution: Current Status, Future Management and Technology Development

Desalination brine is extremely concentrated saline water; it contains various salts, nutrients, heavy metals, organic contaminants, and microbial contaminants. Conventional disposal of desalination brine has negative impacts on natural and marine ecosystems that increase the levels of toxicity and salinity. These issues demand the development of brine management technologies that can lead to zero liquid discharge. Brine management can be productive by adopting economically feasible methodologies, which enables the recovery of valuable resources like freshwater, minerals, and energy. This review focuses on the recent advances in brine management using various membrane/thermal-based technologies and their applicability in water, mineral, and energy recoveries, considering their pros and cons. This review also exemplifies the hybrid processes for metal recovery and zero liquid discharge that may be adopted, so far, as an appropriate futuristic strategy. The data analyzed and outlook presented in this review could definitely contribute to the development of economically achievable future strategies for sustainable brine management.

Integrating a Self-Floating Janus TPC@CB Sponge for Efficient Solar-Driven Interfacial Water Evaporation

Solar-driven photothermal interfacial evaporation is considered as one of the most promising strategies in seawater desalination and wastewater treatment. In desalination, evaporation efficiency and salt resistance are regarded as two inter-constraint measures. Thus, it is still challenging to fabricate solar evaporators with both high evaporation efficiency and excellent salt resistance. In the present work, a self-floating Janus sponge composed of hydrophobic carbon black (CB) coating and hydrophilic porous thermoplastic polyurethane-carbon nanotube (TPC) nanofibrous substrate (TPC@CB) is fabricated via a simple electrospinning and gas templating expansion method. Attributing to the unique trilaminar functional architecture: the upper superhydrophobic solar-absorption coating, the intermediate ultrathin heat localization layer, and the lower cellular thermal insulation layer, the Janus TPC@CB sponge exhibits high evaporation efficiency (1.80 kg m^-2 h^-1 with an energy efficiency of 97.2% under 1.0 solar irradiation) and outstanding salt resistance ability. Moreover, zero liquid discharge in salt-containing wastewater treatment is realized using the Janus TPC@CB sponge as a solar-driven photothermal medium. This work provides a promising approach to seawater desalination and wastewater treatment.

Membrane and Electrochemical Based Technologies for the Decontamination of Exploitable Streams Produced by Thermochemical Processing of Contaminated Biomass

Phytoremediation is an emerging concept for contaminated soil restoration via the use of resilient plants that can absorb soil contaminants. The harvested contaminated biomass can be thermochemically converted to energy carriers/chemicals, linking soil decontamination with biomass-to-energy and aligning with circular economy principles. Two thermochemical conversion steps of contaminated biomass, both used for contaminated biomass treatment/exploitation, are considered: Supercritical Water Gasification and Fast Pyrolysis. For the former, the vast majority of contaminants are transferred into liquid and gaseous effluents, and thus the application of purification steps is necessary prior to further processing. In Fast Pyrolysis, contaminants are mainly retained in the solid phase, but a part appears in the liquid phase due to fine solids entrainment. Contaminants include heavy metals, particulate matter, and hydrogen sulfide. The purified streams allow the in-process re-use of water for the Super Critical Water Gasification, the sulfur-free catalytic conversion of the fuel-rich gaseous stream of the same process into liquid fuels and recovery of an exploitable bio-oil rich stream from the Fast Pyrolysis. Considering the fundamental importance of purification/decontamination to exploit the aforementioned streams in an integrated context, a review of available such technologies is conducted, and options are shortlisted. Technologies of choice include polymeric-based membrane gas absorption for desulfurization, electrooxidation/electrocoagulation for the liquid product of Supercritical Water Gasification and microfiltration via ceramic membranes for fine solids removal from the Fast Pyrolysis bio-oil. Challenges, risks, and suitable strategies to implement these options in the context of biomass-to-energy conversion are discussed and recommendations are made.

Study and evaluation of the characteristics of saline wastewater (brine) produced by desalination and industrial plants

Desalination and industrial plants all around the world generate large amounts of saline wastewater (brine). The discharge of brine from facilities poses a severe environmental threat, while at the same time, the opportunity to recover resources is being lost as discharged brine is rich in valuable metals that could be recovered as salts/minerals. To this aim, this study presents and analyzes for the first time the characteristics of different brine effluents (from industries such as desalination, oil and gas production, petrochemical, aquaculture, pharmaceutical, textile) to prevent environmental pollution and to recover valuable resources (i.e., salts, minerals, metals, chemicals) enabling the concept of waste-to-resource (circular water economy model). The results revealed that the common salinity values in brine effluents range from 0.5 to 150 g/L, while the only exception is the produced water from the oil and gas industry (up to 400 g/L). Brine effluents from all sectors contain sodium, chloride, calcium, and potassium ions in high concentrations, while the production of common salts such as NaCl, CaCl₂, and MgCl₂ from brine can be economically profitable. Besides common ions, precious metals such as lithium, rubidium, and cesium are present in low concentrations (<25 mg/L); however, their extraction from brine effluents can be significantly profitable due to their very high sale price. The treatment and valorization of brine can be implemented by the hybridization of membrane-based, chemical, biological, and thermal-based technologies/processes in minimal and zero liquid discharge (MLD/ZLD) systems.

Techno-economic assessment of zero liquid discharge (ZLD) systems for sustainable treatment, minimization and valorization of seawater brine

The challenge of brine disposal has sparked a lot of interest in advanced strategies for valorizing them through freshwater and salt recovery. This research article examines the technical and economic aspects of zero liquid discharge (ZLD) desalination systems using two different crystallization processes, namely brine crystallizer (BCr) in scenario 1 and wind-aided intensified evaporation (WAIV) in scenario 2 for sustainable treatment, minimization, and valorization of seawater brine. The results indicated that scenario 1 has a higher water recovery (99.14%) than scenario 2 (85.75%) as the crystallization process in scenario 2 (i.e., WAIV) does not recover freshwater; however, water is evaporated through WAIV technology and thus both systems have low brine volumes (<1 m³/day), achieving ZLD conditions. The total energy and cost demands of scenario 1 (22.15 kWh/m³ & US$100.5/day) are greater than those of scenario 2 (15.34 kWh/m³ & US$85.3/day). Both scenarios are viable, with profits ranging from US$180.49/day to US$225.85/day depending on whether only desalinated water or both desalinated water and solid salt are sold. The insight given in this techno-economic analysis will aid in the sustainable valorization and management of brine from several brine-generating industries.

Market Opportunities of Water Treatments Powered by Solar Micro Gas Turbines: Chile and Ecuador Case Studies

Throughout the last decades the developments on desalination field have been focused on energy consumption and costs reduction. However, water recovery and brine disposal are becoming a matter of concern to desalination industry. In this work, a Zero Liquid Discharge (ZLD) unit coupled with a Solar Micro Gas Turbine (SMGT) system is presented to address, among others, the challenges of mining industry in remote areas, in particular, fossil fuel dependence, water availability and pollution derived from effluents disposal. As a way to assess the feasibility of the proposal, a techno-economic analysis of the application in two Southern American regions (Chile and Ecuador) of photovoltaic modules, wind turbines and Solar Micro Gas Turbines is performed. Afterwards, the main novel feature of the new system—i.e., the ZLD unit—is described and a sensitivity analysis on its functioning whilst coupled with the SMGT is carried out. The aim is to propose a preliminary design of the ZLD process. The selection of the optimal ratio between exhaust gases and brine mass flow rates is analyzed, as well as variation in inlet salinity and temperatures. Furthermore, the water which could be recovered from effluents, at the same time that the heat of exhaust gases from SMGT is harvested, is quantified. Lastly, according to the results obtained, a preliminary design of a 10 kWe rated power SMGT system, coupled to Reverse Osmosis (RO) and ZLD units, is proposed.

Economic and Reliability Assessment of Hybrid PRO-RO Desalination Systems Using Brine for Salinity Gradient Energy Production

The energy requirements for desalination have made it an expensive process, however, it is still a viable and cost-effective means of water purification amidst freshwater scarcity. The management and disposal of brine is an external and extra desalination cost due to the effect of brine on the environment. The integration of Pressure Retarded Osmosis (PRO) with the Reverse Osmosis (RO) technique as modelled in this paper enhances brine management. The brine is fed back into the PRO unit to create a salinity gradient for water transfer via membrane and generate salinity gradient energy. The hybrid desalination model is designed to be powered by grid-tied offshore wind power. The use of wind power, a clean, renewable energy source devoid of carbon emission, as the main power source to drive the RO unit reduces the cost and effect of carbon emissions from the grid. The proposed model is assessed using Levelized cost of energy (LCOE), Annualized cost of the system (ACS), and cost of water (COW) as economic matrices. In contrast, loss of energy probability is used as a reliability matrix. Obtained results show a LCOE of 1.11 $/kW, ACW of $110,456, COW of 0.13 $/m3, loss of energy probability of 0.341, a low total carbon emissions of 193,323 kgCO2-e, and zero brine production. Results show that the proposed model is economically viable, technically reliable, environmentally friendly, and generally sustainable.

Deep well injection for the waste brine disposal solution of potash mining in Northeastern Thailand

Under the pressure of the existing world population growth trends, the dercreasing pastoral fields and the increasing duration and incidences of drought and heat stress, the potash fertilizers demand dramaticly increase to enhance the world food production. Asia currently consumes 40% of the world's potash market, yet 70% of world potash exports come from mines in Canada and Europe. Weak collective efforts to produce potassium fertilizers economically pose the risk of global shortages of potash goods and threatening global food security. While the Khorat Plateau in Northeastern Thailand is noted to contain active and promising regional potash deposits, developing a proper potash industry in the region has largely been unsuccessful due to major constraints such as the challenge of establishing a brine disposal solution. This study demonstrates the performance of deep well injection (DWI) as an environmentally friendly alternative to secure waste brine production from the potash mine. The groundwater numerical model demonstrates the movement and penetration of the concentrate during and after deep well injection. The boundary condition was utilized from the regional hydrogeology data. The waste brine injection is based on the waste products of the mine factory. Our simulation shows that the DWI can isolate waste brine with freshwater by injecting it into the deep formation based on the geologic structure and properties analysis. With high porosity and low specific yield, the Khok Kruat formation within Khrat Basin shows a high potential injection rate of 200,000 m3/day, which is 200 times higher than current water brine production rates. Moreover, the salinity can easily dissolve into the target domain with specific formation properties. Hence, the DWI not only boosts the potash industry's image in the long term but also enable sustainable potash mining development in the region. Finally, we recommend that government agencies with regulatory oversight over the DWI must promote further research associated with site characterization, well construction and injection technologies, and monitoring tools in the long term.

Sustainable Treatment and Resource Recovery of Anion Exchange Spent Brine by Pilot-Scale Electrodialysis and Ultrafiltration

The anion exchange (AIX) spent brine, generated during the NDMP-3 resin regeneration process, highly loaded with organic substances mainly humic substances (HSs) and salts (mainly NaCl) remains an environmental concern. In this study, pilot-scale electro dialysis (ED) and ultrafiltration (UF) hybrid technologies were first used to recover NaCl solution as a resin regeneration agent and HSs, which could be utilized as a vital ingredient of organic fertilizer, from the AIX spent brine. Recovered ≈ 15% w/w NaCl solution obtained by two-stage pilot-scale ED can be used to regenerate saturated NDMP-3 anion exchange resins; the regeneration−readsorption performance of NDMP-3 resins was equivalent to that of fresh ≈ 15% w/w NaCl solution. The two-stage dilute solution with low-salt content (0.49% w/w) was further concentrated by pilot-scale UF, so that the HS content in the retentate solution was >30 g/L, which meets the HS content required for water-soluble organic fertilizers. The HS liquid fertilizer could significantly stimulate the growth of green vegetables with no phytotoxicity, mainly due to special properties of HSs. These results demonstrate that ED + UF hybrid technologies can be a promising approach for the sustainable treatment and resource recovery of AIX spent brine.

Developing a reclamation strategy for softening nanofiltration brine: A scaling-free conversion approach via continuous two-stage electrodialysis metathesis

A significant amount of concentrated, scaling-prone brine can be generated during the conversion of unconventional water resources to freshwater, thus necessitating the zero discharge of concentrated brine to meet environmental and resource requirements. In this study, a two-stage feed-and-bleed electrodialysis metathesis (FB-EDM) process was implemented to reclaim softening nanofiltration (SNF) brine. To determine the optimized process parameters, experiments were conducted with various initial diluate to concentrate volume ratios (V_D:V_C), applied voltages, replenishment flow rates (Q_rp), and initial diluate compartment concentration ratios (C_D1:C_D2). The results indicated that these parameters (except for the initial volume ratio) significantly influenced the FB-EDM process. The optimized conditions included a V_D:V_C of 2:1, voltage of 1.5 V per repeating unit, Q_rp of 4 L/h, and C_D1:C_D2 of 1.5:1. The two-stage FB-EDM process operating under the optimized conditions achieved an energy consumption of <0.9 kWh/kg salt, and the total dissolved solids (TDS) in terms of Cl-type and Na-type salts reached 199.1 and 224.4 g/L, respectively; the corresponding overflow rates were 1.17 and 1.14 L/h, respectively. The developed system thus demonstrated approximately 85% TDS removal and ionic conversion of the brine; additionally, the self-crystallization of CaSO₄·2H₂O was realized by blending the Cl-type and Na-type salts. This process therefore represents a suitable method for converting SNF brine into highly-concentrated liquid salts, and provides a reclamation strategy for miscellaneous salts.

Reducing Magnesium within Seawater Used in Mineral Processing to Improve Water Recovery and Rheological Properties When Dewatering Clay-Based Tailings

In areas where access to water for mineral processing is limited, the direct use of seawater in processing has been considered as an alternative to the expense of its desalination. However, efficient flotation of copper sulfides from non-valuable phases is best achieved at a pH > 10.5, and raising the pH of seawater leads to magnesium precipitates that adversely affect subsequent tailings dewatering. Seawater pre-treatment with lime can precipitate the majority of magnesium present, with these solids then being removed by filtration. To understand how such treatment may aid tailings dewatering, treated seawater (TSw) was mixed with raw seawater (Rsw) at different ratios, analyzing the impact on the flocculated settling rate, aggregate size as measured by focused beam reflectance measurement (FBRM), and vane yield stress for two synthetic clay-based tailings. A higher proportion of Tsw (10 mg/L Mg²⁺) led to larger aggregates and higher settling rates at a fixed dosage, with FBRM suggesting that higher calcium concentrations in Tsw may also favor fines coagulation. The yield stress of concentrated suspensions formed after flocculation decreased with higher proportions of Tsw, a consequence of lower flocculant demand and the reduced presence of precipitates; while the latter is a minor phase by mass, their high impact on rheology reflects a small particle size. Reducing magnesium concentrations in seawater in advance of use in processing offers advantages in the water return from thickening and subsequent underflow transport. However, this may not require complete removal, with blending Tsw and Rsw an option to obtain acceptable industrial performance.

Energy efficient vortex-enhanced water evaporation technology for concentrated brine management: Theory and process simulation evaluation

Desalination drinking water systems and industrial processes generating high salinity streams require practical brine management options for disposal and/or treatment. Treatment most often involves large capacity brine concentrating processes, on the order of 2000 m3/day, that rely on water evaporation, vapor compression, and condensation. A new technology adds an aerosol-generating device to the evaporation step with the goal of energy efficient operation even at smaller scales. The principles behind the tornadic flowfield that breaks up and aerosolizes water as air and water flow over the machined surface in the device are introduced. Design of a 6.8 m3/day demonstration system, based on this new technology, producing a NaCl slurry (55 wt% solids) from a 22 wt% NaCl influent is described. Simulations of the system with three influent brine concentrations and three forms of final NaCl concentrate are presented and predicted energy usage is compared to estimates for conventional systems. By varying simulation process parameters, the heat transfer performance of the evaporator/condenser is identified as having a large impact on overall efficiency. The new system is anticipated to be most competitive, on an energy usage basis, with conventional concentrator/crystallizer systems when processing higher salinity brines and producing final concentrates containing precipitated NaCl.

Towards sustainable coal industry: Turning coal bottom ash into wealth

Although the world is gradually moving towards renewable energy resources, the coal industry will continue to be a major energy supply sector in the foreseeable future. However, by-products such as coal fly ash (CFA), coal bottom ash (CBA), and boiler slag are generated during coal combustion, and have become a significant environmental concern. There is an urgent need for transdisciplinary efforts in research, policy, and practice to reduce these by-products substantially. Many studies have focused on the environmental management and comprehensive utilization of CFA. As a comparison, less attention has been paid to CBA. Therefore, this critical review provides a holistic picture of CBA, from the generation, fundamental characteristics, environmental concerns to potential applications, and benefits analysis. Based on the fundamental characteristics, CBA can be considered as a sustainable and renewable resource with great potential to produce value-added materials. High-value applications and current research related to CBA, including construction and ceramic industry, wastewater remediation, soil amelioration, energy catalysis, valuable metals recovery, and material synthesis, are systemically presented and compared. It emphasizes the environmental and economic benefits of the sustainable applications of CBA as well. Particularly, it indicates that CBA is a promising candidate in normal, lightweight, self-compacting, and ultra-high-performance concrete, which shows a reduction in both energy consumption and greenhouse gas emissions during concrete production. This work provides new insights into the greener and sustainable applications of CBA, and it will offer a practical guide for the sustainable development of the coal industry.

Constructing a Solar Evaporator with Salt-Collecting Paper by Stacking Hydrophilic Sponges for Freshwater Production and Salt Collection

Solar water evaporation is universally considered as an effective method to alleviate the freshwater shortage worldwide. A series of three-dimensional, salt-resistant evaporators have been brought out to improve the evaporation performance. However, little attention was paid to the collection of salt from seawater and high salinity brine. In this work, a carbon black polyvinyl alcohol (PVA) sponge was prepared to harvest light using a physical adsorption method to load carbon black on the PVA sponge. The experimental results showed that optimal light absorption (97.8%) and evaporation rate (1.60 kg m^-2 h^-1) were achieved when the carbon black PVA sponge was produced at a carbon black concentration of 1 g L^-1. Moreover, we stacked PVA sponges beneath the carbon black PVA sponge to construct a non-photothermal evaporation area. It was seen that the evaporator with an eight-layer PVA sponge had an excellent evaporation rate as high as 2.35 kg m^-2 h^-1. In addition, the salt-collecting paper, all-black printed by a laser printer, was inserted between the stacked PVA sponges for salt collection, and the eight-layer PVA sponge evaporator with the salt-collecting paper at the fourth floor was tested in a 2 h desalination experiment. The outcome indicated that a square meter of this evaporator can produce about 7.03 L of freshwater and 206 g of salt per day from 10 wt % NaCl solution. As a result, the solar evaporator developed in this work is capable of collecting salt and maintaining a high evaporation rate, which is of great competence in the fields of freshwater production and salt collection.

Brine treatment technologies towards minimum/zero liquid discharge and resource recovery: State of the art and techno-economic assessment

In the framework of minimum liquid discharge (MLD) or zero liquid discharge (ZLD), sustainable brine management can be achieved via appropriate hybrid treatment technologies that provide water reuse, resource recovery, energy recovery and even freshwater production. This paper reviews the state of the art brine treatment technologies targeting MLD/ZLD and resource recovery and highlights their advantages and limitations. The right combination of treatment processes can add a high value to the brine management and shift the focus from removal to recovery and reuse point and help to adopt a more circular economy approach. ZLD technologies targets 100% water recovery using both membrane- and thermal-based technologies, while they are often hindered by high cost and intensive energy requirement. Meanwhile, the recovery of salts and other resources can partially compensate the operation cost of ZLD processes. MLD is a promising option that achieves up to 95% water recovery by using mainly membrane-based technologies. At this point, feasibility assessment is important to assess the environmental and economic sound of technologies. In the second part, we provide a techno-economic assessment of the most common technologies to provide possible benefits on a desalination plant. In the latter sections, innovative brine treatment schemes are discussed aiming MLD/ZLD, while resource recovery from brine and possible valorization routes of the recovered materials are highlighted to help to reduce the overall costs of the plants and to reach the targets of circular economy.

Membrane Distillation for Wastewater Treatment: A Mini Review

Water serves as an indispensable part of human life and production. On account of the overexploitation of traditional water sources, the demand for wastewater recycling is expanding rapidly. As a promising water treatment process, membrane distillation (MD) has been utilized in various wastewater treatments, such as desalination brine, textile wastewater, radioactive wastewater, and oily wastewater. This review summarized the investigation work applying MD in wastewater treatment, and the performance was comprehensively introduced. Moreover, the obstructions of industrialization, such as membrane fouling, membrane wetting, and high energy consumption, were discussed with the practical investigation. To cope with these problems, various strategies have been adopted to enhance MD performance, including coupling membrane processes and developing membranes with specific surface characteristics. In addition, the significance of nutrient recovery and waste heat utilization was indicated.

Lime/Sodium Carbonate Treated Seawater to Improve Flocculation and Sedimentation of Clay-Based Tailings

Seawater treated with lime and sodium carbonate in different proportions to reduce magnesium and calcium contents is used in flocculation and sedimentation tests of artificial quartz and kaolin tailings. Solid complexes were separated from water by vacuum filtration, and factors such as lime/sodium carbonate ratio, kaolin content, flocculation time, and flocculant dose are evaluated. The growth of the aggregates was captured in situ by a focused beam reflectance measurement (FBRM) probe. Solid magnesium and calcium complexes are formed in raw seawater at pH 11, impairing the performance of flocculant polymers based on polyacrylamides. The results show that the settling rate improved when the treatment’s lime/sodium carbonate ratio increased. That is, when a greater removal of magnesium is prioritized over calcium. The amount of magnesium required to be removed depends on the mineralogy of the system: more clay will require more significant removal of magnesium. These results respond to the structural changes of the flocs, achieving that the more magnesium is removed, the greater the size and density of the aggregates. In contrast, calcium removal does not significantly influence flocculant performance. The study suggests the necessary conditions for each type of tailing to maximize water recovery, contributing to the effective closure of the water cycle in processes that use seawater with magnesium control.

Nitrate sources and transformations in surface water of a mining area due to intensive mining activities: Emphasis on effects on distinct subsidence waters

The increase in NO₃^- content in surface water caused by intensive mining activities in Huainan City, China, has attracted considerable attention owing to the deterioration of water quality and the degradation of ecosystems in recent years. The Huainan mining area, which is highly disturbed by anthropogenic activities, was selected as a typical observation area, and the surface water was classified as open subsidence water (OSW), closed subsidence water (CSW), and river water (RW). Moreover, the hydrochemical parameters and the δ¹⁵N and δ¹⁸O values of nitrate were employed to quantitatively trace the sources and biochemical transformation of NO₃^-, and the contribution ratios of different NO₃^- sources were estimated using the stable isotope analysis in R based on the Bayesian model. There was evident nitrification in the study area, but no significant denitrification has occurred. A substantial portion of δ¹⁵N-NO₃^- demonstrated complex sources of NO₃^-. Compared with those of CSW, the NO₃^- compositions of the OSW approached to those of the RW due to river recharge and discharge, and were greatly affected by anthropogenic activities. The proportional contribution of manure and sewage in the OSW was found to be the highest with a mean value of 39.5 % ± 12.3 %, which was followed by that of mine drainage (mean: 22.1 % ± 13.1 %), chemical fertilizer (mean: 17.5 % ± 10.6 %), and soil organic nitrogen (mean: 17.5 % ± 11.6 %). In the RW, the highest mean contribution of manure sewage was 35.2 % ± 9.7 %, which was followed by that of chemical fertilizer (mean: 29.3 % ± 7.2 %), mine drainage (mean: 23.4 % ± 13.0 %), and soil organic nitrogen (mean: 10.9 % ± 8.3 %). In contrast, the contribution of chemical fertilizer to the CSW was the highest with a mean value of 33.9 % ± 13.6 %, which was followed by that of soil organic nitrogen (mean: 26.5 % ± 13.8 %), mine drainage (mean: 18.1 % ± 11.6 %). Therefore, NO₃^- in the surface water of the mining area primarily originates from chemical fertilizers and manure sewage. In addition, the contribution of mine drainage to nitrate in the study area indicates the potential impact of mining activities on surface water. These findings highlight the value of classifying different types of surface water in tracing NO₃^- contamination sources, and provide relevant theoretical basis for tracing nitrate sources in other areas.

The influence of water regime on cadmium uptake by Artemisia: A dominant vegetation in Poyang Lake wetland

An analysis of the influence of water regime on the metal accumulation processes of wetland plants can improve the efficiency of phytoremediation. However, few studies have clearly explored the mechanism of influence of water regime on the process of accumulation of metals by the dominant vegetation in Poyang Lake wetland, the largest freshwater lake in China. The aim of this study was to investigate the influence of water regime (Flooding condition [FC], Dry condition [DC] and alternate dry and flooding condition [DFC]) on the accumulation of cadmium (Cd) by Artemisia selengensis Turcz. ex Bess., a dominant plant in the Poyang Lake wetland. The results indicated that FC treatment significantly enhanced the accumulation of Cd by Artemisia roots compared with DFC and DC treatments. In addition, the DFC treatment significantly increased the translocation of Cd from roots to shoots compared with the FC treatment. A multivariate statistical analysis indicated that the rhizosphere Cd fraction, iron plaque on the root surface and rhizosphere pH directly or indirectly significantly influence the process of accumulation of Cd. The conversion of exchangeable fraction to Fe/Mn oxide bound and organic fraction under the DFC and FC treatments decreased the accumulation of Cd in Artemisia. The formation of increased amounts of iron plaque under the FC treatment may enhance the accumulation of Cd in roots, while it may reduce the translocation of Cd to aboveground tissues. In addition, a higher rhizosphere pH under the FC treatment may promote accumulation of Cd in the root by inducing formation of iron plaque. Similarly, compared with the FC treatment, a lower rhizosphere pH and iron plaque can induce the processes of Cd translocation under the DFC treatment. Based on the bioaccumulation factor, translocation factor and the ratio of root/aerial Cd content, treatment with DC benefited the phytoextraction of Cd, while treatment with DFC and FC enhanced the phytostabilization of Cd by Artemisia. This study provides valuable information for deeply understanding the resilience of wetland ecosystems and for enhancing the phytoremediation with wetland plants using water management.

Current available treatment technologies for saline wastewater and land-based treatment as an emerging environment-friendly technology: A review

Different industrial activities such as agro-food processing and manufacturing, leather manufacturing, and paper and pulp production generate highly saline wastewater. Direct discharge of saline wastewater has resulted in pollution of waterbodies by very high magnitudes. Consequently, an enormous number of pollutants such as heavy metals, salts, and organic matter are also released into the environment threatening the survival of human and biota. Saline wastewater also has significant effects on survival of plants, agricultural activities, and groundwater systems. Several treatments and disposal technologies are available for saline wastewater, but the selection of the most appropriate treatment and disposal technology still remains a major challenge with respect to the economic or technical constraints. Considering the sustainable management of saline wastewater, the present review is an attempt to compile the existing and emerging technologies for the treatment of saline wastewater. Among all the individual and hybrid technologies, land-based treatment systems are proven to be the most efficient technologies considering the energy demands, economic, and treatment efficiencies. Likewise, new and sustainable technologies are the need of hour integrating both the treatment and management and the resource recovery factors along with the ultimate goal of the protection in terms of human health and environmental aspect. PRACTITIONER POINTS: Physico-chemical treatment technologies for saline wastewater. Combined/Hybrid technologies for the treatment of saline wastewater. Land-based treatments as the environment friendly and sustainable method for saline wastewater treatment and disposal. Role of phytoremediation in land-based treatment.

Comparison of Desalination Technologies Using Renewable Energy Sources with Life Cycle, PESTLE, and Multi-Criteria Decision Analyses

Nowadays, desalination continues to expand globally, which is one of the most effective solutions to solve the problem of the global drinking water shortage. However, desalination is not a fail-safe process and has many environmental and human health consequences. This paper investigated the desalination procedure of seawater with different technologies, namely, multi-stage flash distillation (MSF), multi-effect distillation (MED), and reverse osmosis (RO), and with various energy sources (fossil energy, solar energy, wind energy, nuclear energy). The aim was to examine the different desalination technologies’ effectiveness with energy sources using three assessment methods, which were examined separately. The life cycle assessment (LCA), PESTLE, and multi-criteria decision analysis (MCDA) methods were used to evaluate each procedure. LCA was based on the following impact analysis and evaluation methods: ReCiPe 2016, IMPACT 2002+, and IPCC 2013 GWP 100a; PESTLE risk analysis evaluated the long-lasting impact on processes and technologies with political, economic, social, technological, legal, and environmental factors. Additionally, MCDA was based on the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) method to evaluate desalination technologies. This study considered the operational phase of a plant, which includes the necessary energy and chemical needs, which is called “gate-to-gate” analysis. Saudi Arabia data were used for the analysis, with the base unit of 1 m3 of the water product. As the result of this study, RO combined with renewable energy provided outstanding benefits in terms of human health, ecosystem quality, and resources, as well as the climate change and emissions of GHGs categories.

Alleviating the burden of ion exchange brine in water treatment: From operational strategies to brine management

Ion exchange (IX) using synthetic resins is a cost-efficient technology to cope with a wide range of contaminants in water treatment. However, implementing IX processes is constrained by the regeneration of IX resins that generates a highly concentrated brine (i.e., IX brine), the disposal of which is costly and detrimental to ecosystems. In an effort to make the application of IX resins more sustainable in water treatment, substantial research has been conducted on the optimization of IX resins operation and the management of IX brine. The present review critically evaluates the literature surrounding IX operational strategies and IX brine management which can be used to limit the negative impacts arising from IX brine. To this end, we first analyzed the physicochemical characteristics of brines from the regeneration of IX resins. Then, we critically evaluated IX operational strategies that facilitate brine management, including resin selection, contactor selection, operational modes, and regeneration strategies. Furthermore, we analyzed IX brine management strategies, including brine reuse and brine disposal (without or with treatment). Finally, a novel workflow for the IX water treatment plant design that integrates IX operational strategies and IX brine management is proposed, thereby highlighting the areas that make IX technology more sustainable for water treatment.

Moringa oleifera seed defatted press cake based biocoagulant for the treatment of coal beneficiation plant effluent

This study proposes a unique way of preparation of biocoagulant from Moringa oleifera defatted seed press cake. The press cake used in this study is a waste material produced as a by-product during cold press oil making from Moring oleifera seeds. The prepared Moringa oleifera seed defatted press cake based biocoagulant was found more effective than presently used metallic and polymer-based coagulants and flocculants for removal of fine particles of colloidal size from the effluent generated in the process of coal beneficiation. The detailed characterization of Moringa oleifera defatted seed press cake and the prepared biocoagulant for Particle size, Field Emission Scanning Electron Microscopy, Energy Dispersive X-Ray analysis, Zeta Potential, Fourier-transform Infrared Spectroscopy, etc. was done. The biocoagulant has been found effective in 97.4% total suspended solids removal and 97.48% turbidity removal from coal beneficiation plant effluent. The biocoagulant has been found to work satisfactorily under high fluxes of turbidity and total suspended solids with high removal of fine particles. The age of biocoagulant had negligible effect on fine particle removal efficiency (97.4% for fresh to 95% for 3-week-old biocoagulant). Field Emission Scanning Electron Microscopy analysis reveals considerable increase in flocs size from 198 nm to a 20 μ size well-developed flocs. The biocoagulant has proved as an efficient substitute of the metallic and polymer-based coagulants for the efficient treatment of coal beneficiation plant effluent.

Managing and treating per- and polyfluoroalkyl substances (PFAS) in membrane concentrates

Per- and polyfluoroalkyl substances (PFAS), which are present in many waters, have detrimental impacts on human health and the environment. Reverse osmosis (RO) and nanofiltration (NF) have shown excellent PFAS separation performance in water treatment; however, these membrane systems do not destroy PFAS but produce concentrated residual streams that need to be managed. Complete destruction of PFAS in RO and NF concentrate streams is ideal, but long-term sequestration strategies are also employed. Because no single technology is adequate for all situations, a range of processes are reviewed here that hold promise as components of treatment schemes for PFAS-laden membrane system concentrates. Attention is also given to relevant concentration processes because it is beneficial to reduce concentrate volume prior to PFAS destruction or sequestration. Given the costs and challenges of managing PFAS in membrane concentrates, it is critical to evaluate both established and emerging technologies in selecting processes for immediate use and continued research.

Investigating sustainable management of desalination brine through concentration using forward osmosis

A fertilizer drawn forward osmosis (FDFO) process was tested for the concentration of synthetic brine using an industrial-grade fertilizer ammonium sulfate (NH₄)₂SO₄ as the draw solution (DS), NaCl-based synthetic brine as the feed solution (FS), and a commercial forward osmosis (FO) membrane. A bench-scale investigation and a pilot-scale investigation were carried out. By using the highest possible concentration of the DS with a fixed concentration of the FS, the brine generated by reverse osmosis (RO) desalination plants was simulated. The aim of this investigation, performed in batch mode, was to assess the feasibility of using the FDFO process with the tested DS to concentrate the brine by extracting water to dilute the DS. While the main aim of the investigated process was achieving the maximum possible volume reduction of the brine, the resulting DS was further diluted to reduce the nutrients' concentration in the diluted DS to the acceptable levels producing fertilized water that can be used for fertigation. The investigation showed that the proposed process using the tested fertilizer resulted in an average water flux of 8.01 l/h/m², and a volume reduction of the brine of around 12%.

Sustainable disposal of seawater brine by novel hybrid electrodialysis system: Fine utilization of mixed salts

Sustainable seawater brine treatment demands an essential paradigm shift for effective recovery of resources and high value utilization of mixed-salts. Here, a novel hybrid electrodialysis (ED) system was proposed that integrated an innovative hybrid selective ED (HSED) and a developed selective bipolar membrane ED (SBMED). The HSED process allowed simultaneous recovery of major divalent cations and anions from seawater brine when NaCl was selectively enriched. Then, the impure NaCl-rich stream was fed directly into the SBMED process for acid/base preparation without any purification pretreatment. Detailed analysis of the HSED process showed that increasing unit voltage from 2.33 V to 2.67 V would improve the removal ratio of Ca²⁺, Mg²⁺ and SO₄^2- from 54.7%, 41.4% and 13.3% to 78.9%, 76.6% and 32.1%, respectively. In addition, the increment of initial concentration of product streams promoted the transport of various ions from the feed and middle compartments. The fine utilization performance, in terms of ionic removal ratio and fractionation ratio of divalent ions in the HSED process, was more limited by the initial concentration of product streams. Furthermore, the SBMED stack was found to have nearly identical performance over five cycles, indicating that the presence of a trace amount of hardness cations did not induce scaling. The current study thus provided a novel suitable strategy with a perspective of fine utilization for practical applications in sustainable disposal of seawater brine.

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.

Study on anti-scaling of landfill leachate treated by evaporation method

In the mechanical vapor recompression (MVR) treatment of landfill leachate, scaling in the evaporator and heat exchanger poses a serious problem. This study explored the reasons for such scaling and proposed acid or ion-exchange pre-treatments to reduce the alkalinity of the landfill leachate nanofiltration concentrate (LLNC) to prevent scaling. The feasibility of these two methods was evaluated and the technical and economic parameters for application were obtained via experiments. A large amount of HCO₃^- in the LLNC was the main cause of scaling. The acid addition experiment and field application demonstrated that this method could prevent fouling problems. The cost of acid addition was USD 0.18/t. LLNC pre-treatment by ion-exchange showed that a weakly acidic cation-exchange resin performed better than a strongly acidic cation-exchange resin did. The amount of solid residue under an alkalinity of 0 mg/L could be decreased by 92.9% compared with that of raw LLNC during evaporation. Both methods could alleviate scaling and enable the wide application of the MVR evaporation process in landfill leachate treatment.