Search Results (641)

Produced water (PW) generated from oil and gas operations poses a significant environmental challenge due to its high salinity and complex organic–inorganic composition. This study evaluates forward osmosis (FO) as an energy-efficient approach for PW treatment by comparing a commercial cellulose triacetate (CTA) membrane and a fabricated electrospun nanofibrous membrane, both modified with a zwitterionic sulfobetaine methacrylate/polydopamine (SBMA/PDA) coating. Fourier Transform Infrared Spectroscopy (FTIR) spectra verified the successful incorporation of SBMA and PDA through the appearance of characteristic sulfonate, quaternary ammonium, and catechol/amine-related vibrations. Scanning electron microscopy (SEM) imaging revealed the intrinsic dense surface of the CTA membrane and the highly porous nanofibrous architecture of the electrospun membrane, with both materials showing uniform coating coverage after modification. Complementary analyses supported these observations: X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of nitrogen, sulfur, and chlorine containing functionalities associated with the zwitterionic layer; Thermogravimetric Analysis (TGA) demonstrated that surface modification did not compromise the thermal stability of either membrane; and contact-angle measurements showed substantial increases in surface hydrophilicity following modification. Gas chromatography–mass spectrometry (GC–MS) analysis of the Permian Basin PW revealed a chemically complex mixture dominated by light hydrocarbons, alkylated aromatics, and heavy semi-volatile organic compounds. FO experiments using hypersaline PW demonstrated that the fabricated membrane consistently outperformed the commercial membrane under both MgCl₂ and Na₃PO₄ draw conditions, achieving up to ~40% higher initial water flux and total solids rejection as high as ~62% when operated with 2.5 M Na₃PO₄. The improved performance is attributed to the nanofibrous architecture and zwitterionic surface chemistry, which together reduced fouling and reverse solute transport. These findings highlight the potential of engineered zwitterionic nanofibrous membranes as robust alternatives to commercial FO membranes for sustainable produced water treatment. Full article

Reverse osmosis (RO) is the key process for textile dyeing wastewater reuse applications. Membrane fouling reduces both permeability and rejection capability, negatively affecting the technological economy of RO process. Membrane cleaning is critical to recovery of the permeability of fouled RO membranes. Based on multi-batch filtration and cleaning experiments, this study systematically evaluated the RO membrane fouling potential of pre-treated textile dyeing wastewater by a membrane bioreactor and the recovery performance of fouled RO membranes after different cleaning methods. A significant decline (more than 15%) in RO membrane permeability occurred after RO membrane permeate production of 625 L/m² at a water recovery ratio of 60%. Protein-like substances and soluble microbial products were identified as the primary organic foulants via three-dimensional fluorescence excitation-emission matrix spectrometry (3D-FEEM). The single forward flushing with either pure water, acid, alkaline, or sodium hypochlorite solutions with a low active chlorine concentration showed very limited recovery of fouled RO membrane permeability. The combined forward flushing with acid followed by alkaline solutions restored fouled membrane permeability by up to 87% of a new RO membrane. The addition of pure water backwashing at a transmembrane pressure (TMP) of 0.5 MPa after both acid and alkaline solutions combined forward flushing restored fouled membrane permeability by up to 97% of a new RO membrane but deteriorated the rejection capability of the RO membrane. The backwashing parameters were further optimized at a TMP of 0.125 MPa and crossflow velocity (CFV) of 0.5 m/s, achieving fouled RO membrane permeability by up to 96% of a new RO membrane, and there were no negative effects on the rejection capability of the RO membrane. Alkaline forward flushing followed by pure water backwashing was the dominant contributor for fouled RO membrane permeability recovery. A preliminary economic analysis showed that the total chemical cost per RO production was 0.763 CNY/m³ and could be further reduced via removing acid cleaning and replacing combined alkaline flushing and pure water backwashing with alkaline backwashing. Full article

Landfill leachate reverse osmosis (RO) treatment generates a highly concentrated stream rich in recalcitrant organic matter, particularly humic substances (HS), which present potential for recovery and reuse as a biofertilizer. This study evaluated HS recovery from the RO concentrate of the Seropédica Landfill (Rio de Janeiro, Brazil) using a nanofiltration (NF) process with a polyethersulfone membrane (MWCO = 1000 Da) operated at 9 bar. The NF system achieved a volume reduction factor of 2.5, rejecting 70–75% of the organic matter. At the same time, salts were predominantly transmitted to the permeate. The phytotoxicity of recovered HS solution was evaluated through maize (Zea mays L.) germination assays at concentrations ranging from 20 to 100 mg HS/L. All treatments showed germination indices above 100%, indicating the absence of phytotoxicity, and seedling growth significantly improved relative to the control, especially at 20 mg HS/L. Trace metal concentrations in the recovered HS complied with Brazilian standards for irrigation water. Overall, the results show that nanofiltration is highly effective in concentrating humic substances from leachate RO concentrate, minimizing the presence of salts, and contributing to strategies for landfill leachate management. Full article

Reducing the specific energy consumption of reverse osmosis (RO) processes motivates the development of new membrane materials that have enhanced water permeability while maintaining low salt permeability (high rejection). Nanocomposite membranes have shown great promise in achieving these goals, particularly those using nanotubes as fillers. Here, we report on the relationships between the orientations and surface functionalities of imogolite nanotubes (INTs) with water and salt permeabilities for polyamide nanocomposite membranes. An external electric field was used to manipulate the INT orientation within the polyamide active layer. The INT interior and exterior chemistries, respectively, were made hydrophobic using methyl triethoxysilane as a precursor during INT synthesis and post-synthesis modification with alkali-phosphate groups. Irrespective of nanotube orientation or surface chemistry, membrane permeance increased from 0.3 to ≥1.0 L m⁻² h⁻¹ bar⁻¹. A salt permeability comparable to the conventional polyamide membrane was maintained by making the INT pore throat hydrophobic. These findings indicated that salt rejection could be tailored by manipulating the INT interior surface chemistry without sacrificing water permeability. Full article

Microplastics represent a pressing global environmental concern due to their persistence, widespread occurrence, and adverse impacts on aquatic ecosystems and human health. Effective removal of these contaminants from water is essential to safeguard biodiversity and ensure water quality. This work focuses on the pivotal role of membrane-based filtration technologies, including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, membrane bioreactors, and dynamic membranes, in capturing and eliminating microplastics. The performance of these systems depends on key membrane characteristics such as pore size, material composition, hydrophilicity, mechanical strength, and module design, which govern retention efficiency, fouling resistance, and operational stability. Membrane filtration offers a highly effective, scalable, and sustainable approach to microplastic removal, outperforming conventional treatment methods by selectively targeting a wide range of particle sizes and morphologies. By highlighting the critical contribution of membranes and filtration processes, this study underscores their potential in mitigating microplastic pollution and advancing sustainable water treatment practices. Full article

Efficient water recycling in the hydrometallurgical industry requires the dewatering of hypersaline Na₂SO₄ or similar brines via non-evaporative methods. Unfortunately, many non-evaporative methods require the use of specific solutes and are not compatible with complex hydrometallurgical effluents. Forward Osmosis (FO) uses a draw solution to link known non-evaporative water recycling methods with feed solutions that are otherwise incompatible. There is minimal experimental data on the dewatering performance of today’s available commercial FO membranes, especially with hypersaline concentrations (>70,000 mg/L total dissolved solids). This study tests the commercially available Aquaporin HFFO2 hollow fibre FO membrane module with hypersaline Na₂SO₄ or NaCl feed solutions versus a MgCl₂ draw solution. It identifies a key requirement to maintain water flux above a certain threshold to prevent a decrease in Na Rejection or an increase in Mg reverse flux. It also defines a minimum osmotic differential that can be used to parameterize water flux, similar to the temperature of approach in heat exchangers, but to determine the extent of water removal in FO. We demonstrate that even under mildly acidic conditions, existing FO membranes can concentrate Na₂SO₄ to saturation, paving the way for their use in the hydrometallurgical industry. Full article

Cationic surfactants from the group of quaternary ammonium compounds (QACs) are widely used in disinfectants, cosmetics, and household and industrial products. Their strong antimicrobial activity and chemical stability make them valuable in applications but also highly persistent and toxic when released into aquatic environments. This problem has become increasingly relevant during and after the COVID-19 pandemic, when global use of QAC-based disinfectants increased drastically, resulting in their frequent detection in municipal, hospital, and industrial effluents. The concentrations of QACs reported in wastewater range from trace levels to several mg/L, often reaching inhibitory thresholds for biological treatment processes. Although surfactants are not listed in any current European directive, the revised Directive (EU) 2024/1440 classifies micropollutants as a priority group, imposing stricter environmental quality standards and mandatory monitoring requirements. Within this regulatory framework, QACs are recognized as compounds of emerging concern, and their effective removal from wastewater has become a critical challenge. This review summarizes the current knowledge on conventional treatment technologies (coagulation, adsorption, ion exchange, advanced oxidation, and biological processes) and membrane-based methods (ultrafiltration, nanofiltration, reverse osmosis, forward osmosis, and hybrid systems) for the removal of cationic surfactants from water and wastewater. Mechanisms of separation, performance, and operational limitations are discussed. Full article

The integration of Reverse Osmosis (RO) desalination with Renewable Energy (RE) sources offers a sustainable approach to freshwater production, particularly in remote and off-grid regions. However, the variable and intermittent output of RE power can cause operational instability that affects membrane performance and system reliability. This study experimentally evaluated a flat sheet seawater RO membrane under variable conditions emulating a Photovoltaic (PV)-powered system over three days. Three scenarios were examined: (i) steady full-load operation representing PV with battery storage, (ii) variable operation representing sunny-day PV output, and (iii) highly variable operation representing cloudy-day PV output. A Variable Frequency Drive (VFD) regulated by an Arduino microcontroller adjusted high-pressure pump operation in real time to replicate power fluctuations without energy storage. Each scenario operated for eight hours per day and was tested with and without end-of-day rinsing. Under the highly variable cloudy-day scenario without rinsing, water permeability decreased by 37%, salt rejection decreased by 18%, and membrane resistance increased by 37%, indicating compaction and fouling effects. Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR) confirmed structural changes in membranes exposed to fluctuating conditions. These results highlight the need for improved operational strategies to protect membrane longevity in RE-powered desalination systems. Full article

The environmental impact of seawater reverse osmosis desalination in central Chile was assessed using Life Cycle Assessment (LCA) with the EcoInvent database to address the region’s high water stress. The study analyzed the operational phase using 1 m³ of product water as the functional unit, considering power demand, chemicals, and membranes across eight scenarios that varied energy matrix composition, membrane lifespan, water use, and seawater source. Eighteen environmental indicators were evaluated using the ReCiPe 2016 Midpoint (H) method. Results revealed that eight impact indicators were primarily national in origin, while ten exhibited transboundary characteristics. Power demand was the dominant contributor, exceeding 75% of impacts in 17 of 18 categories. A 25% power increase raised environmental impacts by an average of +21.5%, while the projected 2050 renewable energy scenario showed substantial reductions averaging −43.0%. This demonstrates that power consumption is the principal driver of environmental impacts, underscoring the importance of energy-efficiency measures and integration of Non-Conventional Renewable Energies (NCRE), particularly as fossil-based sources constitute the main contributors to environmental burdens at both national and transboundary scales. Full article

Freshwater scarcity in southern Xinjiang has intensified the need for effective utilization of saline–alkaline agricultural drainage. This study evaluates pre-treatment technologies for reverse osmosis (RO) systems to improve water quality and mitigate membrane fouling. Three processes were tested: coagulation–sedimentation–media filtration (G₁), micro-flocculation–media filtration (G₂), and micro-flocculation (G₃) combined with ultrafiltration and varying polyaluminum chloride (PAC) dosages (0–15 mg·L⁻¹). Results show that G₁ and G₂ significantly outperform G₃ in removing turbidity, organic matter, and inorganic ions, achieving SDI₁₅ < 5 and turbidity < 0.3 NTU, meeting RO feedwater standards. Optimal performance occurred at the 7.5–10 mg·L⁻¹ coagulant dosage range, effectively controlling flux decline and fouling. The integrated pre-treatment–ultrafiltration system provides a robust technical framework for saline–alkaline water desalination, offering practical guidance for sustainable water resource utilization in arid agricultural regions. Full article

Pharmaceutically active compounds (PhACs), pesticides, and poly- and perfluoroalkyl substances (PFAS) are increasingly detected in surface waters at trace concentrations, raising concerns for both aquatic systems and, consequently, human health. Conventional solutions are insufficient to achieve complete removal at trace compound concentrations, highlighting the need for advanced separation technologies. This study aims to comprehensively analyze rejection and removal mechanisms of selected PhACs, pesticides, and PFAS present in water solutions at reported environmentally relevant concentrations (300 ng L⁻¹), using two nanofiltration (NF) and one reverse osmosis (RO) polyamide membrane. PhACs, pesticides, and PFAS were selected to cover a broad range of physicochemical properties, specifically molecular mass (MM), dissociation constant (pKa), and octanol–water partition coefficient (logK_o/w). Rejection values ranged from 42.1% (acetaminophen) to apparent 100% (for multiple compounds), depending on water pH, solute properties, and membrane characteristics. Size exclusion and electrostatic interactions were identified as the primary removal mechanisms, with hydrophobic interactions having a lower impact, particularly for carbamazepine, bezafibrate, and perfluorooctane sulfonic acid (PFOS). Addition of sodium chloride (3 g L⁻¹) decreased rejection of most negatively charged compounds due to suppression of membrane surface charge, although clarithromycin and ofloxacin exhibited improved rejection. Presented results provide fundamental insight into compound-specific membrane rejection and highlight the importance of membrane–solute interactions under environmentally realistic conditions. The results support further optimization of NF and RO for targeted compound rejection and provide a baseline for data-driven membrane process modeling. Full article

The global water crisis, intensified by climate change and population growth, underscores the critical need for sustainable water production. Desalination is a pivotal solution, but its energy-intensive nature demands a transition from fossil fuels to renewable sources. However, the inherent intermittency of solar and wind power poses a fundamental challenge to the stable operation of desalination plants. This review provides a comprehensive analysis of a specifically tailored solution: hybrid energy storage systems (HESS) that synergistically combine batteries and hydrogen fuel cells (FC). Moving beyond a general description of hybridization, this study delves into the strategic complementarity of this pairing, where the high-power density and rapid response of lithium-ion batteries manage short-term fluctuations, while the high-energy density and steady output of fuel cells ensure long-duration, stable baseload power. This operational synergy is crucial for maintaining consistent pressure in processes like reverse osmosis (RO), thereby reducing membrane stress and improving system uptime. A central focus of this review is the critical role of advanced energy management systems (EMS). We synthesize findings on how intelligent control strategies, from fuzzy logic to metaheuristic optimization algorithms, are essential for managing the power split between components. These sophisticated EMS strategies do not merely ensure reliability, they actively optimize the system to minimize hydrogen consumption, reduce operational costs, and extend the lifespan of the hybrid energy storage components. The analysis confirms that a lithium-ion battery-fuel cell HESS, governed by an advanced EMS, effectively mitigates renewable intermittency to significantly enhance freshwater yield and overall system reliability. By integrating component-specific hybridization with smart control, this review establishes a framework for researchers and engineers to achieve significant levels of energy efficiency, economic viability, and sustainability in renewable-powered desalination. Full article

The ever-increasing number of discarded end-of-life dialysate polyamide thin-film composite membranes (DEoLMs) from presents both environmental and economic challenges for health centers. Traditional thermo-chemical cleaning techniques have been deployed for the rehabilitation of DEoLMs. This study further investigated the application of chemo-ultrasonication rehabilitation of dialysate-production-related DEoLM for potential reuse in spent dialysate recovery considering salt and creatinine—a typical uremic toxin-removal from water. The DEoLM was rehabilitated using low-concentration citric acid (CA) and sodium lauryl sulfate (SLS) under ultrasonic waves (45 kHz, 30 min agitation). Considering different rehabilitation protocols, the synergistic effects of heating (HT) and the chemical agents, with and without and ultrasonic waves (SC) were evaluated through FTIR, SEM, and EDX analyses, and the performance of the rehabilitated DEoLM was assessed via water flux and permeance, and efficiencies for conductivity and creatinine rejection. The fully integrated protocol chemo-ultrasonication (HT + SC + chemical agents) yielded the highest performance, achieving 93.56% conductivity and 96.83% creatinine removal, with water flux of 113.48 L m⁻² h⁻¹ and permeances of 6.31 L m⁻² h⁻¹ bar⁻¹, at markedly reduced pressures. The chemo-sonic-rehabilitated-DEoLM removed the organic–inorganic foulants beyond thermo-chemical cleaning. This suggests that the sonication waves had a great impact regarding rejuvenating the fouled DEoL dialysate membrane, offering a sustainable, cost-effective pathway for extending membrane life, and supporting sustainable water management to achieve circular economy goals within healthcare centers. Full article

The provision of potable water for armed forces at their operational sites necessitates a robust treatment chain to ensure the production of safe drinking water from potentially contaminated local water sources. Relying on single-use water bottles is not considered an eco-friendly option and on-site production may exhibit limited efficiency depending on the water contamination. This study therefore aimed to define a mobile processing chain that could efficiently produce drinking water on-site while offering a multi-barrier level of protection. To evaluate the system, contaminated water was prepared from different water sources and then spiked with various inorganic contaminants (metals, anions: Cl⁻, F⁻, I⁻, NO₂⁻, NO₃⁻, SO₄²⁻, CN⁻), organic contaminants (e.g., pesticides, petroleum hydrocarbons, polycyclic aromatic hydrocarbons, chlorinated solvents), and energetic compound (perchlorate) at levels ranging from 5 to 50 times the standard water quality criteria. A specific treatment process was defined optimized and evaluated at flow rates reaching 500 L/h. This treatment chain includes the following: a sediment filter, a greensand filter, a cation exchange resin, an anion exchange resin, an activated carbon adsorption filter, ultrafiltration, a UV lamp, and a reverse osmosis (RO) unit. This treatment system successfully met all water quality criteria, providing a reliable and effective alternative to an RO-only treatment regime. Full article