Liquid Discharge Research Articles

Innovations in textile wastewater management: a review of zero liquid discharge technology.

Zero liquid discharge (ZLD) technology emerges as a transformative solution for sustainable wastewater management in the textile industry, emphasizing water recycling and discharge minimization. This review comprehensively explores ZLD's pivotal role in reshaping wastewater management practices within the textile sector. With a primary focus on water recycling and minimized discharge, the review thoroughly examines the economic and environmental dimensions of ZLD. Additionally, it includes a comparative cost analysis against conventional wastewater treatment methods and offers a comprehensive outlook on the global ZLD market. Presently valued at US $0.71 billion, the market is anticipated to reach US $1.76 billion by 2026, reflecting a robust annual growth rate of 12.6%. Despite ZLD's efficiency in wastewater recovery, environmental challenges, such as heightened greenhouse gas emissions, increased carbon footprint, elevated energy consumption, and chemical usage, are discussed. Methodologies employed in this review involve an extensive analysis of existing literature, empirical data, and case studies on ZLD implementation in the textile industry worldwide. While acknowledging existing adoption barriers, the review underscores ZLD's potential to guide the textile industry toward a more sustainable and environmentally responsible future.

Enhanced charge carriers separation/transportation via S-scheme ZnCeS–ZnWO heterostructure nanocomposite for photodegradation of synthetic dyes under sunlight

Domestic wastage and liquid discharge from industries cause serious water pollution and severely damage the life cycle of living species. Therefore, it is necessary to construct efficient photocatalysts for the removal of toxic pollutants from water. Herein, a novel heterostructure ZnWO–ZnCeS nanocomposite was prepared by the sol-gel route and studied its physical and photocatalytic properties using various analytical techniques. Under sunlight irradiation, the ZnWO–ZnCeS photocatalyst eliminated 99.7, 99.1, 99.0 % rhodamine-B (RhB), methylene blue (MB), and safranin-O (SO) dyes within 70 min with excellent performance higher than individual ZnWO and ZnCeS catalysts. The optimization tests exhibit the catalyst loading = 30 mg, dye content = 25 ppm, solution pH = 8 of ZnWO–ZnCeS against MB dye for practical application. The heterojunction of coupled ZnWO and ZnCeS leads to a synergistic effect that facilitates the charge transport and hampers the recombination of photo-induced charge carriers thereby leading to boosted photocatalytic performance. Furthermore, based on the scavenging test, the hydroxyl and superoxide radicals were the reactive species during the photodegradation reaction. The designed photodegradation reaction mechanism has proposed the formation of an S-scheme in ZnWO–ZnCeS that led to the accumulation of electrons at ZnCeS and holes at ZnWO, favoring the formation of reactive species for dye degradation. Moreover, this work provides a novel direction to synthesize S-scheme heterostructure photocatalysts for application in wastewater treatment.

CO2 nanobubbles as a novel kinetic promoter in hydrate-based desalination

The use of CO2 nanobubbles (NBs) was investigated as a sustainable kinetic promoter of gas hydrate formation in hydrate-based desalination (HBD) that does not require any separation steps from the recovered water. Stable CO2 NBs (8.07 ± 0.21× 107 bubbles/mL with 103.15 ± 2.47 nm mean radius and −6.35 ± 1.17 mV zeta potential) were generated and tested in HBD experiments conducted at 274.15 K and 3.58 MPa. The colloidal stability of CO2 NBs increased under pressure: their concentration increased and their size decreased. Low concentrations of dissolved chloride salts reduced the size of CO2 NBs, while high concentrations increased the likelihood of NBs' agglomeration. The induction time for CO2 hydrate formation in the presence of CO2 NBs was reduced by 86.04 %. The desalination results confirmed that CO2 NBs played a significant role in accelerating the process based on the memory effect mechanism. In the presence of CO2 NBs, water recovery reached 68.85 ± 1.82 % and 63.37 ± 2.76 % with an ion removal efficiency of 41.35 ± 6.16 and 40–50 % in a single-stage HBD process for 0.5 M NaCl and synthesized seawater solutions, respectively. These findings could unlock the potential for the further development of HBD of natural saline solutions as well as its deployment in near-zero liquid discharge industrial processes.

Two-phase flow dynamics study in the trapezoidal gas channel of PEM fuel cell based on lattice Boltzmann model

ABSTRACT Water management is a critical challenge in ensuring the performance and durability of low-temperature proton exchange membrane fuel cells (PEMFCs). This study utilizes the phase-field lattice Boltzmann method to conduct three-dimensional numerical simulations, investigating the dynamics of two-phase flow in the cathode gas channel (GC) of PEMFC with a trapezoidal cross-section. The effects of the water inlet location, the surface wettability of GC, the open angle of GC, and the air velocity on liquid water distribution and discharge are analyzed. The results indicate that positioning the water inlet in the middle of the GC significantly enhances PEMFC performance while having minimal impact on average pressure drop. A wall contact angle of 70° or 110°Can optimize fuel cell performance from different directions. Setting a wall contact angle at 70° optimizes gas flow stability and maintains a low-pressure drop value for the GC. A wall contact angle of 110° focuses on optimizing gas reactant diffusion ability into porous electrodes and GC drainage rate. An opening angle of 55° for the trapezoidal gas channel improves overall fuel cell performance. Increasing air velocity facilitates the film flow formation of liquid water on top wall surfaces within the GC.

Reinforced PS-PVDF-WO3 superhydrophobic antiwetting membrane for membrane distillation

Membrane distillation (MD) is an energy-efficient desalination process with abilities to achieve nearly zero liquid discharge and recovery of resources. Nevertheless, MD's transition from laboratory to industrial scale has been largely challenged by expensive and complex fabrication methods for hydrophobic membranes, as well as lack of resistance against wetting and scaling. Present study demonstrates about the development of a hydrophobic electrospun membrane using a low-cost polystyrene (~1.057 $ per kg) polymer blended with PVDF (~80 $ per kg), followed by the surface modification via electrospraying of silane functionalized tungsten trioxide (WO3) nanoparticles. The characteristics of the fabricated membrane in terms of deionized water contact angle revealed ultra-high surface contact angle (~172°) and low sliding angle (<5°). The low thermal conductivity (~0.166 W/mK) of electrospun membrane accredited decreases in temperature polarization during MD operation, resulting in enhanced transportation of water vapors from feed to permeate side. Furthermore, the electrospun membrane attained resilience against wetting, along with stable permeate flux (~25 LMH) and high salt rejection (>99.9 %) with low surface tension (~28 mN/m) saline feed. Tensile tests (firm up to 45 N) and harsh chemical exposure (durable at pH 2 and pH 12) confirmed the structural robustness of the fabricated membrane.

Process optimization of osmotic membrane distillation for the extraction of valuable resources from water streams

The rising demand for sustainable wastewater management and high-value resource recovery is pressing industries involved in, e.g., textiles, metals, and food production, to adopt energy-efficient and flexible liquid separation methods. The current techniques often fall short in achieving zero liquid discharge and enhancing socio-economic growth sustainably. Osmotic membrane distillation (OMD) has emerged as a low-temperature separation process designed to concentrate valuable elements and substances in dilute feed streams. The efficacy of OMD hinges on the solvent’s migration from the feed to the draw stream through a hydrophobic membrane, driven by the vapor pressure difference induced by both temperature and concentration gradients. However, the intricate interplay of heat and mass processes steering this mechanism is not yet fully comprehended or accurately modeled. In this research, we conducted a combined theoretical and experimental study to explore the capabilities and thermodynamic limitations of OMD. Under diverse operating conditions, the experimental campaign aimed to corroborate our theoretical assertions. We derived a novel equation to govern water flux based on foundational principles and introduced a streamlined version for more straightforward application. Our findings spotlight complex transport-limiting and self-adjusting mechanisms linked with temperature and concentration polarization phenomena. Compared with traditional methods like membrane distillation and osmotic dilution, which are driven by solely temperature or concentration gradients, OMD may provide improved and flexible performance in target applications. For instance, we show that OMD—if properly optimized—can achieve water vapor fluxes 50% higher than osmotic dilution. Notably, OMD operation at reduced feed temperatures can lead to energy savings ranging between 5 and 95%, owing to the use of highly concentrated draw solutions. This study underscores the potential of OMD in real-world applications, such as concentrating lithium in wastewater streams. By enhancing our fundamental understanding of OMD’s potential and constraints, we aim to broaden its adoption as a pivotal liquid separation tool, with focus on sustainable resource recovery.

HIGH-TEMPERATURE PROCESSES IN POWDER MATERIALS AT HIGH-VOLTAGE ELECTRIC PULSE CONSOLIDATION

The main features of high-voltage electric pulse consolidation (HVC) of refractory powder materials and the resulting unique capabilities of the method are considered. The electro-thermal processes of HVC at the contacts between powder particles and at the macroscale of the entire consolidated sample are analyzed. The results of experimental studies of the parameters of high-voltage electrical impulse action in the processes of consolidation of high-temperature powder compositions, high-voltage welding of dissimilar materials, as well as high-voltage discharges in liquid are presented. The results of measuring the intensity of thermal radiation of the investigated materials under high-voltage electrical impulse action, recorded by the method of pulse photometry using photodiode sensors, which, together with the Rogowski coil, are components of the measuring complex developed by the authors, are presented.

Synthesis of highly activated polybenzene-grafted carbon nanoparticles for supercapacitors assisted by solution plasma.

The growing demand for electronic storage devices with faster charging rates, higher energy capacities, and longer cycle lives has led to significant advancements in supercapacitor technology. These devices typically utilize high-surface-area carbon-based materials as electrodes, which provide excellent power densities and cycling stability. However, challenges such as inadequate electrolyte interaction, hydrophobicity that impedes ion transport, and high manufacturing costs restrict their effectiveness. This study aims to enhance carbon-based materials by grafting polymer chains onto their surfaces for supercapacitor applications. A simple solution plasma process (SPP), followed by heating, prepared the polymer-grafted carbon materials. Carbon nanoparticles were synthesized from benzene through plasma discharge in liquid under ambient conditions, forming free radical sites on the carbon surface. Subsequently, benzene molecules were grafted onto the surface via radical polymerization during heating. We investigated the structural and morphological properties of the synthesized materials using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and Raman spectroscopy. Additionally, N2 absorption-desorption isotherms were measured, pore structure was analyzed with the Dubinin-Astakhov (DA) average pore size model, and specific surface area was determined using the Brunauer-Emmett-Teller (BET) equation for all synthesized samples. The results indicated that the grafting process was influenced by heating time and drying temperature. Furthermore, the electrical properties of the samples were evaluated using cyclic voltammetry (CV), which demonstrated enhancements in both areal capacitance and cycling stability for the polybenzene-grafted carbon compared to the non-grafted variant. This research illustrates that polymer grafting can effectively improve the performance and stability of carbon-based materials for supercapacitor applications. Future work will aim to optimize these materials for broader applications.

Ilulissat Icefjord Upper‐Layer Circulation Patterns Revealed Through GPS‐Tracked Icebergs

AbstractThe Greenland Ice Sheet has undergone rapid mass loss over the last four decades, primarily through solid and liquid discharge at marine‐terminating outlet glaciers. The acceleration of these glaciers is in part due to the increase in temperature of ocean water in contact with the glacier terminus. However, quantifying heat transport to the glacier through fjord circulation can be challenging due to iceberg abundance, which threatens instrument survival and fjord accessibility. Here we utilize iceberg movement to infer upper‐layer fjord circulation, as freely floating icebergs (i.e., outside the mélange region) behave as natural drifters. In the summers of 2014 and 2019, we deployed transmitting GPS units on a total of 13 icebergs in Ilulissat Icefjord, an iceberg‐rich and historically data‐poor fjord in west Greenland, to quantify circulation over the upper 0–250 m of the water column. We find that the direction of upper‐layer fjord circulation is strongly impacted by the timing of tributary meltwater runoff, while the speed of this circulation changes in concert with glacier behavior, which includes increases and decreases in glacier speed and meltwater runoff. During periods of increased meltwater runoff entering from tributary fjords, icebergs at these confluences deviated from their down‐fjord trajectory, even reversing up‐fjord, until the runoff pulse subsided days later. This study demonstrates the utility of iceberg monitoring to constrain upper‐layer fjord circulation, and highlights the importance of including tributary fjords in predictive models of heat transport and fjord circulation.

Facile fabrication of hydrophobic porous monoliths from charge-driven assembled polymers-stabilized high internal phase emulsion for oil spills reclamation

Oil leakage/spillage and discharge of organic liquids pose severely threat to ecological environment and human health. Herein, hydrophobic porous monolith was fabricated via the polymerization of high internal phase emulsions (HIPEs) stabilized from charge-driven assembled polymers and the introduction of butyl methacrylate (BMA), and the water contact angle is up to 129 ± 2°. The monolith was hierarchical porous, leading to absorb various oils and organic solvents. The absorption capacity of monolith for different solvents ranges from 17.3 to 53.0 g/g, demonstrating excellent absorption. Meanwhile, the monolith shows excellent oil/water separation effect and high cycle efficiency. Therefore, the novel sponge might be an ideal candidate in dealing with oil contamination.

A COMPARATIVE STUDY OF ALUMINUM OXIDE NANOPARTICLES SYNTHESIZED IN PLASMA DISCHARGE UNDER ULTRASONIC CAVITATION AND BY LASER ABLATION FOR CREATION OF COMPOSITE MATERIALS

In this work, aluminum oxide nanoparticles were fabricated by two physical methods: laser ablation in liquid medium and plasma discharge under the action of intensive ultrasonic cavitation. Dynamic light scattering, scanning electron microscopy, and electrokinetic potential measurements were employed to comparatively examine the nanoparticles obtained by both methods. It was found that the synthesized particles had spherical shapes with a size range of about 50-70 nm and relatively narrow particle size distributions and were stable to aggregation and sedimentation. The electrokinetic potential values of the pure particles and the effects of the presence of water-soluble polymer polyethylene glycol were used to examine the surface properties of the nanoparticles. This study demonstrates the effect of ultrasonic action on particle surface activity.

Initial demonstration of microplasma ionization/Orbitrap mass spectrometry for molecular screening of perfluorinated compounds

Diverse PFAS compounds were determined for the first time with the liquid sampling-atmospheric pressure glow discharge (LS-APGD) ionization source coupled to an Orbitrap MS. Unique negative ion spectra and preliminary figures of merit are reported.

Heterogeneous liquid discharge cracking of n-hexadecane as a heavy oil model compound: A way to generate plasma in liquid hydrocarbons at low voltage

Plasma is an excellent way of coupling renewable power resources and poor-quality heavy oil resources into high value petrochemicals. In order to achieve discharge in liquid hydrocarbons under low-voltage operating conditions, it was proposed a new liquid-phase discharge mode - heterogeneous liquid discharge. The aqueous-phase feedstock was injected into n-hexadecane as a heavy oil model compound through a pin electrode, and plasma was generated directly in the liquid feedstocks at room temperature, atmospheric pressure, and low voltage to achieve the in-situ reforming of n-hexadecane and the generation of syngas, C2 hydrocarbons, and other high value-added chemicals. The effects of injection of water and ethanol solution on the gaseous and liquid products, and feedstocks conversion were discussed, and the distribution of various products was explored in detail. Gas production increased with the concentration of injected ethanol up to a maximum of 110.8 mL/min. A n-hexadecane conversion of 2.0% was obtained on injection of 50% ethanol, 4.56 kV, and discharge for 2 min. Varying the ethanol concentration can regulate the composition of the product. The auxiliary effects of water and ethanol on n-hexadecane cracking and the origin of the main gaseous products were examined in the mechanistic analysis section.

Emergy analysis of three industrial reverse osmosis concentrate zero liquid discharge processes: Technical, economic and environmental comparison

Reverse osmosis (RO) technology has been widely applied for advanced treatment of industrial wastewater, but it inevitably produces RO concentrate (ROC) containing high levels of toxic refractory organics and salinity. Evaporation crystallization processes are widely used to achieve zero liquid discharge (ZLD) of industrial ROC, but they have the potential to negatively impact the surrounding environment and economy due to their high energy requirements. It is of significance to evaluate the technical, economic and environmental benefits of ROC ZLD processes to provide a foundation for the extensive uses of ROC ZLD procedures. This work conducted an emergy-based analysis to evaluate the comprehensive benefits of three alternative ROC ZLD processes (scenario A: multiple-effect evaporation (MED); scenario B: ozonation + RO + MED; scenario C: continuous-flow electrolytic system with a front buffer tank (CFS–C) + RO + MED). Compared with scenario A, the resource inputs required for per m3 ROC disposal of scenarios B and C were decreased by 31% and 34% respectively; the emergy investment ratios of scenarios B and C were decreased by 30% and 33% respectively while the emergy yield ratios were both increased by 21%; the environmental loading ratios of scenarios B and C were decreased by 25% and 29% respectively while the environmental sustainability indexes were increased by 58% and 71% respectively. The results showed that scenarios B and C outperformed scenario A in terms of technical, economic, and environmental benefits; additionally, the technical advantages of scenario C outweighed scenario B, and scenario C was finally recommended for future implementation.

Investigation of the Energy Efficiency and the Economic Feasibility of a Novel Zero Liquid Discharge Brine Treatment System

Investigation of the Energy Efficiency and the Economic Feasibility of a Novel Zero Liquid Discharge Brine Treatment System

Pilot-scale evaluation of the sustainability of membrane desalination systems for the concentrate volume minimization of coal chemical wastewater

5 stars represents the best technical performance/highest cost.

Reclaimed seawater discharge – Desalination brine treatment and resource recovery system

With the proliferation of reverse osmosis technology, seawater reverse osmosis desalination has been heralded as the solution to water scarcity for coastal regions. However, the large volume of desalination brine produced may pose an adverse environmental impact when directly discharged into the sea and result in energy wastage as the seawater pumped out is dumped back into the sea. Recently, zero liquid discharge has been extensively studied as a way to eliminate the aquatic ecotoxicity impact completely, despite being expensive and having a high carbon footprint. In this work, we propose a new strategy towards the treatment of brine to seawater level for disposal, dubbed reclaimed seawater discharge (RSD). This process is coupled with existing resource recovery techniques and waste alkali CO2 capture processes to produce an economically viable waste treatment process with minimal CO2 emissions. In this work, we placed significant focus on the electrolysis of brine, which simultaneously lowers the salinity of the desalination brine (56.0 ± 2.1 g/L) to seawater level (32.0 ± 1.4 g/L), generates alkali brine from seawater (pH 13.6) to remove impurities in brine (Mg2+ and Ca2+ to below ppm level), and recovers magnesium hydroxide, calcium carbonate, chlorine, bromine, and hydrogen gas as valuable resources. The RSD is further chemically dechlorinated and neutralised to pH 7.3 to be safe to discharge into the sea. The excess alkali brine is used to capture additional CO2 in the form of bicarbonates, achieving net abatement in climate change impact (9.90 CO2 e/m3) after product carbon abatements are accounted.

Hybrid desalination system for Baltic Sea water: A preliminary study

The world's water resources predominantly comprise salt water. In the face of forecasts of increasing demand for hydrogen obtained by electrolysis, it is becoming important to investigate the feasibility of seawater desalination. As part of a research project, the possibility of using a hybrid zero liquid discharge (ZLD) desalination system to desalinate seawater from the Baltic Sea was examined. In addition to analysing the operating parameters of the system, a detailed physico-chemical examination of the process water was carried out at each stage of treatment. It was found that the reverse osmosis (RO) and multiple-effect desalination (MED) systems allow sufficient water parameters to be obtained to feed the ion exchange (IX) system, and after deionisation it is possible to achieve the water parameters required by proton exchange membrane (PEM), anion exchange membrane (AEM) and alkaline water (AWE) electrolysers. Furthermore, the possibilities of concentrating brine in the multiple-effect desalination system and extracting salt in solid form in the ZLD system were verified.

Characterization of Natural and Synthetic Fabrics for the Treatment of Complex Wastes.

In the present study, nine fabrics have been tested for brackish water treatment with the aim of industrial application under the concept of zero liquid discharge (ZLD). Moisture content was determined, where it was observed that the lignocellulosic fabrics had a moisture content ranging from 2.5 to 8.5%. The wetting contact angle showed that the flax with polylactic acid (LPLA) was the most hydrophobic. The determination of the liquid absorption capacity showed that, of the synthetic fabrics, the one with the highest absorption, both in distilled water and in brackish water, was the polyester (PES) fabric with an absorption of 816% compared to its initial weight. In the natural fabrics, the highest absorption capacity was shown by the wet-laid without treatment (WL-WT) fabric for both distilled water and brackish water, although it required several cycles of operation to maintain this stable absorption. Exposure to brackish water improved the absorption capacity of all samples. Mechanical and thermal characterization showed that the synthetic fabrics were more resistant than the natural fabrics, although they may compete in terms of applicability. The capillarity study showed that the most hydrophilic fabrics completed the test the fastest. Finally, the composting degradation test showed that those fabrics with polylactic acid (PLA) content degraded faster in the first 14 days and thereafter the degradation of the lignocellulosic content showed a slower degradation until 112 days. The Bam fabric did not degrade during the course of the experiment.

Influence of internal design on the performance of pilot vacuum-assisted air-gap membrane distillation modules for brine concentration with solar energy

Membrane distillation (MD) in batch operation is proposed for brine concentration with solar energy in zero liquid discharge (ZLD) desalination processes, but there are some research gaps yet. Energy efficiency is key for implementing the technology with solar energy and there is not enough experience and experimental results of operation of MD pilot modules at high salinity feeds. This research focuses on the experimental evaluation and comparison of two multi-envelope spiral wound commercial membrane distillation modules operating in vacuum-assisted air gap MD at the solar MD pilot facilities of Plataforma Solar de Almería in Spain. These modules have similar membrane area (24 and 25.9 m2) and residence time (large, to maximize thermal efficiency), but different internal design: 6 envelopes 5 m long and 12 envelopes 2.7 m long, respectively. This difference affects mostly the feed circulation velocity for equal feed flow rate. Performance parameters such as permeate production and specific thermal energy consumption (STEC) are compared and experimental models performed and validated for different feed salinities. Permeate quality and specific electrical energy (SEEC) consumption are also evaluated. The results show that the best module for batch operation is the one with a larger number of channels but of shorter length.