Water Treatment Processes Research Articles

Nano Filtration Techniques in Waste Water Treatment

Nano filters, based on nanotechnology to improve filtration processes, offer sophisticated solutions for contaminant removal from liquids and gases. The filters in this group include polymeric membranes with a pore size of 1-100 nanometres, ceramic membranes that are tolerant to chemicals, and carbon nanotube and graphene-based filters with advancedpermeability and selectivity. Recently, differentiated nanomaterials have been developed to make composite membranes with improved performance and durability. However, NF have disadvantages such as membrane fouling and high production costs. In this respect, research is currently being done to come up with solutions to the challenges, optimize the integration of nanomaterials, and realize application possibilities in water treatment, air purification, and industrial processes. On the whole, NF stand as the radical improvement filtration technology has so far achieved, and further research is bound to make them more efficient and cheaper About 17–19 million people in the world lack access to clean water. It is estimated that about 3.4 million people die every year from water scarcity, sanitation, and hygiene-related problems out of which 99% of deaths occurin developing countries. In recent years, water contamination has become a global environmental concern. The paper providesinsights into advancements in wastewater treatment through nano-filters. The paper focuses on evaluating the effectiveness ofnanomembranes in removing containments such as inorganic salts, organic compounds, and heavy metals. Additionally, the paper gives information about performance based on a comparison of the tractional filters and RO in terms of flexibility, durability, efficiency, and cost-effectiveness. Furthermore, it explores the application of NF in industries such as textile, pharmaceuticals, and agriculture and evaluates the versatility and effectiveness in these sectors.

A Critical Assessment of the Process and Logic Behind Fish Production in Marine Recirculating Aquaculture Systems

A recirculating aquaculture system (RAS) represents a forward-looking form of aquaculture. A RAS consists of fish tanks and water treatment processes in a closed loop to sustain the environmental conditions for fish production. However, the rapid industrialization of the technology is fraught with transfer problems. This review justifies a RAS process chain based on fish biology. The underlying concept has been evaluated by the author in experimental and commercial RAS projects. The core idea is that the fish must be considered as a technical subcomponent in a RAS, determining the technology. Fish, when considered as small biological machines, are still a black box in many ways. However, their basic biology and physiology provide all the knowledge to implement them in a technical setting. The information required to understand this concept is presented and discussed based on current scientific knowledge. The conclusion is that the technology is available but needs to be rigorously implemented. If this were carried out, fish production in RASs would be ecologically sustainable, which is already claimed for RASs but is not always the reality in commercial applications.

Visible-light-activated Fe2O3–TiO2 nanoparticles enhance biofouling resistance of polyethersulfone ultrafiltration membranes against marine algae Chlorella vulgaris

This study investigated the modification of polyethersulfone (PES) ultrafiltration membranes with TiO2 and Fe2O3–TiO2 nanoparticles to enhance their hydrophilicity and biofouling resistance against the marine microalgae Chlorella vulgaris. It is a common freshwater and marine microalga that readily forms biofilms on membrane surfaces, leading to significant flux decline and increased operational costs in ultrafiltration processes. The microalgae cells and their extracellular polymeric substances (EPS) adhere to the membrane surface, creating a dense fouling layer that impedes water permeation. The modified membranes were characterized using contact angle measurements, scanning electron microscopy, and pure water flux/resistance tests. Short-term ultrafiltration experiments evaluated the membranes’ antifouling performance by measuring flux decline, flux recovery ratio, and relative flux reduction during C. vulgaris filtration. The TiO2 membrane showed improved hydrophilicity and antifouling over the pristine PES membrane, while the Fe2O3–TiO2 nanocomposite membrane exhibited the best performance. It reduced the water contact angle and showed only a 5% relative flux reduction compared to 60% for the pristine membrane. SEM images confirmed reduced microalgal deposition on the nanocomposite surface. Long-term tests with microalgal cells under dark and visible light conditions in saline water further assessed the membranes’ biofouling resistance. The Fe2O3–TiO2 membrane maintained 59 L/m2 h water flux under visible light after immersion in the microalgal solution, outperforming the pristine (38 L/m2 h) and TiO2 (52 L/m2 h) membranes. This superior antifouling was attributed to photocatalytic generation of reactive oxygen species inhibiting microalgal adhesion. This study demonstrates a promising strategy for mitigating biofouling in membrane-based water treatment and desalination processes.

Advanced nanobubble flotation for enhanced removal of sub-10 µm microplastics from wastewater.

Sub-10 µm microplastics (MPs) in aquatic environments pose significant ecological and health risks due to their mobility and potential to carry harmful microcontaminants. Our effluent analysis from a Hong Kong Sewage Treatment Works shows that traditional treatment often fails to effectively remove these MPs. These small-sized MPs are commonly neglected due to challenges in accurate quantification, analysis, and removal. This study introduces a nanobubble-assisted flotation process that enhances the removal efficiency of both regular and irregular small-sized MPs from wastewater. The proposed process outperforms the traditional flotation process by fostering a more effective interaction between bubbles and MPs, increasing removal rates of MPs from 1 µm to 10 µm by up to 12% and providing a total efficiency boost of up to 17% for various particle sizes. Improvements are attributed to enhanced collision and adhesion probabilities, hydrophobic interactions, as well as better floc flotation. Supported by empirical evidence, mathematical models, and Molecular Dynamics simulations, this research elucidates the nanoscale mechanisms at play. The findings confirm the nanobubble-assisted flotation technique as an innovative and practical approach to removing sub-10 µm MPs in water treatment processes.

Semi-Supervised Soft Computing for Ammonia Nitrogen Using a Self-Constructing Fuzzy Neural Network with an Active Learning Mechanism

Ammonia nitrogen (NH3-N) is a key water quality variable that is difficult to measure in the water treatment process. Data-driven soft computing is one of the effective approaches to address this issue. Since the detection cost of NH3-N is very expensive, a large number of NH3-N values are missing in the collected water quality dataset, that is, a large number of unlabeled data are obtained. To enhance the prediction accuracy of NH3-N, a semi-supervised soft computing method using a self-constructing fuzzy neural network with an active learning mechanism (SS-SCFNN-ALM) is proposed in this study. In the SS-SCFNN-ALM, firstly, to reduce the computational complexity of active learning, the kernel k-means clustering algorithm is utilized to cluster the labeled and unlabeled data, respectively. Then, the clusters with larger information values are selected from the unlabeled data using a distance metric criterion. Furthermore, to improve the quality of the selected samples, a Gaussian regression model is adopted to eliminate the redundant samples with large similarity from the selected clusters. Finally, the selected unlabeled samples are manually labeled, that is, the NH3-N values are added into the dataset. To realize the semi-supervised soft computing of the NH3-N concentration, the labeled dataset and the manually labeled samples are combined and sent to the developed SCFNN. The experimental results demonstrate that the test root mean square error (RMSE) and test accuracy of the proposed SS-SCFNN-ALM are 0.0638 and 86.31%, respectively, which are better than the SCFNN (without the active learning mechanism), MM, DFNN, SOFNN-HPS, and other comparison algorithms.

Preparation of Microelectrolysis Filler Using Coal Slag for the Removal of Hazardous Substances in Contaminated Water.

Presently, the utilization of gasification slag in the context of wastewater treatment is constrained. Furthermore, the presence of dye wastewater and wastewater containing hazardous metals represents a significant threat to human health. Accordingly, the present study prepared a microelectrolytic filler (MF) from gasification slag via a high-temperature roasting method and evaluated its degradation performance in water containing organic matter and harmful metal ions. The impact of varying preparation conditions, including initial solution pH and MF dose, on the degradation process was examined. The removal of methyl blue was found to be 92.21% at an initial pH of 2, a reaction time of 300 min and a dosage of 40 g L-1. The removal of Cu(II), Cd(II), and Pb(II) metal ions was 97.32, 96.58, and 99.38%, respectively, at an initial pH of 4, a reaction time of 180 min, and a dosage of 10 g L-1. Following five cycles, the MF process demonstrated continued efficacy in the removal of dyes and heavy metals from the wastewater. A mechanistic analysis revealed that the water treatment process is not a single adsorption process. Instead, it was found that organic macromolecules undergo chain-breaking reactions, while heavy metal ions undergo redox reactions. The wastewater treatment process comprises a number of distinct strategies, including electrochemical reactions, adsorption, flocculation, and precipitation. These findings illustrate the potential of a gasification slag green recycling approach to treat waste with waste, in alignment with the principles of sustainable development.

An Evaluation of Biochar Derived from Agro-Industrial Waste as an Alternative Material for the Elimination of Pathogenic Load from Water

The contamination of water bodies is becoming more frequent due to uncontrolled discharges into them, including those of domestic or industrial wastewater (WW) characterized by the presence of heavy metals, a high pathogenic load, pesticides, and pharmaceuticals, among other pollutants, which represent a risk to both humans and the health of the ecosystem. Consequently, conventional water treatment processes have been implemented. However, they are not efficient enough. In this regard, exploring and analyzing new alternatives and sustainable systems that efficiently degrade the different pollutants found in WW are required, and biochar can be considered as an attractive treatment option, since it is an adsorbent carbonaceous material that allows for the removal of several pollutants. The generation and use of biochar contribute to the promotion of the circular bioeconomy and the achievement of sustainable development goals by enhancing the reuse and recycling of agricultural and agro-industrial waste as raw material for its production. The objective of this work is to evaluate the utilization of biochar as an alternative material for the elimination of the pathogenic load in water.

Synthesis of magnetic zirconium oxide-iron oxide nanoparticles composite using chemical precipitation process for Pb (II) adsorption

The exploration and utilization of natural raw zircon minerals in Indonesia, particularly in Central Kalimantan, remain largely untapped in their potential as high-tech and commercially valuable substances with eco-friendly properties, particularly in water and industrial wastewater treatment. The primary objective of this research is to enhance the development and synthesis of natural raw zircon minerals by converting them into zirconium oxide and integrating them with magnetic nanoparticles. The magnetic nanoparticle composite material for zirconium oxide (MNP@ZrO2) was synthesized using the chemical co-precipitation method. Zirconium and its oxides have gained significant application in water and wastewater treatment in recent years. Through chemical co-precipitation processes (MNP@ZrO2), the natural raw zircon minerals were transformed into zirconium oxides and combined with magnetic nanoparticles due to their exceptional potential as effective adsorbents for anions and cations in water and industrial treatment processes. In the utilization of Scanning Electron Microscopy (SEM), magnetic nanoparticles with a diameter of less than 50 nm emerged on the surface of the zirconium crystals within the magnetic nanoparticle composites. X-ray diffraction (X-RD) analysis indicated that the treatment of zirconium minerals resulted in 11.19% decrease in the Crystallinity Index and a significant reduction of 98% in silica content. By maintaining a pH level of approximately 7 ± 0.2 over 360 min with a stirring rate of 150 rpm, and at ambient temperature, the optimal conditions for Pb (II) adsorption were achieved with the adsorption capacity of 68.98 mg/g using MNP@ZrO2 as adsorbent. The successful synthesis of magnetic zirconium oxide-iron oxide nanoparticles at various pH levels using the chemical co-precipitation process has facilitated a comprehensive assessment of their performance in Pb (II) adsorption.

Insight into the removal of nanoplastics and microplastics by physical, chemical, and biological techniques.

Plastic pollutants create health crises like physical damage to tissues, upset reproductive processes, altered behaviour, oxidative stress, neurological disorders, DNA damage, gene expression, and disrupt physiological functions, as the biosphere accumulates them inadvertently through the food web. Water resources have become the generic host of plastic wastes irrespective of their particle size, resulting in widespread distribution in aquatic environments. The pre-treatment step of the traditional water treatment process can easily remove coarse-sized plastic wastes. However, the fine plastic particles, with sizes ranging from nanometres to millimetres, are indifferent to the traditional water treatment. To address the escalating problems, the upgradation of different traditional physical, chemical, and biological remediation techniques offers a promising avenue for tackling tiny plastic particles from the water environment. Further, new techniques and hybrid incorporations to the existing water treatment techniques have been explored, specifically removing tiny plastic debris. A detailed understanding of the sources, fate, and impact of plastic wastes in the environment, as well as an evaluation of the above treatment techniques and their limitations and challenges, can only show the way for their upgradation, hybridization, and development of new techniques. This review paper provides a comprehensive overview of the current knowledge and techniques for the remediation of nanoplastics and microplastics.

Visible-light assisted peroxymonosulfate process for efficient water treatment via Fe-O embedded ZIF-62

The development of efficient and environmentally friendly water treatment technologies is essential for the treatment of emerging pollutants. In this study, a ZIF-62 catalyst embedded with Fe-O was prepared for the visible-light assisted activation of peroxymonosulfate (PMS) to achieve the removal of bisphenol A by coupling photogenerated carriers with the non-radical pathway. The embedding of Fe-O narrowed the bandgap width (reduced from 3.07 eV to 2.37 eV), enhanced the overall photoresponse performance, and improved the segregation of photogenerated carriers. The upward shift of the d-band center contributes to the adsorption of PMS. The embedding of Fe-O improves the BPA removal kinetics by a factor of 15.4 (increased from 0.00391 min−1 to 0.06005 min−1). Surface-activated complexes played a dominant role in the removal of BPA in this system, and photogenerated holes (h+) and singlet oxygen (1O2) were also involved in the removal of BPA. In addition, the system has good pH adaptability (pH = 3 ∼ 11) and good environmental suitability. Toxicity assessment showed that the overall toxicity of the intermediates tended to decrease. This study provides new insights into visible-light assisted activation of PMS.

Safety and security of household water purifiers against pathogenic microbial contamination and bio-risk evaluation of their microbial community structures

Household water filters, particularly point-of-use systems, are crucial to ensure safe drinking water consumption by eliminating microbial contaminants. This study evaluated the efficacy of three types of water purifiers (ultrafiltration [UF], nanofiltration [NF], and reverse osmosis [RO]) against microbial contamination. In our experiments, Escherichia coli and bacteriophage MS2 were used as two microbial indicators in daily household settings to track the spatial and temporal profiles of their behavior from the filter inlets to in-UF, NF, and RO water purifiers, and then to effluents. The results showed that both NF and RO water purifiers removed 100 % of the indicator organisms. The UF water purifier achieved 100 % removal of E. coli, but the removal of MS2 phage was poor. The presence of coexisting ions and natural organic matter in tap water can significantly affect the behavior of MS2 phages during the water treatment process. Their presence reduces the charge repulsion effect of the UF membrane on the MS2 phage as well as promotes the migration of the MS2 phage on the post-activated carbon cartridge that was placed in the last unit of the water purifier system, which could increase the pathogen transmission risks in drinking water supplies. The bacterial community structures of the cartridge materials and cartridge effluents from each unit were analyzed by 16S rRNA gene sequencing, which revealed distinct microbial profiles of the different purifiers. Environmental conditions such as pH, nutrient availability, materials, and operational parameters can affect the composition of bacterial communities. Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) was used to examine the surface morphology of the membranes after they were exposed to water contaminants, which demonstrated that the inherent differences in the membrane structure influenced the retention of pollutants and microorganisms on the surfaces. In summary, this study demonstrates that both NF and RO water purifiers can significantly reduce the presence of various enteric and opportunistic pathogenic bacteria in drinking water, leading to safer potable water, whereas UF water purifiers may have certain risks owing to their UF membranes and post-activated carbon. In addition, secondary microbial contamination may be introduced by the post-activated carbon units of water purifiers, especially after long-term usage. Therefore, we concluded that addressing the secondary microbial pollution caused by post-activated carbon after prolonged use and long-term shutdown is essential for maintaining the safety and quality of drinking water.

Performance evaluation on recycling metals from lithium cobaltate by supercritical water combining with leaching-precipitation methods

The recycling of metals from spent lithium-ion batteries is currently a hotspot of research. This paper introduces a novel recovery method that integrates supercritical water and leaching-precipitation techniques to efficiently extract metals from lithium cobaltate electrodes. This study investigates the dissolution behavior of lithium cobaltate in supercritical water, and the interaction between lithium cobaltate and organic impurity (Polyvinylidene Fluoride and N-methylpyrrolidone) during the supercritical water treatment process. Lithium cobaltate reacts with supercritical water to form cobaltous hydroxide and reacts with polyvinylidene fluoride to form cobalt oxide. During the reaction of supercritical water with polyvinylidene fluoride and N-methylpyrrolidone in supercritical water, lithium cobaltate is reduced to cobalt oxide. The addition of N-methylpyrrolidone promotes the reduction of cobalt ion and the decomposition of polyvinylidene fluoride. Subsequently, the cathode materials treated with supercritical water are leached by using hydrochloric acid and sulfuric acid respectively. Cobalt and lithium ions in the leaching solution are precipitated by adding sodium hydroxide and sodium carbonate. The maximum recovery efficiencies of lithium and cobalt are 73 % and 79.60 %, respectively.

Evaluation of the Safe Water Optimization Tool to Provide Evidence-Based Chlorination Targets in Surface Waters: Lessons from a Refugee Setting in Uganda.

The Safe Water Optimization Tool (SWOT) generates evidence-based point-of-distribution free residual chlorine (FRC) targets to adjust chlorine dosing by operators and ensure water quality at point-of-consumption. To investigate SWOT effectiveness in surface waters, we conducted two before-and-after mixed-method evaluations in a Uganda refugee settlement served by piped and trucked surface water systems. We surveyed 888 users on water knowledge, attitudes, and practices; collected 2768 water samples to evaluate FRC,Escherichia coli, and disinfection by-products (DBPs) concentrations; and conducted nine key-informant interviews with system operators about SWOT implementation. After baseline data collection, SWOT chlorination targets were generated, increasing point-of-distribution FRC targets from 0.2 to 0.7-0.8 mg/L and from 0.3 to 0.9 mg/L for piped and trucked systems, respectively. At endline, household point-of-consumption FRC ≥ 0.2 mg/L increased from 23 to 35% and from 8 to 42% in the two systems. With these increases, we did not observe increased chlorinated water rejection or DBPs concentrations exceeding international guidelines. Informants reported that SWOT implementation increased knowledge and capacity and improved operations. Overall, SWOT-generated chlorination targets increased chlorine dosage, which improved household water quality in surface waters although less than previously documented with groundwater sources. Additional operator support on prechlorination water treatment processes is needed to ensure maximally effective SWOT implementation for surface water sources.

Advances in the Separation and Removal of Microplastics in Water Treatment Processes

In this review, we comprehensively analyzed the distribution of microplastics （MPs） in major water ecosystems in China and the fate of MPs during the water treatment process. The removal efficiency of MPs with different colors, sizes, shapes, and materials was also discussed. The results showed that the abundance of microplastics in the aquatic environment was geographically variable and closely related to human activities. Fibrous and transparent （white） microplastics were the most common features in China's water ecosystems and water treatment plants, with polypropylene （PP）, polyethylene （PE）, and polystyrene （PS） being the most common polymer types of microplastics. The removal efficiency of MPs varied from different treatment processes significantly. Pre-treatment and primary treatment in wastewater treatment plants （WWTPs） contributed the most to the removal. In the secondary treatment, the sedimentation tank showed more efficiency than the biological treatment processes. Tertiary treatment processes demonstrated remarkable effectiveness in achieving terminal control of MPs, especially membrane technologies. On the contrary, aeration and hydrodynamic effects may have increased the abundance of MPs in WWTPs. In drinking water treatment plants （DWTPs）, coagulation-sedimentation processes were found to be the most effective in removing MPs, followed by filtration and disinfection processes. Further, both pre-treatment and post-treatment steps also made significant contributions to MPs removal.

Electric-field nanobubbles: A step change in nanobubble engineering, and its “coming of age”

Electric-field nanobubbles: A step change in nanobubble engineering, and its “coming of age” Niall J. English, from Chemical Engineering at University College Dublin, discusses how electric-field nanobubbles have displaced their mechanically-generated counterparts in performance and sustainability. Limited solubility of gases in water, such as oxygen, is a fundamental challenge. In ecosystems and the environment, lack of dissolved oxygen (DO) is a major reason for fish kills and water bodies being blighted by algal blooms, in addition to lack of effectiveness of activated-sludge processes in water treatment or poorer-than-hoped results in irrigation. Nanobubbles (NBs) are tiny gas bubbles on the nanometre (nm) scale. They may be thermodynamically metastable for up to many months, or sometimes even longer, and have enhanced gas-transfer properties and substantial industrial potential. The concept of NBs versus traditional, coarser bubbles – with the latter subject to buoyancy phenomena, while NBs are relatively impervious to rising – in essence, “subverts” Stokes’ Law of bubble rising – and have an excellent area-to-volume ratio. If NBs are generated well – indeed, the art of “nanobubble engineering”, as it were – NBs lead to important and useful applications.

Synthesis of Au/Co3O4/PVA hybrid nanocomposites via eco-friendly method based on pulsed laser ablation process for water treatment

A portable nanostructured nanocomposite film, based on cobalt oxide and gold nanoparticles (NPs) embedded in a polyvinyl alcohol structure (PVA), Au/Co3O4/PVA, was prepared via a novel way based on pulsed laser ablation to be applied as an effective catalytic degradation material for a hazardous chemical structure as nitro compounds. Au/Co3O4/PVA was investigated by the techniques of UV–Vis, FT-IR, SEM, and XRD. From XRD, the decrease in crystallinity of PVA is attributed to the intermolecular hydrogen bonding between PVA and Au/Co3O4. In addition, there are five interplanar peaks, with three shared peaks by both phases and one unique peak for each phase of Au and Co3O4. From FT-IR, the modes observed at a 500–1200 cm-1 wavenumber range correspond to the stretching vibration modes of Au/Co3O4. From UV–VIS, as the embedding of Co3O4 on Au-PVA structure increases, the energy band gap is shifted to a lower value. This is due to the embedding of Co3O4 NPs. From SEM, in the case of embedding PVA with Au NPs, the bright semi-spherical shape of the nanostructured materials has a bright semi-spherical light area. Moreover, in the case of the embedded PVA with Co3O4 NPs, the faint semi-spherical form of the nanostructured materials is discernible. Besides, the catalytic activity performance is tested for the degradation of 4-nitrophenol, which reveales that the reaction followed first-order kinetics, as indicated by linear regression analysis. The results shows that the sample completely convertes 4-nitrophenol to 4-aminophenol within 6 min.

Dual-defect AgBiO3/DCN S-scheme heterojunction for booted photocatalytic removal of Norfloxacin: Interfacial charge transfer, mechanism and toxicity assessment insights

Antibiotics pollution may pose a great risk to ecosystem and human health. In this work, an innovative dual-defect AgBiO3/DCN S-scheme heterojunction was constructed to overcome the sluggish charge separation and transfer issue and showed exceptional photodegradation performance towards norfloxacin (NFL) pollution under the visible light. The degradation efficiency of NFL reached 95.30 % within 120 min respectively, the rate constant was 3.64 times higher than that of defective g-C3N4 (DCN). The systematically characterizations proved that the enhanced photocatalytic activity was benefited from optimized band structures, improved carrier separation efficiency, due to dual defects and S-scheme heterojunction in AgBiO3/DCN. the intermediate degradation products and degradation pathway of NFL were speculated by UPLC-HRMS, and the environmental toxicity degree of degradation products was analyzed according to the T.E.S.T software. The charge transfer pathway was confirmed as an S-scheme mechanism through a combination of band structure analysis, alongside electron paramagnetic resonance (EPR) experiments.The quenching experiments and ESR analyses indicated that h+ and O2•− radicals played predominant roles. The efficient and stable photocatalytic NFL degradation efficiency and broad environmental adaptability proved potential practical application. This work may shed light on designing new dual-defect heterojunction with photocatalytic antibiotic removal capability in the innovative water treatment process.

Ultra-permeable silk-based polymeric membranes for vacuum-driven nanofiltration.

Nanofiltration (NF) membranes are commonly supplied in spiral-wound modules, resulting in numerous drawbacks for practical applications (e.g., high operating pressure/pressure drop/costs). Vacuum-driven NF could be a promising and low-cost alternative by utilizing simple components and operating under an ultra-low vacuum pressure (<1 bar). Nevertheless, existing commercial membranes are incapable of achieving practically relevant water flux in such a system. Herein, we fabricated a silk-based membrane with a crumpled and defect-free rejection layer, showing water permeance of 96.2 ± 10 L m-2 h-1 bar-1 and a Na2SO4 rejection of 96.0 ± 0.6% under cross-flow filtration mode. In a vacuum-driven system, the membrane demonstrates a water flux of 56.8 ± 7.1 L m-2 h-1 at a suction pressure of 0.9 bar and high removal rate against various contaminants. Through analysis, silk-based ultra-permeable membranes may offer close to 80% reduction in specific energy consumption and greenhouse gas emissions compared to a commercial benchmark, holding great promise for advancing a more energy-efficient and greener water treatment process and paving the avenue for practical application in real industrial settings.

Pressure-induced piezoelectric response for mitigating membrane fouling in surface water treatment: Insights from continuous operation and biofouling characterization

Organic fouling and biofouling represents a critical challenge encountered by the membrane-based water treatment process. Herein, a piezoelectric PVDF membrane (PEM), capable of generating electrical responses to hydraulic pressure stimuli, was synthesized and employed for mitigating the fouling in surface water treatment. The surface-hydrophobilized PEM demonstrated sensitive and enhanced underwater output performance in response to increasing transmembrane pressure (TMP) during constant-flux filtration, with signals reaching up to ∼800 mV at a TMP of ∼80 kPa. This in-situ piezoelectric response significantly reduced TMP growth in both short-term (1 h) and long-term (15 days) filtration trials, demonstrating a strong capability to mitigate membrane fouling. Moreover, continuous piezoelectric stimulation effectively inhibited microbial activity and the accumulation of extracellular polymeric substances (EPS) on PEM surface, surpassing the dominant electrokinetic repulsion mechanisms observed in short-term trials. Microbial community analysis suggests that this evolution is primarily due to the targeted impact of piezoelectric stimulation on microbial metabolic behavior. The piezoelectric-induced electrical microenvironment inhibited the growth of microbes associated with high EPS production while promoting the proliferation of electrically active microbes involved in biopolymer digestion. In addition, the PEM demonstrated enhanced permeate quality throughout the filtration process, with DOC and UV254 removal rates increasing from 11.7 % and 15.6 % initially to 28.6 % and 19.5 % by the 15th day, respectively. Given the performance and self-powered capability of PEM compared to current electrified antifouling methods that require an external power supply, these attributes are anticipated to hold practical significance in developing innovative and energy-efficient strategies for mitigating both organic fouling and biofouling.

Persistent luminescent ZnAl-LDH nanosheets for all-weather degradation of nitenpyram and tetracycline: Superoxide radical induction, life cycle analysis and engineering applications

Photocatalysts designed for all-weather applications, capable of efficient charge carrier separation, are set to transform the adoption of photocatalysis-driven advanced oxidation processes in wastewater management. In this investigation, an energy-storing ZnAl-LDH@SrAl2O4:Eu2+, Dy3+ (SALDH) was synthesized successfully, optimized for the photocatalytic selective degradation of NTP and tetracycline hydrochloride (TC) under varying weather conditions, with 100 % degradation of both NTP and TC within 75 min. Remarkably, SALDH demonstrates energy storage capabilities that markedly reduce energy demands relative to traditional photocatalytic approaches. The primary reactive species identified were O2−, and the Fukui index, computed via density-functional theory (DFT), identified the specific interaction sites of O2− on NTP molecules. Utilizing the energy retention properties of SALDH, a novel, environmentally friendly device was engineered for processing organic pollutants in agricultural wastewater. This system harness the energy from solar radiation to induce the oxidation of pollutants. The experiments that were performed in the both artificially prepared lab-scale and actual agricultural WWT plants indicated the degradation efficiencies of 36 % and 37 %, respectively. As seen during the day, both SALDH and persulfate were capable of effectively decomposing organic contaminants; at night, the SA’s luminescence maintained the oxidative ability of ZnAl-LDH. Meanwhile, SALDH combines the corrosion resistance of ZnAl-LDH with good metal compatibility, enabling SALDH to effectively improve the photostability of long afterglow. This work contributes to the existing knowledge on the degradation of organic pollutants by efficient photocatalysts and points to possible implementations in water treatment processes.