Development of a new miniaturized system for ultrafiltration.

Acute decompensated heart failure and fluid overload are the most common causes of hospitalization in heart failure patients, and often, they contribute to disease progression. Initial treatment encompasses intravenous diuretics although there might be a percentual of patients refractory to this pharmacological approach. New technologies have been developed to perform extracorporeal ultrafiltration in fluid overloaded patients. Current equipment allows to perform ultrafiltration in most hospital and acute care settings. Extracorporeal ultrafiltration is then prescribed and conducted by specialized teams, and fluid removal is planned to restore a status of hydration close to normal. Recent clinical trials and European and North American practice guidelines suggest that ultrafiltration is indicated for patients with refractory congestion not responding to medical therapy. Close interaction between nephrologists and cardiologists may be the key to a collaborative therapeutic effort in heart failure patients. Further studies are today suggesting that wearable technologies might become available soon to treat patients in ambulatory and de-hospitalized settings. These new technologies may help to cope with the increasing demand for the care of chronic heart failure patients. Herein, we provide a state-of-the-art review on extracorporeal ultrafiltration and describe the steps in the development of a new miniaturized system for ultrafiltration, called AD1 (Artificial Diuresis).

Evaluación clínica y económica del uso de ultrafiltración en pacientes con insuficiencia cardíaca aguda / Clinical and economic evaluation of the use of ultrafiltration in patients with acute heart failure

ANTECEDENTES: La ICA es la mayor causa de hospitalizaciones en personas de ≥65 años, y está asociada a una tasa de mortalidad y reingreso elevada. La ICA se puede presentar como una primera manifestación de la IC (de novo) o, más frecuentemente, como consecuencia de una descompensación aguda de la IC crónica. Los diuréticos son la base del tratamiento de la ICA con sobrecarga de volumen y congestión. Los más utilizados son los diuréticos de asa. En ciertos pacientes, puede existir una resistencia a estos fármacos, por lo que, para resolver la congestión, se ha empleado la ultrafiltración. La ultrafiltración se refiere a la eliminación mecánica y ajustable de agua plasmática isotónica de la sangre a través de una membrana semipermeable (hemofiltro), mediada por la aplicación de un gradiente de presión hidrostática generado por una bomba. OBJETIVO: Evaluar la eficacia, seguridad y costo-efectividad del uso de ultrafiltración en pacientes con insuficiencia cardiaca aguda. MÉTODOS: Se realizó una búsqueda sistemática y exhaustiva de toda la evidencia disponible en Pubmed, BVS y Cochrane library, obteniendo una revisión sistemática con metaanálisis de confianza alta, de acuerdo a AMSTAR-2, la cual fue utilizada para el análisis cualitativo. RESULTADOS: Se identificaron un total de 780 estudios, de los cuales, 59 estudios fueron revisados a texto completo, obteniendo 4 revisiones sistemáticas, en donde, 3 no cumplieron con criterios de calidad metodológica, consiguiendo una confianza críticamente baja. La revisión sistemática incluida en nuestro análisis, demostró un efecto estadístico nulo en todos los desenlaces evaluados (mortalidad, rehospitalización, mejoría clínica, efectos adversos), a excepción de la rehospitalización por insuficiencia cardiaca a largo plazo, donde el efecto favoreció a la intervención de análisis (ultrafiltración). CONCLUSIÓN: De los datos obtenidos de la evaluación clínica, se identifica que la UF podría reducir la rehospitalización por insuficiencia cardiaca, la cual, es la causa de los mayores gastos por insuficiencia cardiaca aguda en los sistemas de salud. Debido a la certeza limitada de los hallazgos, se debe mantener en vigilancia estrecha a las nuevas publicaciones del tema, para confirmar o modificar la dirección del efecto de los distintos desenlaces.

Polymer monoliths for the concentration of viruses from environmental waters: A review.

Even at low concentrations in environmental waters, some viruses are highly infective, making them a threat to human health. They are the leading cause of waterborne enteric diseases. In agriculture, plant viruses in irrigation and runoff water threat the crops. The low concentrations pose a challenge to early contamination detection. Thus, concentrating the virus particles into a small volume may be mandatory to achieve reliable detection in molecular techniques. This paper reviews the organic monoliths developments and their applications to concentrate virus particles from waters (waste, surface, tap, sea, and irrigation waters). Free-radical polymerization and polyaddition reactions are the most common strategies to prepare the monoliths currently used for virus concentration. Here, the routes for preparing and functionalizing both methacrylate and epoxy-based monoliths will be shortly described, following a revision of their retention mechanisms and applications in the concentration of enteric and plant viruses in several kinds of waters.

Development and validation of a 3D printed antiviral ventilator filter - a comparative study.

BACKGROUND: The current coronavirus infectious disease 2019 (COVID-19) pandemic has caused unexpected pressure on medical supplies, interrupting supply chains and increasing prices. The supply of antiviral filters which form an essential part of the ventilator circuit have been affected by these issues. Three-dimensional (3D) printing may provide a solution to some of these issues. METHODS: We designed and tested 3D printed heat and moisture exchange (HME) and antiviral casing. For each casing we tested two different filter materials derived from a sediment water filter cartridge or 1.5-µm glass fiber filter paper. A polyurethane sponge was used for the HME. Each design was tested for circuit leak, circuit compliance, peak inspiratory pressure and casing integrity using methylene blue dye. RESULTS: We designed, produced, and tested two different types of antiviral filters with six different internal configurations. Overall, we tested 10 modified filter designs and compared them with the original commercial filter. Except for the combination of 1.5-µm filter paper and 5 mm sponge peak inspiratory pressure and circuit compliance of the filters produced were within the operating limits of the ventilator. All In addition, all filters passed the dye test. CONCLUSIONS: Our filter may be of particular importance to those working in low middle-income countries unable to compete with stronger economies. Our design relies on products available outside the healthcare supply chain, much of which can be purchased in grocery stores, hardware stores, or industrial and academic institutions. We hope that these HMEs and viral filters may be beneficial to clinicians who face critical supply chain issues during the COVID-19 pandemic.

Dynamically Tunable Ultrathin Protein Membranes for Controlled Molecular Separation.

Developing the ultrathin membranes for high-performance separation still faces the challenge of both high permeance and selectivity. Herein, a large-area protein membrane was fabricated by the interfacial self-assembly of bovine serum albumin (BSA) and surfactants at the oil/water interface of emulsions. Benefiting from the ultrathin thickness and unique protein-surrounded tortuous channels, the membrane displays ultrahigh permeation flux and selective sieving capability for various molecules ranging from small dye molecules to proteins based on a dual filtration mechanism. More importantly, the rejection precision can also be reversibly regulated by the folding/unfolding transition of proteins to control the effective pore size of transport channels, even under a pressure-driven condition. This dynamically tunable ultrathin protein membrane combines the advantages of high permeance, selectivity, controllability, recyclability, and mechanical stability, which may create new opportunities for advanced applications in extended fields.

Process analytical technology for on-line monitoring of quality attributes during single-use ultrafiltration/diafiltration.

Process analytical technology (PAT) is a fast-growing field within bioprocessing that enables innovation in biological drug manufacturing. This study demonstrates novel PAT methods for monitoring multiple quality attributes simultaneously during the ultrafiltration and diafiltration (UF/DF) process operation, the final step of monoclonal antibody (mAb) purification. Size exclusion chromatography (SEC) methods were developed to measure excipients arginine, histidine, and high molecular weight (HMW) species using a liquid chromatography (LC) system with autosampler for both on-line and at-line PAT modes. The methods were applied in UF/DF studies for the comparison of single-use tangential flow filtration (TFF) cassettes to standard reusable cassettes to achieve very high concentration mAb drug substance (DS) in the order of 100-200 g/L. These case studies demonstrated that single-use TFF cassettes are a functionally equivalent, low-cost alternative to standard reusable cassettes, and that the on-line PAT measurement of purity and excipient concentration was comparable to orthogonal offline methods. These PAT applications using an on-line LC system equipped with onboard sample dilution can become a platform system for monitoring of multiple attributes over a wide dynamic range, a potentially valuable tool for biological drug development and manufacturing.

Streamlining process characterization efforts using the high throughput ambr® crossflow system for ultrafiltration and diafiltration processing of monoclonal antibodies.

Commercial process development for biopharmaceuticals often involves process characterization (PC) studies to gain process knowledge and understanding in preparation for process validation. One common approach to conduct PC activities is by using design-of-experiment, which can help determine the impact process parameter deviations may have on product quality attributes. Qualified scale-down systems are typically used to conduct these studies. For an ultrafiltration/diafiltration (UF/DF) application, however, a traditional scale-down still requires hundreds of milliliters of material per run and can only conduct one experiment at a time. This poses a challenge in resources as there could be 20+ experiments required for a typical UF/DF PC study. One solution to circumvent this is the use of high-throughput systems, which enable parallel experimentation by only using a fraction of the resources. Sartorius Stedim Biotech has recently commercialized the ambr® crossflow high-throughput system to meet this need. In this study, the performance of this system during a monoclonal antibody UF/DF step was first compared with a pilot- and a manufacturing-scale tangential flow filtration (TFF) system at a single operating condition. Due to material limitations, it was then compared to only the pilot-scale TFF system across wider ranges of transmembrane pressure; crossflow rate; and diafiltration concentration in a PC study. Permeate flux, aggregate content, process yield, pH/conductivity traces, retentate concentration, axial pressure drop, and turbidity values were measured at both scales. A good agreement was attained across scales, further supporting its potential use as a scale-down system.

Probing protein rejection behavior of blended PES-based flat-sheet ultrafiltration membranes: A density functional theory (DFT) study.

Membrane fouling is a common problem in membrane technology and causes detrimental effects for the applied membranes such as loss of integrity and productivity. Henceforward, we devoted this work to fabricate membranes that pose favored criteria in the direction of alleviating membrane fouling incidence. Herein, the fabricated membranes were traced via an assortment of both experimental and molecular modeling verifications to understand the mechanism of interaction. To do so, firstly, three different ultrafiltration (UF) membranes had been prepared via facile wet phase inversion method thru dipping a casting solution composed of polyethersulfone-polyvinyl pyrrolidone (PES-PVP) and polyethersulfone-Pluronic P31R1 (PES-P31R1) in a water coagulation bath. Regarding the practical-based data, the pristine PES membrane exhibited the highest rejection of bovine serum albumin (BSA) protein (model foulant) compared with the modified PES-based membranes. The membrane chemical compositions were elucidated with ATR-FTIR Spectroscopy. On the other hand, molecular modeling has been carried out via calculating thermodynamic parameters, level parametric method, and density functional theory (DFT). Thermodynamic parameters analysis indicated that the noticeable difference of BSA rejection may be ascribed to different entropy behavior for the fabricated membranes. In addition, the level parametric method (PM6) and density functional theory DFT: B3LYP with 6-31g (d,p) basis set models clarified the interaction manner of BSA molecules to membrane surfaces.

Fabrication of nanofiltration membrane based on non-biofouling PVP/lecithin nanofibers reinforced with microcrystalline cellulose via needle and needle-less electrospinning techniques.

In this work, polyvinylpyrrolidone nanofibers were electrospun incorporated with lecithin, zero-charge natural segment, as non-biofouling nanofiltration membrane with tunable porous structures. Optimum conditions were studied to obtain nano-pore size capable of nano-scaled objects reduction using needle and needleless electrospinning apparatuses. Fiber diameters were in proportional relationship with PVP concentrations to range from 1.2 um to 34 nm at 10 to 5% wt/v PVP respectively. Microcrystalline cellulose (MCC) was added and PVP fibers were photo-crosslinked to enhance the mechanical strength. Mechanical properties of electrospun fibers were enforced up to 279% in the presence of microcrystalline cellulose while increased by 125% when exposed to photo-crosslinking for 8 h by UV-light radiation. UV-crosslinking has significantly improved the hydrophobicity of the final mat to report contact angle bigger than 90° at 16 h. Protein adhesion test was conducted to indicate the capability of the electrospun membrane to bypass the blood-plasma products. Zero protein adhesion was recorded by adding only 2% wt/v of lecithin.

Filter-Membrane-Based Ultrafiltration Coupled with Surface-Enhanced Raman Spectroscopy for Potential Differentiation of Benign and Malignant Thyroid Tumors from Blood Plasma.

OBJECTIVE: The objective of this study is to evaluate the performance and feasibility of surface-enhanced Raman spectroscopy coupled with a filter membrane and advanced multivariate data analysis on identifying and differentiating benign and malignant thyroid tumors from blood plasma. PATIENTS AND METHODS: We proposed a membrane filter SERS technology for the differentiation between benign thyroid tumor and thyroid cancer. That is to say, by using filter membranes with optimal pore size, the blood plasma samples from thyroid tumor patients were pretreated with the macromolecular proteins being filtered out prior to SERS measurement. The SERS spectra of blood plasma ultrafiltrate obtained using filter membranes from 102 patients with thyroid tumors (70 thyroid cancers and 32 benign thyroid tumors) were then analyzed and compared. Two multivariate statistical analyses, principal component analysis-linear discriminate analysis (PCA-LDA) and Lasso-partial least squares-discriminant analysis (Lasso-PLS-DA), were performed on the SERS spectral data after background subtraction and normalization, as well as the first derivative processing, to analyze and compare the differential diagnosis of benign thyroid tumors and thyroid cancer. RESULTS: SERS measurements were performed in blood plasma acquired from a total of 102 thyroid tumor patients (benign thyroid tumor N=32; thyroid cancer N=70). By using filter membranes, the macromolecular proteins in blood plasma were effectively filtered out to yield high-quality SERS spectra. 84.3% discrimination accuracy between benign and malignant thyroid tumor was achieved using PCA-LDA method, while Lasso-PLS-DA yields a discrimination accuracy of 90.2%. CONCLUSION: Our results demonstrate that SERS spectroscopy, coupled with ultrafiltration and multivariate analysis has the potential of providing a non-invasive, rapid, and objective detection and differentiation of benign and malignant thyroid tumors.

Multi-attribute PAT for UF/DF of Proteins-Monitoring Concentration, particle sizes, and Buffer Exchange.

Ultrafiltration/diafiltration (UF/DF) plays an important role in the manufacturing of biopharmaceuticals. Monitoring critical process parameters and quality attributes by process analytical technology (PAT) during those steps can facilitate process development and assure consistent quality in production processes. In this study, a lab-scale cross-flow filtration (CFF) device was equipped with a variable pathlength (VP) ultraviolet and visible (UV/Vis) spectrometer, a light scattering photometer, and a liquid density sensor (microLDS). Based on the measured signals, the protein concentration, buffer exchange, apparent molecular weight, and hydrodynamic radius were monitored. The setup was tested in three case studies. First, lysozyme was used in an UF/DF run to show the comparability of on-line and off-line measurements. The corresponding correlation coefficients exceeded 0.97. Next, urea-induced changes in protein size of glucose oxidase (GOx) were monitored during two DF steps. Here, correlation coefficients were ≥ 0.92 for static light scattering (SLS) and dynamic light scattering (DLS). The correlation coefficient for the protein concentration was 0.82, possibly due to time-dependent protein precipitation. Finally, a case study was conducted with a monoclonal antibody (mAb) to show the full potential of this setup. Again, off-line and on-line measurements were in good agreement with all correlation coefficients exceeding 0.92. The protein concentration could be monitored in-line in a large range from 3 to 120 g L- 1. A buffer-dependent increase in apparent molecular weight of the mAb was observed during DF, providing interesting supplemental information for process development and stability assessment. In summary, the developed setup provides a powerful testing system for evaluating different UF/DF processes and may be a good starting point to develop process control strategies. Graphical Abstract Piping and instrumentation diagram of the experimental setup and data generated by the different sensors. A VP UV/Vis spectrometer (FlowVPE, yellow) measures the protein concentration. From the data of the light scattering photometer (Zetasizer, green) in the on-line measurement loop, the apparant molecular weight and z-average are calculated. The density sensor (microLDS) measures density and viscosity of the fluid in the on-line loop.

Development of a scalable procedure by a discontinuous crossflow DF/UF to obtain a concentrate of chenopodin from a dead-end centrifugal UF at bench scale.

The aim of this study was to develop a scalable crossflow diafiltration/ultrafiltration procedure for quinoa 11S globulin purification starting at the bench scale using Ultra15 centrifugal filter devices. The electrophoretic profiles of centrifugal ultrafiltration fractions showed a high heterogeneity in the bands, while crossflow ultrafiltration reduced the phenomena of protein sticking to the membrane, avoiding aggregate formation. In the crossflow protein concentration, flux decline curves were studied according to Hermia's fouling mechanisms and the resistance in a series model. High reversible resistance was related to external mechanisms due to complete blockage of the membrane surface followed by cake formation. The crossflow ultrafiltration was the most efficient technique for obtaining 57 kDa chenopodin isolate with higher processing capacity, purity and protein yield. The diafiltration/ultrafiltration process proved to be adequate and easy to handle to scale up the production of the 11S quinoa globulin.

Characterization and influence of floc under different coagulation systems on ultrafiltration membrane fouling.

A hybrid system was developed in this study consisting of different coagulation systems and ultrafiltration (UF). Property and effect of flocs formed in different coagulation systems on ultrafiltration membrane fouling control were investigated. All three coagulation systems, as pretreatment of UF, were effective in improving membrane flux and reducing membrane resistance within an appropriate range of natural organic matters (NOM) concentration. At high initial NOM concentration, the performance of polyaluminum chloride (PAC) on NOM removal and fouling control was severely limited. For PAC-poly dimethyl diallyl ammonium chloride (PAC-PolyDMDAAC) coagulation system, the limitation of initial NOM concentration on removing NOM and alleviating membrane fouling was slightly weakened, indicating composite flocculant PAC-PolyDMDAAC produced larger flocs through combined action of charge neutralization and adsorption bridging. In PAC + PolyDMDAAC dual coagulation system, the combined action of adsorption-bridging effect, sweeping effect, and charge neutralization were the mechanisms under both low and high initial NOM concentration. Although the flocs formed in PAC + PolyDMDAAC dual coagulation system had poor recovery ability compared with those formed in PAC and PAC-PolyDMDAAC coagulation system, flocs formed through adsorption-bridging and sweeping had large size and higher ability to resist shear force, resulting in the formation of cake layer with porous and fluffy structure and less blockage in membrane pore in PAC + PolyDMDAAC dual coagulation system. These results demonstrated that dual coagulation system combined PAC coagulation and PolyDMDAAC flocculation as a pretreatment of UF process can improve the characteristics of flocs and structure of cake layer for improving NOM removal and controlling membrane fouling.

Detection of Cryptosporidium Recovered from Large-Volume Water Samples Using Dead-End Ultrafiltration.

The procedure described here provides instructions for detection of Cryptosporidium recovered from large-volume water samples. Water samples are collected by dead-end ultrafiltration in the field and ultrafilters are processed in a laboratory. Microbes recovered from the filters are further concentrated and subjected to Cryptosporidium isolation or nucleic acid extraction methods for the detection of Cryptosporidium oocysts or Cryptosporidium DNA.

Membrane fouling control by Ca2+ during coagulation-ultrafiltration process for algal-rich water treatment.

Seasonal algal bloom, a water supply issue worldwide, can be efficiently solved by membrane technology. However, membranes typically suffer from serious fouling, which hinders the wide application of this technology. In this study, the feasibility of adding Ca2+ to control membrane fouling in coagulation-membrane treatment of algal-rich water was investigated. According to the results obtained, the normalized membrane flux decreased by a lower extent upon increasing the concentration of Ca2+ from 0 to 10 mmol/L. Simultaneously, the floc particle size increased significantly with the concentration of Ca2+, which leads to a lower hydraulic resistance. The coagulation performance is also enhanced with the concentration of Ca2+, inducing a slight osmotic pressure-induced resistance. The formation of Ca2+ coagulation flocs resulted in a looser, thin, and permeable cake layer on the membrane surface. This cake layer rejected organic pollutants and could be easily removed by physical and chemical cleaning treatments, as revealed by scanning electron microscopy images. The hydraulic irreversible membrane resistance was significantly reduced upon addition of Ca2+. All these findings suggest that the addition of Ca2+ may provide a simple-operation, cost-effective, and environmentally friendly technology for controlling membrane fouling during coagulation-membrane process for algal-rich water treatment.

Understanding the differences in cheese-making properties between reverse osmosis and ultrafiltration concentrates.

Concentrating milk by reverse osmosis (RO) has the potential to increase cheese yield but is known to impair cheese-making properties. The main compositional differences between ultrafiltration (UF) and RO concentrates are the high lactose and mineral contents of the latter. The objective of this work was to determine the distinct effects of high lactose and high minerals on the cheese-making properties of RO concentrate, by supplementing UF concentrate with lactose. The soluble colloidal equilibria of concentrates were studied as well as several other properties: rennet gelation behavior, cheese mass balance, composition, and microstructure. Rennet coagulation time was longer and gel firming rate was lower for RO concentrate than for UF concentrate. Lactose was mainly responsible for these differences. Lactose in RO concentrate was also responsible for the 7% increase of moisture-adjusted cheese yield, relative to UF concentrate. Compared with cheese made from UF concentrate, cheese made from RO concentrate showed higher moisture content, which could not be attributed to lactose but to the high mineral concentration. This study showed the potential of using RO instead of UF concentrate to maximize cheese yield. The approach is, however, limited to applications where post-acidification can be controlled, and will require appropriate strategies to reduce the negative effects of high mineral content in RO concentrate.

Continuous ultrafiltration/diafiltration using a 3D-printed two membrane single pass module.

A 3D printed ultrafiltration/diafiltration (UF/DF) module is presented allowing the continuous, simultaneous concentration of retained (bio-)molecules and reduction or exchange of the salt buffer. Differing from the single-pass UF concepts known from the literature, DF operation does not require the application of several steps or units with intermediating dilution. In contrast, the developed module uses two membranes confining the section in which the molecules are concentrated while the sample is passing. Simultaneously to this concentration process, the two membranes allow a perpendicular in and outflow of DF buffer reducing the salt content in this section. The module showed the continuous concentration of a dissolved protein up to a factor of 4.6 while reducing the salt concentration down to 47% of the initial concentration along a flow path length of only 5 cm. Due to single-pass operation the module shows concentration polarization effects reducing the effective permeability of the applied membrane in case of higher concentration factors. However, because of its simple design and the capability to simultaneously run UF and DF processes in a single module, the development could be economically beneficial for small scale UF/DF applications.

Economic model for obtaining cyclodextrins from commercial cgtase

A repetitive batch process was employed followed by membrane ultrafiltration system to produce low-cost cyclodextrins (CDs) using commercial enzymes Toruzyme® cyclomaltodextrin glucanotransferase (CGTase) and its kinetic parameters were determined. The ultrafiltration system enabled the removalof inhibitory products from the reaction medium, allowing the enzyme to be recovered for reuse. A 10 kDa membrane was used to separate the different CDs produced by the CGTase. The substrates evaluated were maltodextrin, corn starch and cassava starch at 5, 10 and 15% (w/V), in the presence and absence of 10% (V/V) ethanol. After reaction for 132 h, 10% (w/V) cassava starch in the presence of ethanol provided the best results with 32.1 mg/mL of ß-CD. Maximum production occurred after 72 h of reaction, with a yield of 87.4% of ß-CD and an α-CD, ß-CD and γ-CD production ratio of 1:1:0.08 g, respectively. When eight repetitive batches of 72 h followed by ultrafiltration and crystallization of ß-CD were performed, 2.1 g of precipitate was obtained with a purity of 67.6% ß-CD. The supernatant from the crystallization process was lyophilized and resulted in 35.3% α-CD. The developed model can be used industrially for the production of low cost CDs from easily obtained raw material

Molecular traits of phenolic moieties in dissolved organic matter: Linkages with membrane fouling development.

Phenolic moieties are important constituents in dissolved organic matter (DOM) in natural and engineered systems. However, their roles in membrane fouling mechanism during drinking water treatment by ultrafiltration (UF) have remained elusive. Herein, by using water insoluble polyvinylpolypyrrolidone (PVPP) resins, we sequestered the phenolic moieties from a model DOM (Suwannee River DOM, SRDOM) and characterized their molecular profiles using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). Subsequently, their roles in UF membrane fouling propensity were investigated using reconstituted DOM solutions with various concentrations of phenolic moieties. The results showed that the phenolic moieties were of higher molecular weight and rich in unsaturation cyclic structures and oxygen-rich groups. Van Krevelen diagrams revealed that the sequestered sample was rich in aromatics structures and tannins-like compounds while contained less alicyclic organic acids in comparison with the original SRDOM, which was consistent with the aromaticity index (AI) analysis. UF experiments showed that the more phenolic moieties in DOM solution, the severer decline of flux was observed. The phenolic moieties played a significant role in membrane irremovable fouling due to the hydrophobic interactions and their higher molecular weight as evidenced by membrane cleaning tests. By surface characterization, the SRDOM fouled membrane was identified to have a higher water contact angle value and abundant C-O groups, likely due to the adsorption of more hydrophobic phenolic moieties. Overall, these findings highlighted links between phenolic moieties and membrane fouling development, and implied that membrane performance could be improved by pre-removal of phenolic moieties in DOM.

Quantitative analysis of cake characteristics based on SEM imaging during coagulation-ultrafiltration process.

Cake formed by flocs is a crucial factor to affect membrane fouling during coagulation-ultrafiltration process. To investigate the role of floc properties on cake, cake characteristics under various coagulant dosage conditions were calculated by scanning electron microscope (SEM) imaging. Results found that one SEM image with × 5000 magnification could accurately estimate cake porosity with relative error lower than 5.00% for all conditions, whereas more SEM images with × 10,000 magnification or × 20,000 magnification should be applied to calculate cake porosity precisely. This could be explained by different pore information of SEM images with various magnifications. Compared to single SEM image with × 10,000 magnification and × 20,000 magnification, single SEM image with × 5000 magnification contained the most comprehensive pore information and slightly overestimated pore area for pore smaller than 0.4 µm2 due to lower resolution. To verify feasibility by SEM image evaluating cake characteristics, cake porosity calculated by SEM image and Carman-Kozeny equation were analyzed. The results showed that cake porosity estimated by these two methods were nearly the same, proving the feasibility of this method. Moreover, with the increase of coagulant dosage, cake porosity presented similar variation with floc average size, indicating that floc average size was likely to dominate cake porosity in this study. For pore characteristics, pore average characteristic length and pore average area were in accordance with floc fractal dimension, whereas pore fractal dimension and pore amount were consistent with floc average size. This gives specific information about the relation between floc properties and cake characteristics.