Ultrafiltration Control Research Articles

Continuous Organic Characterization for Biological and Membrane Filter Performance Monitoring

Continuous organic characterization at a full‐scale drinking water treatment plant was achieved using fluorescence spectroscopy. The feasibility of this method was demonstrated through monitoring the performance of biological activated carbon contactors (BACCs), which serve as pretreatment for fouling control of ultrafiltration (UF) membranes. Fluorescence monitoring was applied successfully to identify the preferential removal of select fluorescence components and addition of another microbial humic‐like component by the biological filters. Spikes in BACC influent organic matter and fouling development on the downstream UF membranes highlighted the importance of preozonation. To demonstrate possible use of the short‐term continuous fluorescence data, neural networks were used to predict fouling development on downstream UF on the basis of BACC effluent water quality. Short‐term fluctuations in fouling development were well predicted by incorporation of continuous fluorescence characterization data. Continuous organic characterization shows promise for the application of fluorescence spectroscopy for real‐time process optimization and control in drinking water treatment systems.

Control of ultrafiltration membrane fouling caused by algal extracellular organic matter (EOM) using enhanced Al coagulation with permanganate

Abstract This work was aimed to investigate the mechanism for the control of ultrafiltration (UF) membrane fouling caused by algal extracellular organic matter (EOM) using permanganate enhanced aluminum (Al) coagulation. Impacts of Al coagulation, permanganate (KMnO 4 )-aided Al coagulation and in-situ formed manganese oxide (MnO 2 )-aided coagulation on EOM fouling evolution were compared with respect to EOM characteristics and fouling indexes. The Al coagulation using polymeric aluminum (0.4 mg Al mg −1 DOC) alone substantially alleviated the flux decline caused by EOM via reducing organic amounts by 18% and preferentially removing the high-molecular-weight (MW) (>100 kDa) components of EOM. The KMnO 4 -aided Al coagulation obtained even better organic removal than the Al coagulation, especially for the fluorescent components of EOM, due to oxidative degradation and adsorption provided by manganese oxide, and thus resulted in the improved performance in fouling control. The best membrane permeability and fouling reversibility were achieved by the MnO 2 -aided Al coagulation, probably attributed to adsorption of the hydrophilic fractions of EOM on in-situ formed MnO 2 particles. In terms of fouling mechanisms, EOM fouling was governed by multiple mechanisms with standard blocking and cake filtration dominating the fouling formation. The enhanced Al coagulation with KMnO 4 or in situ formed MnO 2 particles decreased the role of cake filtration but boosted the impact of standard blocking by preferentially removing the high-MW biopolymers.

Processing used nuclear fuel with nanoscale control of uranium and ultrafiltration

Current separation and purification technologies utilized in the nuclear fuel cycle rely primarily on liquid–liquid extraction and ion-exchange processes. Here, we report a laboratory-scale aqueous process that demonstrates nanoscale control for the recovery of uranium from simulated used nuclear fuel (SIMFUEL). The selective, hydrogen peroxide induced oxidative dissolution of SIMFUEL material results in the rapid assembly of persistent uranyl peroxide nanocluster species that can be separated and recovered at moderate to high yield from other process-soluble constituents using sequestration-assisted ultrafiltration. Implementation of size-selective physical processes like filtration could results in an overall simplification of nuclear fuel cycle technology, improving the environmental consequences of nuclear energy and reducing costs of processing.

Membrane fouling control and performance enhancement of ultrafiltration of latex effluent

AbstractThe objective of the present study was to minimize membrane fouling of a latex solution either through improving the membrane surface charge or using a pretreated feed. Hydrophilic polysulphone (PSU) and Ultrafilic flat membranes, with a molecular weight cut‐off (MWCO) of 60 000 and 100 000 dalton, respectively, were implemented under a constant flow rate and cross‐flow mode in ultrafiltration of simulated latex effluent. Hydrophobic polyvinylidene difluoride membrane (PVDF) with a MWCO of 100 000 dalton was also tested. The influence of linear alkyl benzene sulphonate (LAS) on the ionic strength of the simulated latex effluent and the surface charge of latex particles at different LAS concentrations was investigated. LAS was also used, at different concentrations and various treatment times, to ensure the enhancement of the antifouling characteristics of the membrane surface. It was concluded that the LAS‐treated membrane surface is much more favourable than the pH‐changed feed pre‐treatment. As such, the total mass of fouling decreased by 44.00 % and 29.60 % in the cases of treated PVDF membrane surface with LAS at a concentration of 0.0001 g/L, and treated latex feed at pH 11, respectively. Nevertheless, LAS was considered to be an ineffective pre‐treatment for limiting the fouling propensity of latex solutions using hydrophilic membranes even at high concentrations and long treatment times.

Effect of soluble and insoluble gas bubbling methods on ultrafiltration fouling control

Fouling phenomenon is well known as a main obstacle in membrane separation technology. In this study, the effects of bubbling with various hydrodynamic factors and gas–liquid solubility were evaluated on fouling control and permeation flux in ultrafiltration of skimmed milk solution. Direct gas injection and carbonated feed, as a new bubbling method, were used for bubbling. In the direct gas injection technique, various two-phase flow patterns (slug and bubble), gas flow rates, and bubbling modes (continuous and intermittent) were investigated during a cross-flow ultrafiltration. The results showed that the both of gas bubbling methods improved the permeation flux during 30-min filtration. The permeation flux was enhanced up to 72 and 40% by direct injecting of N2 and CO2, respectively, while it was only enhanced up to 58% with carbonated feed. The evaluation of hydrodynamic resistance of membranes indicated that the gas bubbling by carbonated feed was more effective on the fouling resistance, while the cake resistance was affected by the gas injection during infiltration. In addition, the slug flow pattern was more effective than the bubble flow pattern on decline of membrane fouling. In the slug flow pattern, the permeate flux increased when medium flow rate was applied. Furthermore, ultrafiltration performance was improved using the intermittent gas bubbling mode. This study indicated that slug flow pattern with insoluble gas has a higher performance than the other ones in preventing fouling and flux enhancement during ultrafiltration processing.

Enhanced Wettability and Transport Control of Ultrafiltration and Reverse Osmosis Membranes with Grafted Polyelectrolytes.

End-functionalized poly(acrylic acid) (PAA-silane) was synthesized with reversible addition-fragmentation chain-transfer (RAFT) polymerization and attached to both polysulfone ultrafiltration (UF) and polyamide reverse osmosis (RO) membranes through a nonimpairing, one-step grafting to approach in order to improve membrane surface wettability with minimal impact on membrane transport performance. After PAA grafting, composition and morphology changes on the membrane surface were characterized with Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Static contact angle on PAA grafted membranes exhibited an increase in surface hydrophilicity and hence a potential enhancement in antifouling performance. The native contact angle on the polysulfone membrane systems was 86° and was reduced to 24° after modification, while the polyamide film contact angle decreased from 58° to 25°. The PAA layer endowed the porous UF membrane with dynamic control over the permeability and selectivity through the manipulation of the solution pH. The UF membrane with a 35 nm average pore size displayed a 115% increase in flux when the contact solution was changed from pH 11 to pH 3. This effect was diminished to 70% and 32% as the average pore size decreased to 20 and 10 nm, respectively. Modified RO membranes displayed no reduction in membrane performance indicating that the underlying materials were unaffected by the modification environment or added polymer. Model polyamide and polysulfone surfaces were reacted with the PAA-silane inside a quartz crystal microbalance (QCM) to help inform the deposition behavior for the respective membrane chemistries.

Concordance of absolute and relative plasma volume changes and stability of Fcells in routine hemodialysis.

Central hematocrit (H) measurements are currently used to track the degree of ultrafiltration-induced hemoconcentration with the aim to detect and prevent excessive intravascular fluid depletion during hemodialysis (HD). Failure to maintain hemodynamic stability is commonly attributed to the misinterpretation of H caused by an unaccountable increase in Fcells , the ratio of whole-body hematocrit to H. It was the aim to examine Fcells under everyday conditions in a group of stable HD patients. Absolute plasma volume (Vp ) and H were concomitantly measured during routine HD in the extracorporeal system in hourly intervals by noninvasive and continuous technology (CritLine-Instrument-III) and indocyanine green dye dilution to derive relative plasma volumes from Vp and H (RPVp , RPVH ), respectively, and to calculate Fcells . Thirteen patients were studied during two midweek treatments (n = 26). Both absolute Vp (P < 0.05) and relative plasma volumes RPVH (P < 0.001) decreased during HD. Vp at any time point was positively correlated to RPVH (r = 0.52). Moreover, relative plasma volumes RPVH and RPVp determined by independent techniques were identical and showed negligible bias (-0.2%) but considerable limits of agreement (-15.6% to +15.3%). Fcells was stable and in the range of 0.9 ± 0.05 throughout HD and not different from the value assumed at the beginning of HD. Although Fcells remains constant in patients on routine dialysis and relative plasma volumes (RPVH and RPVp ) determined by independent techniques are therefore comparable, the variability of experimental conditions during dialysis and the limited accuracy of absolute volume measurements using available technology continues to complicate the ultrafiltration control problem.

Fouling control in ultrafiltration of bovine serum albumin and milk by the use of permanent magnetic field

Membrane separation processes are widely employed for protein concentration in the food industry. The major drawback is permeability reduction caused by concentration polarization and fouling. The present work evaluated the influence of a permanent magnetic field applied to the ultrafiltration process (UF) of protein solutions, as an alternative to improve the permeation performance and the permeability recovery. Permeation tests of bovine serum albumin (BSA) and milk as the feed protein solutions through a 50kDa hydrophilic polyethersulfone (PES) membrane were carried out in a tangential flow module. The feed pH was varied (4.0, 6.5 and 8.0) and ionic strength was modified by sodium chloride (NaCl). Permanent magnets were placed so as to obtain a maximum 0.7T magnetic field perpendicular to the membrane surface. The magnetic induction effect (MI) on the feed solutions was also studied by submitting the feed to the magnetic field for 2h before permeation run. The presence of magnetic field and the MI effect of the solution were effective in increasing both the permeate flux and the recovery of hydraulic permeability. The magnetic field application in the UF of protein solutions has proven to be an attractive alternative for improving process performance.

Separation of surfactants from water by granular activated carbon/ultrafiltration hybrid process

The aim of the study was to determine the efficiency granular activated carbon (GAC) as foul control in ultrafiltration (UF) membrane process. The adsorptive parameters for triton x-100, sodium dodecylbenzene sulfonate (SDBS), and N-dodecylpyridinium chloride on GAC were determined. The equilibrium data fit well to Langmuir adsorption isotherm rather than Freundlich model. Breakthrough curves were obtained from fixed bed experiments, and column parameter was calculated from it. For UF membrane alone and GAC/UF hybrid process, the percent retentions of the selected surfactants under study were determined and the declines in flux were observed. The percent retention was 4, 10, and 22 % for N-dodecylpyridinium chloride, SDBS, and triton x-100, respectively. In the presence of adsorbent, the improved percent retention was 87, 95, and 98 % for triton x-100, SDBS, and N-dodecylpyridinium chloride, respectively. The problems already reported for powdered activated carbon such as cake formation over membrane surface, long backwash time, and blackening of pipes were not observed for GAC.

Assessing the interaction effects of coagulation pretreatment and membrane material on UF fouling control using HPSEC combined with peak-fitting

In this paper, the effects of alum coagulation pretreatment on the removal of natural organic matter (NOM) from surface water, and on fouling control of the subsequent ultrafiltration (UF) membrane filtration, were studied. Two kinds of UF membrane, made from polyvinyl chloride (PVC) and cellulose acetate (CA), respectively, were tested. The dissolved organics were characterized by high performance size exclusion chromatography (HPSEC) with ultraviolet/visible (UV/vis) and dissolved organic carbon (DOC) detectors, in addition to the conventional organic parameters, such as nonpurgeable dissolved organic carbon (NPDOC) and UV254. The results show that coagulation pretreatment could reduce the flux decline of UF membrane filtration by removing some of the NOM. Alum coagulation was found to have higher removal for large molecular weight organics, such as biopolymers and humic substances, than for low molecular weight acids. The results from HPSEC revealed that the PVC membrane removed mainly the biopolymer fraction, while the CA membrane, in addition to biopolymers, also removed some of the more hydrophilic low molecular weight acids. As alum coagulation preferably removed biopolymers over low molecular weight acids, pre-coagulation had less effect on CA membrane flux decline control than on PVC membrane flux decline control.

Haemodialysing babies weighing &lt;8 kg with the Newcastle infant dialysis and ultrafiltration system (Nidus): comparison with peritoneal and conventional haemodialysis

BackgroundTo compare the efficacy of the Newcastle infant dialysis and ultrafiltration system (Nidus) with peritoneal dialysis (PD) and conventional haemodialysis (HD) in infants weighing <8 kg.MethodsWe compared the urea, creatinine and phosphate clearances, the ultrafiltration precision, and the safety of the Nidus machine with PD in 7 piglets weighing 1–8 kg, in a planned randomised cross-over trial in babies, and in babies for whom no other therapy existed, some of whom later graduated to conventional HD.ResultsTwo babies entered the randomised trial; 1 recovered rapidly on PD, the other remained on the Nidus as PD failed. Additionally, 9 babies were treated on the Nidus on humanitarian grounds: 3 because of failed PD, and 3 with permanent kidney failure later converted to conventional HD. We haemodialysed 10 babies weighing between 1.8 and 5.9 kg for 2,475 h during 354 Nidus sessions without any clinically important incidents, and without detectable haemolysis. Single-lumen vascular access was used with no blood priming of circuits. The urea, creatinine and phosphate clearances using the Nidus were around 1.5 to 2.0 ml/min in piglets and babies, and were consistently higher than PD clearances, which ranged from about 0.2 to 0.8 ml/min (p ≤ 0.0002 for each chemical). Ultrafiltration was achieved to microlitre precision by the Nidus, but varied widely with PD. Fluid removal using conventional HD was imprecise and resulted in some hypovolaemic episodes requiring correction.ConclusionThe Nidus can provide HD in the Pediatric Intensive Care Unit (PICU) and outpatient intermittent HD without blood priming for babies weighing <8 kg, It generates higher dialysis clearances than PD, and delivers more precise ultrafiltration control than either PD or conventional HD.

Continuous renal replacement therapy in neonates and small infants: development and first-in-human use of a miniaturised machine (CARPEDIEM)

Peritoneal dialysis is the renal replacement therapy of choice for acute kidney injury in neonates, but in some cases is not feasible or effective. Continuous renal replacement therapy (CRRT) machines are used off label in infants smaller than 15 kg and are not designed specifically for small infants. We aimed to design and create a CRRT machine specifically for neonates and small infants. We prospectively planned a 5-year project to conceive, design, and create a miniaturised Cardio-Renal Pediatric Dialysis Emergency Machine (CARPEDIEM), specifically for neonates and small infants. We created the new device and assessed it with in-vitro laboratory tests, completed its development to meet regulatory requirements, and obtained a licence for human use. Once approved, we used the machine to treat a critically ill neonate The main characteristics of CARPEDIEM are the low priming volume of the circuit (less than 30 mL), miniaturised roller pumps, and accurate ultrafiltration control via calibrated scales with a precision of 1 g. In-vitro tests confirmed that both hardware and software met the specifications. We treated a 2·9 kg neonate with haemorrhagic shock, multiple organ dysfunction, and severe fluid overload for more than 400 h with the CARPEDIEM, using continuous venovenous haemofiltration, single-pass albumin dialysis, blood exchange, and plasma exchange. The patient's 65% fluid overload, raised creatinine and bilirubin concentrations, and severe acidosis were all managed safely and effectively. Despite the severity of the illness, organ function was restored and the neonate survived and was discharged from hospital with only mild renal insufficiency that did not require renal replacement therapy. The CARPEDIEM CRRT machine can be used to provide various treatment modalities and support for multiple organ dysfunction in neonates and small infants. The CARPEDIEM could reduce the range of indications for peritoneal dialysis, widen the range of indications for CRRT, make the use of CRRT less traumatic, and expand its use as supportive therapy even when complete renal replacement therapy is not indicated. Associazione Amici del Rene di Vicenza.

Performance of mesoporous adsorbent resin and powdered activated carbon in mitigating ultrafiltration membrane fouling caused by algal extracellular organic matter

This paper focused on the control of ultrafiltration (UF) membrane fouling caused by extracellular organic matter (EOM) extracted from Microcystis aeruginosa through pretreatment with mesoporous adsorbent resin (MAR) and powdered activated carbon (PAC). The influence of MAR and PAC pretreatments on characteristics of EOM was investigated using molecular weight (MW) fractionation, DAX-8/XAD-4 resin fractionation and fluorescence excitation-emission matrix (EEM) spectroscopy. The results suggested that MAR mainly removed high-MW (>100kDa) fraction of EOM, while PAC primarily adsorbed low-MW (<1kDa) fraction. Both MAR and PAC adsorption removed more hydrophobic fraction than hydrophilic fraction. UF experiments were carried out to evaluate the efficacies of MAR and PAC pretreatments in EOM fouling control. MAR pretreatment significantly reduced the reversible fouling due to the efficient removal of high-MW fraction and the consequent reduction of cake formation; whereas PAC exhibited little ability in alleviating the reversible fouling. Nevertheless, the irreversible fouling, which accounted for a small part of the total fouling, was mitigated by both MAR and PAC pretreatments because they both reduced irreversible adhesion caused by hydrophobic EOM. Overall, with respect to EOM fouling control, MAR was much more efficient than PAC.

Removal of Synthetic Organic Foulants by Granular Activated Carbon Filters and Ultrafiltration Membrane

Abstract In this study granular activated carbon (GAC) was used as pretreatment for foul control in ultrafiltration (UF) membrane process. First the adsorptive parameters for phenol, chlorophenol, nitrophenol and hydroquinone on GAC were determined. The equilibrium data fits well to Langmuir adsorption isotherm rather than Freundlich model. Breakthrough curves were obtained from fixed bed experiments and column parameter were calculated from it. GAC filters were then used in combination with UF membrane system. The percent retentions of the four organic substances under study were determined and the declines in flux were observed. The problems associated with powdered activated carbon like cake formation over membrane surface, long back wash time and blackening of pipes were not observed for GAC.

Practical experience of backwashing with SWRO permeate for UF fouling control

Effectiveness of seawater reverse osmosis (SWRO) permeate backwash on fouling control of seawater ultrafiltration was investigated at a pilot scale. A standard membrane module was used in this pilot to represent full-scale desalination plants. Results of the pilot show a good reproducibility. When the UF permeate was used for backwash, the frequency of chemically enhanced backwash (CEB) was around once per day. However, results of the pilot show that SWRO permeate backwashing could significantly reduce the CEB frequency.

Seawater ultrafiltration fouling control: Backwashing with demineralized water/SWRO permeate

In this study, the effect of demineralized water backwashing on fouling control of seawater ultrafiltration was investigated. Seawater from Scheveningen beach in The Hague and a desalination plant of Evides Company at Zeeland in the Netherlands was used as feed water, while demineralized water and UF permeate were used as backwash water for a fouling control efficiency comparison under different fluxes and backwash durations. Furthermore, demineralized waters with 5 or 50mmol/l NaCl were applied for backwashing as well, to check the influence of monovalent cations on UF fouling control. Additionally, SWRO permeate was used for backwashes in long-term experiments to check the possibility of it replacing demineralized water.Results show that seawater UF fouling control is substantially improved by demineralized water backwashing. However, due to the high salinity of seawater, more water was required to dilute the cation concentration and limit the dispersion effect near the membrane surface than was needed for surface water. A 2-min demineralized water backwash showed better fouling control efficiency than a 1-min backwash. Furthermore, the presence of monovalent cations in the backwash water deteriorated the fouling control efficiency of the backwash, indicating the existence of a charge screening effect. The demineralized water with 5 and 50mmol/l NaCl both showed a similar fouling control efficiency which is better than the UF permeate backwash. The calcium ions in UF permeate probably deteriorates the fouling control efficiency by maintaining a Ca-bridging effect between the membranes and NOM. SWRO permeate backwashing successfully controls membrane fouling as well.

Ultrafiltration control during haemodialysis

Haemodialysis (HD)-induced hypotension is still a severe complication in spite of all the progress in HD treatment. Because of its multifactor causes, HD-induced hypotension cannot be reliably prevented by conventional Ultrafiltration (UF) and sodium profiling in open-loop systems, as they are unable to adapt themselves to actual decreases in Blood Pressure (BP). Therefore, the ultimate goal of this paper is to build a biofeedback system dynamics software to provide automatic control of UF during HD. Furthermore, the treatment should improve patient comfort and be carried out without use of additional body sensors and without additional medication.

Removal of Phenolic Substances from Water by Adsorption and Adsorption-Ultrafiltration

In this work a magnetic adsorbent, magnetic activated carbon (MAC) was prepared and characterized by powdered X-Ray diffraction (XRD). A comparison was made between powdered activated carbon (PAC) and MAC for foul control in ultrafiltration (UF) membrane processes. First, the adsorptive parameters for PAC and MAC were determined for phenol, chlorophenol, nitrophenol, and hydroquinone. Equilibrium data fitted well to the Langmuir model in the studied concentration range of the adsorbates. Adsorption kinetics followed a pseudo second-order kinetic model rather than pseudo first-order kinetic model. These adsorbents were then used in combination with UF membrane. The parameters like percent rejection and flow rate for the hybrid UF/PAC and UF/MAC were determined. The influences of both adsorbents on flow rates and percent rejections were almost equal. The problems associated with PAC in the UF processes like cake formation and blackening of the pipes were not observed for MAC. MAC was removed from the slurry after use through a magnetic process.

Foothold of NPHS2 mutations in primary nephrotic syndrome

Glomerular podocytes are highly specialized cells with a complex cytoarchitecture. Their most prominent features are interdigitated foot processes with filtration slits in between. These are bridged by the slit diaphragm, which plays a major role in establishing the selective permeability of the glomerular filtration barrier. We searched Medline and Pubmed using the combination of keywords "NPHS2", "podocin", "steroid-resistant nephrotic syndrome," and "genetics" to identify studies describing an association between NPHS2 gene and renal disease. The highly dynamic foot processes contain an actin-based contractile apparatus comparable to that of smooth muscle cells. Mutations affecting several podocyte proteins lead to rearrangement of the cytoskeleton, disruption of the filtration barrier, and subsequent renal disease. The fact that the dynamic regulation of the podocyte cytoskeleton is vital to kidney function has led to podocytes emerging as an excellent model system for studying actin cytoskeleton dynamics in a physiological context. Injury to podocytes leads to proteinuria, a hallmark of most glomerular diseases. Recent studies have led to a considerable increase in our understanding of podocyte biology including composition and arrangement of the cytoskeleton involved in the control of ultrafiltration. Moreover, disturbances of podocyte architecture resulting in the retraction of foot processes and proteinuria appear to be a common theme in the progression of an acquired glomerular disease. In hereditary nephrotic syndromes identified over the last few years, all mutated gene products were localized in podocytes. This review integrates our recent physiological and molecular understanding of the role of podocytes during the maintenance and failure of the glomerular filtration barrier.

Why does a mineral oxide adsorbent control fouling better than powdered activated carbon in hybrid ultrafiltration water treatment?

This work focused on the role and effect of adsorbents on natural organic matter (NOM) removal and fouling control in ultrafiltration (UF) membrane systems for water treatment. Two adsorbents, ferrihydrite (FH) and powdered activated carbon (PAC) were compared in terms of the degree of fouling control under the condition where the same amount of dissolved organic carbon (DOC) was removed. The influence of adsorbent cake layers on water permeability was investigated by comparing the UF performance in the presence and absence of adsorbents dosed. Although the same level of DOC removal efficiency was achieved by the two adsorbents, the reduction in fouling varied significantly depending on the size of membrane pores employed. It was found that adsorbent-specific interaction with NOM molecules having multi-dispersed, heterogeneous property may be responsible for different fouling behaviors in ultrafiltration water treatment. The attachment of NOM to PAC particles led to an increase in the cake layer resistance, whereas the reverse happened with NOM-laden FH particles. Scanning electronic microscopy was not able to exhibit the difference in the degree of fouling during UF of lake water that was pretreated with different adsorbents. The membrane fractionation of lake water NOM molecules employed to characterize their size distributions confirmed which portion of NOM present in lake water was removed preferentially by adsorbents, leading to fouling reduction. This helped to interpret and control the fouling behavior when adsorbents were added to the membrane processes.