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PubMedDate not supplied

[Regeneration of sanitaro-hygienic water during long space flights by reverse osmosis].

Experiments on the purification of wash water by means of reverse osmosis membranes MGA-100 were performed. The membrane selectivity with respect to the major components (catamine AB, amine oxide and sodium chloride) was close to 100% whereas membrane permeability was not lower than 70% that of distilled water. The results of a field study in which 330 1 of repeatedly used wash water were reclaimed showed that reverse osmosis can be effectively employed for that purpose.

Membranes, Artificial↗

PubMed2006

The Role of the Tight Junction in Paracellular Fluid Transport across Corneal Endothelium. Electro-osmosis as a Driving Force.

The mechanism of epithelial fluid transport is controversial and remains unsolved. Experimental difficulties pose obstacles for work on a complex phenomenon in delicate tissues. However, the corneal endothelium is a relatively simple system to which powerful experimental tools can be applied. In recent years our laboratory has developed experimental evidence and theoretical insights that illuminate the mechanism of fluid transport across this leaky epithelium. Our evidence points to fluid being transported via the paracellular route by a mechanism requiring junctional integrity, which we attribute to electro-osmotic coupling at the junctions. Fluid movements can be produced by electrical currents. The direction of the movement can be reversed by current reversal or by changing junctional electrical charges by polylysine. Aquaporin 1 (AQP1) is the only AQP present in these cells, and its deletion in AQP1 null mice significantly affects cell osmotic permeability but not fluid transport, which militates against the presence of sizable water movements across the cell. By contrast, AQP1 null mice cells have reduced regulatory volume decrease (only 60% of control), which suggests a possible involvement of AQP1 in either the function or the expression of volume-sensitive membrane channels/transporters. A mathematical model of corneal endothelium predicts experimental results only when based on paracellular electro-osmosis, and not when transcellular local osmosis is assumed instead. Our experimental findings in corneal endothelium have allowed us to develop a novel paradigm for this preparation that includes: (1) paracellular fluid flow; (2) a crucial role for the junctions; (3) hypotonicity of the primary secretion; (4) an AQP role in regulation and not as a significant water pathway. These elements are remarkably similar to those proposed by the Hill laboratory for leaky epithelia.

Animals↗

PubMed2005

A finite element formulation of frequency-dependent electro-osmosis.

In this paper, we model frequency-dependent electro-osmosis in a capillary using the fully nonlinear Navier-Stokes equation (NSE) for viscous, incompressible, and homogeneous flow. We simulate the NSE using the finite element method, computing the solution for a closed capillary and compare it to the closed form solutions. It is confirmed that the second velocity zero crossing is dependent of the capillary radius. The distance of the zero velocity crossing decreases with decreasing capillary radius. It is also shown that the AC electro-osmosis causes a circulation of fluid within the capillary with low frequencies generating the greatest net flow.

Journal Article↗

PubMed1982

Osmosis: a bimodal theory with implications for symmetry.

A theory is advanced that volume transfer across a membrane pore during osmosis takes place in two modes: if solute is sterically excluded from the pore a pressure gradient is set up and viscous flow of solvent results; if solute can enter the pore then osmotic flow is a diffusive phenomenon, and there is no pressure gradient in any part of the pore to which solute has access, even at low concentration due to a repulsive wall field. As a consequence the reflexion coefficients sigma s and sigma f for osmosis and ultrafiltration are not equal, although equality is usually assumed to result from an underlying thermodynamic reciprocity; instead, the two coefficients represent essentially different processes. These results follow from three basic thermodynamic considerations which have usually been overlooked: (i) there is a qualitative difference between a permeable pore and an impermeable one, the latter having a discontinuity of solute activity at the mouth, which the former does not; (ii) the osmotic pressure within the pore is determined by the activity of solute not the concentration; (iii) the effective resistance to flow through a channel depends upon the nature of the régime, being different for diffusive and viscous flow. An expression for sigma s is derived and shown to be compatible with experimental data on polymer membranes and homoporous bilayers.

Cell Membrane↗

PubMed1983

Inability of microorganisms to degrade cellulose acetate reverse-osmosis membranes.

Operational cellulose acetate reverse-osmosis membranes were examined for evidence of biological degradation. Numerous fungi and bacteria were isolated by direct and enrichment techniques. When tested, most of the fungi were active cellulose degraders, but none of the bacteria were. Neither fungi nor bacteria were able to degrade cellulose acetate membrane in vitro, although many fungi were able to degrade cellulose acetate membrane after it had been deacetylated. Organisms did not significantly degrade powdered cellulose acetate in pure or mixed cultures as measured by reduction in acetyl content or intrinsic viscosity or production of reducing sugars. Organisms did not affect the performance of cellulose triacetate fibers when incubated with them. The inability of the organisms to degrade cellulose acetate was attributed to the high degree of acetate substitution of the cellulose polymer. The rate of salt rejection decline was strongly correlated with chlorination of feed water and inversely with densities of microorganisms. These data suggest that microbial degradation of operational cellulose acetate reverse-osmosis membranes is unlikely.

Journal Article↗

PubMed1983

Microbial fouling of reverse-osmosis membranes used in advanced wastewater treatment technology: chemical, bacteriological, and ultrastructural analyses.

Biofouling of reverse-osmosis membranes was investigated at an advanced wastewater treatment facility. Cellulose diacetate membranes operated for approximately 4,000 h became uniformly coated with a mucilaginous fouling layer. The fouling material was approximately 93% water by weight, and nearly 90% of the dehydrated residue was organic in composition. Calcium, phosphorous, sulfur, and chlorine were the major inorganic constituents detected. Protein and carbohydrate represented as much as 30 and 17%, respectively, of the dry weight of the biofilm. Bacteriological plate counts indicated up to 5.6 X 10(6) CFU/cm2 of membrane surface. Accumulation of [3H]glucose in the biofilm and measurement of ATP indicated that the fouling bacteria were metabolically active in situ. The genus Acinetobacter and the Flavobacterium-Moraxella group were the major generic groups associated with the feedwater surface of the membrane, whereas species of the generic groups Acinetobacter, Pseudomonas-Alcaligenes, and Bacillus-Lactobacillus predominated on the permeate water surface. Electron microscopy revealed that the biofilm on the feedwater surface of the membrane was 10 to 20 microns thick and was composed of several layers of compacted bacterial cells, many of which were partially or completely autolyzed. The bacteria were firmly attached to the membrane surface by an extensive network of extracellular polymeric fibrils. Polyester (Texlon) support fibers located on the permeate surface of the reverse osmosis membranes were sparsely colonized, suggesting bacterial regrowth in the product water collection system.

Bacteria↗

PubMed1989

Bacterial colonization of domestic reverse-osmosis water filtration units.

We have analyzed the bacterial content of water from the reservoirs of 300 reverse-osmosis units installed in households. The heterotrophic plate counts on R2A medium (20 and 35 degrees C) ranged from 0 to 10(7) colony forming units per millilitre (cfu/mL). Most reservoirs contained water with bacterial counts between 10(4) and 10(5) cfu/mL. The bacteria identified were Pseudomonas (not aeruginosa), Alcaligenes or Moraxella, Acinetobacter, Flavobacterium, and Chromobacterium. This report emphasizes the importance of bacterial colonization by heterotrophic bacteria in water reservoirs from domestic reverse-osmosis units.

Bacteria↗

PubMed1979

A simple, large scale process for purifying human urinary kallikrein, based on reverse osmosis and ammonium sulfate precipitation.

A simple, large scale process for the purification of human urinary kallikrein is described which is based upon concentration by reverse osmosis, ammonium sulfate precipitation, and gel filtration on a column of Sephadex-G-150. The yield in protein is higher than any reported in the literature to this date; the purified enzyme seems to be identical to that reported by Figueiredo and Mares-Guia at the Kinin-Symposium in Paris, 1978, based on the procedure of Hial, et al., (1974).

Amino Acids↗

PubMed2000

New model to characterise cell-substrate adhesion in the presence of osmosis.

A simple model of cell-substrate adhesion, in response to osmosis change, is derived to describe quantitatively the interrelationships between osmotic inflation, contact area and angle, membrane stretching and adhesion strength. As the cell inflates, the contact area shrinks in dimension, until the cell is eventually lifted off the substrate. The theoretical prediction is consistent with other published data.

Biomechanical Phenomena↗

PubMed1991

Aspects of silicone rubber as an encapsulant for neurological prostheses. Part 1. Osmosis.

Silicone rubber is not, at first sight, a promising material with which to encapsulate a piece of implantable microelectronics expected to last ten or twenty years. It is well known to be very permeable to water. In fact, if correctly applied, it performs very well for ten years, possibly longer. The paper considers the part played by osmosis in achieving satisfactory performance combined with simple technology.

Biomedical Engineering↗

PubMed1995

Photo-osmosis through liquid membrane bilayers. Studies on mixture of bacteriorhodopsin with cytochrome-C, myoglobin, or hemoglobin.

The effect of cytochrome-C, hemoglobin, and myoglobin on photo-osmosis through liquid membrane bilayers generated by bacteriorhodopsin (BR) has been studied. The magnitude of photo-osmotic velocity was found to be much greater when BR was combined with any one of the three pigments than that of BR alone. This has been because of the exclusion of protons and electrons in the illuminated compartment by the action of light, where one acts as the acceptor for the others. The rate of light-induced volume flux of the combined system depends on temperature, intensity, and wavelength of incident light, and the nature and concentration of electron donors and acceptors.

Bacteriorhodopsins↗

PubMed1993

Separation of electrolyte solutions by reverse osmosis.

The paper presented is subdivided into two parts. The first one includes a survey of current notions concerning the physico-chemical nature of interaction potential phi between dissolved molecules or ions and water with a membrane material. Special attention is paid to the structural potential and the potential of image forces. The main conclusion is that the potential of interaction phi determines the major part of phenomena which are relevant for reverse osmosis (RO) separation. In the second part the distribution coefficient gamma = exp (phi) is supposed to be known and a survey of theoretical investigations of RO processes is undertaken. The so called homogeneous model of RO membranes is employed and concentration polarization is taken into account. Two main points in this investigation should be emphasized, that is, taking into account concentration polarization and a theory of RO separation of electrolyte mixtures. The maximum value of rejection coefficient and corresponding optimum velocity of filtration are calculated. Negative rejection of some ions from the mixture is explained, as well as a change in pH of filtrate. The streaming potential is calculated as a function of Peclet number, distribution coefficients, membrane charge and so on in all cases. The suggested theory gives the possibility to explain a number of phenomena in RO separation of electrolyte solutions.

Electrolytes↗

PubMed1979

[Selective diffusion and osmosis: application to the problem of the functioning of the nephron].

In this article, we propose a new hypothesis concerning biological semipermeable membranes, the walls of vessels or tubules of the human organism. As regards the properties of diffusion of the membranes, this hypothesis includes the phenomena of active and passive transport; as far as the properties of diffusion and osmosis are concerned, it takes into account the orientation of the phenomena, which explains its name: hypothesis of selectivity. By applying this theory to the problem of the transport of salts and urea in the nephrons, we demonstrate that this property is a necessary and sufficient condition to explain the part and working of the functional unit of the kidney, i.e., the nephron, and to validate its operating model, subject of our study. No contradiction has appeared within the present experimental results.

Biological Transport↗

PubMed2006

Reverse osmosis processing of organic model compounds and fermentation broths.

Post-treatment of an anaerobic fermentation broth was evaluated using a 150 gal/day, single cartridge prototype reverse osmosis (RO) system. Baseline tests were conducted at 25 degrees C using six organic model compounds representing key species found in the fermentation broth: ethanol, butanol, acetic acid, oxalic acid, lactic acid, and butyric acid. Correlations of the rejection and recovery efficiencies for these organic species, individually and in simulated mixtures, were obtained as a function of feed pressure with and without recirculation of the retentate. The actual fermentation broth obtained from a continuous-flow biohydrogen process was treated by the RO system under the operating conditions similar to those used in the baseline tests, resulting in greater than 95% removal of total organic carbon. These results are encouraging and useful for further studies on the feasibility of incorporating the RO technology into an integrated and field deployable wastewater management and water recovery system.

Anaerobiosis↗

PubMed2006

Ultrasound elastomicroscopy using water jet and osmosis loading: potentials for assessment for articular cartilage.

Research in elasticity imaging typically relies on 1-10 MHz ultrasound. Elasticity imaging at these frequencies can provide strain maps with a resolution in the order of millimeters, but this is not sufficient for applications to skin, articular cartilage, or other fine structures. In this paper, we introduced two methods of ultrasound elastomicroscopy using water jet and osmosis loading for imaging the elasticity of biological soft tissues with high resolutions. In the first system, the specimens were compressed using water jet compression. A water jet was used to couple a focused 20 MHz ultrasound beam into the specimen and meanwhile served as a "soft" indenter. Because there was no additional attenuation when propagating from the ultrasound transducer to the specimen, the ultrasound signal with high signal-to-noise ratio could be collected from the specimens simultaneously with compressing process. The compression was achieved by adjusting the water flow. The pressure measured inside the water pipe and that on the specimen surface was calibrated. This system was easily to apply C-scan over sample surfaces. Experiments on the phantoms showed that this water jet indentation method was reliable to map the tissue stiffness distribution. Results of 1D and 2D scanning on phantoms with different stiffness are reported. In the second system, we used osmotic pressure caused by the ion concentration change in the bathing solutions for the articular cartilage to deform them. When bovine articular cartilage specimens were immerged in solutions with different salt concentration, a 50 MHz focused ultrasound beam was used to monitor the dynamic swelling or shrinkage process. Results showed that the system could reliably map the strain distribution induced by the osmotic loading. We extract intrinsic layered material parameters of the articular cartilage using a triphasic model. In addition to biological tissues, these systems have potential applications for the assessment of bioengineered tissues, biomaterials with fine structures, or some engineering materials. Further studies are necessary to fully realize the potentials of these two new methods.

Algorithms↗

PubMed2003

Treatability of organic fractions derived from secondary effluent by reverse osmosis membrane.

Dissolved organic matters (DOMs) from two batches of secondary effluent collected from a local water reclamation plant were fractionated using column chromatographic method with non-ionic resins XAD-8, AG MP-50 and IRA-96. Seven isolated fractions were obtained from the fractionation study and these fractions were quantified using DOC, UV(254) and SUVA values. The fractionation study revealed that the secondary effluent samples comprised about 47.3-60.6% of hydrophobic and 39.4-52.7% of hydrophilic solutes. The treatability of each isolated fraction was investigated by subjecting each fraction to reverse osmosis (RO) treatment individually. It was noted that RO process could achieve high DOC rejections for acid and neutral fractions (ranging from 80% to 98% removal) probably due to the negative charge of RO membrane. The results obtained also indicated that hydrophobicity of DOMs is significant in determining treatability of organic species by RO process. The performance of RO in terms of DOC rejection of un-fractionated secondary effluent was also investigated to assess possible effects of interactions among organic fractions on their treatability by RO process. It was noted that DOC rejection associated with the un-fractionated secondary effluent was generally higher (ranging from 2% to 45%) than the corresponding rejection obtained from each individual fraction isolated from the secondary effluent. This finding suggested there is a beneficial interaction among the fractions that in turn has contributed towards a better overall DOC rejection performance by RO treatment.

Chromatography↗

PubMed2004

Effects of reverse osmosis isolation on reactivity of naturally occurring dissolved organic matter in physicochemical processes.

A field reverse osmosis system was used to isolate dissolved organic matter (DOM) from two lacustrine and two riverine surface water sources. The rejection of DOM was on the order of 99% and did not vary significantly with pressure. A simple mass balance model using a single measured value of rejection predicted the concentration within the closed-loop isolation system. The effect of operating pressure and solution flux on mass recovery of DOM was evaluated in laboratory and field trials. Under controlled laboratory conditions, >99% of a lacustrine DOM could be accounted for. A fraction of the isolated DOM was not recoverable using hydrodynamic cleaning; however, this fraction was recovered by using a pH 10 NaOH wash solution. The mass recovered in the NaOH solution increased from <1% to >6% with increasing transmembrane pressures from 414 kPa (60 psi) to1000 kPa (145 psi), respectively. This is consistent with fouling that results from an increase in solution flux, and a decrease in tangential crossflow velocity. Under field conditions, mass balances were generally >95% and mass recovery was >90% in all cases. The effects of temperature on solution flux were consistent with changes in fluid viscosity; effects of temperature on membrane diffusivity or morphological properties were small. RO isolation under low pressure conditions designed to maximize DOM recovery had little effect on DOM reactivity evaluated in terms of nanofiltration membrane fouling, XAD-8 resin adsorption, activated carbon adsorption, competition with trichloroethylene for adsorption sites on activated carbon, and molecular weight distribution measured using size exclusion chromatography.

Adsorption↗

PubMed2005

Reverse osmosis membrane rejection for ersatz space mission wastewaters.

Adequate rejection of a variety of inorganic and organic compounds is necessary if reverse osmosis (RO) and nanofiltration (NF) membranes are to be used for space mission wastewater reuse. Three ersatz space mission wastewaters defined by NASA having different pH (2.6-8.9), conductivities (3980-12,640 microS/cm), and amounts of organic compounds (50-2400 mg/L as carbon) were tested to determine the membrane flux and the solute rejection for five RO and two NF membranes that are commercially available. The results show that the rejection of ions depends upon the solution pH which influences electrostatic repulsion. However, the rejection of dissolved organic carbon (DOC) depends upon the composition of the wastewater. The DOC rejection (80-95%) was the highest for the wastewater containing dextran (molecular weight 15-20 k) compared with the other ersatz wastewaters having detergent and urea as the major carbon sources (31-83%). The wastewater having the greatest conductivity (12,640 microS/cm) and DOC (2400 mg/L) showed a greater flux decline (71-96%) than the other ersatz wastewaters (37-82%) having lower conductivities (3980-6980 microS/cm) and DOC (50-660 mg/L) for the RO and NF membranes. The ratio of solute radius (r(i,s)) to effective membrane pore radius (r(p)) was employed to compare ion rejection. For ionic compounds, the rejection is higher than 70% when the r(i,s)/r(p) ratio is greater than 0.5 for both the RO and NF membranes with all wastewaters.

Carbon↗