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PubMed1975

Hemolysis of human erythrocyte induced by a rapid temperature jump.

When an isotonic suspension of human erythrocytes was subjected to a rapid temperature jump (heating time of 2 mus), the following phenomena were observed. Although a jump of 0.05 degrees caused no visible damage to the cell membranes, it facilitated the permeation of [3H]glucose into the cells. A jump of 0.5 degrees induced a hemolysis of the cells. The hemolysis was accompanied by extensive alterations of membrane morphology possibly caused by ruptures of the membranes. Turbidity changes of the suspension after the temperature jump were consistent with a swelling of erythrocytes followed by a shrinking of the swollen cells. The phenomena of the water transport and the hemolysis induced by the temperature jump may be understood by the theory of thermal osmosis (Spanner, D. C. (1954) Symp. Soc. Exp. Biol. 8, 76). Slow heating of the suspension shows no such effects. Thermal osmosis may be an important factor in the water transport and bioenergetics of the living cells.

Biological Transport↗
PubMed2002

Fate of pharmaceuticals during indirect potable reuse.

The scope of this study was directed to examine different wastewater treatment technologies (activated sludge, trickling filter, nanofiltration, reverse osmosis) at full-scale facilities in Arizona and California leading to indirect potable reuse and their capability to remove pharmaceuticals. Additionally, the fate of selected pharmaceuticals was studied during soil-aquifer treatment (SAT) at sites where secondary and tertiary treated effluents are used for subsequent groundwater recharge. Facilities employing longer detention times during treatment (nitrifying and denitrifying plants) showed significant lower effluent concentration for analgesic drugs as compared to trickling filter or activated sludge facilities applying shorter detention times. A similar trend was observed for the lipid regulator gemfibrozil, which was significantly removed in denitrified effluents, whereas a trickling filter treated effluent exhibited concentration of 1,235 ng/L. Antiepileptic drugs, such as carbamazepine and primidone, showed no dependency on the wastewater treatment applied. None of the investigated drugs was detected in tertiary treated effluents after nanofiltration or reverse osmosis. After SAT, analgesic/anti-inflammatory drugs were efficiently removed after retention times of less than 6 months and remaining concentrations were near or below the detection limit of the analytical method. A high potential for biodegradation was also observed for anti-inflammatory drugs in groundwater recharge systems. The antiepileptics carbamazepine and primidone represented the most dominant of all investigated drugs in well treated domestic effluents (nitrifying/denitrifying plants). Removal of carbamazepine and primidone did not seem to occur during travel times of more than 6 years in the subsurface.

Biodegradation, Environmental↗
PubMedDate not supplied

[Organohalogen contamination of a dialysis-water treatment plant].

On March 2001 the regular quality control test of the water used for dialysis in an urban centre using a reverse osmosis system revealed a high level of organo-halogenated contamination. The compounds implicated were: trichloroethylene (trielene) [M.Wt. 131 D], tetrachloroethylene, trichloromethane (chloroform) [M.Wt. 121 D], chlorodibromomethane. The dialysis unit was closed. Water samples were analysed in duplicate. The table shows the values (in ppm or microgram/l) obtained for chloroform at the given times: March 8th, altered sample; March 12th, confirmation sample; March 16th, after osmosis membranes change; March 22nd, after carbon filtration replacement; March 26th, after softener resins substitution. The AAMI doesn't recommend any value for organo-halogenated compounds in dialysis water. In the past, the European Pharmacopoeia and the Italian Health Ministry released some reference values for tap water, values which were extended to water used for dialysis. The values are 1 ppm as reference value, 30 ppm as maximum accepted value for the sum of all organo-halogenated compounds, and 10 ppm as the recommended value. In conclusion, the problem was solved by progressive replacement of the components of the water treatment system, even though the real cause remained undetermined. No clinical symptom was recorded and no level of chloroform or trielene was detected in patients' sera despite the low molecular weight and low protein binding of the compounds. A strict control of the water quality and a more comprehensive and updated reference guide are needed for better and safer dialysis delivery.

Charcoal↗
PubMed2003

Occurrence and removal of endocrine disrupters in landfill leachate treatment plants.

Endocrine disrupting compounds can affect the hormone system in organisms. Industrial chemicals with estrogenic effects were detected in large quantities in landfill leachates. Membrane technology has proven to be an effective barrier to these substances and thus widely applied in the treatment of landfill leachate. The removal techniques under investigation are membrane bioreactors, nanofiltration, activated carbon adsorption, ozonation as well as reverse osmosis. Investigations were conducted at two different landfill leachate treatment plants with a variety of process configurations. The xenoestrogenic substances nonylphenol and bisphenol A were detected in high microg/L-ranges in raw landfill leachate. Membrane bioreactors (MBRs) were capable of removing more than 80% of the nonylphenol load. Final effluent concentrations range between 1-12 microg/L nonylphenol and 3-30 microg/L bisphenol A respectively. Reverse osmosis treatment proved to be less effective in nonylphenol and bisphenol A removal than MBR with further polishing stages like nanofiltration and activated carbon adsorption.

Bioreactors↗
PubMed2004

Removal of endocrine disrupting compounds with membrane processes in wastewater treatment and reuse.

Endocrine disrupting compounds can affect the hormone system in organisms and are the subject of environmental and human health concerns. The effluents of wastewater treatment plants contribute to the emission of estrogenically active substances into the environment. Membrane technology, which is an advanced wastewater treatment option, is the subject of this research. The removal techniques under investigation are membrane bioreactors, reverse osmosis, and nanofiltration. Eleven different nanofiltration membranes were tested in the laboratory set-up. The observed retention of NP and BPA ranged between 70% and 100%. The contact angle is an indicator for the hydrophobicity of a membrane, whose influence on the permeability and retention of NP was evident. Regarding the retention of BPA no dependency on the contact angle was observed. Results of the investigation of a full-scale landfill leachate treatment plant indicate a bisphenol A (BPA) removal of more than 98% with membrane bioreactors and reverse osmosis. The mass balance indicates that biological degradation is the most important removal process in the membrane bioreactor configuration.

Benzhydryl Compounds↗
PubMed2004

Removal of hormones and pharmaceuticals in the Advanced Water Recycling Demonstration Plant in Queensland, Australia.

An advanced water recycling demonstration plant was employed to investigate the effectiveness of a number of treatment technologies in the removal of some residuals of commonly prescribed pharmaceuticals as well as natural and synthetic hormones found in sewage. Analysis of targeted compounds was carried out by solid-phase extraction (SPE) and gas chromatography-mass spectrometry (GC-MS). Initial tests were undertaken to determine the background concentrations of the analytes during various stages of treatment. Subsequent tests, undertaken by spiking with standard solutions of the target compounds provided further information on the removal efficiencies of some selected treatment modules. The results of the study indicate that while ozonation, microfiltration and nanofiltration were partially effective, treatment by reverse osmosis was the most universally successful in the removal of the target residuals. While significantly more data is required for a full evaluation, this initial investigation suggests that reverse osmosis may be an effective means of removing a wider range of pharmaceutically active residuals and hormones from treated sewage.

Australia↗
PubMedDate not supplied

The effect of point-of-use water conditioning systems on community fluoridated water.

The purpose of this investigation was to determine the effect of several point-of-use water conditioning systems on the fluoride concentration in community fluoridated water. Point-of-use water conditioning systems attach at the sink to provide the user with protection from certain water contaminants. A sampling apparatus was constructed to allow collection of water samples before and after conditioning. The apparatus connected the following types of point-of-use water conditioning systems: a faucet water filter, a cellulose fiber filter, an activated carbon filter, a reverse osmosis system, and a distillation unit. These samples were tested by an independent laboratory using colorimetric determination of fluoride concentration. All point-of-use water conditioning systems tested caused a statistically significant reduction in fluoride (P less than .001). Of particular note were reductions in fluoride concentration by the activated carbon filter (81%), the reverse osmosis system (84%), and the distillation unit (99%). These reductions are clinically significant, and necessitate supplementation for optimal fluoride intake. Patients using these water conditioning systems should be advised to have their water tested, and to consider fluoride supplementation to ensure adequate benefit from this caries prevention method.

Carbon↗
PubMed1990

[Prevalence of histological types of bone disease in a hemodialysis center limiting the oral intake of aluminum hydroxide].

UNLABELLED: To assess the prevalence of histologic bone disease in our center where Al(OH)3 intake is restricted, we reviewed 42 bone biopsies performed between 1975 and 1985 in patients dialyzed more than 29 months. Bone biopsies were performed systematically (2/3 of the cases) or because of a mild hypercalcemia (1/3 of the cases). Seventeen of these patients had been dialyzed before 1978 with softened water moderately contaminated by aluminum. Fifteen had always been dialyzed with reverse osmosis treated water and 10 had been exclusively treated by hemofiltration. The prevalence of osteitis fibrosa was 76%, that of osteomalacia null and that of adynamic bone disease 24% (but only 9.5% with positive Aluminon staining). When the 17 patients dialyzed with aluminum contaminated water before 1978 were excluded, only one patient among 25 had an aluminum adynamic bone disease (4%). This low prevalence can probably be explained by the restricted intake of Al(OH)3 thanks to the systematic administration of Ca CO3 and in a few cases of Mg (OH). The adynamic bone disease group has lower serum concentration of PTH and shorter duration on dialysis whereas the serum levels of calcium, phosphorus, magnesium and aluminum and daily dose of Ca CO3, Mg (OH)2 and Al(OH)3 do not differ. The frequency of the positivity of aluminum staining is not statistically different in the 2 groups. In 4 cases, adynamic bone disease without aluminum or iron intoxications is found, associated with a relative hypoparathyroidism. It is not explained by previous parathyroidectomy, diabetes or steroid therapy. CONCLUSIONS: 1) Restriction of aluminum intake and dialysis with reverse osmosis treated water lead to a low prevalence of aluminum bone disease. 2) A new bone disease in uremia is described: the idiopathic adynamic bone disease associated with a relative hypoparathyroidism.

Adult↗
PubMed2000

Determining zeta Potential and Surface Conductance by Monitoring the Current in Electro-osmotic Flow.

In this paper we have outlined a simple procedure for determining zeta potential, zeta(0), and surface conductance, lambda(s), based on current monitoring in electro-osmosis. In these experiments, the average velocity was determined by measuring the amount of time required to completely displace a solution by another solution in the capillary tube. The average velocity during electro-osmosis was found to be independent of capillary size, although it was dependent on the electrolyte concentration and applied electrical field. The measured values of the zeta potential, zeta(0), were found to be independent of capillary size and the applied field, while zeta(0) is strongly dependent on the electrolyte concentration. Calculations of the specific surface conductivity lambda(s) based on current measurements reveal a relationship between lambda(s) and capillary size, in agreement with the results reported in the literature. Copyright 2000 Academic Press.

Journal Article↗
PubMed1976

Effects of unstirred layers or transport number discontinuities on the transient and steady-state current-voltage relationships of membranes.

The effects of current-induced electrolyte accumulation and depletion on the electrical properties of a two-layered membrane system have been examined. The membrane consisted of a charged, ion permselective layer and an uncharged, non-selective layer. The model was designed to reveal the properties of membranes possessing long pores with ionic charges at one end or of ion-selective membranes bounded by highly unstirred aqueous layers. Electrolyte concentration profiles in the inert layer and their time-dependent changes were obtained from solutions of the diffusion equation under the condition of constant current. The profiles were then used to calculate the voltage developed across the membrane at various times after the current is switched on. The theoretical results are presented in the form of i-V curves with reduced coordinates that can be used to obtain time-current-voltage relationships for membranes of the type considered having any thickness of the non-selective layer and bathed in any concentration of any 1:1 electrolyte. Experimental results on a model composite membrane were in good agreement with calculations that assume that ion transport occurs only under the influence of electrical potential and concentration gradients, suggesting that in such systems, the combined effects of convection, osmosis, electro-osmosis, and concentration-dependence of diffusion coefficients, activity coefficients, and transference numbers are small. Voltage fluctuations in the form of periodic spikes were observed experimentally at the limiting current density (the current density at which the electrolyte concentration at one surface of the selective layer goes to 0). These phenomena were not seen when the current was in the direction leading to accumulation of electrolyte in the non-selective (unstirred) layer. Such composite membranes can exhibit S-shaped and N-shaped i-V curves under ramp-voltage and ramp-current clamps, respectively.

Diffusion↗
PubMed2006

Effects of time and point-of-use devices on arsenic levels in Southeastern Michigan drinking water, USA.

Health effects associated with chronic, low-level exposures to arsenic in drinking water (<100 microg/L) remain unclear, in part due to uncertainties in assessing exposure. Drinking water concentrations have been used to assess past exposure to arsenic in epidemiological studies, under the assumption that a single measurement can be used to estimate historical exposure. This study aims to better understand (1) temporal variability in arsenic concentrations in drinking water and (2) the impact of point-of-use (POU) treatment devices on arsenic exposure measurements, and on reliability of the exposure measurement for population-level studies. Multiple drinking water samples were collected at two points in time (an average of fourteen months apart) for 261 individuals enrolled in a case-control study of arsenic exposure and bladder cancer in Michigan. Sources of drinking water included private wells (n = 221), public water supplies (n = 33), and bottled water (n = 7); mean arsenic concentration was highest in private wells (7.28 microg/L) and lowest in bottled water samples (0.28 microg/L). Arsenic concentrations in primary drinking water samples were highly correlated (r = 0.88, p < 0.0001, n = 196), with 3% of the water sources exceeding the United States Environmental Protection Agency's Maximum Contaminant Level (MCL) in one sample but not in the other sample. Measurement reproducibility did not vary by type of POU device (e.g., softener, filter, reverse osmosis system). Arsenic concentrations did differ, however, between samples treated with POU devices and untreated samples taken on the same day. Substantial differences in arsenic concentrations were consistently observed for reverse osmosis systems; other POU devices had variable effects on arsenic concentrations. These results indicate that while a single residential arsenic measurement may be used to represent exposure in this region, researchers must obtain information on changes in water source and POU treatment devices to better characterize population exposures over time.

Arsenic↗
PubMed2001

Membrane rejection of nitrogen compounds.

Rejection characteristics of nitrogen compounds were examined for reverse osmosis, nanofiltration, and low-pressure reverse osmosis membranes. The rejection of nitrogen compounds is explained by integrating experimental results with calculations using the extended Nernst-Planck model coupled with a steric hindrance model. The molecular weight and chemical structure of nitrogen compounds appear to be less important in determining rejection than electrostatic properties. The rejection is greatest when the Donnan potential exceeds 0.05 V or when the ratio of the solute radius to the pore radius is greater than 0.8. The transport of solute in the pore is dominated by diffusion, although convective transport is significant for organic nitrogen compounds. Electromigration contributes negligibly to the overall solute transport in the membrane. Urea, a small organic compound, has lower rejection than ionic compounds such as ammonium, nitrate, and nitrite, indicating the critical role of electrostatic interaction in rejection. This suggests that better treatment efficiency for organic nitrogen compounds can be obtained after ammonification of urea.

Membranes, Artificial↗
PubMed2003

Removal of estrogenic activity from municipal waste landfill leachate assessed with a bioassay based on reporter gene expression.

The leachate of a municipal waste landfill was tested for estrogenic activity using a reporter-gene-based bioassay with a human breast-cancer-derived cell line (MVLN cells). The leachate was processed with two different membrane-employing processes operating in parallel. One process consists of aerobic biological degradation, ultrafiltration, and subsequent adsorption to activated carbon. The second process was a reverse osmosis treatment of the raw leachate. Both processes are common in the treatment of landfill leachate. Here, the efficacy of the two processes to remove "estrogenicity" was compared. Both treatment processes removed more than 97% of the estrogenic activity, calculated as estradiol equivalents (EEQs), but they were not equally effective. After adsorption to activated carbon, no estrogenicity was detected, whereas concentrated effluent of the reverse osmosis treatment still elicited an estrogenic response in the bioassay. On the basis of chemical analysis, it is proposed that bisphenol A was responsible for the majority of estrogenic activity in the raw and treated leachate. Although the contribution of treated leachate to the estrogenic load on the aquatic environment seems to be low compared to that of sewage treatment works, the high estrogenic activity in raw landfill leachate stresses the necessity for the appropriate treatment of these leachates.

Benzhydryl Compounds↗
PubMed2003

Environmental effects caused by olive mill wastewaters: toxicity comparison of low-molecular-weight phenol components.

Olive oil mill wastewaters (OMWs) show significant polluting properties due to their content of organic substances, and because of their high toxicity toward several biological systems. Wastewaters' toxicity has been attributed to their phenolic constituents. A chemical study of wastewaters from a Ligurian oil mill characterized phenolic products such as 1,2-dihydroxybenzene (catechol), derivatives of benzoic acid, phenylacetic acid, phenylethanol, and cinnamic acid. The OMWs were fractioned by ultrafiltration and reverse osmosis techniques and tested for toxicity on aquatic organisms from different trophic levels: the alga Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum); the rotifer Brachionus calyciflorus; and two crustaceans, the cladoceran Daphnia magna and the anostracan Thamnocephalus platyurus. The fraction most toxic to the test organisms was that from reverse osmosis containing compounds of low molecular weight (<350 Da), and this was especially due to the presence of catechol and hydroxytyrosol, the most abundant components of the fraction.

Animals↗
PubMed2000

Osmotic generation of 'anomalous' fluid pressures in geological environments

Osmotic pressures are generated by differences in chemical potential of a solution across a membrane. But whether osmosis can have a significant effect on the pressure of fluids in geological environments has been controversial, because the membrane properties of geological media are poorly understood. 'Anomalous' pressures--large departures from hydrostatic pressure that are not explicable in terms of topographic or fluid-density effects--are widely found in geological settings, and are commonly considered to result from processes that alter the pore or fluid volume, which in turn implies crustal changes happening at a rate too slow to observe directly. Yet if osmosis can explain some anomalies, there is no need to invoke such dynamic geological processes in those cases. Here I report results of a nine-year in situ measurement of fluid pressures and solute concentrations in shale that are consistent with the generation of large (up to 20 MPa) osmotic-pressure anomalies which could persist for tens of millions of years. Osmotic pressures of this magnitude and duration can explain many of the pressure anomalies observed in geological settings. They require, however, small shale porosity and large contrasts in the amount of dissolved solids in the pore waters--criteria that may help to distinguish between osmotic and crustal-dynamic origins of anomalous pressures.

Journal Article↗
PubMed2004

Photogeneration of singlet oxygen by humic substances: comparison of humic substances of aquatic and terrestrial origin.

The singlet oxygen (1(O2)) luminescence of 27 isolated humic substances (HS), natural organic matter, ultrafiltrates, and the synthetic fulvic acid HS1500 has been investigated by time-resolved spectroscopy in buffered D(2)O. The samples include both reverse osmosis isolates from lakes in Scandinavia, Canada, and Germany, and IHSS fulvic and humic acids of aquatic and terrestrial origin. The quantum yields of 1(O2) formation (PhiDelta) obtained on laser excitation at 480 nm ranged between 0.06 (HS1500) and 2.7%(fulvic acid from soil, IHSS). In our study, a general trend towards higher PhiDelta in terrestrial HS was observed. The comparison of reverse osmosis isolates from surface waters collected during fall 1999 and spring 2000 from five Scandinavian sites yielded, in all cases, higher PhiDelta for the spring samples. For the aquatic sampling sites Hietajarvi and Birkenes, PhiDelta even exceeded values of 0.6%, which were found to be typical for terrestrial or soil water material. Investigation of the excitation wavelength dependence of PhiDelta in the spectral range 355-550 nm yielded different spectral shapes for aquatic HS and "non-aquatic" HS, respectively. On the basis of these excitation spectra, 1(O2) production rates were calculated for eight representative HS.

Journal Article↗
PubMed2002

Mechanisms of transjunctional transport of NaCl and water in proximal tubules of mammalian kidneys.

Tight junctions and the intercellular space of proximal tubules are not accessible to direct measurements of fluid composition and transport rates, but morphological and functional data permit analysis of diffusion and osmosis causing transjunctional NaCl and water transport. In the S2 segment NaCl diffuses through tight junctions along a chloride gradient, but against a sodium gradient. Calculation in terms of modified Nernst-Fick diffusion equation after eliminating electrical terms shows that transport rates (300-500 pmol min-1 mm-1 tubule length) and transepithelial voltage of +2 mV are in agreement with observations. Diffusion coefficients are Dtj=1500 microm2 s-1 in the S1 segment, and Dtj=90-100 microm2 s-1 in the S2 segment where apical intercellular NaCl concentration is 132 mM, 1 mM below complete stop (Dtj=0 and Donnan equilibrium). Tight junctions with gap distance 6 A are impermeable to mannitol (effective molecular radius 4 A); reflection coefficients are sigma=0.92 for NaHCO3 and sigma=0.28 for NaCl, because of difference in anion size. The osmotic force is provided by a difference in effective transjunctional osmolality of 10 mOsm kg-1 in the S1 segment and 30 mOsm kg-1 in the S2 segment, where differences in transjunctional concentration contribute with 21 mOsm kg-1 for NaHCO3 and -4 mOsm kg-1 for NaCl. Transjunctional difference of 30 mOsm kg-1 causes a volume flow of 2 nL min-1 mm-1 tubule length. Luminal mannitol concentration of 30 mM stops all volume flow and diffusive and convective transport of NaCl. In conclusion, transjunctional diffusion and osmosis along gradients generated by transcellular transport of other solutes account for all NaCl transport in proximal tubules.

Animals↗
PubMed1998

Urea transporter UT3 functions as an efficient water channel. Direct evidence for a common water/urea pathway.

A family of molecular urea transporters (UTs) has been identified whose members appear to have an exceptionally high transport turnover rate. To test the hypothesis that urea transport involves passage through an aqueous channel, osmotic water permeability was measured in Xenopus oocytes expressing UTs. The UT3 class of urea transporters functioned as efficient water channels. Quantitative measurement of single channel water permeability (pf) using epitope-tagged rat UTs gave pf (in cm3/s x 10(-14)) of 0.14 +/- 0.11 (UT2) and 1.4 +/- 0.2 (UT3), compared with 6.0 and 2.3 for water channels AQP1 and AQP3, respectively. Relative single channel urea permeabilities (purea) were 1.0 (UT2), 0.44 (UT3), and 0.0 (AQP1). UT3-mediated water and urea transport were weakly temperature-dependent (activation energy <4 kcal/mol), inhibited > 75% by the urea transport inhibitor 1,3-dimethylthiourea, but not inhibited by the water transport inhibitor HgCl2. To test for a common water/urea pore, the urea reflection coefficient (sigmaurea) was measured by independent induced osmosis and solvent drag methods. In UT3-expressing oocytes, the time course of oocyte volume in response to different urea gradients (induced osmosis) gave sigmaurea approximately 0.3 for the UT3 pathway, in agreement with sigmaurea determined by the increase in uptake of [14C]urea during osmotic gradient-induced oocyte swelling (solvent drag). In oocytes of comparable water and urea permeability coexpressing AQP1 (permeable to water, not urea) and UT2 (permeable to urea, not water), sigmaurea = 1. These results indicate that UT3 functions as a urea/water channel utilizing a common aqueous pathway. The water transporting function and low urea reflection coefficient of UT3 in vasa recta may be important for the formation of a concentrated urine by countercurrent exchange in the kidney.

Animals↗