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Biomedical subjects

W Giger

Publications and source records attributed to W Giger.

18 recordsLinked to original sources
PubMed2005

Comparing steroid estrogen, and nonylphenol content across a range of European sewage plants with different treatment and management practices.

The effluent of 17 sewage treatment works (STW) across Norway, Sweden, Finland, The Netherlands, Belgium, Germany, France and Switzerland was studied for the presence of estradiol (E2), estrone (E1), ethinylestradiol (EE2) and nonylphenol (NP). Treatment processes included primary and chemical treatment only, submerged aerated filter, oxidation ditch, activated sludge (AS) and combined trickling filter with activated sludge. The effluent strength ranged between 87 and 846 L/PE (population equivalent), the total hydraulic retention time (HRT) ranged between 4 and 120 h, sludge retention time (SRT) between 3 and 30 d, and water temperature ranged from 12 to 21 degrees C. The highest estrogen values were detected in the effluent of the STW which only used primary treatment (13 ng/L E2 and 35 ng/L E1) and on one occasion in one of the STW using the AS system (6.5 ng/L E2, 50.5 ng/L E1, but on three other occasions the concentrations in this STW were at least a factor of 6 lower). For the 16 STW employing secondary treatment E2 was only detected in the effluent of six works during the study period (average 0.7-5.7 ng/L). E1 was detected in the effluent of 13 of the same STW. The median value for E1 for the 16 STW with secondary treatment was 3.0 ng/L. EE2 was only detected in two STW (1.1, <0.8-2.8 ng/L). NP could be detected in the effluent of all 14 STW where this measurement was attempted, with a median of 0.31 microg/L and values ranging from 0.05 to 1.31 microg/L. A comparison of removal performance for E1 was carried out following prediction of the probable influent concentration. A weak but significant (alpha<5%) correlation between E1 removal and HRT or SRT was observed.

Environmental Monitoring↗
PubMed2005

Modeling stochastic load variations in sewer systems.

In wastewater treatment and environmental risk assessments increasing attention is paid to the fate of micropollutants. These are time-consuming, expensive and difficult to detect and quantify. If a substance's load or concentration is subject to high dynamic fluctuations, it is demanding to take representative samples, especially when the "variation" is unknown. Therefore, we developed a concept to model stochastic load variations in sewer systems. We gathered readily available information from existing databases (population and consumption data) and combined it with the characteristics of household activities and appliances. We succeeded in predicting realistic short-term variations of benzotriazole (contained in dishwasher detergents) and validated them with a high-frequency measuring campaign. Benzotriazole stands as an example for other household chemicals, which cannot be measured so easily. All required information used within this case study is also available for other substances and catchments. This allows the forecast of stochastic load variations for many chemical compounds of interest. It helps to plan measuring campaigns, to estimate discharged loads from combined sewer overflows and to have a characteristic input for modeling purposes.

Detergents↗
PubMed2001

Trace determination of fluoroquinolone antibacterial agents in urban wastewater by solid-phase extraction and liquid chromatography with fluorescence detection.

Fluoroquinolones (FQs) are among the most important antibacterial agents (synthetic antibiotics) used in human and veterinary medicine. An analytical method based on reversed-phase liquid chromatography with fluorescence detection was developed and validated for the simultaneous determination of nine FQs and the quinolone pipemidic acid in urban wastewater. Aqueous samples were extracted using mixed-phase cation-exchange disk cartridges that were subsequently eluted by ammonia solution in methanol. Recoveries were above 80% at an overall precision of better than 10%. Instrumental quantification limits varied between 150 and 450 pg injected. The presented method was successfully applied to quantify FQs in effluents of urban wastewater treatment plants. The two most abundant human-use FQs, ciprofloxacin and norfloxacin, occurred in primary and tertiary waste-water effluents at concentrations between 249 and 405 ng/L and from 45 to 120 ng/L, respectively. The identity of FQs in urban wastewater was confirmed by recording full fluorescence spectra and liquid chromatography directly coupled to tandem mass spectrometry. These results indicate that conventional environmental risk assessment overestimates FQ concentrations in surface waters by 1 to 2 orders of magnitude.

Anti-Infective Agents↗
PubMed2001

Arsenic contamination of groundwater and drinking water in Vietnam: a human health threat.

This is the first publication on arsenic contamination of the Red River alluvial tract in the city of Hanoi and in the surrounding rural districts. Due to naturally occurring organic matter in the sediments, the groundwaters are anoxic and rich in iron. With an average arsenic concentration of 159 micrograms/L, the contamination levels varied from 1 to 3050 micrograms/L in rural groundwater samples from private small-scale tubewells. In a highly affected rural area, the groundwater used directly as drinking water had an average concentration of 430 micrograms/L. Analysis of raw groundwater pumped from the lower aquifer for the Hanoi water supply yielded arsenic levels of 240-320 micrograms/L in three of eight treatment plants and 37-82 micrograms/L in another five plants. Aeration and sand filtration that are applied in the treatment plants for iron removal lowered the arsenic concentrations to levels of 25-91 micrograms/L, but 50% remained above the Vietnamese Standard of 50 micrograms/L. Extracts of sediment samples from five bore cores showed a correlation of arsenic and iron contents (r2 = 0.700, n = 64). The arsenic in the sediments may be associated with iron oxyhydroxides and released to the groundwater by reductive dissolution of iron. Oxidation of sulfide phases could also release arsenic to the groundwater, but sulfur concentrations in sediments were below 1 mg/g. The high arsenic concentrations found in the tubewells (48% above 50 micrograms/L and 20% above 150 micrograms/L) indicate that several million people consuming untreated groundwater might be at a considerable risk of chronic arsenic poisoning.

Arsenic↗
PubMed2001

Rapid determination of sulfonated naphthalenes and their formaldehyde condensates in aqueous environmental samples using synchronous excitation fluorimetry.

Sulfonated naphthalenes and their formaldehyde condensates (SNFC) were determined in aqueous environmental samples by spectrofluorimetry. A clean-up step using n-hexane to extract possibly interfering nonpolar compounds such as naphthalene is the only preparatory procedure. Synchronous excitation mode with a gammalambda of 105 nm allows the determination of SNFC in environmental samples without additional clean-up or analyte enrichment. Interferences by humic acids and nitrate occurred only at concentrations higher than 1 mg C L(-1) and 10 mg NO3- L(-1), respectively. The limit of detection was 0.2 microg L(-1), the average recovery was 104% and the confidence interval (95% certainty) was 24%. The response factor for the quantitative determination of total SNFC, depending on the distribution of the different SNFC components, was validated for groundwater from two field sites using an HPLC-FD (fluorescence detection) method as a reference method.

Chromatography, High Pressure Liquid↗
PubMed1999

Selective determination of aromatic sulfonates in landfill leachates and groundwater using microbore liquid chromatography coupled with mass spectrometry.

Aromatic sulfonates (AS) are large-volume chemicals used in many technical processes of, for instance, the textile industry or construction. A LC/MS method for the selective determination of AS in environmental samples, based on a single-quadrupole MS, was developed and validated. The central point of this technique is the use of the compound-specific fragment ion SO3.- as marker for aromatic sulfonates. This negatively charged SO3 radical, together with the fact that AS undergo loss of SO2, allows screening for AS in complex matrixes, even in the presence of sulfate anions. Calibration curves generated from LC/MS data showed good linearity over 3 orders of magnitude, with an absolute limit of detection of approximately 1 ng. The relative standard deviation for mean areas obtained from reconstructed ion chromatograms ranged from 2.9 to 8.6%. Unlike UV detection, this LC/MS method gives similar response for both naphthalene- and benzene-sulfonates. The method presented was successfully applied to landfill leachates and groundwater, downstream of a landfill. Furthermore, this technique allowed identification of an unknown AS found in drain samples.

Chromatography, High Pressure Liquid↗
PubMed1993

Bioaccumulation of the lipophilic metabolites of nonionic surfactants in freshwater organisms.

Nonylphenol (NP), nonlyphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) were determined in different freshwater organisms from the surface waters in the Glatt Valley, Switzerland. Rather high concentrations of the compounds investigated have been found to occur in macrophytic algae, particularly Cladophora glomerata (up to 38 mg kg(-1), 80 mg kg(-1), and 28 mg kg(-1) of NP, NP1EO and NP2EO, respectively), the bioconcentration factors of NP reaching up to 10,000. The concentrations in fish were much lower (NP: < 0.03-1.6 mg kg(-1), NP1EO: 0.06-7.0 mg kg(-1), and NP2EO: <0.03-3.1 mg kg(-1) indicating that biomagnification did not take place. Similar concentrations to those in the fish were determined in different tissues of a wild duck. The estimated bioconcentration factors in fish tissues ranged from 13 to 410 for NP, 3 to 300 for NP1EO and 3 to 330 for NP2EO.

Journal Article↗
PubMed1992

Quantitative determination of sulfonated aliphatic and aromatic surfactants in sewage sludge by ion-pair/supercritical fluid extraction and derivatization gas chromatography/mass spectrometry.

Secondary alkanesulfonate (SAS) and linear alkylbenzene-sulfonate (LAS) surfactants were quantitatively (> 90%) extracted from sewage sludges as their tetrabutylammonium ion pairs using 400 atm of supercritical CO2 for 5 min of static extraction followed by 10 min of dynamic extraction at 80 degrees C. Ion pairs of SAS and LAS quantitatively formed butyl esters in the injection port of the gas chromatograph and were determined by gas chromatography/mass spectrometry without class fractionation of the sewage sludge extracts. Concentrations of SAS and LAS in sludges from five different sewage treatment plants ranged from 0.27 to 0.80 g/kg of dry sewage sluge and from 3.83 to 7.51 g/kg, respectively. Good reproducibility was achieved with RSDs of typically 5% for replicate extractions and analyses. Homologue and isomer distributions of SAS in sewage sludge indicated an enrichment of the more hydrophobic components in sewage sludge during sewage treatment.

Alkanesulfonates↗
PubMed1990

Activity and adaptation of nitrilotriacetate (NTA)-degrading bacteria: field and laboratory studies.

Adaptation of bacterial activity for the degradation of nitrilotriacetate (NTA) was studied using natural sediment samples and an NTA-degrading bacterium (strain ATCC 29600). Sediment samples from a river with persistent levels of NTA had much higher NTA-degradative activity than comparable samples from a less contaminated control site. When sediment from the control site was exposed to high levels of NTA a 5 day lag preceded an abrupt increase in NTA degradation while strain 29600 colonized on sand and grown in the absence of NTA became induced within eight hours. The induction of strain 29600 was compared between bacteria in suspension and cells attached to sand. The sand-associated bacteria became induced 4 to 5 h before the planktonic suspension and displayed over threefold greater specific activity. Suspensions of strain 29600 became adapted within 8 h when placed in membrane diffusion chambers that were immersed within a municipal wastewater reactor containing NTA. These findings support the concept that induction is a part of the process of bacterial adaptation to degrade NTA and sand-associated bacteria can adapt more quickly to and have a greater degradative activity for NTA than planktonic cells.

Adaptation, Biological↗
PubMed1987

Determination of trace levels of phenol and cresols in rain by continuous liquid-liquid extraction and high-performance liquid chromatography.

Trace levels of phenol and methylphenols (cresols) in aqueous samples were determined by continuous liquid-liquid extraction and normal-phase high-performance liquid chromatography with UV-fluorescence detection. The recovery of phenol from water at a concentration of 1.6 micrograms l-1 was 70 +/- 6%. The method successfully measured traces of phenol and cresols extracted from rainwater without further clean-up. The average reproducibility of the method for rain samples was +/- 16%. The results compared well with those obtained by high-resolution gas chromatography-mass spectrometry.

Chromatography, High Pressure Liquid↗
PubMed1987

Determination of linear alkylbenzenesulphonates, alkylphenol polyethoxylates and nonylphenol in waste water by high-performance liquid chromatography after enrichment on octadecylsilica.

An enrichment procedure involving percolation through octadecylsilica cartridges was applied to the extraction of linear alkylbenzenesulphonates (LASs), alkylphenol polyethoxylates (APEOs) and nonylphenol (NP) from treated and untreated municipal waste waters. The analytes were quantitated by reversed-phase high-performance liquid chromatography with UV-fluorescence detection. Recoveries higher than 80% were obtained from the analysis of biologically treated waste waters. The method allows rapid, precise and reliable determination of LASs and APEOs at concentrations as low as 20 and 4 micrograms l-1, respectively.

Benzenesulfonates↗
PubMed1984

4-Nonylphenol in sewage sludge: accumulation of toxic metabolites from nonionic surfactants.

Anaerobically treated sewage sludge was found to contain extraordinarily high concentrations of 4-nonylphenol, a metabolite derived from nonionic surfactants of the nonylphenol polyethoxylate type. Concentrations in activated sewage sludge, in mixed primary and secondary sludge, and in aerobically stabilized sludge were substantially lower, suggesting that the formation of 4-nonylphenol is favored under mesophilic anaerobic conditions. Because 4-nonylphenol may be highly toxic to aquatic life, further research is needed on the fate of 4-nonylphenol after sludge is disposed of in the environment.

Anaerobiosis↗
PubMed1984

Determination of highly volatile organic contaminants in water by the closed-loop gaseous stripping technique followed by thermal desorption of the activated carbon filters.

Very volatile organic contaminants in water were determined by using closed-loop gaseous stripping combined with thermal desorption from the activated carbon filter into a high-resolution gas chromatograph. The operating parameters for quantitative applications were evaluated. The solvent-free thermal desorption procedure permits the determination of compounds that normally elute under the gas chromatographic solvent peak (e.g., dichloromethane and Freons). Sixteen volatile compounds with boiling points in the range -30 to 120 degrees C were determined with an overall recovery of 12-52%. Qualitative determinations of volatiles from a secondary sewage effluent were in good agreement with the results found by two more established methods.

Chromatography, Gas↗
PubMed1978

Bile acid pattern in human amniotic fluid.

Individual bile acids were determined in twenty-nine amniotic fluid specimens obtained from twenty-six women between the 32nd and 41st week of gestation. Total bile acid concentration ranged from 0.4 to 4.8 mumol/l with a mean of 1.57 mumol/l. Besides the two major bile acids of man, cholic acid and chenodeoxycholic acid, 3beta-hydroxy-5-cholenoic acid was found in all, lithocholic acid in ten and deoxycholic acid in nine of the twenty-nine amniotic fluid samples. 3beta-Hydroxy-5-cholenoic acid averaged 39.8% of total bile acids during 32-37 weeks of gestation and 20.2% at term (P less than 0.01). These findings point towards important differences between fetal and adult bile metabolism and may reflect maturation of hepatic bile acid biosynthesis near term.

Amniotic Fluid↗
PubMed1977

[Detection of 3 beta-hydroxy-5-cholenoic acid in human amniotic fluid].

Studies of the bile acids of human meconium suggest that a fetal pathway of bile acid synthesis exists which leads to formation of 3beta-hydroxy-5-cholenoic acid, a bile acid not found in serum of healthy pregnant women. To obtain additional support for this hypothesis, cholic, chenodeoxycholic, and 3beta-hydroxy-5-cholenoic acid were measured in amniotic fluid specimens from 18 pregnant women without liver disease. The finding of a considerable percentage of 3beta-hydroxy-5-cholenoic acid (mean: 34 molar %; range 3-71 molar % of total bile acids) in amniotic fluid strengthens the hypothesis that a fetal pathway of bile acid synthesis exists which begins with oxidation of the cholesterol side chain.

Adolescent↗