bluuebunny/crossref_metadata_2025 huggingface dataset:
Estrogenicity patterns in the Swiss midland river Lützelmurg in relation to treated domestic sewage effluent discharges and hydrology
Authors: Vermeirssen Etiënne L.M. , Suter Marc J.-F. , Burkhardt-Holm Patricia
Published: August 2006

Sewage treatment works (STW) discharge estrogenic effluent into rivers, which leads to variable estrogenicity of river water. Here, we characterize how the factors effluent and hydrology influence the estrogenicity of river water. We selected a river for which good hydrological data are available and collected water samples upstream and downstream from a STW discharge; effluent was sampled as well. Sampling took place during four 12-d periods, associated with the seasons, and always occurred in the morning. We also investigated the estrogenicity along the river, both by grab sampling and by passive sampling. Estrogens were analyzed by a recombinant yeast assay (YES); the estrogenicity of a sample was equated to the 17β-estradiol standard of the YES (ng/L). Estrogenicity upstream from the STW was mostly close to the detection limit of the YES (maximum, 0.4 ng/L). Estrogenicity of effluent ranged between 0.2 and 7.7 ng/L; lower estrogenicity was associated with higher hydraulic retention times. Downstream from the STW, estrogenicity exceeded 1 ng/L on 25% of the days (maximum, 2.1 ng/L). Measured river water estrogenicity correlated positively and significantly with predicted estrogenicity based on effluent estrogenicity and effluent dilution factor. Grab samples taken along the river indicate that no significant sources of estrogens were upstream from the STW; downstream from the STW, the pattern of estrogenicity was highly variable. However, passive sampling showed that the estrogenicity of river water downstream from the STW decreased continuously with increasing distance from the STW, which is largely explained by dilution.
Cholinesterase activity and behavior in chlorpyrifos-exposedRana sphenocephalatadpoles
Authors: Widder Pamela D. , Bidwell Joseph R.
Published: August 2006

Recent studies have found a correlation between organophosphate (OP) pesticide exposure and declines in amphibian populations. We evaluated the hypothesis that this relationship is driven by behavioral changes in developing larvae. Specifically, we examined how exposure to a common OP pesticide, chlorpyrifos, influenced cholinesterase (ChE) activity, mass, and swim speed in Rana sphenocephala tadpoles. We also determined how the presence of natural pond sediments in exposure chambers influenced response to the pesticide and how mass and survival were affected when tadpoles were exposed to an invertebrate (odonate) predator in addition to the pesticide. Mass and swim speed were measured after 4- and 12-d laboratory exposures to 1, 10, 100, and 200 μg/L of chlorpyrifos in test chambers that either did or did not contain pond sediments. These same parameters also were examined in mesocosms dosed with 200 μg/L of chlorpyrifos to evaluate responses under more environmentally realistic conditions. The effect of the invertebrate predators on survival and/or growth of tadpoles was evaluated in the mesocosm study and in separate laboratory experiments. In laboratory tests, no pesticide-induced mortality was observed; however, tadpole ChE activity in the two highest concentrations was significantly lowered, with a longer exposure duration further decreasing activity (maximum inhibition, 43%). Mass also was lower at higher concentrations, but this effect was not enhanced with longer duration of exposure. Reductions in ChE activity of tadpoles exposed in mesocosms were similar to those observed in laboratory experiments for the first 4 d. Tadpole swim speed and survival in the presence of a predator were not affected, with the latter largely resulting from pesticide-induced predator mortality.
Evaluation of statistical methods for left-censored environmental data with nonuniform detection limits
Authors: Sinha Parikhit , Lambert Michael B. , Trumbull V. Lyle
Published: August 2006

Monte Carlo simulations were used to evaluate statistical methods for estimating 95% upper confidence limits of mean constituent concentrations for left-censored data with nonuniform detection limits. Two primary scenarios were evaluated: data sets with 15 to 50% nondetected samples and data sets with 51 to 80% nondetected samples. Sample size and the percentage of nondetected samples were allowed to vary randomly to generate a variety of left-censored data sets. All statistical methods were evaluated for efficacy by comparing the 95% upper confidence limits for the left-censored data with the 95% upper confidence limits for the noncensored data and by determining percent coverage of the true mean (μ). For data sets with 15 to 50% nondetected samples, the trimmed mean, Winsorization, Aitchison's, and log-probit regression methods were evaluated. The log-probit regression was the only method that yielded sufficient coverage (99–100%) of μ, as well as a high correlation coefficient (r2 = 0.99) and small average percent residuals (− 0.1%) between upper confidence limits for censored versus noncensored data sets. For data sets with 51 to 80% nondetected samples, a bounding method was effective (r2 = 0.96–0.99, average residual = −5% to −7%, 95-98% coverage of μ), except when applied to distributions with low coefficients of variation (standard deviation/μ < 0.5). Thus, the following recommendations are supported by this research: data sets with 15 to 50% nondetected samples—log-probit regression method and use of Chebyshev theorem to estimate 95% upper confidence limits; data sets with 51 to 80% nondetected samples— bounding method and use of Chebyshev theorem to estimate 95% upper confidence limits.
The use of in situ and stream microcosm experiments to assess population- and community-level responses to metals
Authors: Clark Jeffrey L. , Clements William H.
Published: August 2006

We conducted field and stream microcosm experiments to assess population-level (density, size distribution) and community-level (species richness metrics, multivariate analysis of community composition) responses of macroinvertebrates to heavy metals in the Arkansas River, a mining-polluted stream in Colorado, USA. Experiments were conducted in spring and summer to coincide with early and late developmental stages (i.e., instars) of the mayfly Rhithrogena hageni. Results of field experiments showed significant mortality at metal-contaminated sites during summer when mayfly populations were dominated by small, early instars (mean dry wt = 0.13 mg). In contrast, no significant mortality was observed in spring when organisms were larger (mean dry wt = 1.78 mg). Multivariate analyses based on abundance of dominant taxa clearly separated reference and metal-impacted stations in summer experiments but showed little separation in spring. We observed no significant effects of metals on species richness, number of mayfly species, or EPT (species richness of Ephemeroptera, Plecoptera, and Trichoptera) in either field experiment. Using stream microcosms, we established concentration-response relationships between heavy metals and R. hageni density, species richness, mayfly richness, and EPT. Density of R. hageni was generally more sensitive to metals than measures of species richness, and summer populations of R. hageni were more sensitive to metals than spring populations. Because the presence of large, relatively tolerant individuals in spring coincided with periods of higher metal concentrations, R. hageni was protected from toxic effects in this system. We conclude that phenology and developmental stage are important factors influencing responses of some aquatic macroinvertebrates to metals. Thus, timing bioassessments to coincide with the presence of these sensitive life stages can improve our ability to detect subtle contaminant effects.
Combined effects of temperature acclimation and cadmium exposure on mitochondrial function in eastern oysters Crassostrea virginica Gmelin (Bivalvia: Ostreidae)
Authors: Cherkasov Anton S. , Ringwood Amy H. , Sokolova Inna M.
Published: August 2006

Cadmium and temperature have strong impacts on the metabolic physiology of aquatic organisms. To analyze the combined impact of these two stressors on aerobic capacity, effects of Cd exposure (50 μg/L) on mitochondrial function were studied in oysters (Crassostrea virginica) acclimated to 12 and 20°C in winter and to 20 and 28°C in fall. Cadmium exposure had different effects on mitochondrial bioenergetics of oysters depending on the acclimation temperature. In oysters acclimated to 12°C, Cd exposure resulted in elevated intrinsic rates of mitochondrial oxidation, whereas at 28°C, a rapid and pronounced decrease of mitochondrial oxidative capacity was found in Cd-exposed oysters. At the intermediate acclimation temperature (20°C), effects of Cd exposure on intrinsic rates of mitochondrial oxidation were negligible. Degree of coupling significantly decreased in mitochondria from 28°C-acclimated oysters but not in that from 12°C- or 20°C-acclimated oysters. Acclimation at elevated temperatures also increased sensitivity of oyster mitochondria to extramitochondrial Cd. Variation in mitochondrial membrane potential explained 41% of the observed variation in mitochondrial adenosine triphosphate synthesis and proton leak between different acclimation groups of oysters. Temperature-dependent sensitivity of metabolic physiology to Cd has significant implications for toxicity testing and for extrapolation of laboratory studies to field populations of aquatic poikilotherms, indicating the importance of taking into account the thermal regime of the environment.
Chronic toxicity of polycyclic aromatic compounds to the springtailFolsomia candidaand the enchytraeidEnchytraeus crypticus
Authors: Droge Steven T.J. , Paumen Miriam León , Bleeker Eric A.J. , Kraak Michiel H.S. , van Gestel Cornelis A.M.
Published: August 2006

An urgent need exists for incorporating heterocyclic compounds and (bio)transformation products in ecotoxicological test schemes and risk assessment of polycyclic aromatic compounds (PACs). The aim of the present study therefore was to determine the chronic effects of (heterocyclic) PACs on two terrestrial invertebrates, the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus. The effects of 11 PACs were determined in chronic experiments using reproduction and survival as endpoints. The results demonstrated that as far as narcosis-induced mortality is concerned, effects of both homocyclic and heterocyclic PACs are well described by the relationship between estimated pore-water 50% lethal concentrations and log Kow. In contrast, specific effects on reproduction varied between species and between compounds as closely related as isomers, showing up as deviations from the relationship between pore-water 50% effect concentrations and log Kow. These unpredictable specific effects on reproduction force one to test the toxicity of these PACs to populations of soil invertebrates to obtain reliable effect concentrations for use in risk assessment of PACs.
Transgenerational retention and maternal transfer of selenium inDaphnia magna
Authors: Lam Isaac K.S. , Wang Wen-Xiong
Published: August 2006

We examined transgenerational retention and maternal transfer of selenium (Se) in three consecutive generations (F0, F1, and F2) of Daphnia magna. The F0 generation was exposed to dietary selenium (as selenite) only, and the F1 and F2 generations received only the maternally derived selenium from F0 and F1, respectively. Algal food Scenedesmus obilquus was radiolabeled with 0.56 μM Se, and the finial Se concentration in the algae was 115.6 μg Se/g dry weight. After 10 d feeding, the initial Se concentration in the F0 prior to depuration was 0.72 μg Se/g wet weight. The Se retention within the same generation was comparable at different food concentrations, but it increased across the consecutive generations regardless of the food concentration, suggesting that Se elimination was dependent on the source of Se accumulation (dietary vs maternally derived). Retention was also comparable among different batches of offspring within the same generation. Reproduction rate increased with increasing food concentration but decreased across the successive batches in F1. The 10-d overall maternal transfer efficiency increased with increasing food concentration in all generations. Approximately 19 to 24% of Se in F0 was transferred maternally to F1 during reproductive events, but the efficiency decreased considerably from F1 to F2. Maternal transfer also decreased in the later batches of F1. The transfer efficiency to each neonate showed a negative relationship with food concentration in both F0 and F1, suggesting that the Se transfer to the offspring was compromised by the reproduction rate. We concluded that dietary-derived Se (from F0) was more efficiently transferred to the offspring (F1) than the maternally derived Se (from F1) transferred to F2; thus it is necessary to separate the dietary and maternal contributions to the overall Se accumulation in Daphnia.
Quantum chemistry based quantitative structure-activity relationships for modeling the (sub)acute toxicity of substituted mononitrobenzenes in aquatic systems
Authors: Zvinavashe Elton , Murk Albertinka J. , Vervoort Jacques , Soffers Ans E.M.F. , Freidig Andreas , Rietjens Ivonne M.C.M.
Published: August 2006

Fifteen experimental literature data sets on the acute toxicity of substituted nitrobenzenes to algae (Scenedesmus obliquus, Chlorella pyrenoidosa, C. vulgaris), daphnids (Daphnia magna, D. carinata), fish (Cyprinus carpio, Poecilia reticulata), protozoa (Tetrahymena pyriformis), bacteria (Phosphobacterium phosphoreum), and yeast (Saccharomyces cerevisiae) were used to establish quantum chemistry based quantitative structure-activity relationships (QSARs). The logarithm of the octanol/water partition coefficient, log Kow, and the energy of the lowest unoccupied molecular orbital, Elumo, were used as descriptors. Suitable QSAR models (0.65 < r2 < 0.98) to predict acute toxicity of substituted mononitrobenzenes to protozoa, fish, daphnids, yeast, and algae have been derived. The log Kow was a sufficient descriptor for all cases, with the additional Elumo descriptor being required only for algae. The QSARs were found to be valid for neutral substituted mononitrobenzenes with no -OH, -COOH, or -CN substituents attached directly to the ring. From the 100,196 European Inventory of Existing Commercial Substances (EINECS), 497 chemicals were identified that fit the selection criteria for the established QSARs. Based on these results, an advisory tool has been developed that directs users to the appropriate QSAR model to apply for various types of organisms within specified log Kow ranges. Using this tool, it is possible to obtain a good indication of the toxicity of a large set of EINECS chemicals and newly developed substituted mononitrobenzenes to five different organisms without the need for additional experimental testing.
Activity corrections for ionization constants in defined media
Authors: Smith S.A. , Chen S.
Published: August 2006

Correcting ionization constants for activity effects can have a larger impact on some ionic species than correcting for temperature effects. Computer trials compared two pH calculation methods, and showed that an interpolation algorithm found a precise charge balance quickly but was unstable under certain conditions, while a slower pH search method was stable under all test conditions. The optimal calculation strategy was a hybrid of these two approaches. The hybrid calculation method is stable, quick, includes activity and temperature corrections, does not need kinetic rate constants, allows all known ionic species to be included, and allows for easy addition of new chemical species.
Use of the ADM1 to investigate the effects of acetoclastic methanogen population dynamics on mesophilic digester stability
Authors: Straub A.J. , Conklin A.S.Q. , Ferguson J.F. , Stensel H.D.
Published: August 2006

The ADM1 was employed to assess the effect of variations in solids hydrolysis and acetoclastic methanogen process characterizations on municipal digester stability relating to excess acetate utilization capacity. First-order single- and dual-pathway hydrolysis rate functions and single and competitive acetoclastic methanogen rate functions were implemented in the ADM1. The acetate capacity number (ACN), defined as the ratio between the maximum acetate utilization rate and the average acetate production rate, was used to index digester instability. Simulations of a single CSTR at steady state indicate a similar ACN can be obtained with a 12-day SRT digester dominated by Methanosarcina sp and a 24-day SRT digester dominated by Methanosaeta sp. An increase in ACN with a decrease in SRT representing Methanosarcina sp. selection was observed for particulate feed loadings from 40 g COD/L to 90 g COD/L. Feeding frequency and dual-pathway hydrolysis were found to have less effect on the ACN than the competitive acetoclastic model structure.
Applications and limitations of ADM 1 in municipal wastewater solids treatment
Authors: Johnson B.R. , Shang Y.
Published: August 2006

The ADM 1 model has been implemented in a steady-state whole wastewater plant simulator. The ADM 1 model has been in use with good success for approximately 2 years on a wide range of wastewater treatment facilities. However, a number of modifications were necessary to allow it to be used in the context of municipal wastewater treatment. It was found that the model's use was greatly simplified if used in conjunction with a larger plant simulator to assist in the feed fractionation. It was also found that a better fit to actual operating data was achieved if some of the slowly biodegradable particulate fraction was partitioned into ADM particulate fractions other than the composite fraction.

Another significant limitation of the model is in the absence of phosphorus modeling. The ADM model needs to have phosphorus handling for all the relevant fractions, and needs to include the handling of inorganic reactions such as struvite precipitation and metal phosphate/metal hydroxide precipitation. Activity effects on chemical equilibria are significant when considering phosphorus. Also of importance in wastewater treatment is the fate of sulfur compounds. This includes the generation of H2S in the digester gas and the fate of the sulfur species in the digested sludge (as a predictor of odour-generating potential).
ADM1 application for tuning and performance analysis of a multi-model observer-based estimator
Authors: Morel E. , Tartakovsky B. , Guiot S.R. , Perrier M.
Published: August 2006

Anaerobic digestion model no.1 (ADM1) was used for tuning and performance analysis of the multi-model observer based estimator (mmOBE). The mmOBE was based on the variable structure model (VSM) of the anaerobic digestion model, which consists of several local submodels, each of which describes a typical process state. Depending on the hydraulic retention time, ADM1 simulated the methanogenic, organic overload, and acidogenic states of the process. These simulations allowed for optimising tunable parameters of the mmOBE. Owing to relatively slow process dynamics, a data acquisition interval as large as one day was sufficient to obtain acceptable accuracy. The simulations of mmOBE performance showed excellent rate of mmOBE convergence to ADM1 outputs. Moreover, mmOBE successfully estimated key kinetic parameters, such as maximal transformation rates of CODs, VFAs, and methane. These estimations can be used in the development of the advanced knowledge-based process system, which uses both available measurements and estimations of key kinetic parameters for extended diagnosis of failures and process trend analysis.
Removal of Azo Dye from Water by Magnetite Adsorption–Fenton Oxidation
Authors: Rongcheng Wu , Jiuhui Qu
Published: August 2006

The aim of this study is to highlight the possibility of using powder magnetite adsorption–Fenton oxidation as a method for removal of azo dye acid red B (ARB) from water. The adsorption properties of magnetite powder towards ARB were studied. The oxidation of adsorbed ARB and regeneration of magnetite adsorbent at the same time by Fenton reagent (hydrogen peroxide [H2O2] + iron (II) [Fe2+]) in another treatment unit with a smaller volume was also investigated. The efficiency of Fenton oxidation of ARB was compared for the reaction carried out in solution and on magnetite. The magnetic separation method was used to recover magnetite after adsorption or regeneration. The results indicated that the adsorption rate was fast. The capacity was strongly dependent on pH and inorganic anions, and pH 3.8 was optimal for the adsorption of ARB. The adsorption can be described well using the Langmuir model. The oxidation was more efficient for ARB adsorbed on magnetite than in solution. The adsorption capacity of magnetite increased significantly after regeneration, which was the result of an increase in surface area of the adsorbent and change of elemental ratio (oxygen:iron [O:Fe]) on the surface. The maximum adsorption capacity for ARB was 32.4 mg/g adsorbent.
Chemical Oxygen Demand Reduction Of Various Wastewater Types Using Magnetic Field‐assisted Fenton Reaction
Authors: Krzemieniewski Miroslaw , Debowski Marcin , Dobrzynska Adriana , Zielinski Marcin
Published: August 2006

Constant magnetic field (CMF) was investigated for its potential to intensify chemical oxygen demand (COD) removal in wastewater when applied with a generalized Fenton reaction. Various types of industrial and domestic wastewater were tested in the experiment. A significant dependence was observed between the wastewater type, dose of reacting substances, time of exposure to CMF, effectiveness of COD removal, and the rate of the advanced oxidation process. The use of CMF resulted in the improvement of the treatment process; however, the efficiency depended to a great extent on the type of wastewater and characteristics of the contained organic matter. Domestic wastewater seemed to be most amenable to the applied treatment (82% COD reduction). The least reduction in COD occurred for wood industry wastewater. In the analyzed wastewater, intense oxidation was observed during the first 60 minutes of the process. Longer reaction time did not increase COD reduction, with the exception of wood industry wastewater. The experiment revealed the possibility of applying smaller doses of the Fenton's reagent, thereby keeping up unchanged treatment efficiency, provided that CMFs are applied.
Measurement of Biosolids Compost Odor Emissions from a Windrow, Static Pile, and Biofilter
Authors: Rosenfeld Paul , Grey Mark
Published: August 2006

A pilot study was conducted to compare odor emissions from a windrow process and an aerated static pile and to determine the odor reduction efficiency of a pilot two‐phase biofilter for odor control of biosolids composting. Chemical compounds identified as responsible for odors from biosolids composting include ammonia, dimethyl disulfide, carbon disulfide, formic acid, acetic acid, and sulfur dioxide (or carbonyl sulfide). Aeration was found to reduce the concentration of ammonia, formic acid, and acetic acid by 72, 57, and 11%, respectively, compared with a nearby windrow, while dimethyl sulfide, carbon disulfide, and sulfur dioxide (or carbonyl sulfide) concentrations were below detection limits. Using dilution‐to‐threshold olfactometry, aeration followed by biofiltration was found to reduce the odor from biosolids composting by 98%. Biofiltration also altered the character of odor emissions from biosolids composting, producing a less offensive odor with an earthy character. Biofiltration was found to reduce the concentration of ammonia, dimethyl disulfide, carbon disulfide, formic acid, acetic acid, and sulfur dioxide (or carbonyl sulfide) by 99, 90, 32, 100, 34, and 100%, respectively. The concentrations of those odorants were estimated to be 3700, 110000,26,37,5, and 1.2 times reported human detection limits before the two‐phase biofilter, respectively, and 42,9600, 18,0,3, and 0 times human detection limits after the biofilter, respectively.
Effects of Chlorination on the Adhesion Strength and Deflocculation of Activated Sludge Flocs
Authors: Mascarenhas T. , Mikkelsen L. H. , Nielsen P. H.
Published: August 2006

A side effect of the application of chlorine for controlling filamentous bulking is deflocculation of floc‐forming bacteria, which may cause unacceptable effluent deterioration depending on dosing. It was assumed that chlorine may adversely affect the adhesion ability of floc bacteria, promoting their erosion in shear flow. The effect of chlorination on the strength of activated sludge flocs was investigated. The adhesion–erosion (AE) model developed by Mikkelsen and Keiding was used to interpret results from deflocculation tests with varying shear and solids concentration. The AE model yields the adhesion enthalpy (δHG/R) of cells in sludge flocs and parameters from the model were used to quantify the sludge in terms of floc strength. Two activated sludges with different initial characteristics were studied. The resulting model parameters showed that the AE model was suitable for quantifying the bond energy of particles to the activated sludge exposed to chlorine. For one activated sludge, adhesion of cells was largely unaffected by the applied chlorine doses. A second sludge showed reduced adhesion strength with chlorine, leading to increasing deflocculation. The simple batch test and AE model proved valuable for assessing the effect of chlorination on the flocs in activated sludge. By use of these procedures, it is possible to determine acceptable chlorine dosing to avoid excessive deflocculation and effluent deterioration.
Case Study I: Application of the Divalent Cation Bridging Theory to Improve Biofloc Properties and Industrial Activated Sludge System Performance—direct Addition Of Divalent Cations
Authors: Higgins Matthew J. , Tom Lou Ann , Sobeck David C.
Published: August 2006

The objectives of this study were to examine the application of the divalent cation bridging theory (DCBT) to improve settling, dewatering, and effluent quality in pilot‐scale reactors and a full‐scale system treating an industrial wastewater. This was accomplished by lowering the monovalent‐to‐divalent (M/D) cation ratio by direct divalent cation addition. Research has shown that the M/D ratio is a potential indicator for settling and dewatering problems at wastewater treatment plants, and M/D ratios above 2 have been associated with poor settling, dewatering, and effluent quality. The M/D ratio of the wastewater in this study ranged from 6 to 20. The cations studied were calcium and magnesium. Results showed that the addition of calcium improved floc properties compared to control reactors with no calcium addition. The reductions in sludge volume index, effluent chemical oxygen demand (COD), and effluent total suspended solids (TSS) were approximately 35, 34, and 55%, respectively, when the M/D ratio was decreased to approximately 2:1. In addition, the cake solids from a belt filter press simulator increased by 72% and the optimum polymer dose required forconditioning was reduced by 70% in the reactor fed the highest calcium concentration when compared to control reactors with no calcium addition. The addition of calcium also decreased the negative effect of high filamentous organism numbers. In general, the addition of magnesium (Mg2+) had similar effects on effluent quality and dewatering properties, although some differences were measured. A full‐scale test using calcium addition was performed. Measurements of effluent quality and floc properties were performed before, during, and after the calcium (Ca2+) addition period. The average M/D ratio during these periods was 6.2, 4.6, and 14.0, respectively. The addition of Ca2+ decreased the effluent five‐day biochemical oxygen demand, effluent TSS, and effluent COD. The increased Ca2+ concentration also improved dewatering measured by a decrease in specific resistance to filtration and capillary suction time. Overall, the addition of divalent cations to the pilot‐ and full‐scale activated sludge systems improved floc properties and the data fit well with the DCBT.
Laboratory‐Scale Comparison of Anaerobic‐Digestion Alternatives
Authors: Reusser Steve , Zelinka Greg
Published: August 2006

Laboratory‐scale digesters were used to perform side‐byside evaluations of alternative digestion systems including thermophilic– mesophilic‐phased digestion (TPAD), acid/methane‐phased digestion, mesophilic digestion, and the performance of the thermophilic stage of TPAD alone. Total detention times in the systems evaluated varied from 8 to 20 days. Temperatures in the mesophilic stage of TPAD were varied from 35 to 43.3°C and temperatures in the thermophilic stage were varied from 55 to 58.9°C. The purpose of the study was to evaluate volatile solids (VS) reduction and thickening properties of the different systems. Parameters evaluated included solids, volatile acids, gas production and quality, various chemical constituents of the sludge, and thickening properties using polymer and ferric chloride plus polymer. The TPAD systems were found capable of higher VS destruction at total detention times of 10 and 12.5 days compared to single‐stage mesophilic or thermophilic digestion at 15 to 20 days. A laboratory‐scale thickening test was performed to evaluate thickening properties. Based on obtaining 95% capture in the test, the polymer demand of mesophilic and acid–methane‐phased digestion was the lowest. The TPAD system required approximately 180% of the dosage of the mesophilic sludge and thermophilic sludge required approximately 310% of the dosage. Temperatures of 40.5 and 43.3 8 C in the mesophilic stage of TPAD were found to increase the polymer requirement and decrease the VS reduction of the TPAD system. Higher temperatures (above 56.1°C) and lower detention times (less than 15 days) in the thermophilic digesters seemed to result in problems with degradation of volatile acids, particularly propionic acid. Water Environ. Res., 76, 360 (2004).
A Direct Comparison of U.S. Environmental Protection Agency's Method 304B and Batch Tests for Determining Activated‐Sludge Biodegradation Rate Constants for Volatile Organic Compounds
Authors: Cano Manuel L. , Wilcox Mark E. , van Compernolle Remi
Published: August 2006

Biodegradation rate constants for volatile organic compounds (VOCs) in activated‐sludge systems are needed to quantify emissions. One current U.S. Environmental Protection Agency method for determining a biodegradation rate constant is Method 304B. In this approach, a specific activated‐sludge unit is simulated by a continuous biological treatment system with a sealed headspace. Batch experiments, however, can be alternatives to Method 304B. Two of these batch methods are the batch test that uses oxygen addition (BOX) and the serum bottle test (SBT). In this study, Method 304B was directly compared to BOX and SBT experiments. A pilot‐scale laboratory reactor was constructed to serve as the Method 304B unit. Biomass from the unit was also used to conduct BOX and modified SBT experiments (modification involved use of a sealed draft‐tube reactor with a headspace recirculation pump instead of a serum bottle) for 1,2‐dichloroethane, diisopropyl ether, methyl tertiary butyl ether, and toluene. Three experimental runs ‐ each consisting of one Method 304B experiment, one BOX experiment, and one modified SBT experiment ‐ were completed. The BOX and SBT data for each run were analyzed using a Monod model, and best‐fit biodegradation kinetic parameters were determined for each experiment, including a first‐order biodegradation rate constant (K1). Experimental results suggest that for readily biodegradable VOCs (i.e., K1 > 10 L/g volatile suspended solids [VSS]•h) the two batch techniques can provide improved means of determining biodegradation rate constants compared with Method 304B. In particular, these batch techniques avoid the Method 304B problem associated with steady‐state effluent concentrations below analytical detection limits. However, experimental results also suggest that the two batch techniques should not be used to determine biodegradation rate constants for slowly degraded VOCs (i.e., K1 < 0.1 L/g VSS•h).
Modeling Microbial Kinetics in an Anaerobic Sequencing Batch Reactor ‐ Model Development and Experimental Validation
Authors: Bagley David M. , Brodkorb Toby S.
Published: August 2006

Anaerobic sequencing batch reactors (ANSBRs) typically have not been used to treat wastewater, possibly because of the potential rapid acidification that may occur with batch feeding of an anaerobic reactor. To investigate ANSBR capabilities, a simulation model was developed and experimentally validated. The model explicitly considers different microbial populations in an anaerobic community, predicts formation and consumption of intermediate products as a function of hydrogen partial pressure, predicts system pH, and considers inhibition caused by pH and hydrogen partial pressure. Simulation model results agreed well with experimental results from three separate tests using a laboratory‐scale ANSBR receiving glucose. Experimental and simulation results indicated that, for the same organic loading rate, reactor performance improved with a slower fill cycle. The model may be used to rapidly identify other opportunities to improve the capability of ANSBRs to treat a variety of wastewater types.
An Integer Program for Optimizing Sanitary Sewer Rehabilitation Over a Planning Horizon
Authors: de Monsabert Sharon , Ong Chee , Thornton Paul
Published: August 2006

Inflow and infiltration (I/I) associated with sanitary sewer pipeline and manhole defects have been known to cause unnecessary treatment expenditures. It is estimated that 10% or more of treated wastewater sources can be attributed to extraneous I/I. This paper documents an optimization model that analyzed costs and benefits of reducing the amount of I/I through selected rehabilitation methods recommended following a closed‐circuit TV inspection over a 20‐year planning horizon. An integer program was formulated using the General Algebraic Modeling System to optimize the sewer rehabilitation schedule and present value costs of repairs and I/I treatment. Results of a detailed analysis and the optimal rehabilitation schedule for a subshed of the Little Huntington Creek sewer system in Fairfax County, Virginia, are presented.
In Situ Septic Tank Effluent Denitrification Using a Sulfur‐Limestone Process
Authors: Zhang Tian C. , Shan Jun
Published: August 2006

Septic tanks are the second largest source of groundwater nitrate contamination. In this study, the feasibility of coupling a conventional lateral field with a sulfur‐limestone (S/L) layer to treat nitrate in septic tank effluent was investigated using column reactors to simulate the septic tank soil adsorption system. The effects of different hydraulic loading rates, nitrogen loading rates, depth of SIL layers, and ratio of SIL‐to‐gravel on reactor performance were investigated. The profiles of ammonium, nitrite, nitrate, sulfate, calcium, and other parameters along the depth of reactors were measured. Significant nitrification was observed in the sand layer, while significant denitrification was observed in the S/L layer. Sulfate and hardness were produced in accordance with stoichiometric relationships. The results demonstrate that the S/L method is very effective in denitrification, while production of sulfate and hardness and existence of sulfide in effluent may be limiting factors in its application.
Cellular properties of human erythrocytes preserved in saline–adenine–glucose–mannitol in the presence of L‐carnitine
Authors: Arduini Arduino , Minetti Giampaolo , Ciana Annarita , Seppi Claudio , Brovelli Augusta , Profumo Antonella , Vercellati Cristina , Zappa Manuela , Zanella Alberto , Dottori Secondo , Bonomini Mario
Published: August 2006

L‐Carnitine (LC) in the preservation medium during storage of red blood cells (RBC) can improve the mean 24‐hr percent recovery in vivo and increase RBC life‐span after reinfusion. The purpose of the study was to investigate the differences in the biochemical properties of RBCs stored in the presence or absence of LC, and the cell‐age related responses to storage conditions and to LC. RBC concentrates in saline‐adenine‐glucose‐mannitol (SAG‐M) were stored in the presence or absence of 5 mM LC at 4°C for up to 8 weeks. RBC subpopulations of different densities were prepared by centrifugation on Stractan density gradient. Cells were sampled at 0, 3, 6, and 8 weeks, and hematological and cellular properties analyzed (MCV, MCHC, 4.1a/4.1b ratio as a cell age parameter, intracellular Na+ and K+). After 6 weeks, MCV of RBC stored in the presence of LC was lower than that of controls (6 weeks MCV: controls 95.4 ± 1.8 fl; LC 91.5 ± 2.0 fl; n = 6; P < 0.005). This was due to swelling of control cells, and affected mainly older RBCs. LC appeared to reduce or retard cell swelling. Among the osmotically active substances whose changes during storage could contribute to cell swelling, only intracellular Na+ and K+ differed between stored control RBCs and LC‐treated cells. LC reduces the swelling of older cells during storage at 4°C in SAG‐M, possibly by acting on the permeability of cell membrane to monovalent cations. Am. J. Hematol., 2006. © 2006 Wiley‐Liss, Inc.
Combined D‐dimer and clinical probability are useful for exclusion of recurrent deep venous thrombosis
Authors: Aguilar Carlos , del Villar Valentin
Published: August 2006

It is estimated that up to one‐third of patients with a history of deep venous thrombosis (DVT) present with symptoms of recurrent DVT. Our objective was to investigate both the diagnostic value of D‐dimer (DD) and safety of a standard diagnostic algorithm including clinical assessment, plasma DD levels, and compression venous ultrasound as diagnostic tools in outpatients presenting with clinically suspected acute recurrent DVT of the lower limbs. We have enrolled 105 outpatients with a previous history of confirmed DVT and clinically suspected recurrent DVT. A 3‐month follow‐up period was carried out for patients in whom DVT was initially excluded. Prevalence of DVT in our study population was 44.8% (47/105). DD was negative in 17.1% of cases (18/105) and DVT could be ruled out in 15.2% of patients evaluated (16/105) on the basis of an unlikely clinical probability and a negative DD result. Only one false negative DD result in a patient scored as likely for DVT was found. Sensitivity, specificity, positive and negative predictive value of DD for the diagnosis of DVT were 97.9% (95% CI 88.9–99.6%), 29.3% (95% CI 19.2–42.0%), 52.9% (95% CI 42.5–63.0) and 94.4% (95% CI 74.2%–99.0), respectively. Sensitivity was 100% (95% CI 75.7–100) in the group of patients in whom DVT was considered unlikely. A diagnostic strategy combining clinical evaluation and DD has proved to be useful for the exclusion of DVT in subjects with clinically suspected recurrent DVT, especially in patients included in the lower clinical pretest probability group. Am. J. Hematol., 2006. © 2006 Wiley‐Liss, Inc.
Reversible posterior leukoencephalopathy syndrome after repeat intermediate‐dose cytarabine chemotherapy in a patient with acute myeloid leukemia
Authors: Saito Bungo , Nakamaki Tsuyoshi , Nakashima Hidetoshi , Usui Takako , Hattori Norimichi , Kawakami Keiichiro , Tomoyasu Shigeru
Published: August 2006

A 56‐year‐old man was admitted to our hospital with leukocytosis, anemia, and thrombocytopenia. Acute monoblastic leukemia was diagnosed. Two subsequent courses of consolidation chemotherapy consisted of conventional doses of cytarabine and intermediate‐dose cytarabine. Intermediate‐dose cytarabine was infused intravenously every 12 hr for 6 days. On day 15 after the final infusion of cytarabine, the patient suffered headache, and on day 21, he experienced a decrease in sensation on the sole of his left foot. Magnetic resonance imaging (MRI) of the brain revealed widespread areas of white matter edema. Cerebrospinal fluid (CSF) examination revealed an increase in the number of cells to 31 mm−3; the majority were lymphocytes. No infiltration of leukemia cells was seen. After 2 months, brain MRI findings were normal. The clinicoradiologic features of the case were consistent with reversible posterior leukoencephalopathy syndrome (RPLS). RPLS in the present case was unlikely to have been caused by direct neurotoxicity because (1) the doses of cytarabine (500 mg/m2; total dose 9.2 g) were much smaller than those in reported cases and were repeatedly infused until RPLS developed; (2) the RPLS developed 21 days after the final infusion of cytarabine, a much longer period than previously reported; (3) the slight leukocytosis in the CSF observed on day 33 might also have been related to the cellular immune responses evoked by the infused cytarabine. These details suggest not only that direct cerebral neurotoxicity of cytarabine but also that some type of allergic response may have been involved in the development of RPLS. Am. J. Hematol., 2006. © 2006 Wiley‐Liss, Inc.
Prevalence of building‐related symptoms as an indicator of health and productivity
Authors: Niemelä Raimo , Seppänen Olli , Korhonen Pirjo , Reijula Kari
Published: August 2006

Background

The prevalence of building‐related symptoms (BRS) is commonly used to characterize the indoor air quality in office buildings. To analyze the costs of building renovation and the improvement of the indoor environment, it is useful to quantitatively relate the prevalence or intensity of BRS to productivity. The intent of this study is to summarize the links between the BRS and productivity, and demonstrate this linkage in two case buildings.

Material and Methods

A literature was surveyed for studies that measured simultaneously the prevalence or intensity of BRS and subjectively reported or objectively measured productivity. Case studies in two office environments were performed. An association between the prevalence of BRS and productivity of workers in a call center and in an insurance office were investigated. In the first case study, the productivity was expressed using the direct productivity metrics, namely the number of telephone contacts during active working hours while in the second case, the productivity was assessed by using the data concerning sick leave rates.

Results

Employees who report more BRS also have more often absences which relate to indoor environment quality (IEQ). Their productivity is lower than those who have better IEQ in their offices. Despite uncertainties related to the data concerning recorded sick leave and self‐reported productivity, the number of studies showing an association between BRS and productivity or sick leave suggests that such a relationship exists. The present case studies also demonstrated an association between the BRS and the direct productivity. Based on the data from the call center, a reduction of 10%‐units in the prevalence of general symptoms (such as fatigue, headache, nausea, etc.) corresponded with a gain of 1.5% in performance. Based on the findings in the insurance company, a reduction of 10%‐units in the prevalence of irritation symptoms corresponded with a decrease of 0.7% in the short‐term absenteeism.

Conclusions

A review of 23 studies suggests that a linkage exists between typical BRS and productivity indicators such as task or work performance or absence from work. Quantitative associations between BRS and productivity were demonstrated in two office environments. Quantitative associations between BRS and economic metrics enable cost‐benefits analysis. Am. J. Ind. Med. 2006. © 2006 Wiley‐Liss, Inc.
Therapeutic effects for hypersensitivity pneumonitis induced by Japanese mushroom (Bunashimeji)
Authors: Tsushima Kenji , Furuya Shino , Yoshikawa Sumiko , Yasuo Masanori , Yamazaki Yoshitaka , Koizumi Tomonobu , Fujimoto Keisaku , Kubo Keishi
Published: August 2006

Background

Bunashimeji‐related hypersensitivity pneumonitis is found among workers who cultivate the mushroom in indoor facilities. An evaluation of protective measures was initiated using the outcomes of clinical, immunological, and radiological findings.

Methods

Twenty‐two patients presented with symptoms of HP; all were employed cultivating Bunashimeji mushrooms in indoor facilities. After hospitalization, 6 of 22 patients quit their job to avoid exposure to spores (Avoidance group). Sixteen patients continued to work used a mask for 3 months, and were then divided into two subgroups: Mask alone (seven patients) and mask plus oral prednisolone (Mask + PSL) (nine patients). The erythrocyte sedimentation rate (ESR), serum Krebs von der Lungen‐6 (KL‐6), surfactant protein‐D (SP‐D), lymphocyte stimulation test (LST), ground‐glass scores in chest high‐resolution computed tomography (HRCT), and bronchoalveolar lavage (BAL) were assessed before and after treatment.

Results

Complete avoidance resulted in a significant decrease in LST. There was a significant decrease after PSL treatment in serum KL‐6, SP‐D, and total cell counts in the BAL fluid in the Mask + PSL group. In the Mask alone group, serum KL‐6, SP‐D, ground‐glass scores in chest HRCT and total cell counts in BAL fluid showed high levels compared with the other two groups.

Conclusions

Complete cessation was the best treatment for hypersensitivity pneumonitis. The use of a mask was ineffective for patients with a high serum KL‐6 and SP‐D concentration and severe ground‐glass opacity on chest HRCT. Initial treatment with PSL is recommended for these patients with high levels of total cell counts in BAL fluid. Am. J. Ind. Med. 2006. © 2006 Wiley‐Liss, Inc.
Patterns of fatigue among seafarers during a tour of duty
Authors: Wadsworth Emma J.K. , Allen Paul H. , Wellens Benjamin T. , McNamara Rachel L. , Smith Andrew P.
Published: August 2006

Background

Work‐related fatigue is associated with sickness absence and mental and physical health problems, and may increase the risk of accidents and injuries at work. Relatively little is known about fatigue among seafarers, particularly during a tour of duty. The aim of this study was to describe the pattern of day to day fatigue among seafarers during a tour at sea.

Methods

Participants from the offshore support, short sea and coastal, and deep sea sectors of the UK shipping industry completed daily diaries. Information about sleep and fatigue was collected each day on waking and retiring.

Results

Fatigue on waking was a more sensitive measure of cumulative occupational fatigue than fatigue on retiring. Fatigue on waking increased between the start and end of tour. This increase took place in particular during the first week at sea, and was most apparent among those on shorter tours of duty.

Conclusions

Day to day changes in fatigue are measurable, and may vary among particular sub‐groups of seafarers. Used among larger groups, such a diary method could help identify times and activities associated with the greatest risk. Am. J. Ind. Med. 2006. © 2006 Wiley‐Liss, Inc.