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The solid-phase microextraction (SPME) technique has been widely applied to sample the environmental matrices for organic compounds. The success of employing SPME requires knowledge of the coating-matrix partition coefficients of analytes. Polydimethylsiloxane (PDMS) is the most widely used polymeric coating for the SPME device. In this study, the quantitative structure activity relationships (QSAR) for the PDMS-water (K fw ) and PDMS-gas partition coefficients (K fg ) of organic compounds were established using E-Dragon software and multiple linear regression analysis. K fw was significantly correlated to the BLTA96 descriptor, implying that the PDMS-water partition coefficients were primarily determined by the polarity of analyte molecules. In addition, K fg was significantly dependent on the Harary H index, i.e., molecular connectivity index or polarizability, of the organic compounds. If the organic compounds were grouped in alkanes and aromatic hydrocarbons, K fw and K fg were well proportional to their octanol–water partition coefficients. The statistical results of internal and external validation, determined by the square of the coefficient of multiple correlation (R 2 ≥ 0.865) and the leave-one-out cross-validation (Q 2 ≥ 0.751), showed that the QSAR models developed herein have good stability and great predictive power among the molecular descriptors and SPME/PDMS partition coefficients. The results of this study will facilitate the practical applications of SPME as a greener methodology.

The permeability of aromatic hydrocarbons, i.e. BTEX and styrene, through PVC pipes was investigated using a 6-cm pipe-bottle model with direct solid-phase microextraction (SPME) sampling. It was found that an aromatic hydrocarbon with a large molecular size or low polarity may be less permeable through PVC pipes. In addition, the diffusion coefficients of BTEX and styrene in PVC pipes ranged from 4.87 to 7.64 × 10 −8 cm 2 /s. According to the simulation results of a one-dimensional diffusion model, it is speculated that diffusion transport of benzene and toluene in PVC pipes may have non-Fickian behavior. The advantage of using the innovated test model is that SPME provides a nondestructive analytical means to monitor the concentrations of organic compounds in pipe-water. Therefore, the pipe-bottle model developed herein has potential applications in determining the resistance of polymeric pipes to permeation by solvents in the aqueous solution.

The organic content of municipal solid waste has long been an attractive source of renewable energy, mainly as a solid fuel in waste-to-energy plants. This study focuses on the potential to use microbial fuel cells to convert municipal solid waste organics into energy using various operational conditions. The results showed that two-chamber microbial fuel cells with carbon felt and carbon felt allocation had a higher maximal power density (20.12 and 30.47 mW m-2 for 1.5 and 4 L, respectively) than those of other electrode plate allocations. Most two-chamber microbial fuel cells (1.5 and 4 L) had a higher maximal power density than single-chamber ones with corresponding electrode plate allocations. Municipal solid waste with alkali hydrolysis pre-treatment and K3Fe(CN)6 as an electron acceptor improved the maximal power density to 1817.88 mW m-2 (~0.49% coulomb efficiency, from 0.05–0.49%). The maximal power density from experiments using individual 1.5 and 4 L two-chamber microbial fuel cells, and serial and parallel connections of 1.5 and 4 L two-chamber microbial fuel cells, was found to be in the order of individual 4 L (30.47 mW m-2) > serial connection of 1.5 and 4 L (27.75) > individual 1.5 L (20.12) > parallel connection of 1.5 and 4 L (17.04) two-chamber microbial fuel cells . The power density using municipal solid waste microbial fuel cells was compared with information in the literature and discussed.

A pipe-bottle model with a volume of 125 mL was proposed to estimate the permeability of benzene and toluene for the polyvinyl chloride (PVC) water pipes. The concentrations of permeant in pipe-water were directly sampled using the solid phase microextraction (SPME) technique. The permeability coefficients of benzene and toluene were 0.07 and 0.025 μg/cm/hr, respectively, indicating toluene is less permeable through the PVC pipe. Using a transient mass diffusion equation and appropriate initial and boundary conditions, the simulation studies of the concentration profiles of benzene in pipe-water implied that swelling of the PVC pipe wall might have a significant effect on the permeation experiments. The new pipe-bottle model is a less time-consuming and more sensitive means to determine the chemical resistance of polymeric pipes to permeation by organic solvents.

Phthalates (PAEs) have high solubility in polymers and are added as plasticisers to increase the flexibility and plasticity of polymeric materials. In this study, methanol, hexane, ethyl ether and acetone were used for the extraction of PAEs from chemical protective gloves at temperatures of 20–80 °C. DEHP (di-2-ethylhexyl phthalate) and DBP (di-n-butyl phthalate) were extracted from neoprene, nitrile and PVC glove samples using the above four solvents. The extraction level of DEHP from the glove samples was proportional to the Log K ow values of the extraction solvents. This result implied that PAEs were more soluble in non-polar solvents and were likely to be extracted from the gloves. Increasing the extraction temperature resulted in a higher extraction of DBP and DEHP from the gloves. In the ASTM F739 permeation method, the aromatic solvents permeated through the glove samples and dissolved DEHP. If the permeant and DEHP had similar solubility parameters, DEHP was likely to be leached from the gloves. The modelling results indicated that the permeation behaviour of the organic solvent in the PVC glove was non-Fickian diffusion. It was speculated that the plasticiser increased the diffusion coefficients of the permeants in the PVC gloves. This study suggested that the potential dissolution and leaching of PAEs from chemical protective gloves should be a concern for workers who handle organic solvents.

Phthalate esters (PAEs) have been widely added as the plasticizer to increase the flexibility and ductility of polymeric materials. In this study, organic solvents, such as methanol, hexane, ethyl ether and acetone, were used for the direct extraction of plasticizers in neoprene, nitrile, and PVC gloves, under a temperature range of 20-80°C. The results showed that DEHP (Di-2-ethylhexyl phthalate) and DBP (Di-n-butyl phthalate) were analyzed in all three glove samples. The extraction capability of PAEs from the PVC gloves was the highest, while that from the neoprene gloves was the lowest. It was found that the extraction capabilities of DEHP from the glove samples were proportional to Log Kow of the extraction solvents. This result implied that PAEs were more soluble in a non-polar solvent and likely to be extracted from the glove samples. In addition, the amount of extracted PAEs increased with the experimental temperatures. As workers wearing the chemical protective gloves, there is a need to understand the dissolution potential of PAEs in the gloves and to assess the skin exposure of PAEs.

Several studies have focused on the potential impact of children's hearing loss on learning and development. Recently, numerous teenage students have been found to be fond of listening to music on personal devices and participating in recreational music activities. The objective of this study was to investigate teenage students' hearing impairment, their experience with recreational noise exposure, and their self-reported hearing. The participants were 1878 first-year students at a university in Taiwan. The result of the pure tone audiometry test showed that 11.9% of the participants had one or two ears with a hearing threshold over 25 dB. Over the past year, approximately 80.9% of the participants had taken part in at least one loud-noise recreational activity, and 90.9% of the participants were in the habit of using earphones. Among the participants, 190 students with a high level of recreational noise exposure were assigned to the exposure group, and 191 students with a low level of recreational noise exposure constituted the control group. The exposure group had more hearing problems than the control group, but no significant difference existed between the two groups in the pure tone audiometry test (p=0.857). It is suggested that the schools should reinforce hearing health education and proactively provide intervention measures, such as hearing tests, evaluation of noise exposure, and hearing protection.

Road traffic noise exposure has been associated with auditory and non-auditory health effects, but few studies report noise characteristics. This study determines 24-h noise levels and analyzes their frequency components to investigate associations between seasons, meteorology, land-use types, and traffic. We set up 50 monitoring stations covering ten different land-use types and conducted measurements at three times of the year to obtain 24-h-average A-weighted equivalent noise levels (LAeq,24h) and frequency analyses from 2013 to 2014 in Taichung, Taiwan. Information on land-use types, road parameters, traffic flow rates, and meteorological variables was also collected for analysis with the annual averages of road traffic noise and its frequency components. The annual average LAeq,24h in Taichung was 66.4 ± 4.7 A-weighed decibels (dBA). Significant differences in LAeq,24h and frequency components were observed between land-use types (all p-values

A cold, electrodeless method was used to prepare bimetals (Fe/Cu, Fe/Ni) and trimetals (Fe/Cu/Ni) for the treatment of trichloroethylene (TCE). With Fe/Cu, the degradation of TCE was observed to increase with increasing copper content up to 9.26 % (w/w) with a first-order degradation rate constant approximately 10 times faster than that of zero-valent iron (ZVI) alone. For copper content greater than 9.26 %, the TCE degradation rate decreased. Dechlorinated compounds were initially observed but they were transitory and accounted for no more than 9 % of initial TCE mass on a carbon molar basis. Ethylene was the primary end product of TCE reduction. Similarly for Fe/Ni, increasing rates of degradation were observed with increasing amounts of nickel with a maximum degradation rate constant of about 30 times higher than that of ZVI alone. However, the amount of nickel needed to reach the maximum rate was only 0.25 %. When copper and nickel were plated onto iron, the maximum reaction rate constant was approximately 50 times higher than that of ZVI. The maximum degradation of TCE was observed for a copper and nickel content of 4.17 % and 0.40 %, respectively. The experimental results indicated that TCE degradation was enhanced by more than one order of magnitude when copper and/or nickel was plated onto the zero-valent iron. However, copper or nickel plated onto iron by the elctrodeless process was found to leach out during the reaction which may, in turn, impact the contaminated water.

A direct immersion solid phase microextraction (DI-SPME) method was developed for the analysis of dentin monomers in saliva. Dentine monomers, such as triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA) and 2,2-bis-[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl]-propane (Bis-GMA), have a high molecular weight and a low vapor pressure. The polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber with a medium polarity was employed for DI-SPME, and 215 nm of detection wavelength was found to be optimum in the chromatogram of HPLC measurement. The calibration range for DI-SPME was 0.30–300 μg/mL with correlation coefficients ( r ) greater than 0.998 for each analyte. The DI-SPME method achieved good accuracy (recovery 96.1–101.2%) and precision (2.30–8.15% CV) for both intra- and inter-day assays of quality control samples for three target compounds. Method validation was performed on standards dissolved in blank saliva, and there was no significant difference ( p > 0.2) between the DI-SPME method and the liquid injection method. However, the detection limit of DI-SPME was as low as 0.03, 0.27 and 0.06 μg/mL for TEGDMA, UDMA and Bis-GMA, respectively. Real sample analyses were performed on commercial dentin products after curing for the leaching measurement. In summary, DI-SPME is a more sensitive method that requires less sample pretreatment procedures to measure the resin materials leached in saliva.

The chemical resistance of chlorinated hydrocarbons in starch/polyvinyl alcohol (PVA) blends has been investigated using a permeation cell with an in-cell solid phase microextraction (SPME) sampling device. The chlorinated hydrocarbon with a large molecule size or lower polarity was found to be less permeable through the starch/PVA blends. The tensile strength and chemical resistance of chlorinated hydrocarbons decreased with an increase in the starch content of blends. For the starch/PVA blends, the solubility of chlorinated hydrocarbons was inversely proportional to their molecular weight, molar volume and log Kow. The diffusion coefficients and solubility of permeants were proportional to the content of starch in the starch/PVA blends. It is plausible that the blends will be inclined to the starch characteristics as the plasticizer (i.e. glycerin) disrupts the rigidity arrangements of the starch and PVA. The present work provides information on the extent of organic compound permeation through starch/PVA blends for the practical application.

Polydimethylsiloixane (PDMS) is commonly used as the coated polymer in the solid phase microextraction (SPME) technique. Based on the principle of partitioning, PDMS/SPME can be a fast, economic and solvent-free sampling method to extract volatile organic compounds (VOCs) from gaseous or aqueous samples. This study experimentally investigated the adsorption of benzene and toluene onto PDMS/SPME, and estimated the effective diffusion coefficients of benzene and toluene in the PDMS coating. The results showed that the effective diffusion coefficients of these two compounds did not change with the concentrations of the gaseous or aqueous samples. The effective diffusion coefficients were found to linearly increase with the stirring speeds of the aqueous solution. The empirical model proposed in this study can be used to estimate the effective diffusion coefficients and extraction time at different stirring speeds, which will contribute to the practical applications of the SPME technique.

N,N-dimethylformamide (DMF) and methyl ethylketone (MEK) are the hazardous chemicals commonly used in the synthetic leather industries. Although chemical protective gloves provide adequate skin exposure protection to workers in these industries, there is currently no clear guideline or understanding with regard to the use duration of these gloves. In this study, the permeation of DMF/MEK mixture through neoprene gloves and the desorption of chemicals from contaminated gloves were conducted using the ASTM F739 cell. The acceptable use duration time of the gloves against DMF/MEK permeation was estimated by assuming a critical body burden of chemical exposure as a result of dermal absorption. In a re-exposure cycle of 5 days, decontamination of the gloves by aeration at 25 °C was found to be inadequate in a reduction of breakthrough time as compared to a new unexposed glove. However, decontamination of the gloves by heating at 70 or 100 °C showed that the protective coefficient of the exposed gloves had similar levels of resistance to DMF/MEK as that of new gloves. Implications of this study include an understanding of the use duration of neoprene gloves and proper decontamination of chemical protective gloves for reuse.

Polydimethylsiloxane (PDMS)-coated devices were employed to remove benzene from an aqueous solution in a batch reactor. Because of significant swelling of the PDMS membrane, the diffusion of benzene in PDMS exhibited pseudo-Fickian behavior. Based on the solution-diffusion model, the diffusion, solubility and permeation coefficients of benzene in PDMS membrane were obtained and found to be dependent on the benzene concentration of the aqueous solution. The sorption isotherm of benzene solution in PDMS membrane was of the Freundlich type and similar to linear partition. A mass transfer model provided good simulations of the results of aqueous benzene sorbed by the PDMS-coated Tellerette packing using the permeability obtained by the separate sorption experiments. The PDMS extraction technique can be applied to remove benzene from industrial wastewater, especially for lower concentrations.

Many volatile organic compounds (VOCs) are emitted during the manufacturing of thin film transistor liquid crystal displays (TFT-LCDs), exposure to some of which has been reported to be associated with kidney dysfunction, but whether such an effect exists in TFT-LCD industry workers is unknown. This cross-sectional study aimed to investigate the association between exposure to VOCs and kidney dysfunction among TFT-LCD workers. The results showed that ethanol (1811.0+/-1740.4 ppb), acetone (669.0+/-561.0 ppb), isopropyl alcohol (187.0+/-205.3 ppb) and propylene glycol monomethyl ether acetate (PGMEA) (102.9+/-102.0 ppb) were the four dominant VOCs present in the workplace. The 63 array workers studied had a risk of kidney dysfunction 3.21-fold and 3.84-fold that of 61 cell workers and 18 module workers, respectively. Workers cumulatively exposed to a total level of isopropyl alcohol, PGMEA and propylene glycol monomethyl ether> or =324 ppb-year had a significantly higher risk of kidney dysfunction (adjusted OR=3.41, 95% CI=1.14-10.17) compared with those exposed to

The permeation resistance of neoprene gloves to N , N -dimethylformamide (DMF) and methyl ethylketone (MEK) was conducted using the ASTM F739 test method. The permeability coefficients and standardized breakthrough time were found to be significantly different ( p

The permeation of binary and ternary mixtures of benzene, toluene, ethyl benzene and p-xylene through nitrile gloves were investigated using the ASTM F739 test cell. The more slowly permeating component of a mixture was accelerated to have a shorter breakthrough time than its pure form. The larger differences in solubility parameter between a solvent mixture and glove resulted in a lower permeation rate. Solubility parameter theory provides a potential approach to interpret the changes of permeation properties for BTEX mixtures through nitrile gloves. Using a one-dimensional diffusion model based on Fick's law, the permeation concentrations of ASTM F739 experiments were appropriately simulated by the estimated diffusion coefficient and solubility. This study will be a fundamental work for the risk assessment of the potential dermal exposure of workers wearing protective gloves.

Volatilization of VOCs was investigated using a 55-gal laboratory-scale model in which air sparging experiments were conducted with a vertical air injection well. In addition, X-ray imaging of an air sparging sand box showed air flows were in the form of air bubbles or channels depending on the size of the porous media. Air–water mass transfer was quantified using the air–water mass transfer coefficient which was determined by fitting the experimental data to a two-zone model. The two-zone model is a one-dimensional lumped model that accounts for the effects of air flow type and diffusion of VOCs in the aqueous phase. The experimental air–water mass transfer coefficients, K G a, obtained from this study ranged from 10 −2 to 10 −3 1/min. From a correlation analysis, the air–water mass transfer coefficient was found to be directly proportional to the air flow rate and the mean particle size of soil but inversely proportional to Henry's constant. The correlation results implied that the air–water mass transfer coefficient was strongly affected by the size of porous media and the air flow rates.

In this study, the permeation resistance of nitrile and neoprene gloves to benzene and 1,2-dichloroethane was investigated using two permeation cells according to the ISO 6529, ASTM F739, and EN 374-3 standard test methods. The permeability coefficients were found to significantly increase with the flow rate of the collection medium. The appropriate flow rate of nitrogen collection should be higher than 75 and 150 mL/min for the ISO 6529 and ASTM F739 cells, respectively. For an open-loop system, the permeability coefficient of the ISO 6529 cell was obviously greater than that of the ASTM F739 cell, and the difference between these two cells was statistically significant. On the other hand, the breakthrough time was about 20–30 min for either the ISO 6529 or ASTM F739 cell at different flow rates of nitrogen collection. Fick's diffusion coefficient and solubility of permeant in the polymer glove can be specified as alternative test results for standard methods.

The chemical resistance of eight organic solvents in high density polyethylene (HDPE) geomembrane has been investigated using the ASTM F739 permeation method and the immersion test at different temperatures. The diffusion of the experimental organic solvents in HDPE geomembrane was non-Fickian kinetic, and the solubility coefficients can be consistent with the solubility parameter theory. The diffusion coefficients and solubility coefficients determined by the ASTM F739 method were significantly correlated to the immersion tests (p

Experiments on the permeation of several chlorinated and aromatic hydrocarbons through high-density polyethylene (HDPE) geomembranes were conducted using the ASTM F-739 standard test method. The diffusion coefficients were estimated by a one-dimensional diffusion equation based on Fick’s second law, and the solubilities of the solvents in HDPE were determined by the steady state permeation rates. The one-dimensional transient model was able to simulate the permeation concentrations and implied that equilibrium partition between organic solvent and HDPE geomembrane was not achieved during the initial permeation. The solubilities of organic solvents in the HDPE geomembranes obtained by immersion tests or weight gain methods of permeation experiments were not an appropriate boundary condition for the model simulation of permeation. It was found that the diffusion coefficients and solubilities of organic solvents correlated well with their molecular weights and dipole moment, respectively. The present work pr...

Several farms on the north seashore of Taiwan were contaminated with cadmium and lead since the early 1980s. At the contaminated site, the average soil concentrations of cadmium and lead, analyzed in 1982 and 1996, ranged from 385 to 44 mg∕kg and 3,336 to 464 mg∕kg , respectively. In this study, the exposure and risk assessment were conducted using an environmental fate and transport model, RESRAD-CHEM, to estimate carcinogenic risk and noncarcinogenic risk for cadmium and lead on a population exposed to the pollutants. Using the concentration data of 1982, the RESRAD-CHEM model was able to appropriately estimate the residual concentrations of cadmium and lead for 1996. Since there were no carcinogenic slope factors available for several exposure pathways, the cancer risk assessment of cadmium was estimated using the inhalation pathway only. The estimated carcinogenic risks were 5.5–7.6 ( 10−6 ) using the 1982 concentration data. The maximum hazard index was estimated to be 488 and significantly higher fo...

The dissolution, diffusion, and volatilization of a free-phase benzene glob in the presence of air sparging were measured in laboratory-scale air sparging reactors and modeled using a dissolution.diffusion.volatilization (DDV) model. The estimated dissolution rate coefficients (K\Df\N) from the DDV model ranged from 0.0050 to 0.017 mm/min while the estimated volatilization rate coefficients (K\DL\N) ranged from 0.012 cm/min to 0.029 mm/min. The DDV model fitted well the aqueous phase migration of benzene for air channels spaced at 45 and 60 mm. For air channels spaced at 30 mm, the model fitted the aqueous migration at most locations except above the benzene glob where the model underestimated the experimentally determined concentrations. However, the mass removed using the gas phase concentrations as predicted by the model were 65% of the actual mass removed. These observations suggest that other mass transport mechanisms may influence benzene mass removal, especially when the air channels are close to the benzene glob.

Ultrafiltration (UF) studies were conducted on latex and ink rinse wastewaters to assess the potential of concentrating the wastewater and recovering the permeate for reuse and recycling purposes. The physicochemical characteristics of the ink and latex wastewater suggested that the quality of both wastewaters was strongly dependent on the rinse process. A 4-fold and 7-fold concentration of ink and latex wastewater, respectively, may be achieved depending on the initial physicochemical characteristics of the wastewater. The UF system concentrated the latex wastewater to a total solids (TS) concentration of 275 g/L (approx. 28%) and to 99 g/L (approx. 10%) for ink wastewater. The permeates had turbidities ranging from 0.13 to 0.4 NTU. However, a significant percentage of the TS remained in the permeate of the ink wastewater which may require further treatment before it can be reused. For latex wastewater, it is likely that the retentate can be reused along with the permeate for rinsing purposes. For the ink wastewater, both pore blocking and cake resistance models were able to describe the change in flux with time. However, for the latex wastewater, pore blocking seemed to describe the flux with time data better than the cake resistance models. The fouling coefficient, K, for the pore blocking model was found to be a function of the TS present in the latex wastewater. © 2004 Elsevier B.V. All rights reserved.

This study aims to explore the efficiency of using online education as an intervention measure to prevent occupational hazards in a clinical nursing setting. The subjects were 320 female nursing staff from two hospitals in Taiwan. The questionnaire results indicated that the subjects primarily experienced human factor occupational hazards, as well as psychological and social hazards. Specifically, 73.1% and 69.8% of the subjects suffered from poor sleep quality and low back pain, respectively. After web-based learning, the experimental group had higher post-test scores than the control group in terms of knowledge, attitudes, and practices (KAP). However, there was only a significant difference (p &lt, 0.05) in their knowledge about the prevention of occupational hazards. It is suggested that an online discussion may enhance nursing staff’s participation in web-based learning, and further facilitate their comments on negative factors. The findings can highly promote nursing staff’s attitudes and practices toward preventing occupational hazards through web-based learning.

Nonequilibrium air-water mass transfer experiments for six volatile organic compounds (VOCs) were conducted using a bench-scale air sparging system. VOCs used were carbon tetrachloride, trichloroethylene, tetrachloroethylene, chloroform, dichloromethane, and toluene. The average particle size of the porous media used ranged from 0.278 to 1.71 mm. The air-water mass transfer coefficients were estimated by fitting the experimental data to a lumped parameter model. The model assumed that the saturated porous media under air sparging conditions consisted of two zones. In the mass transfer zone, VOCs were directly impacted by the flow of air in the air channels, while in the bulk water zone, VOCs were not directly affected by the air flow in the air channels. The estimated air-water mass transfer coefficients (K{sub G}a) were found to increase for higher injected air flow rates and for larger mean particle sizes of porous media but were inversely proportional to the Henry`s law constant of the VOCs. An empirical correlation was developed by correlating the Sherwood number with the Peclet number, the Henry`s law constant, and the mean particle size of porous media. The estimated fraction (F) of the total volume of the porous media directly affected by air channels was between 5more » and 20% for fine sand, indicating that a small fraction of the porous media was affected by the advecting air stream.« less

Polydimethylsiloxane (PDMS) is commonly used as the coated polymer in the solid phase microextraction (SPME) technique. In this study, the partition coefficients of organic compounds between SPME/PDMS and the aqueous solution were compiled from the literature sources. The correlation analysis for partition coefficients was conducted to interpret the effect of their physicochemical properties and descriptors on the partitioning process. The PDMS-water partition coefficients were significantly correlated to the polarizability of organic compounds (r = 0.977, p &lt, 0.05). An empirical model, consisting of the polarizability, the molecular connectivity index, and an indicator variable, was developed to appropriately predict the partition coefficients of 61 organic compounds for the training set. The predictive ability of the empirical model was demonstrated by using it on a test set of 26 chemicals not included in the training set. The empirical model, applying the straightforward calculated molecular descriptors, for estimating the PDMS-water partition coefficient will contribute to the practical applications of the SPME technique.

The substance di-2-ethylhexyl phthalate (DEHP) is widely used as a plasticizer in chemical protective gloves to improve their flexibility and workability. However, it is possible that workers using protective gloves to handle various solvents may be exposed to DEHP leached by the solvents. Using an ASTM F739 permeation cell, it was found that BTEX solvents permeating through the glove samples dissolved DEHP from the gloves. Even without continuously contacting the permeant, DEHP was released from the contaminated glove samples during the desorption experiments. The DEHP leaching amounts were found to be inversely correlated to the permeability coefficients of BTEX in the glove samples. This result implied that the larger the amount of DEHP released from the glove samples, the higher the permeation resistance of gloves. Although chemical protective gloves provide adequate skin exposure protection to workers, the dermal exposure model developed herein indicates that leaching of DEHP from the glove samples may pose a potential health risk to the workers who handle BTEX. This study suggests that the selection of protective gloves should not only be concerned with the chemical resistance of the gloves but also the health risk associated with leaching of chemicals, such as DEHP, used in the manufacturing of the gloves.

This study aimed to investigate the effects of eight metals on the anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) in bioreactors. Anaerobic bioreactors containing 200 mL MSW mixed completely with 200 mL sludge seeding. Ca and K (0, 1000, 2000 and 6000 mg L−1) and Cr, Ni, Zn, Co, Mo and W (0, 5, 50 and 100 mg L−1) of various dose were added to anaerobic bioreactors to examine their anaerobic digestion performance. Results showed that except K and Zn, Ca (~728 to ~1461 mg L−1), Cr (~0.0022 to ~0.0212 mg L−1), Ni (~0.801 to ~5.362 mg L−1), Co (~0.148 to ~0.580 mg L−1), Mo (~0.044 to ~52.94 mg L−1) and W (~0.658 to ~40.39 mg L−1) had the potential to enhance the biogas production. On the other hand, except Mo and W, inhibitory concentrations IC50 of Ca, K, Cr, Ni, Zn and Co were found to be ~3252, ~2097, ~0.124, ~7.239, ~0.482, ~8.625 mg L−1, respectively. Eight spiked metals showed that they were adsorbed by MSW to a different extent resulting in different liquid metals levels and potential stimulation and inhibition on MSW anaerobic digestion. These results were discussed and compared to results from literature.

This study aims at investigating the effects of MSW incinerator fly ash (FA) and bottom ash (BA) on the anaerobic co-digestion of OFMSW with FA or BA. It also simulates the biogas production from various dosed and control bioreactors. Results showed that suitable ashes addition (FA/MSW 10 and 20 g L(-1) and BA/MSW 100 g L(-1)) could improve the MSW anaerobic digestion and enhance the biogas production rates. FA/MSW 20 g L(-1) bioreactor had the higher biogas production and rate implying the potential option for MSW anaerobic co-digestion. Modeling studies showed that exponential plot simulated better for FA/MSW 10 g L(-1) and control bioreactors while Gaussian plot was applicable for FA/MSW 20 g L(-1) one. Linear and exponential plot of descending limb both simulated better for BA/MSW 100 g L(-1) bioreactor. Modified Gompertz plot showed higher correlation of biogas accumulation than exponential rise to maximum plot for all bioreactors.

An onsite wastewater treatment facility normally has a treatment capacity of 5-200 population equivalents. The small system is receiving increasing attention in Asia countries to make up for the shortage of public sewer system. While many countries rely on large centralized system, small systems in Taiwan have significantly contributed to the treatment of municipal wastewater (21.6%) to make up for the low sewer connection (17.0%). To resolve disputes on the design criteria of primary settlers in small systems recommended by the government, a nationwide survey of 350 permit applications were conducted. This result of the survey revealed that 53% adopted self-proven criteria to reduce the size of the primary settlers using a design flow rate (Q) of 10 m(3)/d or less. The official design criteria were thus analyzed by using two new approaches of design criteria, scale-down factor and sludge blanket height ratio, as proposed in this study. The analysis indicated that sizing of primary settlers must consider the diurnal flow fluctuation and storage of settled sludge in primary settlers for a sufficient period of time, preferably up to 6 months. The official design criteria may be too conservative for Q5m(3)/d, but inadequate for Q20 m(3)/d. Based on the result of this study, new measures are suggested to strengthen the onsite program.

The partition coefficients of 51 organic compounds between SPME/PDMS and gas were compiled from the literature sources in this study. The effect of physicochemical properties and descriptors on the partitioning process of partition coefficients was explicated by the correlation analysis. The PDMS-gas partition coefficients were well correlated to the molecular weight of organic compounds (r = 0.832, p < 0.05). An empirical model, consisting of the molecular weight and the polarizability, was developed to appropriately predict the partition coefficients of organic compounds. The empirical model for estimating the PDMS-gas partition coefficient will contribute to the practical applications of the SPME technique.

Several researchers have studied the diffusion of organic solvents through chemical protective gloves and have estimated the diffusion coefficients by using various models. In this study, permeation experiments of benzene, toluene, and styrene through nitrile and Neoprene gloves were conducted using the ASTM F-739 standard test method. The diffusion coefficients were estimated using several models from the literature. Using a one-dimensional diffusion equation based on Fick's second law and the estimated diffusion coefficients, the permeation concentrations were simulated and compared with the experimental results. The modeling results indicated that the solubility of the solvent in the glove materials obtained by immersion tests was not an appropriate boundary condition for organic solvent permeation through the polymer gloves. The modeling work of this study will assist industrial hygienists to assess exposure of chemicals to workers through the chemical protective gloves.

Effective diffusion coefficients for the permeation of several organic solvents through nitrile gloves were experimentally investigated using the American Society for Testing and Materials (ASTM) F-739 test cell method. Fick's effective diffusion coefficients for benzene, toluene, ethyl benzene, xylene, and styrene were estimated to be 0.61+/-0.02, 0.50+/-0.06, 0.27+/-0.02, 0.31+/-0.03, and 0.21+/-0.03 (x10(-6)cm(2)/s), respectively. These results were comparable to results found by others using different permeation models. Using a transient mass diffusion equation and appropriate initial and boundary conditions, the effective diffusion coefficients were found to adequately simulate the concentration profiles of the organic solvents in the collection chamber during the permeation test. The effective diffusion coefficients were found to be inversely correlated to the molecular weight of the compounds. The results of this study can be used to estimate the exposure to workers using nitrile gloves.