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At least 91 records · Page 5Linked to original sources
PubMed2002

Biodegradation of VOCs from printing press air by an on-site pilot plant bioscrubber and laboratory scale continuous yeast cultures.

The volatile organic compound composition (VOCs) of printing press air was found to contain mostly ethanol, but also ethyl acetate, 1-propanol, 2-propanol, 1-methoxy-2-propanol and 3-ethoxy-1-propanol. A pilot plant bioscrubber inoculated with a mixed microbial population was constructed on-site. The bioscrubber was able to treat the polluted gas efficiently. It, however, suffered from strong wall growth and blockages in the column. The efficiencies of the pilot plant and a bioreactor is compared. The yeasts Candida guilliermondii and Saccharomyces cerevisiae known to tolerate ethanol were selected instead of mixed population to avoid the wall growth a nd blockages inthe bioreactor. The removal of the VOCs both individually and as a complex mixture was tested in a microcultivation system and in continuous chemostat cultures with and without cell recycling. The Candida yeast could use all the compounds as a carbon source while growth of S. cerevisiae was markedly slower on the methoxylated and ethoxylated propanols. Best total removal of the VOCs was 99% and achieved by C. guilliermondii. The only compound that was not totally removable in the chemostat experiment with C. guilliermondii was 1-methoxy-2-propanol. In laboratory scale the total and volumetric removal of VOCs by C. guilliermondii was more efficient compared to the pilot plant encouraging to scale up and applying the yeast bioreactor to real field conditions.

Air Pollutants, Occupational↗
PubMed2002

Diffusion studies of VOC mixtures in a building material.

Volatile organic compound (VOC) adsorption by indoor materials will reduce peak concentrations, and subsequent desorption will prolong the presence of a compound indoors. Diffusion within materials plays an important role in this context. The purpose of this paper is to present two experimental set-ups to study VOC diffusion, and to show corresponding experimental results. The Field and Laboratory Emission Cell (FLEC) is in both cases an integral part of the set-up. The mass flow of VOC mixtures across gypsum board is studied. Diffusion of less polar VOCs in gypsum board can be fast (diffusion coefficients of 0.001-0.003 m2/h). Diffusion coefficients of chlorinated compounds are correlated with boiling points and molecular areas. Different compounds show similar diffusion properties.

Adsorption↗
PubMed2005

Development of a solid phase microextraction (SPME) method for the sampling of VOC traces in indoor air.

Solid-phase microextraction (SPME) was studied for the measurement of volatile organic compounds (VOCs) in indoor air. An adsorptive PDMS/Carboxen fibre was used and an analytical methodology was developed in order to overcome competitive adsorption. Kinetics and adsorption isotherms were investigated for different sample volumes and model compounds. In order to evaluate competitive adsorption on the fibre, these compounds were studied alone and in mixture. From the results obtained, the operating conditions allowing co-adsorption of the target compounds were determined: the air sample is enclosed in a 250 mL glass bulb where the SPME fibre is exposed until adsorption equilibrium. This procedure was combined with GC/MS analysis for the identification and quantification of VOCs in indoor air. The performances were determined by using a standard gas containing 10 VOCs representative of indoor environments (acetaldehyde, acetone, BTX, alpha-pinene, trichloroethylene, alkanes). The detection limits were determined in single ion monitoring mode and for a signal to noise ratio of 3. Except acetaldehyde (6 microg m(-3)), they are all below 0.5 microg m(-3). Calibration curves are linear up to 10 micromol m(-3) for all the compounds with good correlation coefficients (above 0.99). The reproducibility ranges from 6 to 12% according to the compound. The methodology was then applied to the comparison of the VOCs content in classrooms of two different schools.

Adsorption↗
PubMed1998

Exposure assessment model for odor causing VOCs volatilization from stored pig slurry.

A mathematical model taking into account source depletion with time and the actual thickness of manure layer was derived to evaluate indoor inhalation exposure dynamics to three selected odor causing volatile organic compounds (VOC-odors) of p-cresol, toluene, and xylene volatilization from stored pig slurry. The model assumes that pig slurry is undisturbed and the VOC-odors released in a contaminated layer and transported through a clean layer as well as a manure-air interface boundary. The model simulates time-dependent volatilization, the depletion of source contaminant via both volatilization and degradation, and could be used with a contaminated zone of finite thickness. For a given VOC-odor, the predicted total exposure and resulting manure cleanup criteria can be a large variability depending on the model whether a finite or infinite manure layer thickness was considered. Results obtained from model comparisons suggest that the model incorporating depth-varying of manure layer and contaminant source depletion is more suitable to evaluate the VOC-odor exposure dynamics in swine housing bioclimate.

Air Pollution, Indoor↗
PubMed2005

External capillary condensation and adsorption of VOCs onto activated carbon fiber cloth and felt.

Adsorption isotherms of some volatile organic compounds (VOCs), present in air at concentrations ranging from 10 to 2500 mg m(-3), were performed onto activated carbon fiber cloth and felt. The VOCs loading air were isopropanol, toluene, acetone, methyl ethyl ketone, ethyl acetate and dichloromethane. Isotherm adsorption data were generated. These experimental values were modeled by the equation of Dubinin and co-workers and by the Langmuir relation. Model parameters are discussed as a function of adsorbent materials and VOC structure. Adsorption capacity was generally found higher for the cloth than for the felt. An effect of external capillary condensation onto the felt of compounds with high surface tension was demonstrated for VOC concentrations above 1500 mg m(-3).

Adsorption↗
PubMed1991

Thermal and catalytic incinerators for the control of VOCs.

The emission of Volatile Organic Compounds (VOCs) is attracting increasing concern both from the public and by government agencies. Among the many available control technologies for the treatment of VOC containing waste streams, incineration offers an ultimate disposal strategy rather than a means for collecting or concentrating the offending compounds. This paper describes the major, commercially available thermal and catalytic incinerator systems that are designed to treat dilute, VOC containing gas streams. Qualitative guidelines are presented whereby the technologies can be compared. In addition, an example waste stream is used to illustrate a simplified procedure for calculating the material and energy balances for each of the incinerators. The resulting parameters will be used in a companion paper to estimate the capital and operating costs associated with each design. In this manner, a first estimate can be obtained of the costs of cleaning a waste stream containing low levels of VOCs.

Chemistry, Organic↗
PubMed1995

Determination of VOC emission rates and compositions for offset printing.

The release rates of volatile organic compounds (VOC) as fugitive emissions from offset printing are difficult to quantify, and the compositions are usually not known. Tests were conducted at three offset printing shops that varied in size and by process. In each case, the building shell served as the test "enclosure," and air flow and concentration measurements were made at each air entry and exit point. Emission rates and VOC composition were determined during production for (1) a small shop containing three sheetfed presses and two spirit duplicators (36,700 sheets, 47,240 envelopes and letterheads), (2) a medium-size industrial in-house shop with two webfed and three sheetfed presses, and one spirit duplicator (315,130 total sheets), and (3) one print room of a large commercial concern containing three webfed, heatset operations (1.16 x 10(6) ft) served by catalytic air pollution control devices. Each test consisted of 12 one-hour periods over two days. Air samples were collected simultaneously during each period at 7-14 specified locations within each space. The samples were analyzed by gas chromatography (GC) for total VOC and for 13-19 individual organics. Samples of solvents used at each shop were also analyzed by GC. Average VOC emission rates were 4.7-6.1 kg/day for the small sheetfed printing shop, 0.4-0.9 kg/day for the industrial shop, and 79-82 kg/day for the commercial print room. Emission compositions were similar and included benzene, toluene, xylenes, ethylbenzene, and hexane. Comparison of the emission rates with mass balance estimates based on solvent usage and composition were quite consistent.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗
PubMed1998

Evaluation of trickle bed air biofilter performance as a function of inlet VOC concentration and loading, and biomass control.

The 1990 Amendments to the Clear Air Act have stimulated strong interest in the use of biofiltration for the economical, engineered control of volatile organic compounds (VOCs) in effluent air streams. Trickle bed air biofilters (TBABs) are especially applicable for treating VOCs at high loadings. For long-term stable operation of highly loaded TBABs, removal of excess accumulated biomass is essential. Our previous research demonstrated that suitable biomass control for TBABs was achievable by periodic backwashing of the biofilter medium. Backwashing was performed by fluidizing the pelletized biological attachment medium with warm water to about a 40% bed expansion. This paper presents an evaluation of the impact of backwashing on the performance of four such TBABs highly loaded with toluene. The inlet VOC concentrations studied were 250 and 500 ppmv toluene, and the loadings were 4.1 and 6.2 kg COD/m3 day (55 and 83 g toluene/m3 hr). Loading is defined as kg of chemical oxygen demand per cubic meter of medium per day. Performance deterioration at the higher loading was apparently due to a reduction of the specific surface of the attached biofilm resulting from the accumulation of excess biomass. For a toluene loading of 4.1 kg COD/m3 day, it was demonstrated that the long-term performance of biofilters with either inlet concentration could be maintained at over 99.9% VOC removal by employing a backwashing strategy consisting of a frequency of every other day and a duration of 1 hr.

Air Pollution↗
PubMed2001

The use of indoor air measurements to evaluate intrusion of subsurface VOC vapors into buildings.

The implementation of a risk-based corrective action approach often requires consideration of soil vapor migration into buildings and potential inhalation exposure and risk to human health. Due to the uncertainty associated with models for this pathway, there may be a desire to analyze indoor air samples to validate model predictions, and this approach is followed on a somewhat frequent basis at sites where risks are considered potentially significant. Indoor air testing can be problematic for a number of reasons. Soil vapor intrusion into buildings is complex, highly dependent on site-specific conditions, and may vary over time, complicating the interpretation of indoor air measurements when the goal is to deduce the subsurface-derived component. An extensive survey of indoor air quality data sets highlights the variability in indoor volatile organic compound (VOC) concentrations and numerous sources that can lead to elevated VOC levels. The contribution from soil vapor is likely to be small relative to VOCs from other sources for most sites. In light of these challenges, we discuss how studies that use indoor air testing to assess subsurface risks could be improved. To provide added perspective, we conclude by comparing indoor air concentrations and risks arising from subsurface VOCs, predicted using standard model equations for soil vapor fate and intrusion into buildings, to those associated with indoor sources.

Air Pollution, Indoor↗
PubMed1993

Corona destruction: an innovative control technology for VOCs and air toxics.

This paper discusses the work and results to date leading to the demonstration of the corona destruction process at pilot scale. The research effort in corona destruction of volatile organic compounds (VOCs) and air toxics has shown significant promise for providing a valuable contribution to critical U.S. Environmental Protection Agency and national goals of reducing the health effects associated with exposures to hazardous air pollutants. The corona destruction technology could be especially useful in future years in helping industry meet the residual risk requirements of the Clean Air Act Amendments of 1990. Since 1988, EPA has conducted research in the area of corona destruction of VOCs and air toxics. EPA's interest in corona destruction of molecular species started with modeling of a point-plane reactor for destroying toxic organic compounds. EPA's goal is to develop a technology capable of controlling low concentration streams at low capital and operating costs. The purpose of this work is to develop an industrial scale corona reactor capable of efficiently and cost-effectively destroying VOCs and air toxics at ambient temperature and pressure. Results show that corona destruction is a promising control technology for many VOC-contaminated air streams, especially at low concentrations. Cost comparisons are presented for corona destruction and conventional control devices, carbon adsorption, catalytic incineration and thermal incineration.

Journal Article↗
PubMed2006

Multivariate evaluation of VOCs in buildings where people with non-specific building-related symptoms perceive health problems and in buildings where they do not.

UNLABELLED: Volatile organic compounds (VOCs) were sampled in buildings where people with non-specific building-related symptoms perceive health problems and in buildings where they do not. In total, nine persons and 34 buildings were included in the study. The obtained VOC data was evaluated using multivariate methods, to investigate possible systematic differences in air quality of 'problem' and 'non-problem' buildings. All individual compounds were included as variables in a multivariate partial least squares (PLS) data analysis. 'Problem' and 'non-problem' buildings separated into two distinct groups, showing that air samples of the two groups of building were chemically different. PRACTICAL IMPLICATIONS: The study showed that there was an identifiable systematic difference in the collected VOC data between buildings causing and not causing problems for people with non-specific building-related symptoms (also called sick building syndrome, SBS). This is an important indication that even such volatile organic compounds that can be sampled by commonly used adsorbents are of importance for the presence of such symptoms. By coordination of procedures for sampling and analysis of VOCs in buildings between laboratories, to get large datasets and more general models, the method can become a useful diagnostic measure in evaluating indoor air and to identify chemical compounds and sources that contribute to SBS problems.

Environmental Exposure↗
PubMed2004

Outdoor, indoor, and personal exposure to VOCs in children.

We measured volatile organic compound (VOC) exposures in multiple locations for a diverse population of children who attended two inner-city schools in Minneapolis, Minnesota. Fifteen common VOCs were measured at four locations: outdoors (O), indoors at school (S), indoors at home (H), and in personal samples (P). Concentrations of most VOCs followed the general pattern O approximately equal to S < P less than or equal to H across the measured microenvironments. The S and O environments had the smallest and H the largest influence on personal exposure to most compounds. A time-weighted model of P exposure using all measured microenvironments and time-activity data provided little additional explanatory power beyond that provided by using the H measurement alone. Although H and P concentrations of most VOCs measured in this study were similar to or lower than levels measured in recent personal monitoring studies of adults and children in the United States, p-dichlorobenzene was the notable exception to this pattern, with upper-bound exposures more than 100 times greater than those found in other studies of children. Median and upper-bound H and P exposures were well above health benchmarks for several compounds, so outdoor measurements likely underestimate long-term health risks from children's exposure to these compounds.

Air Pollutants↗
PubMed2002

Remove volatile organic compounds (VOCs) with membrane separation techniques.

Membrane separation, a new technology for removing VOCs including pervaporation, vapor permeation, membrane contactor, and membrane bioreactor was presented. Comparing with traditional techniques, these special techniques are an efficient and energy-saving technology. Vapor permeation can be applied to recovery of organic solvents from exhaust streams. Membrane contactor could be used for removing or recovering VOCs from air or wastewater. Pervaporation and vapor permeation are viable methods for removing VOCs from wastewater to yield a VOC concentrate which could either be destroyed by conventional means, or be recycled for reuse.

Bioreactors↗
PubMed2006

[VOC emission situation and control measures of gas station in China].

The emission factor is used to estimate the volatile organic compound (VOC) emission caused by gas station. After considering the economical, social and population factors, the activity rate was modified, and then the fuel consumption and VOC emission trend in the next 20 years can be predicted. The result shows the VOC emission from gas station in China 2002 was 187.6kt and this number will increase to 1196kt in 2030 if no further control measures will be implemented. And the economic loss caused by gasoline vapor arrived to 0.75 billion RMB in 2002 and will be 4.78 billion RMB in 2030. The cost-benefit approach of the commercially available gasoline vapor recovery technologies in China included Stage I, Stage II and on-board refueling vapor recovery (ORVR) were analyzed, and the result shows introducing these three systems will bring larger reduce of VOC emission, and the combination of them can do a even better job. Compared with Stage II, ORVR is more efficient and cheaper, but it will take long time to implement ORVR. And it will take at least 11 years in China to convert to ORVR above 80%. So Stage II vapor recovery system may be a short term option while ORVR should be treated as the ultimate solution for controlling the vapor emission from gas stations in the future.

Air Pollutants↗
PubMed2006

[Photocatalytic degradation of formaldehyde and VOCs in air on the porous nickel mesh coated with nanometer TiO2].

Three different metal ions doped TiO2 photocatalysts, which were prepared by the sol-gel method, were immobilized to porous nickel mesh by coating. The photocatalytic degradation activity of the supported photocatalyst on formaldehyde and volatile organic compounds (VOCs) was investigated. The results show that the nanometer TiO2 has an anatase structure. The photocatalytic degradation rate of formaldehyde and VOCs of 1.5% La3+ doped TiO2 coated on porous nickel mesh at 90 min are: 94% and 87%, higher than undoped TiO2: 83% and 72%, Fe3+ doped TiO2: 62% and 62%, Ag+ doped TiO2: 86% [Chinese character: see text] 81%. The orders of photocatalytic degradation rate on formaldehyde and VOCs with different content of La3+ doped TiO2 are as follows: 1.5% > 1% > 2% > undoped, 1.5% is the optimum La3+ doped content. Decreasing circular wind speed and using 254 nm or 365 nm ultraviolet wavelength will not influence the photocatalytic degradation rate of formaldehyde and VOCs.

Air Pollutants↗
PubMed2006

Comparison of two solid-phase microextraction methods for the quantitative analysis of VOCs in indoor air.

Competitive adsorption on adsorptive solid-phase microextraction (SPME) fibres implies careful determination of operating conditions for reliable quantitative analysis of VOCs in indoor air. With this objective, two analytical approaches, involving non-equilibrium and equilibrium extraction, were compared. The average detection limit obtained for GC-MS analysis of nine VOCs by the equilibrium method is 0.2 microg m(-3), compared with 1.9 microg m(-3) with the non-equilibrium method. The effect of the relative humidity of the air on the calibration plots was studied, and shown to affect acetone adsorption only. Hence, the concentrations that can be accurately determined are up to 9 micromol m(-3). The methods were then applied to indoor air containing different concentrations of VOCs. The non-equilibrium method, involving short extraction time, can be used for detection of pollution peaks whereas equilibrium extraction is preferable for measurement of sub-microg m(-3) ground concentration levels.

Adsorption↗
PubMed2005

Variability in VOC concentrations in an urban area of Delhi.

The variability of pollutants is an important factor in determining human exposure to the chemicals. This study presents the result of investigation of variability of Volatile organic compounds (VOCs) in urban area of Delhi, capital of India. Fifteen locations, in five categories namely residential, commercial, industrial, traffic intersections and petrol pump were monitored for one year every month during peak hours in morning and evening. Measurement focused on target VOCs as defined by USEPA. Variability was divided into measurement, spatial, temporal and temporal-spatial interaction components. Temporal component along with temporal-spatial interaction were found to be the major contributors to the variability of measured VOC concentrations. Need of continuous monitoring to capture short-term peak concentration and averages is evident.

Air Pollutants↗
PubMed2005

Uncertainty assessment of VOC emissions from paint in The Netherlands using the NUSAP system.

We demonstrate an innovative approach to uncertainty assessment known as the NUSAP system, to assess qualitative and quantitative uncertainty for the case of emissions of volatile organic compounds (VOC) from paint in The Netherlands. Using expert elicitation, we identified key sources of error, critical assumptions, and bias in the monitoring process. We assessed pedigree and probabilistic uncertainty of all input quantities. We used four pedigree criteria to assess the strength of the knowledge base: proxy representation, empirical basis, methodological rigour and degree of validation. Using Monte Carlo analysis, we assessed sensitivity and propagation of uncertainty. Results for sensitivity and pedigree were combined in a 'NUSAP Diagnostic Diagram', which effectively highlighted the assumption for VOC percentage of imported paint as the weakest spot in the monitoring of VOC emissions. We conclude that NUSAP facilitates systematic scrutinization of method and underlying assumptions and structures creative thinking on sources of error and bias. It provides a means to prioritise uncertainties and focus research efforts on the potentially most problematic parameters and assumptions, at the same time identifying specific weaknesses in the knowledge base. With NUSAP, nuances of meaning about quantities can be conveyed concisely and clearly, to a degree that is not possible with statistic methods only.

Air Pollutants↗