Biomedical subjects

Jean-Louis Fanlo

Publications and source records attributed to Jean-Louis Fanlo.

8 recordsLinked to original sources

PubMed2005

Dispersion of odorous gases in the atmosphere - Part I: Modeling approaches to the phenomenon.

The study of odor dispersion, particularly its modeling, is an important decision tool for estimating the impact of human activities on the environment and its populations. In this sense, software to model the dispersion of odorous gases was developed and is presented. It is based on the theory established by Högström on the odor dispersion of puff emissions. This theory is applied to Gaussian models and takes the frequency of values for odor intensity over any time period into account. Such a model is able to consider the instantaneous characteristics of odor perception by human beings. Nine approaches that explore several solutions within the Gaussian domain for the atmospheric dispersion problem are proposed in software named ODODIS (ODOr DISpersion Software). This software was developed to test the different solutions. Four of these solutions are based on the punctual (or point source) emission or classic equation; two are based on the instantaneous punctual emission equation; and the other three, on the prolonged punctual emission equation (puff models). Measuring units used for the input data may be g s(-1) or OU (Odor Units). The software developed here satisfies the need to obtain instantaneous data of either a passive or an odorous gas at a specific point of an area. The simulation time varies depending on the purpose of the analysis. Mean concentration values may be obtained by integrating the instantaneous results generated by the model.

Air Pollutants↗

PubMed2005

Biofiltration of volatile organic compounds.

The removal of volatile organic compounds (VOCs) from contaminated airstreams has become a major air pollution concern. Improvement of the biofiltration process commonly used for the removal of odorous compounds has led to a better control of key parameters, enabling the application of biofiltration to be extended also to the removal of VOCs. Moreover, biofiltration, which is based on the ability of micro-organisms to degrade a large variety of compounds, proves to be economical and environmentally viable. In a biofilter, the waste gas is forced to rise through a layer of packed porous material. Thus, pollutants contained in the gaseous effluent are oxidised or converted into biomass by the action of microorganisms previously fixed on the packing material. The biofiltration process is then based on two principal phenomena: (1) transfer of contaminants from the air to the water phase or support medium, (2) bioconversion of pollutants to biomass, metabolic end-products, or carbon dioxide and water. The diversity of biofiltration mechanisms and their interaction with the microflora mean that the biofilter is defined as a complex and structured ecosystem. As a result, in addition to operating conditions, research into the microbial ecology of biofilters is required in order better to optimise the management of such biological treatment systems.

Aerobiosis↗

PubMed2005

Comparison and development of dynamic flux chambers to determine odorous compound emission rates from area sources.

Two dynamic flux chambers for direct measurement of odorous compound emissions from quiescent liquid surfaces were investigated under simulated conditions in the laboratory. Initially, a flux chamber built according to the model recommended by French standard NF X 43-104 was studied. This chamber was used in two different ways. The first led to a lack of precision concerning emissions rates from the sampled liquid surface, whereas the second led to an overestimation of the measurements. The second part of the study was devoted to an improved dynamic flux chamber, built according to the feedback from the results obtained using the normalised sampling system. Laboratory tests showed good accuracy and precision. This work underlines the importance of the aerodynamic performances of a dynamic sampling system.

Air Movements↗

PubMed2004

Evaluation of dispersion methods for enumeration of microorganisms from peat and activated carbon biofilters treating volatile organic compounds.

To enumerate microorganisms having colonized biofilters treating volatile organic compounds, it is necessary firstly to evaluate dispersion methods. Crushing, shaking and sonication were then tested for the removal of microflora from biofilters packing materials (peat and activated carbon). Continuous or discontinuous procedures, and addition of glass beads had no effect on the number of microorganisms removed from peat particles. The duration of treatment also had no effect for shaking and crushing, but the number of microorganisms after 60 min of treatment with ultrasound was significantly higher than that obtained after 0.5 min. The comparison between these methods showed that crushing was the most efficient for the removal of microorganisms from both peat and activated carbon. The comparison between three chemical dispersion agents showed that 1% Na-pyrophosphate was less efficient, compared with 200 mM phosphate buffer or 1% Na-hexametaphosphate. To optimize the cultivation of microorganisms, three different agar media were compared. Tryptic soy agar tenfold diluted (TSA 1/10) was the most suitable medium for the culture of microflora from a peat biofilter. For the activated carbon biofilter, there was no significant difference between Luria Bertoni, TSA 1/10, and plate count agar. The optimized extraction and enumeration protocols were used to perform a quantitative characterization of microbial populations in an operating laboratory activated carbon biofilter and in two parallel peat biofilters.

Air Pollution↗

PubMed2003

Headspace SPME followed by GC/PFPD for the analysis of malodorous sulfur compounds in liquid industrial effluents.

Headspace SPME was used to analyse malodorous sulfur compounds in liquid industrial effluents. A pulsed flame photometric detector (PFPD) was selected for a specific and sensitive analysis. Two fibres, PDMS/Dvb and PDMS/Carboxen, which are particularly convenient for extracting small and volatile molecules were tested. To compare these fibres, both sensitivity and artefact formation were considered. The PDMS/Carboxen fibre showed the lower limits of detection and moreover the least artefact formation yields. It was therefore selected and headspace SPME extraction conditions were optimised. Limits of detection of the target compounds evaluated were 12-31 ng L(-1) and repeatability was around 7%. Due to the adsorption mechanism involved, extraction is strongly influenced by the sample matrix and the low affinity compounds can suffer displacement effects. To investigate the occurrence of this phenomenon, two sampling times corresponding to non-equilibrium (5 min) and equilibrium conditions (60 min) were investigated. An external calibration was carried out by using standard solutions for both sampling times. The developed procedure was then compared to the standard addition method on a real industrial effluent. The results obtained from the two methods and for the two extraction times were in good agreement, demonstrating that even a long sampling time can be used. Therefore, the simple and timesaving external calibration was defined as relevant for an accurate quantification of sulfur compounds by headspace SPME.

Journal Article↗

PubMed2003

Evaluation of solid-phase microextraction for time-weighted average sampling of volatile sulfur compounds at ppb concentrations.

The potential of solid-phase microextraction (SPME) for time-weighted average (TWA) sampling of volatile sulfur compounds in air at ppb concentrations was investigated. The target compounds (hydrogen sulfide, methanethiol (MeSH), ethanethiol (EtSH), dimethyl sulfide (Me2S), and dimethyl disulfide (Me2S2)) were extracted using SPME with a Carboxen-poly(dimethylsiloxane) fiber coating, and diffusion was controlled by keeping the fiber retracted within the needle of the sampling device. The effects of several important experimental variables (air velocity, direction of air flow, analyte concentration, humidity, temperature, extraction time) were studied. The uptake by the fiber was not affected by the direction of the air flow or the air velocity. The effects of concentration, humidity, temperature, and extraction time were examined in experiments with a central composite face design. The results showed that all or most of the investigated parameters had a significant impact on the uptake rates of H2S, MeSH, EtSH, and Me2S, which invalidated time-weighted average sampling of these compounds by SPME under the tested conditions. Moreover, reverse diffusion of H2S, MeSH, and EtSH occurred at 40% relative humidity. For Me2S2, the uptake rate had a variation of only 8% within the whole experimental domain, and the experimental value derived for the uptake rate was consistent with the theoretical value. This result was confirmed by comparative analyses of industrial samples by the standard addition method. Therefore, SPME appears to be a suitable technique for TWA sampling of Me2S2 using the Carboxen-poly(dimethylsiloxane) fiber coating. Finally, in an investigation of potential losses during storage of the fiber, no significant losses of the target compounds were detected after 3 days at -80 degrees C.

Journal Article↗

PubMed2003

Development of a quantification method for the analysis of malodorous sulphur compounds in gaseous industrial effluents by solid-phase microextraction and gas chromatography-pulsed flame photometric detection.

A quantification method for malodorous sulphur compounds in gaseous industrial effluents using solid-phase microextraction sampling followed by gas chromatography-pulsed flame photometric detection has been developed. A comparative study showed that polydimethylsiloxane-Carboxen fibre led to sufficient sensitivity to achieve the microg m(-3) human perception levels of the five analytes studied (hydrogen sulphide, methanethiol, ethanethiol, dimethyl sulphide, dimethyl disulphide). However, this coating is known to suffer from competitive adsorption, which may lead to inaccurate quantification. Therefore, external calibration can only be used under a limited range of concentrations, which were determined from Fick's diffusion law. This approach was tested on a real gaseous sample and compared with the standard addition method. Good correlations were found for ethanethiol, dimethyl sulphide and dimethyl disulphide. However, for more volatile sulphur compounds (i.e., hydrogen sulphide and methanethiol), the easy-to-use external calibration could not be applied and standard additions had to be performed for accurate quantification.

Calibration↗

PubMed2003

Biological treatment process of air loaded with an ammonia and hydrogen sulfide mixture.

The physico-chemical characteristics of granulated sludge lead us to develop its use as a packing material in air biofiltration. Then, the aim of this study is to investigate the potential of unit systems packed with this support in terms of ammonia and hydrogen sulfide emissions treatment. Two laboratory scale pilot biofilters were used. A volumetric load of 680 g H2S m(-3) empty bed day(-1) and 85 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to a unit called BGSn (column packed with granulated sludge and mainly supplied with hydrogen sulfide); a volumetric load of 170 g H2S m(-3) empty bed day(-1) and 340 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to the other called BGNs (column packed with granulated sludge and mainly supplied with ammonia). Ammonia and hydrogen sulfide elimination occur in the biofilters simultaneously. The hydrogen sulphide and ammonia removal efficiencies reached are very high: 100% and 80% for BGSn; 100% and 80% for BGNs respectively. Hydrogen sulfide is oxidized into sulphate and sulfur. The ammonia oxidation products are nitrite and nitrate. The nitrogen error mass balance is high for BGSn (60%) and BGNs (36%). This result could be explained by the denitrification process which would have occurred in anaerobic zones. High percentages of ammonia or hydrogen sulfide are oxidized on the first half of the column. The oxidation of high amounts of hydrogen sulfide would involve some environmental stress on nitrifying bacterial growth and activity.

Air Pollutants↗