Anne-Claude Romain

Using the classification model of an electronic nose to assign unknown malodours to environmental sources and to monitor them continuously

Abstract The paper provides some considerations resulting from measurements with electronic noses around real sources of malodour in the environment: compost facilities, printing houses, paint shops, waste water treatment plants, rendering plants, settling ponds of sugar factories. The study aims at supplying the concrete information requested by the final user in the field: either a warning signal when the malodour level exceeds some given threshold value, the identification of the source of an odour detected on site, or on-line identification and monitoring of an odour in the field. Very simple instruments are used, either in the laboratory or directly in the field, with a home-made portable e-nose, based on tin oxide sensors. Even with such simple operating conditions, the classification results with DA and PCA are fairly good. The classification functions calibrated with the statistical procedure, on the basis of the learning phase, are used to recognise and to monitor a given malodour. This odour is sometimes mixed with other odorous interferences in the field. The observations reveal some features useful in the frame of the development of a field detector.

Use of a simple tin oxide sensor array to identify five malodours collected in the field

Abstract A laboratory-made malodour sensing system including 12 commercial tin oxide gas sensors (Figaro Engineering) is used to identify five typical sources of olfactive annoyance: printing houses, paint shop in a coachbuilding, wastewater treatment plant, urban waste composting facilities and rendering plant. In this work, all the samples are collected in the field from real malodours in uncontrollable conditions. The ability of the system to predict the origin of unknowns odoriferous samples is investigated. The test of various pre-processing data algorithms shows that the best classification results are obtained with a parameter free of the sensor base-line. The differences in sensor responses among the five odours are shown by icon plots and confirmed by principal component analysis, which highlights four representative clusters. Classification models calibrated by discriminant analysis and artificial neural network are validated on unknowns samples. Chemical relationships between the sensors and the classification results proves that the recognition is not fortuitous. In spite of the influence of environmental parameters, results demonstrate the ability of a simple system to detect and identify typical olfactive annoyances.

Upscaling of an electronic nose for completely stirred tank reactor stability monitoring from pilot-scale to real-scale agricultural co-digestion biogas plant

This study investigated the use of an electronic nose for on-line anaerobic reactor state monitoring at the pilot-scale level and then upscaling to the full-scale level. E-nose indicator was compared to classical state indicators such as pH, alkalinity, volatile fatty acids concentration and to other gas phase compounds. Multivariate statistical process control method, based on principal component analysis and the Hotellings T(2) statistics was used to derive an indicator representative of the reactor state. At the pilot-scale level, the e-nose indicator was relevant and could distinguish 3 process states: steady-state, transient and collapsing process. At the full-scale level, the e-nose indicator could provide the warning of the major disturbance whereas two slight disturbances were not detected and it gave one major false alarm. This work showed that gas phase relation with anaerobic process should be deeper investigated, as an e-nose could indicate the reactor state, focusing on the gas phase.

Potential of a Network of Electronic Noses to Assess in Real Time the Odour Annoyance in the Environment of a Compost Facility

This paper presents a complete approach of continuous odour monitoring around an industrial plant, with an e-nose network named FIDOR, providing in real time the five components of the odour annoyance, the frequency, the intensity, the duration, the offensiveness and the impact on the receptor. Such FIDOR network was placed in the immediate surroundings of a compost facility in Belgium. Results show a good coherence between information provided by FIDOR system and odour level assessment with human noses. Some interesting correlations are also found between e-nose responses at different distances in a same radial direction from the source. The discussion is mainly focused on the potentialities and the limitations of such system.

STUDY OF THE CRYSTALLIZATION PROCESS IN BI2-XPBXSR2CA2CU3O10-Y GLASS SYSTEMS - OPTICAL POLARIZED-LIGHT MICROSCOPY, ELECTRICAL AND MAGNETIC-PROPERTIES

Synthesis of Bi2-xPbxSr2Ca2Cu3O10-y (x=0 and x=0.3) has been performed using the glass recrystallization route technique. After splat quenching, the samples were annealed at 820, 850 or 870 degrees C for 96 or 144 h (with one intermediary grinding). High-resolution polarization micrographs and electrical (and magnetic susceptibility) measurements have been taken. Various growth mechanisms can thus be checked, and the physical properties are studied in relation to the microstructure. It is found that the 2223 phase does not crystallize directly from the amorphous one but results from a dissolution-reprecipitation process. The stability of the 2212 phase is emphasized. The 2201 phase precipitates at high temperature and rapidly reacts with the melt to form the 2223 phase. The kinetics of the lead-substituted sample seems to be controlled by the Ca2PbO4 phase, which acts as a flux.

Long Term Stability Of Metal Oxide‐Based Gas Sensors For E‐nose Environmental Applications: an overview

The e‐nose technology has enormous potentialities for in site monitoring of malodors. However a number of limitations are associated with the properties of chemical sensors, the performances of the signal processing and the realistic operation conditions of environmental field. From the experience of the research group in the field, the metal oxide based gas sensors (Figaro type) are until now the best chemical sensors for long term application, more than one year of continuous working in the field. To be usable for malodors measurement in the field, the e‐nose has to deal with the lack of long term stability of these sensors. The drift and the sensors replacement have to be considered. In order to appraise the time evolution of the sensors and the effect on the results of an electronic nose, experimentation has been performed during three years on two identical sensor arrays. The two arrays contain the same six Figaro sensors and are in the same sensor chamber of the e‐nose system. Both arrays have worke...

An alternative approach of the e-nose training phase in odour impact assessment

Odour emissions are causing serious nuisance for the population, especially in the surrounding of waste water treatment plants (WWTP) and solid waste treatment plants. Extended exposure to odours generate undesirable reactions ranging from emotional stresses such as unease, discomfort, headaches, or depression to physical symptoms. Odour emission characterization is currently discussed in international literature for opportune implementation. Measurement of emissions can be achieved using different methods (analytical, sensorial and/or senso-instrumental) that have different advantages and problems. Among these techniques, there is a growing interest towards the environmental applications of electronic noses. Electronic nose is the only technique that allows continuous monitoring of odours. However, at present there are several limitations affecting the application of electronic nose in the environmental sector. The study investigates the electronic nose potentialities in the environmental sector. Scope of this research activity is to investigate an alternative method to build training data set necessary to distinguish different odour sources generated by solid waste treatment facilities through electronic nose application. The proposed methodology is based on the straightforward application of the electronic nose directly in field with the aim to reduce the time to build the complete data set. Results highlight the great efficiency of the proposed approach to reduce the time to build the complete data set, to maximize the electronic nose capability of operating a qualitative classification of odour sources.

Application of Chemical Mass Balance Methodology to Identify the Different Sources Responsible for the Olfactory Annoyance at a Receptor-site.

The olfactory annoyance perceived at a receptor site of an industrial area is often the result of a combination of different smells, emitted by several industrial sources. The major issue in the case of complaints is to identify the main responsible of such pollution. For this purpose, tools able to determine the contribution of each source directly where the annoyance is perceived would simplify this identification. In this work, we use the source-receptor model CMB (Chemical Mass Balance) generally used for air pollution studies, by applying it for the first time to odour signatures. The contributions of VOC sources, coming from a waste treatment plant containing 3 potential sources of olfactory annoyance (waste storage, production of biogas, and compost piles of green wastes), and perceived at a village located downwind, are studied by chemical analyses and finally compared to olfactometric methods.

Comparison low cost chemical sensors analytical instruments for odour monitoring in a municipal waste plant

The gas sensing performances of low cost commercial chemical sensors are compared to the ones of standardized chemical analysers. Real time measurements are performed on the field of three municipal solid waste plants (MSW). Long-term campaigns of several months have been organised during the period 2010- 2015. The sensors and the reference analysers have worked simultaneously. The selected sensors are commercial metal oxide semiconductor gas sensors (MOx, Figaro). The sensors-array devices are developed at the ULg laboratory (SAM). Analysers are certified and operated by the official Wallonia public scientific institute (ISSeP). In addition to odour, other target compounds are considered: methane, ammonia, hydrogen sulfide, but also NMHC as limonene, pinene and BTEX The laboratory has a long experience in using chemical sensors for odour in-field measurements, especially for landfills and composting plants. The aim of this study is to evaluate the performances of chemo-resistors array for continuous monitoring of compounds typical of municipal wastes in comparison to reference analysers. It highlights weaknesses and strengths of the two kinds of devices. The obtained results are considered for odour event detection as well as for chemical compound quantification and are discussed to evaluate the efficiency of metal oxide sensors for a low cost gas emissions assessment.

Relevance of the resident diary method to map odour sources.

The odour annoyance in the surroundings of an indust rial park in Belgium was evaluated through diaries completed by 42 residents during about two years. The studied area includes 13 potential odour emitting f acilities. The questionnaire aimed at providing twice-daily an odour annoyance rating on a 5-level scale together with an odour type. Data processing and interpretation stressed more pa rticul rly on the two types of result that can be extracted from resident diaries, i.e. a nnoyance percentage and annoyance level. The plausibility of the responses is examined as well. Mapping odour sources in this particular case of multi-source facility is ma de possible through the use of odour roses. With respect to first results obtained for y ear 2008, more recent data provide more detailed information concerning the role of ea ch facility to explain the whole odour annoyance. The resident diary method proves t o be relevant, especially in the case of an industrial area, provided that validatio n checks are performed to insure the data reliability.