Gilles Adam

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.

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.