Réduction du risque sanitaire en méthanisation agricole : impact des traitements thermiques et électriques pulsés sur les bactéries sporulantes ou non

Résumé fourni par la source

Agricultural anaerobic digestion (AD) is subject to regulations (EC) 1069/2009 and (EU) 142/2011, which require heat treatment at 70 °C for 1 hour (HT) prior to AD of animal by-products. This HT presents a technical and economic challenge. This thesis project aims to evaluate the impact of AD and sanitation treatments on different bacterial models (enterococci, notably Enterococcus faecalis and Enterococcus faecium, and clostridia, via the study of Clostridioides difficile and Clostridium novyi as a non-toxic model of Clostridium botulinum group III).Under in vitro conditions, enterococci are inactivated by HT and pulsed electric fields (5 log10 reduction,< 3 ms, at 25 kV·cm-1). In contrast, clostridial spores, particularly C. novyi, require much higher temperatures (> 100 °C) to be inactivated.On a pilot scale, thermophilic AD achieves a greater reduction in enterococci than mesophilic AD (3.5 log10 and 1.8 log10 respectively). The application of a HT upstream of the AD does not eliminate enterococci in the digestate.For C. difficile, AD (mesophilic or thermophilic) and storage for 4 months post-AD do not result in significant reduction.For C. novyi, only HT after mesophilic AD allows for a small but significant reduction (< 1 log10). Post-AD storage for 4 months results in a reduction of C. novyi (from 0.7 to 1.6 log10), suggesting that this storage stage could be an avenue to explore for the management of contaminated effluents.In conclusion, this study shows that AD and HT do not eliminate C. difficile and C. novyi.

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