Deciphering the effect of propionic acid on anaerobic digestion of sludge: gas production and microbial community structure
Résumé
This study investigates the impact of propionic acid (HPro) on anaerobic digestion (AD). HPro is an intermediate compound naturally generated during AD but inhibitory at excessive concentrations. To decipher the inhibition mechanisms, propionate, pH changes, and sodium ions were tested in addition to HPro, in batch mesophilic AD microcosms fed with municipal sewage sludge. Methane production experienced greater inhibition as the initial concentration of HPro increased, and was totally inhibited at 6 g/L HPro. The primary cause of inhibition was the low pH, as shown by comparison with NaPro, NaCl and HCl. Consistent with the inhibition, the abundance of methanogenic archaea and of the bacterium Syntrophomonas decreased with the addition of HPro. Methanogens and their syntrophic partners could therefore be interesting targets to develop inhibition biomarkers. We thereby provide one of the most in-depth study regarding HPro inhibition mechanisms during AD.
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