Inhibition of anaerobic digestion of urban sewage sludge by sodium propionate: biogas production and microbial community shift in continuous reactors
Résumé
Anaerobic digestion (AD) is a well-established technology for processing waste streams such as sewage sludge and agricultural waste to produce biogas. However, the accumulation of volatile fatty acids, particularly propionic acid (an intermediate product), can hinder biogas production. Studies have indicated that even low propionic acid concentrations can impede biogas generation from digestion. However, propionic acid is usually in its ionized form in the pH range in which AD processes work. Limited data exist regarding the precise propionate concentration that inhibits anaerobic digestion of various substrates. In this recent study using 5-L reactors for the AD of urban sewage sludge, no inhibition was observed at low NaPro concentrations (up to 1.95 g/L). At 7.78 g NaPro/L, slight biogas disruption occurred, and significant inhibition (− 40%) was noted at the highest concentration (13 g NaPro/L). While the inhibitory NaPro concentration in this study exceeded the literature values (typically <2 g/L), this aligns with our previous findings in smaller-scale batch experiments.
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