Full-scale mesophilic anaerobic sludge digester: microbial community dynamics from start-up to steady state

This study aimed at investigating bacterial and archaeal dynamics in a full-scale mesophilic digester for the treatment of activated sludge, during the start-up phase up to steady state operation. Microorganisms developed in the reactor were investigated using the high throughput 16S rRNA gene sequencing. The results showed that most of the reads were affiliated with hydrolitic and fermentative bacteria, mainly belonging to Bacteroidetes phylum, which increased up to 22% of the total sequences over time. Moreover, methanogenic community was represented mainly by acetoclastic microorganisms, namely Methanosaeta. Real Time PCR revealed an enrichment of bacteria and methanogens once the steady state was reached. Furthermore, activated sludge was studied to evaluate the microbial core selected by the operating conditions of the wastewater treatment plant.