The effects of wastewater loading rate on the interactions between the dominant populations in activated sludge microbiome

This study characterized the interaction of dominant microbial constituents in activated sludge during the period after increases of wastewater loading rate and resulting ammonia accumulation by employing 16S rRNA gene sequencing-based co-occurrence network analysis. Two-hundred dominant populations accounting for ca. 81.8% of total activated sludge microbiome were identified. Co-occurrence analysis of dominant populations revealed that two Nitrosomonas-type ammonia-oxidizing bacteria have a large number of interactions with bacteria having relatively low abundances. A bulking-associated Thiothrix organism has a positive interaction with Nitrosomonas and diverse bacterial populations. These observations suggest that Nitrosomonas, Thiothrix, and other organisms may affected by the increase of loading rate.