Mass-immigration determines the assembly of activated sludge microbial communities

Abstract

The assembly of bacterial communities in wastewater treatment plants (WWTPs) is affected by immigration via wastewater streams, but the impact and extent of bacterial immigrants are still unknown. Here, we quantify the effect of immigration at the species level in 11 Danish full-scale activated sludge (AS) plants. All plants have different source communities but have very similar process design, defining the same overall environmental growth conditions. The AS community composition in each plant was strongly reflected by the corresponding influent wastewater (IWW) microbial composition. Most species in AS across the plants were detected and quantified in the corresponding IWW, allowing us to identify their fate in the AS: growing, disappearing, or surviving. Most of the abundant species in IWW disappeared in AS, so their presence in the AS biomass was only due to continuous mass-immigration. In AS, most of the abundant growing species were present in the IWW at very low abundances. We predicted the AS species abundances from their abundance in IWW by using a partial least square regression model. Some species in AS were predicted by their own abundance in IWW, while others by multiple species abundances. Detailed analyses of functional guilds revealed different prediction patterns for different species. We show, in contrast to the present understanding, that the AS microbial communities were strongly controlled by the IWW source community and could be quantitatively predicted by taking into account immigration. This highlights a need to revise the way we understand, design, and manage the microbial communities in WWTPs.

Microbial community-based production of single cell protein from soybean-processing wastewater of variable chemical composition

“…Although Firmicutes was the most prevalent phylum in the soybean processing wastewaters, Proteobacteria became dominant in the enriched microbial biomass in the reactors. Therefore, the massive immigration of bacteria present in the influent did not determine the structure of the microbial community in the reactors, contrary to what has been reported for full-scale activated sludge plants (Dottorini et al, 2021). A similar observation was made in a full-scale membrane bioreactor plant where the influent bacterial populations contributed little to relative abundances of the core activated sludge community (Zhang & Meng, 2021).…”

Diversity and Ecophysiology of the Genus OLB8 and Other Abundant Uncultured Saprospiraceae Genera in Global Wastewater Treatment Systems

“…However, as only a few genera were present and abundant in most WWTPs globally, we have mainly focused on these, although many other genera and species could be abundant in a few plants across the world. The huge variation from plant to plant may be due to the high impact of immigration from different source communities to the WWTPs (Dottorini et al, 2021) (van Veen et al, 1973;Xia et al, 2008). Our study showed that all analyzed genera have the potential to degrade different polysaccharides such as starch and many amino acids and may grow under both oxic and anoxic conditions.…”

Wastewater Influent Microbial Immigration and Contribution to Resource Consumption in Activated Sludge Using Taxon-Specific Mass-Flow Immigration Model

“…solids residence time [SRT] < 3 days) 5,6 or at low temperatures with microbial activities maintained near or below washout SRTs such as nitrification activity during winter. 7 The effects of influent microbiome input to the activated sludge processes have drawn interests on general heterotrophic organisms [8][9][10] and specific functional microbes such as nitrifiers and polyphosphate accumulating organisms (PAO). 7,[11][12][13] Until now, detailed influent microbiome input has largely been neglected in conventional process modeling frameworks, e.g., activated sludge models (ASMs).…”

“…The effects of influent microbiome input to the activated sludge processes have drawn interests on general heterotrophic organisms 8-10 and specific functional microbes such as nitrifiers and polyphosphate accumulating organisms (PAO). 7, 11-13 Until now, detailed influent microbiome input has largely been neglected in conventional process modeling frameworks, e.g., activated sludge models (ASMs).…”