Microbial biogeography across a full-scale wastewater treatment plant transect: evidence for immigration between coupled processes

Abstract

Wastewater treatment plants use a variety of bioreactor types and configurations to remove organic matter and nutrients. Little is known regarding the effects of different configurations and within-plant immigration on microbial community dynamics. Previously, we found that the structure of ammonia-oxidizing bacterial (AOB) communities in a full-scale dispersed growth activated sludge bioreactor correlated strongly with levels of NO2 (-) entering the reactor from an upstream trickling filter. Here, to further examine this puzzling association, we profile within-plant microbial biogeography (spatial variation) and test the hypothesis that substantial microbial immigration occurs along a transect (raw influent, trickling filter biofilm, trickling filter effluent, and activated sludge) at the same full-scale wastewater treatment plant. AOB amoA gene abundance increased >30-fold between influent and trickling filter effluent concomitant with NO2 (-) production, indicating unexpected growth and activity of AOB within the trickling filter. Nitrosomonas europaea was the dominant AOB phylotype in trickling filter biofilm and effluent, while a distinct "Nitrosomonas-like" lineage dominated in activated sludge. Prior time series indicated that this "Nitrosomonas-like" lineage was dominant when NO2 (-) levels in the trickling filter effluent (i.e., activated sludge influent) were low, while N. europaea became dominant in the activated sludge when NO2 (-) levels were high. This is consistent with the hypothesis that NO2 (-) production may cooccur with biofilm sloughing, releasing N. europaea from the trickling filter into the activated sludge bioreactor. Phylogenetic microarray (PhyloChip) analyses revealed significant spatial variation in taxonomic diversity, including a large excess of methanogens in the trickling filter relative to activated sludge and attenuation of Enterobacteriaceae across the transect, and demonstrated transport of a highly diverse microbial community via the trickling filter effluent to the activated sludge bioreactor. Our results provide compelling evidence that substantial immigration between coupled process units occurs and may exert significant influence over microbial community dynamics within staged bioreactors.

Regional synchrony in full-scale activated sludge bioreactors due to deterministic microbial community assembly

“…Previous studies investigating the impact of immigration from raw influent on activated sludge community structure have found highly variable estimates for the fraction of OTUs shared between influent and activated sludge, from 5-10% OTU overlap (Lee et al, 2015) to 35% . Communities from linked processes within a single WWTP also show evidence for within-plant immigration (Wells et al, 2014) further suggesting that both selection and mass effect mechanisms influence community assembly. Although we did not find strong evidence that local immigration affected synchrony, it is possible that synchrony could be explained in part by region-wide changes in influent community structure, in addition to direct effects on the activated sludge community.…”

Microbial rRNA gene expression and co‐occurrence profiles associate with biokinetics and elemental composition in full‐scale anaerobic digesters

“…Lower Hill numbers with codigestion have been observed in prior works (Ziels et al ., ) and may be caused by the enrichment of specialized microorganisms on influent substrates with certain organic matter compositions. Higher diversity in the SS digesters could also have been attributed to immigration of populations from the PS+WAS feed source, as was shown to occur in other biological wastewater treatment processes (Wells et al ., ). There were no significant differences within intragroup diversity (i.e.…”

Influence of influent wastewater communities on temporal variation of activated sludge communities

“…Influent wastewater is presumed to be a main source of bacterial diversity in activated sludge bioreactors (Sloan et al, 2006;Wells et al, 2014) since diverse bacterial species are present in influent wastewater. For example, McLellan et al (2010) estimated the bacterial richness of influent wastewater as Chao1 index ranged from 1819 to 3695 operational taxonomic units (OTUs) based on pyrosequencing of bacterial 16S rRNA genes.…”