Disturbance and temporal partitioning of the activated sludge metacommunity

Abstract

The resilience of microbial communities to press disturbances and whether ecosystem function is governed by microbial composition or by the environment have not been empirically tested. To address these issues, a whole-ecosystem manipulation was performed in a full-scale activated sludge wastewater treatment plant. The parameter solids retention time (SRT) was used to manipulate microbial composition, which started at 30 days, then decreased to 12 and 3 days, before operation was restored to starting conditions (30-day SRT). Activated sludge samples were collected throughout the 313-day time series in parallel with bioreactor performance ('ecosystem function'). Bacterial small subunit (SSU) rRNA genes were surveyed from sludge samples resulting in a sequence library of 4417 000 SSU rRNA genes. A shift in community composition was observed for 12-and 3-day SRTs. The composition was altered such that r-strategists were enriched in the system during the 3-day SRT, whereas K-strategists were only present at SRTsX12 days. This shift corresponded to loss of ecosystem functions (nitrification, denitrification and biological phosphorus removal) for SRTsp12 days. Upon return to a 30-day SRT, complete recovery of the bioreactor performance was observed after 54 days despite an incomplete recovery of bacterial diversity. In addition, a different, yet phylogenetically related, community with fewer of its original rare members displaced the pre-disturbance community. Our results support the hypothesis that microbial ecosystems harbor functionally redundant phylotypes with regard to general ecosystem functions (carbon oxidation, nitrification, denitrification and phosphorus accumulation). However, the impacts of decreased rare phylotype membership on ecosystem stability and micropollutant removal remain unknown.

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

“…In addition to their importance for protecting environmental and public health, engineered environments such as activated sludge have been shown to be valuable environments to study fundamental microbial ecology phenomena (Daims et al, 2006), in part due to their physical partitioning into ecological 'islands' with well-defined and monitored ecosystem functions. Wastewater microbiology has informed our understanding of community assembly mechanisms (Ofiteru et al, 2010;Wells et al, 2011;Kim et al, 2012), resilience and stability (Werner et al, 2011;Vuono et al, 2014), and identified novel microbes and metabolic pathways (Strous et al, 1999;van Kessel et al, 2015). Translating this knowledge into effective strategies for 'microbial resource management' (Verstraete et al, 2007) remains a challenge due to the high diversity and dynamics in activated sludge bioreactors, even during times of functional stability.…”

Functional maintenance and structural flexibility of microbial communities perturbed by simulated intense rainfall in a pilot-scale membrane bioreactor

“…It remains to be clarified which environmental factors select and shape the oligotrophic bacterial populations in the perturbed MBR. Nevertheless, such functional redundancy and niche differentiation are essential for the maintenance of the microbial community function, i.e., the stabilization of reactor performances, as reported in the other wastewater treatment plants (Allison and Martiny 2008;Vuono et al 2015). On the other hand, OTU IV (Solitalea-related Flavobacteriia bacterium) showed a drastic increase after the event i, so that became the second most abundant OTU at day 22 (relative abundance 6.8 %; Fig.…”

Ionic liquid biodegradability depends on specific wastewater microbial consortia

“…Environmental factors, such as precipitation, temperature and pH can influence cell density, waste concentration and specific nitrification rates. However, operating conditions, including organic loading rate, feed composition, reactor configuration and solids retention time (SRT) can all influence microbial diversity as well (Pholchan et al, 2010;Vuono et al, 2015). For example, a press disturbance experiment investigating reduction in SRT from 30 days to 12 or 3 days resulted in a shift in sludge microbial community composition from K-strategists to r-strategists, with demonstrated losses in bacterial diversity following the disturbances (Vuono et al, 2015).…”

“…Once in the aeration tank, presence or absence of nutrients and cofactors , adaptation of aeration tank microbial communities to operating conditions (e.g. Vuono et al, 2015), co-metabolism with other waste streams (Fischer and Majewsky, 2014) and physiochemical environmental parameters (e.g. Pholchan et al, 2010) can all substantially influence biodegradation rates of ILs in sewage sludge.…”

“…However, operating conditions, including organic loading rate, feed composition, reactor configuration and solids retention time (SRT) can all influence microbial diversity as well (Pholchan et al, 2010;Vuono et al, 2015). For example, a press disturbance experiment investigating reduction in SRT from 30 days to 12 or 3 days resulted in a shift in sludge microbial community composition from K-strategists to r-strategists, with demonstrated losses in bacterial diversity following the disturbances (Vuono et al, 2015). Our observation that significant temporal variation is based on DO and temperature aligns with results of previous studies that have examined activated sludge community composition using high throughput sequencing techniques (Kim et al, 2013).…”