Bacterial Community Dynamics in Full-Scale Activated Sludge Bioreactors: Operational and Ecological Factors Driving Community Assembly and Performance

Abstract

The assembling of bacterial communities in conventional activated sludge (CAS) bioreactors was thought, until recently, to be chaotic and mostly unpredictable. Studies done over the last decade have shown that specific, and often, predictable random and non-random factors could be responsible for that process. These studies have also motivated a “structure–function” paradigm that is yet to be resolved. Thus, elucidating the factors that affect community assembly in the bioreactors is necessary for predicting fluctuations in community structure and function. For this study activated sludge samples were collected during a one-year period from two geographically distant CAS bioreactors of different size. Combining community fingerprinting analysis and operational parameters data with a robust statistical analysis, we aimed to identify relevant links between system performance and bacterial community diversity and dynamics. In addition to revealing a significant β-diversity between the bioreactors’ communities, results showed that the largest bioreactor had a less dynamic but more efficient and diverse bacterial community throughout the study. The statistical analysis also suggests that deterministic factors, as opposed to stochastic factors, may have a bigger impact on the community structure in the largest bioreactor. Furthermore, the community seems to rely mainly on mechanisms of resistance and functional redundancy to maintain functional stability. We suggest that the ecological theories behind the Island Biogeography model and the species-area relationship were appropriate to predict the assembly of bacterial communities in these CAS bioreactors. These results are of great importance for engineers and ecologists as they reveal critical aspects of CAS systems that could be applied towards improving bioreactor design and operation.

EPS producing microorganisms from municipal wastewater activated sludge

“…Similar results were obtained by Xia [27] who investigated the microbial community structure in response to different ratios of carbon to nitrogen (C/N of 3:1, 5:1, and 10:1) in wastewater sludge. The carbon content as well as C/N ratio of activated sludge collected in 2010 by Subramanian was different from those collected in 2013 in present research, Secondly Valentin [28]reported that biochemical oxygen demand (BOD), influent total suspended solid (TSS), solid retention time (SRT), food/microorganisms (F/M), seem to have the strongest influence on the bacterial communities composition in the bio-reactors. The very low values of F/M in the wastewater treatment plant suggest that the microbial community was starving contributing to high mortality rate among the microbial populations.…”

Understanding the Linkage between Elevation and the Activated-Sludge Bacterial Community along a 3,600-Meter Elevation Gradient in China

“…Sixtythree families, representing 79 to 91% of the classified sequences, including Rhodocyclaceae, Xanthomonadaceae, Verrucomicrobiaceae, Nitrosomonadaceae, Alcaligenaceae, and Cytophagaceae, were commonly shared by all samples. Most of the shared families were also shared in many other studies (3,24).…”

“…Thus, the declining trend in WWTP microbial community richness might also be influenced by the climatic conditions at high elevations, which are characterized by more extreme temperature fluctuations, low air pressure, and stronger UV radiation. It has been reported that the amounts of endemic stress genes, such as 24 genes responsive to extreme temperature stress and the obgE gene for the response to radiation stress, are enriched in the microbial community on the Tibetan grassland (12). This implies that fewer and fewer bacteria can adapt to the extreme physiological challenges on the Tibetan Plateau.…”

The effect of malathion on the activity, performance, and microbial ecology of activated sludge

“…The second point is related to functional redundancy. The application of molecular methods has permitted scientists to show that numerous microbial species can carry out the same biochemical functions during wastewater treatment (He et al, 2010;Hesselsoe et al, 2009;Siripong and Rittmann, 2007;Valentin-Vargas et al, 2012). This redundancy permits COD and nutrient removal to continue in the presence of inhibitors; more resistant subgroups substitute for those that are impaired.…”