Microbial diversity differences within aerobic granular sludge and activated sludge flocs

Abstract

In this study, we investigated during 400 days the microbial community variations as observed from 16S DNA gene DGGE banding patterns from an aerobic granular sludge pilot plant as well as the from a full-scale activated sludge treatment plant in Epe, the Netherlands. Both plants obtained the same wastewater and had the same relative hydraulic variations and run stable over time. For the total bacterial population, a similarity analysis was conducted showing that the community composition of both sludge types was very dissimilar. Despite this difference, general bacterial population of both systems had on average comparable species richness, entropy, and evenness, suggesting that different bacteria were sharing the same functionality. Moreover, multi-dimensional scaling analysis revealed that the microbial populations of the flocculent sludge system moved closely around the initial population, whereas the bacterial population in the aerobic granular sludge moved away from its initial population representing a permanent change. In addition, the ammonium-oxidizing community of both sludge systems was studied in detail showing more unevenness than the general bacterial community. Nitrosomonas was the dominant AOB in flocculent sludge, whereas in granular sludge, Nitrosomonas and Nitrosospira were present in equal amounts. A correlation analysis of process data and microbial data from DGGE gels showed that the microbial diversity shift in ammonium-oxidizing bacteria clearly correlated with fluctuations in temperature.

Effects of Wash-Out Dynamics on Nitrifying Bacteria in Aerobic Granular Sludge During Start-Up at Gradually Decreased Settling Time

“…Granular sludge provides different ecological niches due to its compact structure and the substrate gradients (which evolve as the granule size increases). The variety of niches together with the high biomass retention time facilitates high species diversity [33]. Therefore, it can be speculated that the increasing diversity after day 40 in the present study is related to an increase in nitrate respiration (denitrification), as indicated by the concomitant decrease in effluent nitrate concentration in R2 (Figure 3d).…”

“…However, the diversity of steady-state granular sludge can be remarkable. In a study by Winkler et al [33], the microbial community of a pilot-scale steady-state aerobic granular sludge reactor exhibited similar richness and evenness as that for a full-scale activated sludge reactor. Granular sludge provides different ecological niches due to its compact structure and the substrate gradients (which evolve as the granule size increases).…”

Directed evolution to produce sludge communities with improved oxygen uptake abilities

“…This change in diversity alone could play an important role in culture adaptation to an oxygen-stressed environment, since it is widely documented that diversity is generally positively correlated to functional stability of a system (Winkler et al 2013).…”

- Taxonomic Precision of Different Hypervariable Regions of 16S rRNA Gene and Annotation Methods for Functional Bacterial Groups in Biological Wastewater Treatment

“…The richness and diversity patterns, which are commonly used to characterize biological and wastewater systems (Liu et al, 1997;Borcard et al, 2011;Gonzalez-Gil and Holliger, 2011;Winkler et al, 2012), were used to compare the evolution of the overall bacterial community structure under wash-out and steady-state conditions (Figure 8). In addition to the drop in richness and diversity during early-stage granulation reported in Weissbrodt et al (2012a), wash-out conditions more intensively impacted on these indices.…”

“…Other denitrifiers that presumably do not take up VFA anaerobically were present in the full anaerobic-aerobic AGS ecosystems. Denitrifying metabolic activities and utilization of exopolysaccharides as electron donors in AGS systems should be investigated further based on previous knowledge gained from activated sludge systems (Finkmann et al, 2000;Thomsen et al, 2007;Ni et al, 2009;Nielsen et al, 2012b).The richness and diversity patterns, which are commonly used to characterize biological and wastewater systems (Liu et al, 1997;Borcard et al, 2011;Gonzalez-Gil and Holliger, 2011;Winkler et al, 2012), were used to compare the evolution of the overall bacterial community structure under wash-out and steady-state conditions (Figure 8). In addition to the drop in richness and diversity during early-stage granulation reported in Weissbrodt et al (2012a), wash-out conditions more intensively impacted on these indices.…”