Performance and microbial community composition dynamics of aerobic granular sludge from sequencing batch bubble column reactors operated at 20 °C, 30 °C, and 35 °C

Abstract

Two bubble column sequencing batch reactors fed with an artificial wastewater were operated at 20 degrees C, 30 degrees C, and 35 degrees C. In a first stage, stable granules were obtained at 20 degrees C, whereas fluffy structures were observed at 30 degrees C. Molecular analysis revealed high abundance of the operational taxonomic unit 208 (OTU 208) affiliating with filamentous bacteria Leptothrix spp. at 30 degrees C, an OTU much less abundant at 20 degrees C. The granular sludge obtained at 20 degrees C was used for the second stage during which one reactor was maintained at 20 degrees C and the second operated at 30 degrees C and 35 degrees C after prior gradual increase of temperature. Aerobic granular sludge with similar physical properties developed in both reactors but it had different nutrient elimination performances and microbial communities. At 20 degrees C, acetate was consumed during anaerobic feeding, and biological phosphorous removal was observed when Rhodocyclaceae-affiliating OTU 214 was present. At 30 degrees C and 35 degrees C, acetate was mainly consumed during aeration and phosphorous removal was insignificant. OTU 214 was almost absent but the Gammaproteobacteria-affiliating OTU 239 was more abundant than at 20 degrees C. Aerobic granular sludge at all temperatures contained abundantly the OTUs 224 and 289 affiliating with Sphingomonadaceae indicating that this bacterial family played an important role in maintaining stable granular structures.

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

“…Even a gradually decreased settling time does not always lead to the prompt start of nitrification. Ebrahimi et al [30] observed no nitrification in a reactor operated at 20˝C for more than 60 days, although the settling time was decreased gradually, at a similar rate to that used in the present study. Although there are still too few examples from which to draw any comprehensive conclusions, it is clear that the decrease rate must be adjusted to the operational conditions and configuration of the reactor in order to achieve the goal of rapid nitrification start-up.…”

“…The dissimilarity between the bacterial community of the seed sludge and that of the granules continued to increase ( Figure 5). During start-up, decreased richness and evenness compared to the seed sludge has been previously reported [16,30]. The decreased diversity is presumably a consequence of the wash-out conditions typical of the start-up in granular sludge reactors.…”

“…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). During start-up, decreased richness and evenness compared to the seed sludge has been previously reported [16,30]. The decreased diversity is presumably a consequence of the wash-out conditions typical of the start-up in granular sludge reactors.…”

Chemicals and Allied Products Waste Treatment

“…Determination was made in the first stage that Lepothrix sppwas present at 30 °C, while 20° acetate was consumed in anaerobic condition and biological phosphorus removal by Rhodocyclacae-affiliating OUT 14 at 30 and 35° Celsisus acetate was completed and phosphorus removal did not occur as high [71].…”

Operation mode and external carbon dose as determining factors in elemental composition and morphology of aerobic granules

“…It has been shown that the selection of operational parameters such as hydraulic retention time (HRT), temperature, a COD/N ratio of the infl uent and organics loading (Cydzik-Kwiatkowska and Wojnowska--Baryła 2011, Ebrahimi et al 2010, Muda et al 2011) affects the morphology of granules and their species composition. The variations of Ca, Mg and K concentrations in the infl uent dictate the amounts of these ions in granules (Schönborn et al 2001).…”