Functional analysis of microbial communities in aerobic–anaerobic sequencing batch reactors fed with different phosphorus/carbon (P/C) ratios

Abstract

Fluorescence in situ hybridization (FISH) was used to analyse the community composition of a sequencing batch reactor (SBR) operating with aerobic-anaerobic cycling and fed acetate as its sole carbon source. Phosphorus was removed from the SBR microbiologically. Marked shifts in the community structure occurred as the phosphorus/carbon (P/C) ratio in the feed was changed. When the P/C ratio was shifted from 1 :10 to 1 :50, FISH analysis showed that the percentage of β-Proteobacteria fell from ca 77 % of the total bacteria to ca 38 %. This decrease in the β-Proteobacteria coincided with a reduction in both the proportions of the β-proteobacterial Rhodocyclus-related phosphorus-accumulating bacteria and the biomass phosphorus content. Both the α-and β-proteobacterial ' G-bacterial ' populations assimilated acetate and synthesized PHA anaerobically. The α-Proteobacteria are considered responsible for glycogen production in these SBR systems.

The effects of carbon/phosphorus ratio on polyphosphate- and glycogen-accumulating organisms in aerobic granular sludge

“…De Kreuk and van Loosdrecht (2004) showed by semi-quantitative FISH analysis (subjective approximation) that PAO community in GSBR can be almost completely replaced by GAOs when dosage of phosphate is stopped. Similar changes in abundance of Rhodocyclus-related PAOs, but in flocculent sludge, were observed by Kong et al (2002) in a laboratory-scale reactor fed with acetate as a sole carbon source.…”

From macro to lab-scale: Changes in bacterial community led to deterioration of EBPR in lab reactor

“…It is well known that a high COD/P ratio (above 50 mg COD mg -1 P) in wastewater is highly detrimental to EBPR as this promotes the growth of GAOs [4,21,28,29], but the COD must have a sufficient portion of VFAs or readily biodegradable COD to achieve efficient P removal [3,4,21]. The COD/P ratio in the influent in the current study was 35 and resulted in a DOC/P ratio of 12.…”

“…When Kong et al [28] fed a lab-scale SBR with acetate and a C/P ratio of 10 (close to the ratio examined in our research), the sludge was dominated by Betaprotebacteria (77% as revealed by FISH analysis) and P was totally removed from wastewater microbiologically. However, when the C/P ratio was increased to 50:1, the percentage of Betaprotebacteria fell to 38%.…”

“…The performance of EBPR systems depends on the competition of PAOs with GAOs, so it is desirable to minimise the growth of the latter in reactors [33]. Most research is carried out in lab-scale SBRs fed with a single carbon source, usually acetate or propionate [10,12,[27][28][29][30][31][32]49]. Due to the nature of these experiments conducted with highly enriched cultures, key aspects of PAO and GAO ecophysiology and their competition in full-scale systems need elucidation.…”

“…Most experiments have been carried out with highly enriched PAO (or GAO) cultures in lab-scale reactors fed with a single carbon source, typically acetate or propionate [11,12,[27][28][29][30][31][32][33][34]. In the current study a mixture of organic substrates was used to provide a higher diversity of substrates in the influent.…”