Biomass granulation in an aerobic:anaerobic-enhanced biological phosphorus removal process in a sequencing batch reactor with varying pH

Biotechnology Research Centre, La Trobe University, Bendigo, VIC 3552, Australia.
Journal of Industrial Microbiology (Impact Factor: 2.44). 05/2009; 36(7):885-93. DOI: 10.1007/s10295-009-0566-3
Source: PubMed


Long-term influences of different steady-state pH conditions on microbial community composition were determined by fluorescence in situ hybridization (FISH) in a laboratory scale reactor configured for enhanced biological phosphorus removal (EBPR). Chemical profiles were consistent with shifts in populations from polyphosphate-accumulating organisms (PAO) to glycogen-accumulating organisms (GAO) when pH fell from pH 7.5 to 7.0 and then to 6.5. While biomass was both dispersed and flocculated at pH 7.5, almost complete granulation occurred gradually after pH was dropped to 7.0, and these granules increased in size as the pH was reduced further to 6.5. Reverting back to pH 7.5 led to granule breakdown and corresponding increases in anaerobic phosphate release. Granules consisted almost entirely of Accumulibacter PAO cells, while putative GAO populations were always present in small numbers. Results suggest that low pH may contribute to granulation under these operational conditions. While chemical profiles suggested the PAO:GAO balance was changing as pH fell, FISH failed to reveal any marked corresponding increase in GAO abundances. Instead, TEM evidence suggested the Accumulibacter PAO phenotype was becoming more like that of a GAO. These data show how metabolically adaptable the Accumulibacter PAO can be under anaerobic:aerobic conditions in being able to cope with marked changes in plant conditions. They suggest that decreases in EBPR capacity may not necessarily reflect shifts in community composition, but in the existing population metabolism.

Download full-text


Available from: Simon Jon McIlroy, Jan 06, 2015
  • Source
    • "EBPR with glucose as a dominant carbon source was likely due to increased glucose-induced intracellular acidification forcing PAOs to shift from polyphosphate and glycogen metabolism (PAO metabolism) to glycogen metabolism (GAO metabolism). A shift from PAO phenotype to GAO phenotype due to reduction in pH has also been demonstrated by Ahn et al. (2009) using fluorescence in situ hybridization (FISH) probes. They noted neither a reduction in population density of Accumulibacter nor an increase in population density of GAOs with decreasing pH in the reactor fed with acetate as a sole carbon source. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The effects of glucose on enhanced biological phosphorus removal (EBPR) activated sludge enriched with acetate was investigated using sequencing batch reactors. A glucose/acetate mixture was serially added to the test reactor in ratios of 25/75%, 50/50%, and 75/25% and the EBPR activity was compared to the control reactor fed with 100% acetate. P removal increased at a statistically significant level to a near-complete in the test reactor when the mixture increased to 50/50%. However, EBPR deteriorated when the glucose/acetate mixture increased to 75/25% in the test reactor and when the control reactor abruptly switched to 100% glucose. These results, in contrast to the EBPR conventional wisdom, suggest that the addition of glucose at moderate levels in wastewaters does not impede and may enhance EBPR, and that glucose waste products should be explored as an economical sustainable alternative when COD enhancement of EBPR is needed.
    Full-text · Article · Jul 2012 · Bioresource Technology
  • Source
    • "The biomass was aerated overnight to exhaust any residual carbon sources and stored PHA. Then 800 mL of biomass was washed twice, resuspended in the same volume of a synthetic wastewater (Ahn et al., 2009) and stirred in a 1-L Schott bottle sparged with nitrogen (N 2 ) gas (to create an anaerobic environment) for 1 h. Sodium acetate was then added to yield a total concentration of 75 mg L À1 carbon. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The in situ ecophysiology of alphaproteobacterial filamentous Cluster III Defluviicoccus present in enhanced biological phosphorus removal (EBPR)-activated sludge systems was evaluated using FISH-MAR and histochemical staining methods. These organisms, sharing the Nostocoida limicola morphotype, are known to be responsible for serious episodes of activated sludge bulking. The data presented here also demonstrate an ability to assimilate short-chain fatty acids and synthesize poly-β-hydroxyalkanoates (PHA) anaerobically, and then utilize this stored PHA under aerobic conditions, but with no corresponding synthesis of polyphosphate. These features are consistent with an in situ phenotype of glycogen-accumulating organisms (GAO), populations thought to lower the efficiency of EBPR systems by outcompeting polyphosphate-accumulating organisms (PAO) for substrates in their anaerobic feed phase. Survey data indicate that these GAO are as commonly seen as the known PAO in full-scale EBPR-activated sludge systems, which suggest that they might play important roles there, and therefore should not be viewed just as laboratory curiosities.
    Full-text · Article · Oct 2010 · FEMS Microbiology Ecology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Glycogen-accumulating organisms (GAO) are thought to out-compete the polyphosphate-accumulating organisms (PAO) in activated sludge communities removing phosphate (P). Two GAO groups are currently recognized, the gammaproteobacterial Candidatus 'Competibacter phosphatis', and the alphaproteobacterial Defluviicoccus vanusrelated tetrad forming organisms (TFOs). Both are phylogenetically diverse based on their 16S rRNA sequences, with the latter currently considered to contain members falling into three distinct clusters. This paper identifies members of an additional fourth Defluviicoccus cluster from 16S rRNA gene clone library data obtained from a laboratory-scale activated sludge plant community removing P, and details FISH probes designed against them. Probe DF181A was designed to target a single sequence and DF181B designed against the remaining sequences in the cluster. Cells hybridizing with these probes in the biomass samples tested always appeared as either TFOs or in large clusters of small cocci. Members of the Defluviicoccus-related organisms were commonly found in full-scale wastewater treatments plants, sometimes as a dominant population. © 2009 Society for Applied Microbiology and Blackwell Publishing Ltd.
    No preview · Article · Dec 2009 · Environmental Microbiology Reports
Show more