Identification of Some of the Major Groups of Bacteria in Efficient and Nonefficient Biological Phosphorus Removal Activated Sludge Systems

Abstract

To investigate the bacteria that are important to phosphorus (P) removal in activated sludge, microbial populations were analyzed during the operation of a laboratory-scale reactor with various P removal performances. The bacterial population structure, analyzed by fluorescence in situ hybridization (FISH) with oligonucleotides probes complementary to regions of the 16S and 23S rRNAs, was associated with the P removal performance of the reactor. At one stage of the reactor operation, chemical characterization revealed that extremely poor P removal was occurring. However, like in typical P-removing sludges, complete anaerobic uptake of the carbon substrate occurred. Bacteria inhibiting P removal overwhelmed the reactor, and according to FISH, bacteria of the β subclass of the class Proteobacteria other than β-1 or β-2 were dominant in the sludge (58% of the population). Changes made to the operation of the reactor led to the development of a biomass population with an extremely good P removal capacity. The biochemical transformations observed in this sludge were characteristic of typical P-removing activated sludge. The microbial population analysis of the P-removing sludge indicated that bacteria of the β-2 subclass of the class Proteobacteria and actinobacteria were dominant (55 and 35%, respectively), therefore implicating bacteria from these groups in high-performance P removal. The changes in operation that led to the improved performance of the reactor included allowing the pH to rise during the anaerobic period, which promoted anaerobic phosphate release and possibly caused selection against non-phosphate-removing bacteria.

Analysis of the microbial community structure and function of a laboratory scale enhanced biological phosphorus removal reactor

“…As a consequence, the system became robust giving it greater resistance to occasional perturbations, more stable leading to nearly constant phosphorus removal, and improved its EBPR capacity, relative to the period with pH control. An improvement in reactor stability and phosphorus removal efficiency was reported by Bond et al (1999a) when they removed pH control in the anaerobic period. However, in that study, the aerobic pH was controlled at 7.…”

“…This difference could be caused by a different microbial community development under the different pH operating conditions. Bond et al (1999a) reported a sludge with a GAO phenotype and dominated by betaproteobacteria from subgroups other than 1 and 2 when operation was with complete pH control at 7. Subsequently, when the pH was controlled at 7 only during the aerobic period, the sludge demonstrated a PAO phenotype and the microbial community was more diverse but composed of 55% betaproteobacteria from subgroup 2.…”

“…Glycogen-accumulating organisms were identified as members of a novel gammaproteobacteria cluster recently reported by others (Nielsen et al, 1999; (Crocetti et al 2000) 17.2 4.1 6.0 2.7 na c na A sludge (Crocetti et al 2000) 15.1 4.1 6.0 1.3 1.8 na Laboratory scale continuous process (Wentzel et al, 1988) 14.4-15.6 3.2-5.5 6.0 na na na S sludge (Bond et al, 1999b) 12.3 4.2 6.0 2.0 4.8~100:~0 Laboratory sludge (Liu et al, 1997) d 12.1 4.0 6.0 2.7 8.2 87.7:11.8 Laboratory sludge (Liu et al, 1997) d 9.1 3.3 6.0 2.3 7.1 83.2:15.4 EBPR model (Smolders et al, 1994a) -3.0 6.0 3.0 8.2 90.0:10.0 P sludge (Bond et al, 1999a) 8.8 2.8 6.0 4.0 8.2 80.6:19.4 Portuguese sludge (this study) a 8.6 2.1 6.0 6.7 10.3 62.3:37.7 Sludge (Satoh et al, 1992) d 6.3 2.6 6.0 4.0 8.0 88.2:9.6 Laboratory sludge (Liu et al, 1997) d 6.0 2.7 6.0 4.7 8.8 79.1:18.3 T sludge (Bond et al, 1999b) 2.0 0.2 6.0 8.6 9.4 72.2:27.8 Q Sludge (Bond et al, 1999a) 1.8 0.2 6.0 8.6 9.5 68.9:31.1 Laboratory SBR (Cech and Hartman, 1993) 1.8~0 6.0 na na na Laboratory sludge (Liu et al, 1997) et al, 2001) and described as 'Candidatus Competibacter phosphatis' (Crocetti et al, 2002) (henceforth called Competibacter). This was confirmed in our sludge by using FISH, and by post-FISH chemical staining for PHA (Nile Blue), demonstrating EBPR PHA cycling in these organisms which were amorphous groups of large coccobacilli.…”

“…The TFOs in our SBR sporadically demonstrated GAO phenotype. The TFOs are GAOs for one full scale plant in Australia, but there are also reports of non-GAO TFOs (Bond et al, 1999a) and even more reports where the phenotype of the TFOs is not determined. In a recent publication, the first reported G bacteria of Cech and Hartman (1993), Amaricoccus kaplicensis, was found unable to take up acetate anaerobically and store it as PHA and consequently A. kaplicensis is not a GAO (Falvo et al, 2001).…”

“…The GAO phenotype has not been observed in pure culture, but it has been demonstrated in highly enriched cultures by chemical analysis (Fukase et al ., 1985;Satoh et al ., 1994;Bond et al ., 1999a) and by microscopy at a cellular level (Crocetti et al ., 2002). To date one GAO has been unequivocally identified as belonging to a novel cluster of bacteria in the gammaproteobacteria radiation (Nielsen et al ., 1999;Dabert et al ., 2001;Crocetti et al ., 2002).…”