THE ROLE OF RHODOCYCLUS-LIKE ORGANISMS IN BIOLOGICAL PHOSPHORUS REMOVAL: FACTORS INFLUENCING POPULATION STRUCTURE AND ACTIVITY
Abstract:This research focused on PAO populations, especially those of Rhodocyclus-related PAOs, and their relationships to EBPR performance. For this purpose, a lab-scale sequencing batch reactor (SBR) and six full-scale wastewater treatment plants (WWTPs) performing EBPR were surveyed. Batch-scale acetate uptake and inorganic phosphate (Pi) release and uptake experiments were conducted to evaluate the EBPR activity of each sludge. Typical Pi and acetate profiles were observed and EBPR activity was found to be positively correlated to PAO abundance, as determined using 4',6-Diamidino-2-phenylindole (DAPI) to stain intracellular polyP. The abundance of Rhodocyclus-related organisms was investigated using fluorescent in situ hybridization (FISH). Rhodocyclus-related organisms were present in all full-scale EBPR plants, at levels ranging from 9% to 24% of total cells. The fraction of Rhodocyclus-related organisms with high polyP content (Rhodocyclus-related PAOs) was also determined. More than 84% of Rhodocyclus-related organisms were involved in EBPR in these six plants. However, Rhodocyclus-related PAOs were only a fraction (40%-70%) of the total PAO population, suggesting the involvement of non-Rhodocyclus-related PAOs in the full-scale EBPR plants. The variation of Rhodocyclus-related PAO abundance among plants suggests that multiple factors (e.g. plant configuration, BOD:TP ratio, chemical addition and solids retention time) may be acting hierarchically to structure PAO communities.
Document Type: Research Article
Publication date: January 1, 2005
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