Confronting Assumptions of Phosphorus-Accumulating Organisms and Glycogen-Accumulating Organisms: Peaceful Coexistence in a Carbon-Limited Sidestream EBPR Demonstration

Abstract

Enhanced biological phosphorus removal (EBPR) is strongly influenced by the influent ratio of readily biodegradable carbon to soluble phosphorus due to the preferences of phosphorus-accumulating organisms (PAO). The sidestream EBPR (S2EBPR) process redirects a portion of return activated sludge (RAS) to a sidestream fermenter, increasing the availability of biodegradable carbon. In this study, we assessed the performance and microbial community structure of a full-scale S2EBPR demonstration supplemented with external carbon dosing. By the end of the 10 month study period, the demonstration achieved a median effluent orthophosphate of 0.3 mg/L. The microbial community consisted of a common core microbiome in the RAS fermenter, EBPR basin, and nitrification basin. The most abundant PAO detected were Ca. “Dechloromonas phosphorivorans”, while the canonical PAO Ca. “Accumulibacter” and Tetrasphaera were observed in lower relative abundance. In addition to non-canonical PAO enrichment, the glycogen-accumulating organism Ca. “Competibacter” proliferated throughout the study and at some points outnumbered PAO taxa by 30 to 1 with no tangible performance impacts. This study provides insights into successful S2EBPR implementation at a low-carbon facility and improves our understanding of microbial community structure and key PAO and GAO in S2EBPR systems.

Exploring Community and Kinetic Shifts in Nitrifying Microbial Communities in Low Dissolved Oxygen Activated Sludge Facilities for Energy-Efficient Biological Nitrogen Removal

“…However, recent findings have shown that Candidatus Accumulibacter and Candidatus Competibacter can coexist without impacts on overall process performance. 48 The presence of Denitratisoma (1% of total reads in CRWS) also confirms the presence of bacteria involved in denitrification or partial denitrification; these heterotrophic bacteria were previously confirmed to directly convert NO 2 − to N 2 . 49 The occurrence of denitrifying bacteria could be explained by the low DO operation of CRWS and by the possibility of the activated sludge flocs performing simultaneous nitrification and denitrification (SND).…”

“…Candidatus Competibacter (18.7% of total reads in CRWS) is a glycogen-accumulating organism (GAO) and is considered a competitor for carbon during EBPR because it consumes VFAs but does not take up phosphorus. However, recent findings have shown that Candidatus Accumulibacter and Candidatus Competibacter can coexist without impacts on overall process performance . The presence of Denitratisoma (1% of total reads in CRWS) also confirms the presence of bacteria involved in denitrification or partial denitrification; these heterotrophic bacteria were previously confirmed to directly convert NO 2 – to N 2 .…”

Assessing the performance of polyphosphate accumulating organisms in a full‐scale side‐stream enhanced biological phosphorous removal

“…This suggests that the operational conditions of the S2EBPR need enhancement to bolster the competition of PAOs against other competitors, aiming for a more stable and efficient biological P removal. Recently, Farmer et al (2023) reported that the relative abundance of Tetrasphaera and Dechloromonas was as high as Ca. Accumulibacter in their monitoring of the microbial community of a full-scale S2EBPR system (Farmer et al, 2023).…”

“…Recently, Farmer et al (2023) reported that the relative abundance of Tetrasphaera and Dechloromonas was as high as Ca. Accumulibacter in their monitoring of the microbial community of a full-scale S2EBPR system (Farmer et al, 2023). However, their study was published after our microbial community analysis was concluded.…”

Minimizing biological sludge generation in a sidestream enhanced biological phosphorus removal (S2EBPR) system: full-scale evaluation and modeling insights

“…10 Unlike a conventional EBPR process, the S2EBPR involves recirculating a portion of RAS to an anaerobic SSR to stimulate the growth and activity of PAO. 11,12 In the literature, the anaerobic SSR is also commonly referred to as a sidestream fermenter or RAS fermenter.…”