Denitrification of nitrate and nitrite by 'Candidatus Accumulibacter phosphatis' clade IC.
Phosphate accumulating organisms (PAO) are assumed to use nitrate as external electron acceptor, allowing an efficient integration of simultaneous nitrogen and phosphate removal with minimal organic carbon (COD) requirements. However, contradicting findings appear in literature regarding the denitrification capacities of PAO due to the lack of clade specific highly enriched PAO cultures. Whereas some studies suggest that only PAO clade I may be capable of using nitrate as external electron acceptor for anoxic P-uptake, other studies indicate that PAO clade II may be responsible for anoxic P-removal. In the present study, a highly enriched PAO clade IC culture (>99% according to FISH) was cultivated in an SBR operated under Anaerobic/Oxic conditions and subsequently exposed to Anaerobic/Anoxic/Oxic conditions using nitrate as electron acceptor. Before and after acclimatization to the presence of nitrate, the aerobic and anoxic (nitrate and nitrite) activities of the PAO I culture were assessed through the execution of batch tests using either acetate or propionate as electron donor. In the presence of nitrate, significant P-uptake by PAO I was not observed before or after acclimatization. Using nitrite as electron acceptor, limited nitrite removal rates were observed before acclimatization with lower rates in the acetate fed reactor without P-uptake and slightly higher in the propionate fed reactor with a marginal anoxic P-uptake. Only after acclimatization to nitrate, simultaneous P and nitrite removal was observed. This study suggests that PAO clade IC is not capable of using nitrate as external electron acceptor for anoxic P-removal. The elucidation of the metabolic capacities for individual PAO clades helps in better understanding and optimization of the relation between microbial ecology and process performance in enhanced biological phosphate removal processes.
Department of Civil Engineering, Faculty of Engineering, Ain Shams University, 1 El Sarayat St., Abbassia, 11517 Cairo, Egypt; Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands. Electronic address: sondos.abdel-hakim@eng.asu.edu.eg.
Sondos A
SA
Saad
Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands; Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands. Electronic address: laurenswelles@gmail.com.
Laurens
L
Welles
Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands. Electronic address: b.a.abbas@tudelft.nl.
Ben
B
Abbas
Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands. Electronic address: c.lopezvazquez@unesco-ihe.org.
Carlos M
CM
Lopez-Vazquez
Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands. Electronic address: m.c.m.vanloosdrecht@tudelft.nl.
Mark C M
MCM
van Loosdrecht
Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands; Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands. Electronic address: d.brdjanovic@unesco-ihe.org.
Damir
D
Brdjanovic
D019149:Bioreactors; D058440:Denitrification; D009566:Nitrates; D009573:Nitrites; D010758:Phosphorus / Q000378:metabolism; D012722:Sewage
D009566:Nitrates; D009573:Nitrites; D012722:Sewage; D010758:Phosphorus
Acetate; Denitrification; EBPR; Nitrate; Nitrite; Propionate; ‘ Candidatus accumulibacter phosphatis’ clade I