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 denitri...

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Bibliographic Details
Published in:Water research (Oxford) 2016-11, Vol.105, p.97-109
Main Authors: Saad, Sondos A., Welles, Laurens, Abbas, Ben, Lopez-Vazquez, Carlos M., van Loosdrecht, Mark C.M., Brdjanovic, Damir
Format: Article
Language:English
Subjects:
Acclimatization
Acetate
Acetates
Anaerobic conditions
Bioreactors
Culture
Denitrification
EBPR
Enrichment
Nitrate
Nitrates
Nitrite
Nitrites
Phosphates
Phosphorus - metabolism
Propionate
Sewage
‘ Candidatus accumulibacter phosphatis’ clade I
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Summary: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. ‘ Candidatus Accumulibacter phosphatis’ clade IC. [Display omitted] •A highly enriched Accumulibacter clade IC culture was obtained.•Accumulibacter clade IC did not perform anoxic dephosphatation over nitrate.•In the presence of nitrite Accumulibacter clade IC can perform anoxic dephosphatation.•PHB/PHV ratio in PHA does not affect the anoxic phosphate uptake ability.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2016.08.061