Improvement of carbon usage for phosphorus recovery in EBPR-r and the shift in microbial community. (15th July 2018) - Wong, Pan Yu
Abstract: Enhanced biological phosphorus removal and recovery (EBPR-r) is a biofilm process that makes use of polyphosphate accumulating organisms (PAOs) to remove and recover phosphorus (P) from wastewater. The original process was inefficient, as indicated by the low P-release to carbon (C)-uptake (Prel /Cupt ) molar ratio of the biofilm. This study successfully validated a strategy to improve the Prel /Cupt ratio by at least 3-fold. With an unchanged supply of carbon in the recovery stream, an increase in the hydraulic loading in stages I, II and III (7.2, 14.4 and 21.6 L, respectively) resulted in a 43% increase in the Prel /Cupt ratio (0.069, 0.076 and 0.103, respectively). The ratio further increased by 150% (from 0.103 to 0.255) when the duration of the P uptake period was increased from 4 h (stage III) to 10 h (stage IV). Canonical correspondence analysis showed that, correlated to the 3-fold increase in the Prel /Cupt ratio, there was an increase in the abundance of PAOs (" Candidatus Accumulibacter " Clade IIA) and a decrease in the occurrence of glycogen accumulating organisms (GAOs) (family Sinobacteraceae ). However, the four stage operation impaired denitrification, resulting in a 5-fold reduction in the Nden /Pupt ratio. The decline in denitrification was consistent with a decrease in the abundance of denitrifiers including denitrifying PAOs (family Comamonadaceae and " Candidatus Accumulibacter " Clade IA). Overall, a strategy to facilitate more efficient use of carbon was validated, enabling a 3-fold carbon saving for P recovery. The new process enabled up to 80% of the wastewater P to be captured in a P-enriched stream (>90 mg/L) with a single uptake/release cycle of recovery. Highlights: A strategy to optimise the Prel /Cupt ratio by 3-folds was validated. 80% of the wastewater P was captured as a P-enriched recovery stream (>90 mg-P/L). Impact of optimisation on the bacterial community was revealed.