Interrogating the performance and microbial ecology of an enhanced biological phosphorus removal/post‐anoxic denitrification process at bench and pilot scales

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Research focused on interrogating post‐anoxic enhanced biological phosphorus removal (EBPR) at bench and pilot scales. Average bench‐scale effluent ranged from 0.33 to 1.4 mgP/L, 0.35 to 3.7 mgNH 3 ‐N/L, and 1.1 to 3.9 mgNO x ‐N/L. Comparatively, the pilot achieved effluent (50th percentile/average) of 0.13/0.2 mgP/L, 9.7/8.2 mgNH 3 ‐N/L, and 0.38/3.3 mgNO x ‐N/L under dynamic influent and environmental conditions. For EBPR process monitoring, P:C ratio data indicated that 0.2–0.4 molP/molC will result in stable EBPR; relatedly, a target design influent volatile fatty acid (VFA):P ratio would exceed 15 mgCOD/mgP. Post‐anoxic EBPR was enriched for Nitrobacter spp. at 1.70%–20.27%, with Parcubacteria also dominating; the former is putatively associated with nitritation and the latter is a putative fermenting heterotrophic organism. Post‐anoxic specific denitrification rates (SDNRs) (20°C) ranged from 0.70 to 3.10 mgN/gVSS/h; there was a strong correlation ( R 2 = 0.94) between the SDNR and % Parcubacteria for systems operated at a 20‐day solids residence time (SRT). These results suggest that carbon substrate potentially generated by this putative fermenter may enhance post‐anoxic EBPR. Practitioner Points Post‐anoxic EBPR can achieve effluent of <0.2 mgP/L and <12 mgN/L. The P:C and VFA:P ratios can be predictive for EBPR process monitoring. Post‐anoxic EBPR was enriched for Nitrobacter spp. over Nitrospira spp. and also for Parcubacteria , which is a putative fermenting heterotrophic organism. Post‐anoxic specific denitrification rates (20°C) ranged from 0.70 to 3.10 mgN/gVSS/h. BLASTn analysis of 16S rDNA PAO primer set was shown to be improved to 93.8% for Ca. Accumulibacter phosphatis and 73.2%–94.0% for all potential PAOs.