Interrogating the Performance and Microbial Ecology of an EBPR/Post-Anoxic Denitrification Process at Bench and Pilot Scales.

Research focused on interrogating post-anoxic enhanced biological phosphorus removal (EBPR) at bench and pilot scale. Average bench-scale effluent ranged from 0.33-1.4 mgP/L, 0.35-3.7 mgNH 3 -N/L, and 1.1-3.9 mgNO x -N/L. Comparatively, the pilot achieved effluent (50 th 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 0.2-0.4 molP/molC will result in stable EBPR; related, a target design influent volatile fatty acid (VFA):P ratio would exceed 15 mgCOD/mgP. Post-anoxic EBPR 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 (20°C) ranged from 0.70-3.10 mgN/gVSS-hr; there was a strong correlation (R 2 =0.94) between the SDNR and %Parcubacteria for systems operated at a 20 d SRT. These results suggest carbon substrate potentially generated by this putative fermenter may enhance post-anoxic EBPR.