Phosphorous Requirements in a Post Denitrification MBBR at a Combined Limit of Technology Nitrogen and Phosphorous Plant

MBBR post denitrification pilot was implemented at the Blue Plains AWTP. The objective was to assess the impact of phosphorus (P) on the denitrification process and compliance risk related to the effluent total phosphorus limit of 0.18 mg/L. P requirements were assessed during warm (22°C) and cold (13°C) operating conditions. P limitation impacts were not observed during warm temperature period, where effluent NOx-N averaged 0.5 mg/L. Significant performance degradation was observed in the P-limited train during the cold period, with an average effluent NOx-N of 4.5 mg/L, while P-unlimited train did not demonstrate degradation in performance. The findings of this study imply that P-limited effects become apparent as wastewater temperatures begin to decrease but not apparent during periods where the temperature and loadings are quite stable and the biomass is well established. The implications for full scale operations are that supplemental P may be required as significant changes in temperature or loading occur to support increased biomass growth.