Impact of Phosphorous Limitation on Partial Denitrification/Anammox Polishing Filters

Development of a partial denitrification – anammox (PdNA) biofiltration strategy as a final treatment step would allow stringent nitrogen limits to be met while minimizing the use of external carbon for denitrification. For plants that are also required to meet stringent phosphorus (P) limits, removing phosphorus in upstream processes causes limitations for organisms in denitrification filters. Since little is known about the impact of P in PdNA systems, the goal of this study was to understand the impact of P limitation on the performance of PdNA filters for two different media types: sand and expanded clay. Overall, there was no statistical difference in performance between the two media types. P limited conditions severely impacted PdN efficiency and ammonium removal potential in both PdNA filters. Once, both P limitation and inhibition due to sodium bisulfite addition for chlorine removal was eliminated, PdN efficiencies above 70% were achieved using glycerol as the carbon source. NH4+ removal through anammox was greater than 5 mg-N/L and reached overall total nitrogen removal rates similar to conventional denitrification filters.