Full‐scale transition from denitrification to partial denitrification – anammox (PdNA) in deep‐bed filters: operational strategies for and benefits of PdNA implementation

This study shows for the first time more than two years of operation of a mainstream anammox application at full-scale under temperate climate. This implementation of partial denitrification – anammox (PdNA) in deep bed filters at the HRSD York River treatment plant was demonstrated to achieve the benefits of shortcut nitrogen removal without nitrite oxidizing bacteria (NOB) out-selection. The transition from denitrification to PdNA filters required bleeding ammonium to the filters using an optimized ammonium vs NOx (AvN) control in the upstream aeration tanks and maintaining a nitrate residual in the filter effluent through feedforward/feedback control. The latter actions led to savings of 85% in methanol, 100% in alkalinity, and 35% in capacity enhancement. Up to 6 mg NH4+-N/L with an average of 2.2±0.98 mg NH4+-N/L was removed through the anammox pathway which accounted for about 15% of the overall plant nitrogen removal. Anammox enrichment was confirmed by activity testing and molecular analysis. The large excess of AnAOB capacity present in the filters (5-10 times more than normal operation) resulted in stable and reliable operation through winter conditions and showed potential for further intensification.