New insights on biological nutrient removal by coupling biofilm-based CANON and denitrifying phosphorus removal...

It was difficult to obtain a stable and efficient biological nutrient removal for high-strength wastewater treatment, the possibility of exploiting innovative CANDPR process, integrating biofilm-based completely autotrophic nitrogen removal over nitrite (CANON) with denitrifying phosphorus removal (DPR) was evaluated to resolve the difficulty. Results revealed that the excellent NH₄⁺-N, PO₄^3--P and COD removal efficiencies of 96%, 96% and 91%, were achieved respectively under a high nitrogen loading rate (0.79 kg·m^-3·d^-1) without adding organic matters during 320 days operation. Promoting NO_x^--N recirculation demonstrated as an efficient strategy for further nutrient depletion, facilitating the enhanced NO₃^--N removal to 100% with the considerably high P-uptake performance. Batch tests confirmed that denitrifying phosphorus accumulating organisms (DPAOs) using NO₃^--N as electron acceptors accounting for 68% in total PAOs. Dechloromonas was identified as dominating genus in DPR, while Nitrosomonas (1.31%), Candidatus_Kuenenia (5.53%) and Candidatus_Brocadia (1.77%) contributed to the desirable nitrogen removal, indicating that cooperative consortia of DPAOs, AOB and AnAOB were harvested during long-term operation. The CANDPR process was verified to be energy-saving and treatment-reliable for renovating of existing plants.