Novel control strategy employing anaerobic/aerobic/anoxic/aerobic/ anoxic mode to enhance endogenous denitrification and anammox for municipal wastewater treatment

Anaerobic/Aerobic/Anoxic (AnOA) n OA) process utilizes endogenous denitrification to remove nitrogen. However, low endogenous denitrification activity critically restricts its application owing to insufficient carbon sources. In this study, a novel control strategy employing anaerobic/aerobic/anoxic/aerobic/anoxic (AOAOA) mode was introduced to treat low Carbon/Nitrogen (C/N) ratio municipal wastewater over 262 days. The concentration of total inorganic nitrogen (TIN) was only 3.9 +/- 2.0 mg/L in the effluent, with a high nitrogen removal efficiency (NRE) of 94.3 %. The relative abundance of Candidatus Competibacter increased from 1.2 % to 2.3 %, ensuring an efficient endogenous denitrification process. Additionally, Candidatus Brocadia enriched from 0.02 % to 0.6 %, contributing to 63.1 % nitrogen removal during the anoxic stage in Phase III. This study presents a promising approach for enhancing endogenous denitrification and anammox in the AnOA n OA process, contributing to sustainable wastewater treatment.