Start-up and nitrogen removal performance of CANON and SNAD processes in a pilot-scale oxidation ditch reactor

[Display omitted] •CANON and SNAD were started successfully in a pilot-scale oxidation ditch.•Aeration time / non-aeration time was proposed as a key operation parameter.•Braided type carriers provided a suitable environment for the growth of AnAOB. In this study, the completely autotrophic nitrogen removal over nitrite (CANON) process was started successfully in a pilot-scale oxidation ditch. The influent ammonia nitrogen (NH4+-N) concentration was about 40 mg/L, while the effluent NH4+-N and total nitrogen (TN) concentrations were 2.81 mg/L and 7.80 mg/L, respectively. The average removal efficiency of TN was 82.17%. After the employment of CANON to deal with actual domestic wastewater, a simultaneous partial nitrification, anaerobic ammonium oxidation (ANAMMOX), and denitrification (SNAD) process was gradually started. During operation of the reactor, both hydraulic retention time (HRT) and aeration / non-aeration time were important parameters for the biological treatment effect and effluent quality of the SNAD process. The HRT of 15 h, and an aeration / non-aeration time of 3 h/1 h was recommended as the optimal operating parameters in the SNAD process. Sludge activity and high-throughput sequencing analyses showed that the carriers provided a suitable environment for the attachment and growth of anaerobic ammonia-oxidizing bacteria, thus ensuring the reaction of ANAMMOX. This study can provide a deeper understanding on the application of SNAD treatment of domestic wastewater in an oxidation ditch-type continuous flow reactor.