[Startup Strategies for the SNAD Granular Sludge Process at Low Temperature].

To study the effect of the startup strategies on the simultaneous partial nitrification, ANAMMOX, and denitrification (SNAD) granular sludge processes, these processes were initiated by starting the completely autotrophic nitrogen removal over nitrite (CANON) process and anaerobic ammonia oxidation-denitrification (SAD) process at 12.7℃ and 18.3℃, respectively. The results show that the ammonia nitrogen was almost completely removed and the total nitrogen removal rate reached 86.7% after the R1 reactor was successfully started. When the ammonia concentration was low, the total nitrogen removal rate in the effluent decreased to 75.3%, the total nitrogen concentration in the effluent was~10 mg·L-1 , and excessive proliferation of the NOB was observed. The total nitrogen concentration in the effluent exceeded the 1A level of the integrated discharge standard of water pollutants applied in Beijing City. After the R2 reactor was successfully started, the effluent contained almost no ammonia nitrogen and the total nitrogen removal rate was~89.1%, that is, slightly higher than that of the R1 reactor. When the ammonia concentration was low, the concentration of ammonia nitrogen in effluent was less than 1.0 mg·L-1 and the total nitrogen concentration in the effluent was less than 6 mg·L-1 . The concentrations of ammonia nitrogen and total nitrogen in the effluent reached the 1A level of the integrated discharge standard of water pollutants applied in Beijing City. First, the startup of the SAD process gradually eliminated the NOB from the system through anaerobic operation in the initial stage of the startup, maintained the stability of the system, provided a good basis for the subsequent aeration to start the SNAD process, maintained the stable operation of the reactor, and the long-term discharge of total nitrogen reached the standard.