Abstract: Anammox was successfully transited from heterotrophic
denitrification and autotrophic denitrification in two upflow biofilm reactors,
respectively. The results showed that the volumetric loading rate and nitrogen
removal efficiency in the reactor transited from heterotrophic denitrification
were higher than that in its counterpart. When the hydraulic retention time was
12 h or so, the total nitrogen loading rate was about 0.609 kg
N/(m^3·d), and the effluent ammonia and nitrite
concentrations were less than 8.5 mg/L and 2.5 mg/L, respectively. The upflow
anammox biofilm reactor was capable of keeping and accumulating the
slow-growing bacteria efficiently. During operation of the reactor, the biomass
color was gradually turned from brownish to red, and the ratio of ammonia
consumption, nitrite consumption and nitrate production approached the
theoretical one. These changes could be used as an indicator for working state
of the reactor.