[Quick Start-up Performance of Combined ANAMMOX Reactor Based on Different Inoculated Sludge Types]

In order to determine the optimal sludge source of anaerobic ammonium oxidation (ANAMMOX) and the rapid formation of ANAMMOX granular sludge, two CAMBRs (combined ABR and MBR) were compared for ANAMMOX enrichment with different inoculated sludge types, the anaerobic granular sludge (R1) and flocculent denitrifying sludge (R2). The results showed that ANAMMOX was successfully initiated after 45 d (R1) and 60 d (R2) in both reactors, respectively. The enrichment processes are divided into three different phases, lag phase, activity elevation phase, and stationary phase but the removal rules of nitrogen in each phase were different. In the steady phase, the average removal rates of NH₄⁺-N and NO₂^--N were higher than 95%. In addition, the red ANAMMOX granular sludge with the main diameter of 0.8-1.6 mm was formed in R1 while the flocculent sludge and irregular block with a low degree of granulation were mainly developed in R2. The phenomenon of red granular sludge floating in the two reactors was also observed. The quantitative relationship analysis between NH₄⁺-N, NO₂-N, and NO₃^--N showed the occurrence of nitrate-dependent ANAMMOX, which resulted in the oxidation of excess ammonia and the typical nitrite-dependent ANAMMOX occurred in R2.