Microbial Community Analysis of Anammox Biomass in Laboratory-Scale Anammox Reactors
Microbial community diversity analysis in three laboratory-scale anammox reactors using sequencing batch reactor (SBR) and two continuous stirred tank reactors (CSTR) with and without recirculation line across two operational phases with 1.63 g L-1 dry weight (dw) in Phase I and increased to 5.44 g L-1 dw in Phase II was conducted. Microbial diversity in the inoculum, decreased during reactors operation. Community analysis revealed a shift in composition. In Phase II, Shannon entropy indices for SBR and CTSR2 were 4.77 and 4.61, respectively. CSTR1 had 5.04, indicating its lower performance.  Jettenia caeni became the predominant anammox species. Functional gene analysis revealed a positive correlation between the anammox-specific 16S rRNA gene (amx) abundance and NRE, while nirS and nirK gene copy numbers were inversely related to the reactor performance for both NRE and N2O emissions. The copy numbers of nosZ genes for both clade I and clade II varied in Phase II across different reactors, which potentially contributed to the differences in N2O emission reductions observed during this phase.