Assessment of reactor configurations and key factors for enhanced anammox-based nitrogen removal

Wastewater treatment processes are continually evolving to meet stringent environmental standards while optimizing energy consumption and operational costs. With significant advantages over more traditional approaches, the anammox process has become a hopeful substitute for nitrogen removal. The objective of this work was to evaluate upflow anaerobic sludge blanket reactor (UASBR), moving bed biofilm reactor (MBBR), and sequential batch reactor (SBR) among diverse reactor configurations, in culturing anammox bacteria and achieving nitrogen removal efficiencies. Synthetic wastewater containing NH₄⁺-N concentration and NO₂^--N concentration of 80 ± 5 mg/L was introduced to the reactors, and observations were made for up to 150 days. This study found that the MBBR demonstrated superior anammox activity, achieving a total nitrogen removal efficiency (TNRE) of 94 ± 3%, SBR exhibited a TNRE of approximately 85 ± 3%, while UASB displayed TNRE of 73 ± 3%. The effect of varying carbon-to-nitrogen (C/N) ratios on nitrogen removal efficiencies was investigated, revealing a decrease in TNRE as the C/N ratio increased from 3 to 8. This study demonstrated the enhancing and inhibitory effects of C/N ratio, NO₂^--N, and Fe concentrations. It revealed that Fe concentrations between 1 and 5 mg/L increase specific anammox activity (SAA), while concentrations between 5 and 10 mg/L negatively impact it. Additionally, NO₂^--N concentrations above 150 mg/L significantly reduce SAA. Furthermore, a 16S rRNA metagenomic analysis of MBBR sludge samples revealed the significant presence of Candidatus Brocadia bacteria, constituting 20.4% of the microbial community. This research highlights the potential of MBBR in fostering anammox reactions and achieving efficient nitrogen removal in wastewater treatment applications.