Saline conditions effect on the performance and stress index of anaerobic ammonium oxidizing (anammox) bacteria

Abstract

In this study, a lab-scale sequencing batch reactor dominated by freshwater anammox bacteria (FAB) was used to study the performance and stress index of the anammox bacteria at various saline conditions. The reactor with an effective volume of 1.8 L was operated for about 160 days. The nitrogen-loading rate was maintained at 0.364 kg-N m 3d 1 throughout the operational period. At the start-up phase, the seed biomass acclimation to the lab bioreactor showed an inconsistent performance. However, a stable performance was observed after day 38. The average substrate removal efficiency was 92% during most of the operational period. Anammox stress index; a ratio of dissolved Adenosine Triphosphate (dATPamx) to total Adenosine Triphosphate (tATPamx) showed an irrefutable correlation between NaCl concentration, anammox stress and microbial community. A drop in the biomass cellular ATP at 5 g L 1 salinity led to a significant decrease in the Specific Anammox activity. Candidatus Brocadia was identified as the main anammox species and its relative abundance reduced along the stepwise salinity increment