Enhanced nitrogen removal performance of nitrogen-rich saline wastewater by marine anammox bacteria: Based on different influent loading strengths

In an anaerobic sequential batch reactor (SBR), marine anammox bacteria (MAB) were able to enhance microbial activity in nitrogen-rich saline wastewater and it was significantly affected by influent substrate composition and loading strength. This study therefore enhanced nitrogen removal efficiency by adjusting the influent nitrogen loading strength of MAB-inoculated anaerobic SBRs and assessed the correlation with the bacterial community. The results displayed that the system obtained optimal nitrogen removal efficiency (TN = 83.52%, NH4–N = 90.14%, and NO2–N = 83.57%) as the strength of influent nitrogen loading was increased to 201.35 mg L−1 for NH4–N and 266.42 mg L−1 for NO2–N. Moreover, the increase in the strength of influent nitrogen loading also enhanced the anammox 16S rRNA abundance (4.09 × 108 copies g−1) and ladderanes content (22.49 ng g−1dw). Analysis of 15N isotope further illustrated that all systems were dominated by anammox (average ra = 95.22%). In conclusion, these findings provide scientific guidance for the management of eutrophic seawater and contribute to the realization of industrial applications for the treatment of nitrogen-rich saline wastewater. [Display omitted] •Increasing influent nitrogen loading strength enhances anammox nitrogen removal of saline wastewater.•Influent nitrogen load strength significantly affected the abundance of nitrogen transforming microorganisms.•Summed ladderanes increased with the increasing influent nitrogen loading strength.