Nitrogen Removal Characteristics of a Novel Salt-Tolerant Bacterium and its Application on Bioaugmentation for Marine Recirculating Aquaculture System Biofilter

While heterotrophic nitrification-aerobic denitrification (HN-AD) shows potential for nitrogen removal, treating high-salinity mariculture wastewater remains challenging. In this study, Pseudomonas aeruginosa SH3, a salt-tolerant strain of HN-AD-capable, was isolated from mariculture wastewater. The strain achieved removal efficiencies of 99% for NH­4+-N, 70% for NO2-N, and 84% for NO3-N at a salinity of 30. Single-factor experiments demonstrated that strain SH3 effectively removed either ammonia or nitrite when utilizing citrate as the carbon source, with C/N ratios ranging from 10 to 20, maintaining pH within 7-9, temperatures varying from 25°C to 35°C, and salinity levels between 25 and 40. Subsequently, its complete genome annotation revealed the involvement of at least four pathways in nitrogen metabolism. Finally, bioaugmentation with the addition of strain SH3 proved effective in reducing the start-up period by 14 days and ensuring stable performance of the moving bed biofilm reactor in marine recirculating aquaculture systems.