Potential role of Bacillus amyloliquefaciens in promoting dissolved organic nitrogen (DON) conversion in activated sludge systems

With the continuous development of wastewater treatment technology, dissolved organic nitrogen (DON) has become the effluent's main component of total nitrogen. The discharged DON has the potential to stimulate algal growth and form toxic nitrogenous disinfection by-products (N-DBPs), which have a significant impact on the environment. To solve this problem, To solve this problem, a bioaugmentation system was constructed to reduce the DON concentration in the effluent by introducing Bacillus amyloliquefaciens into the activated sludge system. The results showed that Bacillus amyloliquefaciens had efficient ammonification performance, producing at least 140 mg/L of ammonia nitrogen within 42h. In treating synthetic organic nitrogen wastewater, a 15% dosing of Bacillus amyloliquefaciens showed the best performance in removing nitrogenous pollutants, increasing 18.36% and 21.83% in removing DON and ammonia nitrogen, respectively, which was consistent with the experimental hypothesis. Three-dimensional fluorescence spectrum (3D-EEM) spectroscopy analysis showed that tryptophan protein-like fluorescence intensity decreased by 0.014 R.U., much higher than C2 and C3, the main DON components removed. LC-OCD-OND results showed that the enhanced system had a good removal effect on low molecular weight and hydrophilic DON, resulting in a 16% and 2% reduction in proportions, respectively. Microbial functional analysis showed that introducing Bacillus amyloliquefaciens induced the formation of microbial communities related to DON degradation, increasing related functional categories (including organic matter degradation, signal transduction, and energy metabolism), thus improving DON removal. Bioaugmentation with Bacillus amyloliquefaciens has excellent potential for removing DON from wastewater.