Ammonia assimilation: A double-edged sword influencing denitrification of Rhodobacter azotoformans and for nitrogen removal of aquaculture wastewater

NO3--N and NH4+-N are two prevalent nitrogenous pollutants in aquaculture wastewater posing a significant health risk to aquatic animals. R. azotoformans ATCC17025 can rapidly denitrify to remove NO3--N, assimilating NH4+-N. The study investigated the influence of ammonia assimilation on bacterial denitrification. Results revealed that low concentration of NH4+-N (<= 0.3 mM) accelerated denitrification, whereas high concentration inhibited it. RT-qPCR indicated that the inhibition of NO reduction under high concentration of NH4+-N was the primary cause of denitrification depression, whereas low concentration of NH4+-N enhanced the synthesis of practically all enzymes involved in denitrification. Finally, nitrogen-rich aquaculture effluent was effectively treated in lab-scale using a semi-continuous operation that provided an appropriate NH4+-N concentration for denitrification. This semi-continuous operation treated wastewater 2 times faster than the batch operation and the content of nitrogen decreased to effluent standard. The study can provide guidance for nitrogen removal of aquaculture wastewater with bioaugmentation.

Automated summary

The study found that NH4+-N concentration significantly influences bacterial denitrification. Low concentrations of NH4+-N can accelerate denitrification, while high concentrations can inhibit it.