A new strategy to simultaneous removal and recovery of nitrogen from wastewater without N2O emission by heterotrophic nitrogen-assimilating bacterium

Biological assimilation that recovery the nitrogen from wastewater in the form of biomass offers a more environmentally friendly solution for the limitations of the conventional wastewater treatments. This study reported the simultaneous removal and recovery of nitrogen from wastewater without N2O emission by a heterotrophic nitrogen-assimilating Acinetobacter sp. DN1 strain. Nitrogen balance, biomass qualitative analysis, genome and enzyme studies have been performed to illustrate the mechanism of nitrogen conversion by strain DN1. Results showed that the ammonium removal followed one direct pathway (GOGAT/GDH) and three indirect pathways (NH4+ -> NH2OH -> NO -> NO2- -> NH4+ -> GOGAT/GDH; NH4+ -> NH2OH -> NO -> NO2- -> NO3- -> NO2- -> NH4+ -> GOGAT/GDH; NH4+ -> NH2OH -> NO -> NO3- -> NO2- -> NH4+ -> GOGAT/GDH). Nitrogen balance and biomass qualitative analysis showed that over 70 % of the ammonium in the wastewater was converted into intracellular nitrogen-containing compounds and stored in the cells of strain DN1. Traditional denitrification pathway was not detected and the ammonium was removed through assimilation, which makes it more energy-saving for nitrogen recovery when compared with Haber-Bosch process. This study provides a new direction for simultaneous nitrogen removal and recovery without N2O emission by the heterotrophic nitrogen-assimilating bacterium.

Automated summary

Biological assimilation of nitrogen from wastewater to biomass offers an environmentally friendly solution. This study demonstrates the simultaneous removal and recovery of nitrogen from wastewater by a nitrogen-assimilating Acinetobacter sp. DN1 strain without N2O emission. The mechanism involves direct and indirect pathways for ammonium removal and the conversion of over 70% of the ammonium into intracellular nitrogen-containing compounds. This research provides a new direction for nitrogen removal and recovery without N2O emission.