Sustainable treatment of nitrate-containing wastewater by an autotrophic hydrogen-oxidizing bacterium

Bacteria are key denitrifiers in the reduction of nitrate (NO3--N), which is a contaminant in wastewater treatment plants (WWTPs). They can also produce carbon dioxide (CO2) and nitrous oxide (N2O). In this study, the autotrophic hydrogen-oxidizing bacterium Rhodoblastus sp. TH20 was isolated for sustainable treatment of NO3--N in wastewater. Efficient removal of NO3--N and recovery of biomass nitrogen were achieved. Up to 99% of NO3--N was removed without accumulation of nitrite and N2O, consuming CO2 of 3.25 mol for each mole of NO3--N removed. The overall removal rate of NO3--N reached 1.1 mg L-1 h(-1) with a biomass content of approximately 0.71 g L-1 within 72 h. TH20 participated in NO3--N assimilation and aerobic denitrification. Results from N-15-labeled-nitrate test indicated that removed NO3--N was assimilated into organic nitrogen, showing an assimilation efficiency of 58%. Seventeen amino acids were detected, accounting for 43% of the biomass. Nitrogen loss through aerobic denitrification was only approximately 42% of total nitrogen. This study suggests that TH20 can be applied in WWTP facilities for water purification and production of valuable biomass to mitigate CO2 and N2O emissions. (C) 2022 Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences, Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences.