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

Bacteria are key denitrifiers in the reduction of nitrate (NO(3)(−)-N), which is a contaminant in wastewater treatment plants (WWTPs). They can also produce carbon dioxide (CO(2)) and nitrous oxide (N(2)O). In this study, the autotrophic hydrogen-oxidizing bacterium Rhodoblastus sp. TH20 was isolated for sustainable treatment of NO(3)(−)-N in wastewater. Efficient removal of NO(3)(−)-N and recovery of biomass nitrogen were achieved. Up to 99% of NO(3)(−)-N was removed without accumulation of nitrite and N(2)O, consuming CO(2) of 3.25 mol for each mole of NO(3)(−)-N removed. The overall removal rate of NO(3)(−)-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 NO(3)(−)-N assimilation and aerobic denitrification. Results from (15)N-labeled-nitrate test indicated that removed NO(3)(−)-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 CO(2) and N(2)O emissions.