Biological Nitrous Oxide Abatement by Paracoccus denitrificans in Bubble Column and Airlift Reactors

摘要

Nitrous oxide (N_2O), with a global warming potential 300 times higher than that of CO_2, represents 6.2 % ofthe total greenhouse gas emission inventory worldwide. Furthermore, N_2O is considered the most critical O_3-depleting substance emitted in this XXI century. In spite of the environmental relevance of this pollutant, verylittle research on biotechnologies for the treatment of N_2O emissions has been conducted. In this study, thepotential of a bubble column (BCR) and an internal loop airlift (ALR) bioreactors of 2.3 L was evaluated for theabatement of N_2O from industrial emissions from nitric acid plants along 62 days of operation. The systemswere inoculated with a methylotrophic Paracoccus denitrificans strain (DSM 413) and continuously suppliedwith methanol as a carbon and electron donor source for the anoxic reduction of N_2O. The simulated wastegas consisted of a N_2 gas stream containing 1 ± 0.1 % of O_2 and 3377 ± 312 ppmv of N_2O at the inlet of theBCR and 1 ± 0.1 % of O_2 with N_2O concentration of 3617 ± 342 ppm_v at the inlet of the ALR. This N_2-ladenstream was supplied at a constant flow rate of 110 ml min~(-1) in each reactor. The performance of the BCR wascharacterized by a steady state N_2O removal efficiency (RE) of 87 ± 3 % with CO_2 productions of 308 ± 36 gm~(-3) d~(-1) and total suspended solid (TSS) concentrations of 867 ± 109 mg L~(-1). On the other hand, the ALRshowed a N_2O RE of 88 ± 2 % with productions of CO_2 of 346 ± 28 g m~(-3) d~(-1) and TSS concentrations of 874 ±88 mg L~(-1). This work constitutes, to the best of our knowledge, the first systematic study of a biotechnology forthe continuous abatement of N_2O from nitric acid plants.