Effects of oxygen content on the simultaneous microbial removal of SO2 and NOx in biotrickling towers

This study uses microbial methods to research the influence of oxygen (O-2) content on the removal efficiency of sulfur dioxide (SO2) and nitrogen oxides (NOx) in a tandem twin-towers desulfurization and denitrification process system. Oxygen can play a significant role in biotrickling towers. Other important factors had already been optimized prior to the study, including inlet concentration, gas flow rate, and temperature. SO2 and NOx were prepared by a chemical method. A gas flow meter was used to regulate nitrogen (N-2) that had been stored in steel cylinders. In this way, the O-2 content was adjusted in the biotrickling towers by controlling the N-2 flow rate. Five gradients of O-2 content were selected for investigation, namely 4, 8, 12, 16, and 20%. Results indicated that the SO2 removal efficiency from mixed gas (SO2 and NOx) can reach 100%, from all of the five O-2 gradients, in biotrickling towers. In a tandem twin-towers desulfurization and denitrification process system, the NOx removal efficiency and the inlet concentration of nitrogen dioxide (NO2) gradually increased as the O-2 content increased. Specifically, the average removal efficiency of NOx increased from 49.28 to 80.85% as the O-2 content changed from 4 to 20%. The oxygen levels influenced the removal of NOx but the SO2 removal efficiency in mixed gas was always stable.