Biological Removal NOx from Simulated Flue gas in aerobic biofilter, by Jiang R., Huang S.B. and Yang J.

A bench-scale biofiltration system was developed to evaluate the NOx removal efficiency
under high oxygen concentration. The system had been running for 120 days and kept on a
steady NOx removal rate above 80%. A stable NOx removal with an efficiency of more than
80% from the gas phase can be obtained by the bioreactor concept, when flue gas containing
NO (400-600 ppmv) and a certain O2 concentration (0-20%). In the blank experiment, less than
35% NO was removed as oxygen increased. The tendency of the three curves about NO
removal rate with various O2 concentrations was mainly similar but some differences in the
highest and lowest removal rate happened in the definite O2 concentration range. Oxygen was
shown to have a significant effect on NOx removal at the first two or three days when oxygen
concentration increased sharply. The higher concentration NO influent gas contained, the
longer time the microflora need to regain activities. Compared with humidifier, microbial
regenerator which was incorporated in biofilter can improve aerobic denitrifying bacteria
activity by applying alternating oxic–anoxic conditions in the presence of nitrate and nitrite.
Oxidation-Reduction Potential (ORP) and Dissolved Oxygen (DO) were used to control the
dose of carbon source.