Simultaneous removal of nitric oxide and sulfur dioxide in a biofilter under micro-oxygen thermophilic conditions: Removal performance, competitive relationship and bacterial community structure.

The efficiency of a biofilter to simultaneously remove nitric oxide (NO) and sulfur dioxide (SO2) was investigated under thermophilic (48 ± 2 °C) micro-oxygen (3 vol%) conditions. After the start-up stage (Days 0-14), the stable operation period was divided into three stages. SO2 inlet concentration remained 500 mg/m3, NO inlet concentrations were 300 mg/m3 (Days 15-40), 500 mg/m3 (Days 41-70) and 700 mg/m3 (Days 71-100). In each stable stage, the removal efficiency of NO and SO2 exceeded 90%, the maximum removal rates of NO and SO2 were 98.08% and 99.61%, respectively. The final products of SO2 were mostly sulphur. Nitrate-reducing bacteria inhibited sulphate-reducing bacteria. Illumina high-throughput sequencing confirmed that the relative abundance of nitrate-reducing bacteria was positively correlated with NO removal efficiency, the relative abundance of sulphate-reducing bacteria was related to the conversion rate of sulphur.