Effect of gaseous mercury on nitric oxide removal performance and microbial community of a hybrid catalytic membrane biofilm reactor

Abstract The effect of gaseous elemental mercury on nitric oxide removal performance, microbial community and microbial nitrogen metabolism of a hybrid catalytic membrane biofilm reactor (HCMBR) were evaluated. A gaseous Hg 0 concentration of 25 ± 5 μg·m −3 reduced the NO removal efficiency of HCMBR from 86.4% to 41.9%. In 80 days of operation, NO removal efficiency was up to 68.8%, and Hg 0 removal efficiency achieved 81.7%, respectively. The addition of gaseous elemental mercury affected the microbial community structure and changed microbial nitrogen metabolism, as shown by metagenomics sequencing method. Some phyla, such as Azospirillum , and Delftia , increased in abundance, whereas others, such as Weeksella , decreased. Hg 0 could combine with merP and be transported by merT, and then be oxidized into Hg 2+ by KatG or KatE. The nitrogen metabolism related processes such as catalysis, nitrification and denitrification, ammoniation and biological nitrogen fixation processes, exists in HCMBR and HCMBRHg.