Lower levels of oxygen content and carbon-to-nitrogen ratio in sludge drying off-gas balances simultaneous anammox and denitrification in a membrane biofilm reactor for synergistic bio-decontamination of trimethylamine and nitric oxide.

Combustion flue gas-heated sludge drying (FGHSD) is a sustainable strategy but may generate off-gas containing trimethylamine (TMA) and nitric oxide (NO). Present TMA biofiltration techniques can not completely eliminate nitrogen. This study investigated synergistic biodecontamination of TMA and NO in simulated off-gas by a simultaneous anammox denitrification membrane biofilm reactor (SADMBfR). The optimal removal efficiencies of TMA and NO attained 97% at 2% O2 content and 1.02C/N ratio in a 140-day operation. TMA-degrading bacteria (TDB), anammox bacteria (AnAOB), and denitrifying bacteria (DNB): Pseudomonas, Bacillus, Ca. Brocadia, Ca. Kuenenia, Ca. Jettenia, Thauera, Paracoccus, etc. synergistically converted TMA and NO to N2. TMA acted as the initial donor, while NO and O2 acted as the terminal acceptors, and thereby to establish a bio-redox. At a proper level of C/N and O2, oxygenases/dehydrogenases-mediated TMA degradation was enzymatically activated with sufficient O2, substrates, and donors; SAD proceeded efficiently with balanced electron competition between O2 and NO, enhanced anammox, and eliminated nitrifiers. TMA degradation and SAD had mutual promotion. TDB degraded TMA to DMA, MMA, and NH3 via oxygenation and dehydrogenation. DNB oxidized TMA-derived HCHO to CO2 in aerobic denitrification. AnAOB converted TMA-derived NH3 and NO to N2 via anammox. Finally, TMA and NO mixotrophically metabolized into CO2 and N2, with C and N thoroughly eliminated. This finding can provide a feasible and greener solution to synergistic FGHSD off-gas deodorization and denitration.