Effect of Key Operating Parameters on NOx Removalin a Fungal Biofilter

摘要

Vapor-phase bioreactors containing the fungus Exophiala lecanii-corni have the potentialto be a treatment alternative for nitrogen oxides (NOx) emissions from small-scalesources. In the current study, the NOx removal in a fungal bioreactor was evaluated as afunction of NOx loading rates and EBCTs, and the effect of CO2 on NOx removal wasexamined under aerobic conditions. Also, the influence of NOx on toluene degradationand fungal respiration in the bioreactors was investigated.The NOx elimination capacity of the bioreactors increased as a function of NOx loadingrate over the range of 14.9 to 151 g NOx/m3/hr. When the NOx loading rate exceeded 60g NOx/m3/hr, the NOx removal efficiency in the bioreactors declined to less than 55 %.However, when the loading rate was decreased to 38 g NOx/m3/hr, the NOx removalefficiency increased to 76 %. For a given NOx loading rate, the NOx eliminationcapacity of the bioreactor declined at high gas flow rates corresponding to lower EBCTsas expected. At a 38 g NOx /m3/hr loading rate, NOx removal in the bioreactors was notinfluenced by the presence of high CO2 concentrations. In addition, the NOx removalprocess in the bioreactors is not directly affected by O2 concentrations in the range of 2.6% to 15.6 %. Since lower toluene removal activity was observed in the presence of NOx,lower CO2 evolution from the bioreactors was expected. However, the CO2 evolutionfrom the bioreactor increased substantially when NOx was present. The reason thepseudo-endogenous respiration rate of the fungal biofilm increased when exposed to NOxis unclear. However, it is postulated that the fungus may require additional energy todetoxify NO and nitrite species.