Quantitative responses of nitrous oxide accumulation to genetic associations across a temperature gradient within denitrification biofilters.

Increased nitrous oxide (N 2 O) in the atmosphere is of global concern. Biofiltration has been studied for gaseous nitrogen treatments in drinking water environments; however, the molecular mechanisms mediating N 2 O accumulation in denitrification biofilters have not been quantified. Five denitrification biofilters were developed in this study and all achieved high removal efficiencies for total nitrogen (TN: 72.4–92.7%), nitrate nitrogen (NO 3 − -N: 88.6–98.2%) and chemical oxygen demand (COD: 79.3–90.0%) across a low-temperature gradient (5–25 °C). Denitrification coupling with anaerobic ammonium oxidation (ANAMMOX) and dissimilatory nitrate reduction to ammonium (DNRA) processes yielded the presently robust treatment performance. Nitrite availability limited TN removal at 5–15 °C. Our findings indicate that temperature affected N 2 O accumulation indirectly by controlling the balance of nitrite versus N 2 O reductase carrying microorganisms. In addition, our results demonstrated that genetic association was an important index reflecting the relative intensity of N 2 O accumulation at low temperatures. [ABSTRACT FROM AUTHOR]