Genetic associations as indices of nitrogen cycling rates in an aerobic denitrification biofilter used for groundwater remediation.

An aerobic denitrification biofilter (ADB) for groundwater remediation was developed with high removal efficiencies (total nitrogen (TN): 82.3–95.8%; NO 3 − -N: 93.2–98.2%). Nitrate (NO 3 − -N) transformation rates stabilized between 21.0 and 23.4 g/(m 3 h), whereas nitrite (NO 2 − -N) and ammonium (NH 4 + -N) transformation rates remained less than 6.0 g/(m 3 h) as the dissolved oxygen (DO) level increased from 1.0 mg/L to 6.0 mg/L. Nitric oxide (NO) and nitrous oxide (N 2 O) accumulated with great fluctuations (NO: 0–1.6 × 10 −3 g/(m 3 h); N 2 O: 0.1–1.1 g/(m 3 h)) throughout the experiment. This study suggested that gene associations reflect quantitative relationships with aerobic denitrification rates and can provide useful information regarding aerobic denitrification processes in groundwater. Especially, the qnorB / nosZ ratio acts as the main driver for NO 3 − -N and NH 4 + -N transformation, while the qnorB / nosZ ratio followed by the ( nirS + nirK )/ nosZ ratio serve a dominant role in the accumulation of N 2 O and NO. [ABSTRACT FROM AUTHOR]