Effects of aerating disturbances on nitrification-denitrification at sediment-water interface

In this research, a home-made river-simulated setup was used to investigate the coupling of nitrification-denitrification at sediment-water interface with different aerating depths of 10 cm, 15 cm, 25 cm and 35 cm, which could provide references for the optimized fix-up of aerators and tackling the problem of nitrogen excess in treating malodorous river. Results showed that the turbulence at sediment-water interface decreased firstly and then increased with the increasing of disturbance depth. Among them, the turbulence level at sediment-water interface was the highest (Re= 3 044) with the aeration disturbance depth of 10 cm, while the turbulence degree was the lowest (Re=1 713) with the aeration depth of 25 cm. Compared with the controlled condition, the aerated disturbances could facilitate the nitrification processes and reduce the ammonium level of the overlying water to a relatively low degree (below 0.50 mg/L), which indicated that aeration could manipulate the release of endogenous ammonium. Additionally, the reoxygenation rate and nitrification rate increased with the decrease of aerated depths. Comparatively, the disturbance depth of 25 cm could be deemed as the relatively optimized condition in terms of the effective nitrification-denitrification. On this running, the reduction of total nitrogen in the overlying water could reach 51.5% and the rate of nitrifying and denitrifying at sediment-water interface were (41.6±3.1)% and (32.1±0.7)%, respectively.