Abstract:
In order to improve the nitrogen removal rate of residential sewage by ecological gravel beds, four kinds of constructed ecological gravel bed were designed, including
Schoenoplectus tabernaemontani bed,
Phragmites australis bed,
Typha orientalis bed and blank bed without vegetation. The effects of two inflow modes, i.e. continuous inflow and intermittent inflow, on the removal of TN, N
-N, and N
-N were studied. The hydraulic load (HL) was 7.5 cm∕d and the hydraulic retention time (HRT) was 1.8 d under the continuous inflow, while the HL was 7.5 cm∕d and the HRT was 5.4 d under the intermittent inflow. The results show that there exists great difference of the nitrogen removal efficiency between two inflow modes for different ecological gravel beds. The removal rates of TN and ammonia nitrogen under continuous inflow were in the order of
Typha orientalis bed>
Schoenoplectus tabernaemontani bed > blank bed >
Phragmites australis bed, with the highest removal rates by
Typha orientalis bed, which removal rate of TN and ammonia nitrogen were 77.68% and 81.33%, respectively; the removal rates of nitrate nitrogen were in the order of blank bed>
Phragmites australis bed>
Tyha orientalis bed>
Schoenoplectus tabernaemontani bed, with thee highest removal rates by blank bed, which removal rate of nitrate nitrogen was 65.29%. The removal rates of TN and ammonia nitrogen under intermittent inflow were in the order of
Schoenoplectus tabernaemontani bed >
Phragmites australis bed >
Typha orientalis bed> blank bed, and the effect of
Schoenoplectus tabernaemontani bed was the best, which removal rate of TN and ammonia nitrogen were 89.54% and 91.79%, respectively; the removal rates of nitrate nitrogen were in the order of
Schoenoplectus tabernaemontani bed>
Typha orientalis bed>blank bed>
Phragmites australis bed, the
Schoenoplectus tabernaemontanid bed was the best with a removal rate of 46.43%. The removal efficiency of ammonia nitrogen and TN were better improved by intermittent inflow in plant systems. The removal rate of TN and ammonia nitrogen increased by 19.63% and 14.76% in
Phragmites australis bed, and the removal rate of TN and ammonia nitrogen increased by 19.14% and 18.60% in
Schoenoplectus tabernaemontani bed, respectively.