水平潜流人工湿地沿程脱氮效率

Efficiency of Horizontal Subsurface Flow Constructed Wetland along Water Flow for Nitrogen Removal

为探讨不同水生植物砾石水平潜流人工湿地的沿程脱氮效率,选择了花叶芦竹、旱伞草、再力花、香蒲、芦苇5种挺水植物,均匀种植于长13 m、宽4.5 m的砾石水平潜流湿地,测定了不同植物湿地系统对低污染水的沿程脱氮效率。结果表明,处理两种浓度(总氮10 mg/L和20 mg/L)低污染水时,总氮和氨氮的去除率表现为芦苇>再力花、旱伞草>香蒲>花叶芦竹>未种植,硝态氮和亚硝态氮的去除率表现为花叶芦竹、香蒲、芦苇>再力花>旱伞草、未种植。处理总氮10 mg/L的低污染水时,未种植、花叶芦竹、芦苇、再力花和香蒲湿地对总氮、氨氮、硝态氮和亚硝态氮沿程去除率总体呈下降趋势,尤其是芦苇湿地在1/3段即达到了77.95%的去除效率;砾石填料潜流湿地中芦苇、香蒲的种植长度5 m左右为宜,花叶芦竹、旱伞草、再力花的种植长度9 m左右为宜。处理总氮20 mg/L的低污水时,不同植物湿地系统的总氮、氨氮、硝态氮和亚硝态氮沿程去除率基本呈现前端去除效率高,中部略有降低,后部又有所上升;芦苇、香蒲、旱伞草和再力花至少种植13 m以上,可使湿地出水达到一级A标准,芦苇为最佳选择。因此,应根据不同污染负荷下挺水植物的生长和沿程脱氮效率来设置砾石填料湿地床的规模。

In order to understand effect of different macrophytes on nitrogen removal along water flow in horizontal subsurface flow constructed wetland, five macrophytes plants such as Arundo donax var. versicolor, Cyperus alternifolius, Thalia dealbata, Typha orientalis, Phragmites australias were selected and planted in constructed wetland with a length of 13 m and width of 4.5 m. The concentration and removal efficiency of nitrogen along water flow were conducted. The results showed that the order of TN and NH+4-N removal efficiency was P. australias> T. dealbata, C. alternifolius> T. orientalis> A. donax var. versicolor > unplanted. The removal efficiency of NO-3-N and NO-2-N were as follows: A. donax var. versicolor, T. orientalis, P. australias> T. dealbata> C. alternifolius, unplanted. When treating 10 mg/L TN wastewater, removal efficiency of TN, NH+4-N, NO-3-N and NO-2-N in unplanted, A. donax var. versicolor, P. australias, T. dealbata and T. orientalis wetland was declined along water flow. Their removal efficiency was highest in 1/3 beds closed to inlet, especially in P. australias wetland with 77.95%. The suitable length of P. australias and T. orientalis planation was almost 5 m, while A. donax var. versicolor, C. alternifolius and T. dealbata was around 9 m. When treating 20 mg/L TN wastewater, removal efficiency was present this pattern: higher in closed inlet, slight decreased in middle and increased in closed outlet. The water quality of effluent in wetland that P. australias, T. orientalis, C. alternifolius and T. dealbata should be planted for at least 13 m could reach the first class A standard. P. australias was the best choice. Therefore, the scale of wetland bed should be adjusted according to the growth and nitrogen removal efficiency of plants under different pollution loads.