基于污水厂尾水的人工湿地系统中水体氮的水流方向分布特征及污染评价

天津临港人工湿地是以污水厂尾水为水源的组合人工湿地,为探究其水体形态氮的分布特征和污染状况,以该湿地系统为研究对象,采集并分析了湿地水样,基于GIS克里格插值法,对湿地水体形态氮和典型理化性质的分布和污染特征进行了研究,结合单因子污染指数法评价了水体污染程度。结果表明：湿地水体TN浓度为0.657~5.576 mg·L⁻¹,其中${{rm{NO}}_3^ - }$-N (0.095~3.920 mg·L⁻¹)浓度相对较高,占TN的49.2%;沿水流方向,TN、${{rm{NO}}_3^ - }$-N和${{rm{NO}}_2^ -} $-N的分布趋势基本一致,从入水口至景观湖呈逐渐降低趋势;${{rm{NH}}_4^ +} $-N的分布相对复杂,在潜流和表流湿地下游与景观湖交汇处浓度最高,表流湿地浓度最低;pH和EC分别对${{rm{NH}}_4^ + }$-N和${{rm{NO}}_3^ - }$-N的分布特征具有较大的影响作用。根据单因子污染指数法,湿地水体TN超标(P_i>1),调节塘TN污染最为严重,调节塘可作为TN优控区。以上结果有助于深入认识以污水厂尾水为水源的组合人工湿地中氮污染物的赋存形态及分布特征。

Nitrogen distribution characteristics and pollution assessment in water along the water flow direction in a constructed wetland system treating the tailwater from wastewater treatment plants

Tianjin Lingang constructed wetland is a hybrid constructed wetland based on the tailwater of wastewater treatment plants. In order to explore the distribution characteristics and pollution status of nitrogen in water, the water samples in this wetland system were collected and analyzed. Based on the GIS Kriging interpolation method, the distribution and pollution characteristics of nitrogen species and typical physical and chemical properties of wetland water were studied; then the degree of water pollution was evaluated by single factor pollution index method. The results indicated that TN concentration in water of wetland was in the range of 0.657 to 5.576 mg·L−1, of which ${rm{NO}}_3^ - $-N concentration was relatively high (0.095~3.920 mg·L-1) and accounted for 49.2% of TN. Along the water flow direction, the distribution of TN, ${rm{NO}}_3^ - $-N and ${rm{NO}}_2^ - $-N was similar, which showed a gradual decrease from the entrance to the landscape lake. The distribution of ${rm{NH}}_4^ + $-N was relatively complicated. The highest concentration of ${rm{NH}}_4^ + $-N occurred at the junction between landscape lake and the lower reaches of subsurface and surface flow wetlands, while the ${rm{NH}}_4^ + $-N concentration in the surface-flow wetland was the lowest. pH and EC had relative high effect on the distribution characteristics of ${rm{NH}}_4^ + $-N and ${rm{NO}}_3^ - $-N. According to the single factor pollution index method, TN concentration in the wetland exceeded the standard (Pi >1), and the TN pollution was most serious in the regulation pond, which could be used as a priority control area for TN. The above results are conducive to deeply understand the occurrence and distribution characteristics of nitrogen pollutants in the hybrid constructed wetland treating the tailwater from the wastewater treatment plant.