人工湿地对二级出水中NH_3-N、TP去除效果

Purification effect of constructed wetland on NH_3-N and TP removal from secondary effluent

在水力停留时间为1～7d的条件下,研究石菖蒲、美人蕉、水芋、杜鹃、一叶兰和袖珍椰子等6种植物湿地系统在表面流情况下对二级出水中NH3-N、TP的去除效果。结果显示,6种植物湿地系统对二级出水中NH3-N、TP的去除效果存在差异,但随着水力停留时间的加长,各系统的总体变化趋势较为接近。分析认为,植物的吸收不是污水中N、P去除的主要原因,但植物的环境适应性对NH3-N的去除有一定影响。在中水回用的设计中,湿地植物的选择可以从美学角度出发,选择具有较强环境适应性的湿地或水生植物,以增加湿地系统的景观效果;同时在以二级出水为原水的表面流人工湿地设计中,水力停留时间不宜大于4d。

The present paper is inclined to report its research results of the removing effect of NH3-N and TP of the following 6 species of plants, such as Acorus gramineus Soland in Ait., Canna chineresisw, Calla palustris L. , Rhododendron simsii Planch, Aspidistra elatior Blume and the Chamaedorea elegans Mart on the surface constructed wetland on the condition of letting them stay in water from 1 to 7 days. The media were composed of 0.15 m gravel and 0.15 m mixture of sand and soil, with the volume ratio of sand to soil being 2 ： 1. The plants were then let to grow in six 0.5 m×1.0 m of a concrete pond that filled with a further 0.3 m of effluent from an oxidation ditch operated in a sequential batch mode with wastewater drained from a university. The water was sampled everyday for NH3- N and total P and let to stay for 1 to 7 days in a control pond devoid of plants. The levels of total P and NH3- N were found to decline to the upper-limit of 60% - 77.6% of initial for total P and 86.7%-98% for NH3- N four days later. Since the levels remained constant for NH3- N but rose for total P, after a four-day retention would make the said nutrients diminished with little left in the ponds. Thus it can be concluded through analysis that the plant＇s absorption is not the main cause of NH3- N and total P removal for the constructed wetland, rather, it has to be the effect given by the plants＇ adaptability that plays the role. Thus, in the process of wastewater recycling design, it is recommended to choose plants in accordance with their own aesthetic merits to enhance the landscape effect of a wetland system with the recommended length of the plants residing in water, that is, no more than 4 days in the surface constructed wetland design.