Simulation of removal ammonia and nitrate from wetlands constructed by different hydrophytes

Abstract

分别以芦苇、花叶水葱和苦草构建成小规模人工湿地模拟系统,开展不同类型水生植物湿地中无机氮(硝态氮和铵态氮)去除效果的试验.试验结果表明:在分别以芦苇、花叶水葱和苦草构成的模拟湿地单元中,虽然氧化还原等环境条件呈现较大差异,但不同类型水生植物湿地单元的铵态氮和硝态氮的去除率并没有显著差别,这与以往关于不同类型水生植物对氮素去除贡献的认识有所不同;水生植物对模拟湿地体系中氮素的去除具有重要作用,在相对较低的氮负荷(NH₄⁺-N约为2.85mg/L,NO₃^--N约为1.07mg/L,相当于一般城市污染河流)条件下,有水生植物湿地单元中铵态氮和硝态氮的10d去除率分别在39.32%和21.91%以上,而无水生植物的空白湿地单元对铵态氮和硝态氮的10d去除率分别只有34.68%和13.86%;在提高模拟湿地体系水体氮(NH₄⁺-N约为5.50mg/L,NO₃^--N约为3.37mg/L,是一般城市污染程度的2倍)负荷条件下,有水生植物湿地单元中铵态氮和硝态氮的10d去除率分别大于或等于66.87%和78.92%以上,而无水生植物的空白湿地单元对铵态氮和硝态氮的10d去除率仅为40.62%和31.77%,为人工湿地对原污水或初沉池出水的处理提供了有力依据.试验结果还表明,水生植物能有效促进湿地的氮素转化过程,显著缩短无机氮素在湿地中的寄宿时间.;The hydrophyte has an important effect on removing nitrogen in the wetland system. This paper studied the nitrogen removal rate of the simulated wetland systems with Phragmites communis, Scirpus tabernaemontani cv.Zebrinus. and Vallisneria spiralis L. respectively. The hydrophytes had changed the redox condition markedly, however no significant discrepancies were found on the nitrogen removal rate. For the low nitrogen load (2.85mg/L for NH₄⁺_-N and 1.07mg/L for NO₃^-_-N), the ten-day removal rate of Ammonium and Nitrate of the wetland systems with and without hydrophytes were 39.32% and 21.91%, 34.68% and 13.86% respectively. In contrast, for the high nitrogen load (5.50mg/L for NH₄⁺_-N, and 3.37mg/L for NO₃^-_-N), the ten-day removal rate of Ammonium and Nitrate of the wetland systems with and without hydrophytes were 66.87% and 78.92%, 40.62% and 31.77% respectively. The hydrophyte could promote the process of nitrous transfer and shorten the time of the nitrous stay in the wetland.