植物生理生态特性对人工湿地脱氮效果的影响

Influence of plant eco-physiology characteristics on nitrogen removal effect in constructed wetlands

人工湿地污水处理系统中,植物对脱氮效果起着非常重要的作用。为了明确人工湿地植物生理生态特性对脱氮效果的影响,藉此优选高效耐寒的湿地植物,进而提出可行的强化脱氮措施,在大量试验的基础上,详细测定了芦苇、美人蕉等典型湿地植物在不同生长条件下对湿地脱氮效果、溶解氧分布状态的影响,以及植物光合、蒸腾特性对湿地脱氮效果的影响。结果表明:在本试验范围内,芦苇、美人蕉湿地脱氮效果最佳;茶花湿地低温条件下运行稳定。植物净光合速率与溶解氧分布、总氮和氨氮去除率显著正相关,而植物蒸腾速率与湿地氨氮去除率显著相关。适当增加植物种植密度有利于提高人工湿地脱氮效果,但种植过密对提高溶解氧水平和总氮去除率反而不利。植物生长周期对湿地脱氮影响显著,植物收割方式对脱氮效果影响较大,清除植物地上茎叶既不破坏植物根区微环境,可有效防止茎叶腐烂向系统重新释氮。此外,由于湿地前端溶解氧水平急剧下降,故建议适当增加前端植物种植密度。

Plants play an important role in nitrogen removal in constructed wetland wastewater treatment system. The research purpose was to clarify the influence of plant eco-physiology characteristics on nitrogen removal effect in constructed wetland and to select out appropriate high-efficiency cold-resistance wetland plants. Therefore, feasible methods to enhance nitrogen removal effect were proposed. Based on a lot of experiments, the influence of traditional wetland plants, such as reed （Phragmites communis trin.）, canna （Canna generalis.） et al., on nitrogen removal effect and dissolved oxygen distribution in different growth conditions was investigated. The influence of plant photosynthesis and transpiration characteristics on nitrogen removal effect in constructed wetland was researched. Results indicated that nitrogen removal efficiency was highest in wetlands with reed and canna, while wetland with camellia （Camellia japonica.） operated stably in low temperature area. Plant net photosynthesis rate （Pn） was remarkably related with DO level, removal effect of TN and NH4^＋-N, and transpiration rate （Tr） was related with removal effect of NH4^＋-N. Nitrogen removal effect could be enhanced by increasing appropriately planting density, but DO level and TN removal effect would decreased if planting too close. Nitrogen removal effect was significantly influenced by plant growth period. Besides, plant harvest way had influence too. The micro-environmental characteristics around root-zone would not be destroyed and nitrogen releasing back to system by plant decay was avoided if caudexes and leaves were harvested before winter. Because DO level decreased sharply in front-end of wetland, planting density in front-end was proposed to increase appropriately.