Dynamics of nutrient release from solid carbon sources of wetland plants and its effect on the efficiency of nitrogen removal from artificial wetland water bodies

Abstract

污水低碳氮比(C/N)是影响人工湿地氮去除效果限制因素，传统的碳源添加及利用存在成本较高、补充困难的局限性. 本研究契合“就地取材，原位处理”的废物利用原则，选择人工湿地常见的水生植物和农业废弃物(玉米芯、稻草)作为对照，对比了挺水植物(香蒲、美人蕉)、浮叶植物(莲)、沉水植物(菹草)、湿生植物(南荻、短尖苔草)的释碳能力，初步确定了以香蒲、美人蕉、南荻为代表的植物具有较好的释放碳能力，在中国湿地中分布广泛，且均对水体二次污染较小. 以南荻、美人蕉、玉米芯作为碳源添加的模拟人工湿地实验验证表明，在低碳氮比的模拟表流人工湿地投入植物碳源，能有效提高系统的脱氮效率，对照组、南荻组、美人蕉组和玉米芯组的出水总氮浓度分别为(5.24±0.07)、(4.50±0.10)、(3.75±0.17)和(2.97±0.18)mg/L，对应的去除率分别为58%、64%、70%和76%，确定南荻和美人蕉植物残体以及改性材料均残体和改性材料适合作为人工湿地中原位利用的外加碳源. 本研究探索了通过湿地植物配置解决人工湿地水体低C/N比的问题，为提高湿地脱氮效果提供了有意义的新途径.;The low carbon to nitrogen ratio (C/N) of wastewater is a limiting factor of nitrogen removal in artificial wetlands, and traditional carbon sources are costly and difficult to replenish. This study, taking aquatic plants and agricultural wastes (corn cobs and rice straw) which commonly exist in artificial wetlands as a reference, compared the carbon release capacity of water-supporting plants (Typha orientalis and Canna indica), floating-leaf plants (Nelumbo nucifera), submerged plants (Potamogeton crispus), and wet plants (Triarrhena lutarioriparia and Carex brevicuspis). The results show that the plants, such as Typha orientalis, Canna indica and Triarrhena lutarioriparia, which widely distribute in wetlands of China, have high carbon release capacities and have less secondary pollution to water bodies. The experiments of artificial wetlands added with Triarrhena lutarioriparia, Typha orientalis and corn cob as carbon source explored that addition of plant carbon source in the surface flow of artificial wetlands with low C/N ratio could effectively improve the denitrification efficiency of the system. Total nitrogen concentration of the control group, Triarrhena lutarioriparia group, Typha orientalis group and corn cob group were (5.24±0.07), (4.50±0.10), (3.75±0.17) and (2.97±0.18) mg/L, respectively. Correspondingly, the removal rates account for 58%, 64%, 70% and 76%, respectively. It is confirmed that plant residues and modified materials of Triarrhena lutarioriparia and Canna indica were appropriate as an in-situ source of additional carbon in artificial wetlands. Exploring the low C/N ratio in artificial wetlands through wetland plant configuration would provide a new way to improve wetland denitrification.