氧调控下复合垂直流人工湿地脱氮研究

Removal Nitrogen of Integrated Vertical-Flow Constructed Wetland Under Aeration Condition

溶解氧是人工湿地脱氮的重要限制性因子,调控湿地内氧状态分布是提高其脱氮效果的关键所在.为此,研究了夏、冬季时氧调控下复合垂直流人工湿地(IVCW)中氧状态的变化规律、脱氮效果及净化机制.结果表明,氧调控下IVCW中氧状态改善明显,夏、冬季时好氧Ⅰ区范围(以深度表示)分别从22 cm、17 cm扩大至53 cm、44 cm;即使冬季植物枯萎时,氧调控下IVCW沿水流方向仍可依次形成好氧Ⅰ区-缺氧区-好氧Ⅱ区(O-A-O)3个功能区,而冬季时常规IVCW仅有好氧Ⅰ区-缺氧区(O-A)2个功能区.氧调控下IVCW的有机物降解和硝化能力显著增强,尤其是冬季时COD、TN、NH 4+-N的平均去除率分别提高了12.2%、6.9%、15.1%;并且采用8 h∶16 h的间歇停曝方式,出水中NO 3--N浓度无明显增加.另外,好氧Ⅰ区是IVCW中污染物去除的主要区域,氧调控主要是增强了该功能区的净化能力.因此,氧调控措施对于IVCW系统的优化与应用具有重要意义.

Oxygen is an important limit factor of nitrogen removal in constructed wetlands,so it is the key point for improving nitrogen removal efficiency of constructed wetlands that the optimization of oxygen distribution within wetlands.Therefore,oxygen status,nitrogen removal and purification mechanism of integrated vertical-flow constructed wetland（IVCW） under aeration condition in summer and winter have been studied.The results showed that both oxygen levels and aerobic zones were increased in the wetland substrates.The area of oxic zoneⅠ（expressing with depth） extended from 22 cm,17 cm to 53 cm,44 cm,in summer and winter,respectively.The electric potential（Eh） profiling demonstrated that artificial aeration maintained the pattern of sequential oxic-anoxic-oxic（O-A-O） redox zones within the aerated IVCW in winter,while only two oxic-anoxic（O-A） zones were present inside the non-aerated IVCW in the cold season.The decomposition of organic matter and nitrification were obviously enhanced by artificial aeration since the removal efficiency of COD,TN and NH 4＋-N were increased by 12.2%,6.9% and 15.1% in winter,respectively.There was no significant accumulation of NO 3--N in the effluent with an aeration cycle of 8 h on and 16 h off in this experiment.Moreover,we found that oxic zoneⅠ was the main region of pollutants removal in IVCW system,and artificial aeration mainly acted to enhance the purification capacity of this oxic zone in the aerated IVCW.These results suggest that aeration is important for optimization and application of IVCW system.