基质结构对潜流人工湿地氮磷降解规律的影响

Effect of substrate structure on pollutant degradations through substrate of horizontal subsurface flow constructed wetlands

构建单层结构及多层结构水平潜流人工湿地小试实验系统,对城市污水处理厂尾水进行深度处理,研究基质结构对人工湿地床体中氮、磷沿程变化规律的影响。实验结果表明,单层基质结构人工湿地氮、磷的降解主要集中在深度为50~85 cm之间的床体表层,底层区域(0~50 cm)浓度变化不显著;多层结构人工湿地床体中氮、磷的降解由进水口到出水口呈较为规律的推流变化,与单层结构系统相比,污染物降解主要发生区域有所扩大,集中在深度为40~85 cm的床体表层,且床体底层0~40 cm氮磷降解同样存在,只是降解速率略有降低。按照填料渗透系数进行多层填充的设计方式能够显著提升潜流人工湿地对污染物的净化性能,单层结构人工湿地系统对氨氮和总磷的平均去除率分别为40.1%和52.9%,而多层结构的平均去除率则为60.4%和73.1%。

Two parallel pilot-scale subsurface flow constructed wetlands with single layer and multi- layer substrate structure were built for treating the effluents of municipal wastewater treatment plants to determine the effects of substrate structure on nitrogen and phosphorus transports and degradations through the substrate. The results indicated that nitrogen and phosphorus removal occurred mainly in the upper layer(50 ~ 85 cm) and the variations of the pollutants in the bottom layer(0 ~ 50 cm)were not significant in the single layer constructed wetlands. In contrast,the majority of pollutant removal occurred in a larger region( from 40 ~ 85 cm deep) in the multi-layer constructed wetland with a plug flow trend. The nitrogen and phosphorus removal with a smaller degradation rate was also appeared in the bottom layer. It was shown that the constructed wetland performance could be obviously improved with the multi-layer substrate structure designed according to the permeability coefficient of the fillers. Mean removal efficiencies of NH+4-N and TP in the single layer constructed wetland were 40. 1% and52. 9%,while mean removals in the multi-layer unit were 60. 4% and 73. 1%,respectively.