植物种类与水力负荷对人工湿地去除污染物的交互作用

人工湿地去污效能不仅受水力负荷(HL)影响,还与植物种类有关。为研究这2种因素对污染物去除的交互作用,根据植物根系长度,分别构建短根型、中根型及长根型植物潜流人工湿地中试系统,在运行稳定后,考察不同植物种类在不同水力负荷(152、230、305和460 mm/d)下的去污效果。结果表明:植物种类对COD去除率的影响差别不显著,对氮磷去除率有显著影响,且去除率符合长根型 > 中根型 > 短根型;水力负荷对COD、TN、NH4+-N和TP的去除均有显著影响,随着水力负荷减小去除率均逐渐升高;植物种类与水力负荷的交互作用对各污染物去除率均有显著影响,且受水力负荷影响较大,TN、NH4+-N的去除在水力负荷较小时交互作用较明显,COD去除的最优HL为230 mm/d。因此,在人工湿地设计时应考虑植物种类与水力负荷的交互作用。

Interaction of plant species and hydraulic loading on pollutant removals in constructed wetland

This study demonstrates that the pollutant removal efficiency in a constructed wetland was not only affected by hydraulic loading, but also by plant species. In order to research the interaction of these two factors on the removal of pollutants, short-root, middle-root, and long-root plant subsurface in constructed wetland systems (pilot-scale) were established. Once the systems reached stable operating conditions, the removal efficiencies of pollutants were investigated under different hydraulic loading rates (152, 230, 305 and 460 mm/d). The results showed that plant species had a significant effect on the removal of nitrogen and phosphorus, but they did not substantially influence the removal of the chemical oxygen demand (COD). The removal rates of nitrogen and phosphorus decreased in the following order: long-root system > middle-root system > short-root system. Hydraulic loading had a significant effect on the removal rates of COD, total nitrogen (TN), NH4+-N, and total phosphorous (TP), and removal rates increased as the hydraulic loading decreased. The interaction of plant species and hydraulic loading had significant effects on the removal rate of pollutants, and the system was more readily affected by hydraulic loading. When hydraulic loading rates were smaller, the interaction was more obvious for the processes of TN and NH4+-N removal. The optimal hydraulic loading rate was found to be 230 mm/d for COD removal. Overall, these findings suggest that it is worth considering the interaction of plant species and hydraulic loading rates in the design of constructed wetlands.