Influence of plant tillering and root volume on flow pattern and water purification of vertical down flow wetlands for domestic wastewater treatment

摘要

Four kinds of plants with tap, tuber and fibrous root system were chosen and their root volumenwas manipulated by tillering control in this study. Plant tillering could be described by Logisticnfunction, means that controlling the initial planting density in the wetland is unnecessary.nTherefore, the minimum planting density for each plant could be considered, and this will havencost benefits for planting wetlands. There is a positive correlation between plant tillering and rootndevelopment, especially on reed and Juncus effusus L, coefficient of association between abovegroundnplant weight and root weight, as well as plant tillering and root volume of which reachedn0.93–1.Those coefficient of association of Cannaceac and Cyperus alternifolius L were in thenrange 0.43–0.69. In the process that root breakthrough the substrate, root could open up thenclogged soil, which increased porosity of substrate by 3–44% than the non-planted one, althoughnroot also occupied the space in the substrate. The adjoint transverse pressure of root growthnwould homogenize the substrate, which randomly increased Peclet number of substrate byn6–90% than the non-planted one. No regularity correlation was found between wastewaternpurification and above-ground plant biomass or root volume. Root plays more role on porositynimprovement than substrate homogenization and water purification in VF for domesticnwastewater treatment.