Abstract
Zeolite has been often used for water purification by plant and bed filter materials. Kanumatsuchi, a kind of volcanic ash soil, has the ability of adsorption of phosphorus. But the feature of the water purification system with plants and Kanumatsuchi as bed filter materials is still unknown. In this study, an experiment of water purification using two series of ditches filled with Kanumatsuchi has been carried out. Forage crops (Sorghum; Sorghum vulgare and Sesbania; Sesbania cannabina) were planted in one ditch, and flowers and herbs (Garden Petunia ; Petunia × hybrida, French Marigold; Tagetes patula, Basil; Ocimum basilicum and etc.) were planted in another ditch. Nitrogen and Phosphorus average loading rate to the ditches during experiment (6 months) was 0.99-1.06 and 0.22-0.24 g · m-2 · d-1. The average nitrogen removal rate of the forage crop ditch and the flowers & herbs ditch was 0.52 and 0.14 g · m-2 · d-1. The phosphorus average removal rate of the forage crop ditch and the flowers & herbs ditch was 0.22 and 0.24 g · m-2 · d-1. But the phosphorus concentration of effluent from the flowers & herbs ditch increased near the end of the experiment.
The biomass production of forage crops was larger than that of flowers & herbs. Analysis of nitrogen and phosphorus concentration of plants shows that forage crops uptake larger nitrogen and phosphorus than flowers and herbs. Results of the experiment suggest that a combined effect of the uptake by plants and the adsorption by Kanumatsuchi leads high phosphorus removal in this system. And we can conclude that the increasing of phosphorus absorption by plants results in sustaining of the absorption ability of Kanumatsuchi.
