Many studies have reported on the removal of pollutants from wastewater using aquatic plants. The water hyacinth has been the most widely used and its system is the most well established. This system however, has a few problems in practical use. The purpose of this study is to obtain basic information on a new system that can substitute for a conventional system or be used as a secondary system to assist the conventional one. We first envisioned a model of this new system and then conducted a preliminary experiment using a small experimental unit to simulate the new system. The experiment showed that mung beans were a suitable plant for our study. Their removal rate of pollutants was the highest before they developed leaves and started photosynthesis. We found that nutrients were expelled outside the plant root when nutrient concentration inside the plant tissue became too high.