矢島, 聡

渡邊, 幸雄

YAJIMA, Satoru

WATANABE, Yukio

The objective of this study was to determine the nutrient removal by aquatic fern (Salvinia molesta) from treated municipal wastewater or eutrophied lake water. The results obtained are as follows: 1. In the laboratory experiment with artificial media, S. molesta can be grown with broad range of pH from 4 to 8. Fresh weight of S. molesta became twice after 4.5 days in this experimental condition. S. molesta preferred NH_4-N to NO_3-N in the nutrient solution. The amounts of absorbed nutrients were 3.5-5mg N and 1-1.5mg P per one gram of fresh weight. 2. In the experiment using the treated wastewater, concentration of NO_2-N increased up to 18ppm after ten days, but the disorder was not appeared in the plant. S. molesta can be grown in the low concentration of phosphorus (0.1ppm) in the treated wastewater. However, the higher concentration of phosphorus (1ppm) enhanced plant growth and increased nitrogen absorption by plant. The phosphorus added at this level was absorbed almost completely by S. molesta. 3. The fresh weight of S. molesta cultured with the water from Tega lake became about four times of initial weight during ten days. Nitrogen and phosphorus concentrations decreased remarkably in the culture media. According to these results, it is suggested that S. molesta has high potential as aquatic plant for wastewater treatment because of the rapid growth rate and high ability of nutrient removal from wastewater or entrophied lake water.