抄録
Chitosan, acetylated of chitin, is a biodegradable cationic polymer. The objective of this study is to assess the applicability of chitosan for on-site treatment agent of turbid water caused by a river improvement work. The results of jar-tests indicate that flock of chitosan is much larger than that of aluminum sulfate, and turbidity treated by chitosan under moving water condition is much lower than that of aluminum sulfate. Residual turbidity shows good accordance with Reynolds number both in jar tests and in elliptical waterway tests. This means that by using Reynolds number as an indicator, jar test can predict residual turbidity in a river. Acute toxicity tests using Oryzias latipes indicate that 48hr-LC50 is about 5mg/L, and 48hr-EC50 is between 5mg/L and 7.5mg/L. Since the estimated optimal dosage of chitosan in a river is lower than 1ppm, chitosan has no acute toxicity in practical use. Applying chitosan to a river causes 1.1 ppm of BOD increase. The cost of chitosan is three times higher than that of aluminum sulfate.
