In 2002, Japan enacted environmental standards for dioxins contaminated sediment. A nationwide sediment dioxins survey of public waters found sediment exceeding environmental standards in some rivers: a problem requiring countermeasures. The Eco-tube is a permeable geotextile container with soft and high water content sediment deposited in rivers, lakes, and marshes. It promotes dewatering of the sediment, and the filtering function of the tubes c§an purify the drain and enclose toxic substances such as dioxins. After dewatering, they are used to build embankments by taking advantage of their tensile strength. This report describes a trial execution of Eco-tubes that enclose dioxins contaminated sediment. The trial followed preliminary testing: measuring the quantity and turbidity of the drain by pressurized filtering test to examine the geotextile’s filtering performance and select the coagulant. Next, 0.2m3 tubes of the selected material were filled with sediment and used for laboratory experiments based on the actual execution, confirming the dewatering speed and filtering effectiveness of the method. The trial applied 2 patterns (5 cases) based on the test results. (1) Filling high density tubes with sediment already containing coagulant. (2 cases) (2) Filling tubes with sediment and adding coagulant into drain. (3 cases) Results: (1) Drain of 130pg-TEQ/g dioxins contaminated sediment becomes 2.4pg-TEQ/l. (2) Drain including the 960pg-TEQ/l dioxins went down 0.42pg-TEQ/l by adding coagulant. Pattern (2) was much easier to execute, and more effectively reduced turbidity of the water. The tube height fell to 1/2 to 1/7 of maximum height in about 5 months. These findings confirmed that Eco-tube enclose dioxins contaminated sediment and reduce the volume of sediment by dewatering.
Masuya, Yugo; Taninaka, Hitoshi; Takahashi, Isamu; and Kohashi, Hidetoshi
"Enclosing Dioxins Contaminated Sediments By Geotextile Tubes,"
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy:
Vol. 13, Article 32.
Available at: http://scholarworks.umass.edu/soilsproceedings/vol13/iss1/32