Collaborative Reserach: Geotextile Tubes for the Sustainable Dewatering

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The objective of this research project is to develop polysaccharide-based alternatives to synthetic polyacrylamide-derived polymer flocculants, and to explore the possibility of using natural fiber-based geotextiles for the dewatering application. The dredging of sediments from harbors, lakes, canals, tailings ponds, and other bodies of water has attracted a significant amount of public interest in recent years. Dredged sediments are generally high in water content that must be disposed of in environmentally and economically sustainable ways. The handling and disposal of these materials typically require dewatering, the process whereby liquid is removed from the materials to increase the percent solids to acceptable levels. A decade ago, the dewatering of high water content materials (1-10 percent dry solids) was performed almost exclusively with settling ponds, mechanical presses, and centrifuges. More recently, geotextile tubes have been successfully used for dewatering high water content materials by many industries. The need to maximize the retention of materials and minimize the time required for dewatering has led to the common addition of synthetic cationic or anionic acrylamide-derived polymers in geotextile tube applications. While these polymers have become an essential component of geotextile tube dewatering, concerns exist regarding their safety. In addition, there is a wide disparity in the performance indices and test methods that are currently being used to evaluate geotextile tube performance. This project will be the first systematic study of its kind which aims to develop polysaccharide-based alternatives to synthetic polyacrylamide-derived polymer flocculants, and to explore the possibility of using natural fiber-based geotextiles for the dewatering application. The acute toxicity of natural and synthetic polymer flocculants will be tested using the fish embryo toxicity test with zebrafish. The study will also include bench-scale and pilot-scale simulation tests on sediment with clay minerals and organic matter. The tests will be critically evaluated and a new performance standard for the evaluation of geotextile tubes for dewatering sediments will be developed. A mathematical model which incorporates the fundamental properties of sediment, polymers, and geotextiles will be developed to evaluate the long-term performance of geotextile tubes.This project addresses an important problem related to the dredging, the dewatering of dredged materials in an efficient, safe and sustainable manner. Webinars will be developed to provide an overview of the use of geotextile tubes, their benefits, and the findings from this study. The webinars will be advertised through national organizations, such as the North American Geosynthetics Society (NAGS) and the American Society of Civil Engineers (ASCE). The PIs will present their research results at the annual ASTM D-35 committee meetings and will take an active role in developing performance standards for the bench-scale tests used for the dewatering evaluation of geotextile tubes. Two middle school teachers will be involved in the project. The teachers will develop teaching modules, in collaboration with the PIs, which will be used to disseminate information on geotextile tubes to middle-school students.