Comparative dewatering performance of slurries conditioned with synthetic polymers vs. eco-friendly polymers

Geotextile tubes have been used to dewater a variety of materials, including dredged sediments, mine tailings and mineral fines, municipal sewage sludge, and a variety of agricultural, manufacturing, and industrial wastes. Synthetic polymers, typically polyacrylamide-based, are commonly used in geotextile tube dewatering applications as flocculants to enhance the rate of dewatering and the retention of fines. Depending on the specific nature of the flocculant, flocculation of fine particles occurs by charge neutralization, bridging, or a combination of both. Polyacrylamide-based polymers, however, may have a negative impact on the environment due to toxicity and non-biodegradability. This possible negative impact necessitates the assessment of eco-friendly polymers for flocculation. Studies have identified a number of natural flocculants, particularly polysaccharides and polysaccharide derivatives, as effective flocculants in other engineering applications. These natural flocculants are potential low-cost biodegradable alternatives to non-renewable, non-biodegradable synthetic polymers. In this study, pressure filtration tests (PFT) were used to investigate and compare the dewatering performance of a natural polysaccharide-based flocculant to that of a synthetic polyacrylamide-based polymer when applied to a fine grained, non-plastic sediment. PFT results indicate that the natural polymer demonstrates good potential for use as a flocculant in geotextile tube dewatering.