Fate and Transport of Particulate Matter in Geotextile Tube Dewatering of Dioxin and Furans Contaminated Sediments

Abstract

Geotextile tube dewatering is a pre-treatment method frequently utilized in the remediation of high-water content materials. Given the association that some contaminants (e.g. dioxins and furans) have with the particulate matter in contaminated sediments, understanding the fate and transport of this particle matter during the dewatering process is essential. This thesis attempts to provide a novel examination of the fate and transport of particle matter during geotextile dewatering. A sediment known to contain dioxin and furans was used to investigate this problem. To show the prevalence of dioxins and furans (PCDD/F) in the Boat Harbour (BH) sediment used in this thesis, organic sediment contaminants were assessed using secondary monitoring data collected between 1992-2015. Historical secondary monitoring data showed that sediment PCDD/F concentrations exceeded highest effect thresholds posing severe ecological health risks. A field sampling program was undertaken to assess the variability of the physical characteristics of BH contaminated sediment. It was demonstrated that by understanding sediment variability, composite samples can be shown to be an efficient method of obtaining representative samples. For this sediment, geotextile tube dewatering was compared to more conventional dewatering methods (i.e. centrifuge, sedimentation) in the context of how geotextile dewatering performs at reducing particulate matter in dewatering effluent. Filtrate quality of suspended solids was examined for differences based on three dewatering techniques assessed. All methods provided effective removal of particulate matter during dewatering, but geotextile dewatering could be a more cost-effective and practical solution for dewatering of these sediments. Pressure filtration tests as well as transport tests were conducted to investigate the effect of pressure and filter cake formation on particle transport during the geotextile dewatering. Also, a HYDRUS 1-dimensional model was employed to simulate experimental particle transport results. Modeling outputs suggest that both attachment and detachment mechanisms are involved in a given particles fate and transport during geotextile dewatering. It was also shown that different parameters such as confining pressure and filter cake properties influence the particle transport. Furthermore, HYDRUS was used to predict the particles transport during the geotextile tube dewatering under different circumstances, the findings of which are presented in this thesis.