Optimizing dewatering and soft tailings consolidation by enhancing tailings’ composition

In order to reclaim ultra-soft tailings (e.g. oil sands) ponds great amount of research and technology work has been performed over the years to optimize the dewatering and consolidation of Fine Fluid Tailings (FFT), including the use of different chemical flocculants and mechanical deposition approaches. Yet, traditionally flocculation, hence settling, and consolidation are treated as two independent processes. Here integrate these two processes, proving how implementation of certain types of flocculants influences the consolidation rates and strength of the deposit. Laboratory studies on small scale settling columns carried out at Deltares tested the settling and consolidation rates, and the strength development of FFT samples treated with different flocculants dosage under different water chemistry and pH conditions. These systematic tests revealed distinct correlations between flocculation and consolidation and strength properties. These studies also enabled us to find specific laboratory and analytical tools to assess the relevant properties of the tailings. We will show that using what is generally called "zeta potential” (in fact “electrophoretic”) measurements allow obtaining fast and reliable information about the tailings’ composition, such to estimate the required flocculant dose to optimize geotechnical properties. This, combined with the analytical methods to estimate consolidation rates from settling column, allowed us to distinctly correlate flocculation with consolidation.Applied Science, Faculty ofMining Engineering, Keevil Institute ofUnreviewedOthe

Tubifex : A biological method for dewatering oil sands tailings

In Northern Alberta’s oil sands region, there are more than 800 million m³ tailings occupying more than 180 km² of tailings ponds. The suspended solids (mostly silts and clays), gradually densify to 25 to 40 wt% solids in 2-5 years. It is important to assist in the dewatering process of oil sands tailings to facilitate their reclamation. An innovative method is presented in this paper to address the challenges with rapid dewatering using self-reproductive earth worms, Tubifex, which offers the potential to improve the dewatering. Comparable column tests between Tubifex-treated and non-treated oil sands tailings were conducted. Test results showed that: (a) the solid-water mud line of Tubifex-treated tailings decreases faster than non-treated tailings; (b) after settling within 2 month, the solids content of Tubifex-treated tailings was 21% more than the non-treated tailings, and 15% more than the initial tailings which have been under self-weight consolidation for years. Test results imply that the Tubifex treatment method may be promising in the settling and dewatering of oil sand tailings.Applied Science, Faculty ofMining Engineering, Keevil Institute ofUnreviewedOthe

Placement of caps on soft and fluid tailings

This paper describes a concept for placing a cap over soft or fluid tailings deposits using a floating platform for hydraulic cap placement, and compares it to two standard cap placement methods: 1) mechanical placement using earthwork equipment and 2) hydraulic beaching. Hydraulic placement from a water platform has a number of potential uses in the mining industry to manage tailings, and may be one of the more cost-effective methods to consolidate soft tailings in locations where strength is too low for land-based cap placement methods. Supplementary elements, such as installation of wick drains or other drainage features to aid consolidation can be deployed from a water platform as well. General costs of construction are compared to illustrate the competitiveness of water-platform-based capping approaches. Placing caps hydraulically from a water platform can be an alternative to other methods of dealing with fluid tailings (such as centrifuging and thin-lift drying). It offers opportunities to reduce tailings related-risk and closure liabilities, and can prove more practical and more cost-effective than land-based methods, particularly for capping very soft to fluid tailings.Applied Science, Faculty ofMining Engineering, Keevil Institute ofUnreviewedOthe

Improving engineering properties of mature fine tailings using Tubifex

The present study investigated the effects of Tubifex (Oligochaeta: Tubificidae) treatment on the dewatering process of mature fine tailings (MFT). Experiments testing the survival rate showed that Tubifex can survive at 20 °C and 4 °C. MFT with initial solids content (Sc) of 30% of total mass were treated in 11 settling columns by three Tubifex densities, 1400, 2000 and 4200 individuals·m−2. Test results showed that the mean survival rate at 20 °C and 4 °C on the 28th day stayed around 85%. Tubifex enhanced MFT dewatering by providing compacted tailings with 11.6% and 66.7% higher Sc and undrained shear strength compared with nontreated tailings. Tubifex accelerated pore water pressure dissipation. Tubifex did not affect the chemical composition of tailings except for a decrease in sulfate content. The Sc of tailings treated by Tubifex increased by 67.4% within nine months, which was 129% greater than the Sc increase of the nontreated tailings after 11 months.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Salt marsh construction as a nature-based solution in an estuarine social-ecological system

Constructed salt marshes as a Nature-Based Solution for coastal defense offer additional benefits over conven- tional engineering, but project realization is often hampered by practical and governmental obstacles. We assessed the execution of a local-scale salt marsh construction project as a Nature-Based Solution (NBS) with respect to the regional-scale Social-Ecological System (SES) in an explicitly linked NBS-SES framework. A local municipality came up with various plans to develop its waterfront but these proved unrealizable without wider stakeholder participation. Crucial for success was that the local initiative was turned into an NBS integrating livability, bio- diversity and flood safety, and that it was linked to the governance systems and actors in a regional SES. The chosen NBS consists of a city beach and two salt marshes, a salt marsh park that is open to the public and a pioneer salt marsh that is only accessible for research. The pioneer salt marsh was constructed by raising the seabed to around mean high tide with sand obtained from a capital dredging project. It was used as a large-scale natural experiment in salt marsh construction. To test the effect of enrichment with silt and clay on initial salt marsh development, six hectare-scale compartments were created in which mud was mixed with sand in the top 1.0 m of the bed to three mud contents of on average 8%, 25% and 48%. Heavy machinery was needed to mix mud through the upper meter of the sandy bed. Mixing mud was softening the sediment causing the machines to sink into the 48% mud enriched bed. To test whether seeding with a pioneer plant species accelerates salt marsh development, fragments of Salicornia procumbens plants were seeded in half of three compartments. Field observations between November 2018 to September 2020 showed that seeding of Salicornia plant fragments re- sulted in significant differences in vegetation cover and species richness in the first growing season. Mud content showed significant positive effects on vegetation cover and species richness in the two monitored growing sea- sons, where the compartments with on average 7–9% mud had the lowest vegetation cover and species numbers. When constructing a salt marsh by raising sand and mixing mud, a mud content of 25% is practically feasible and results in high vegetation cover and species richness

Beneficial and nature-based sediment use - Experiences from Dutch pilots

The natural sediment cycle is disrupted and impacted by human interventions world-wide, such as dams in rivers, port developments in estuaries, dredging activities for the maintenance of existing ports and waterways, and pollution from industrial activities. Coasts, shores, lakes and rivers suffer from an imbalance in sediment quantity and poor sediment quality. This impacts human industrial activities (e.g. navigation, logistic and tourism), life and safety (e.g. space for living, flood safety, food security and loss of productivity). In addition, shortage of sand cause by excessive sand mining or lack of sand in the environment in many locations of the world brings a special focus on fine and soft sediment, generally considered an unsuitable resource if not a contaminated waste. In line with this world-wide demand, EcoShape - Building with Nature is executing various pilots in the Netherlands and Indonesia to improve knowledge and demonstrate practical nature-based solutions regarding management, use and reuse of (fine and soft) sediments. These pilots are bonded in the EcoShape Living Lab for Mud initiative. These pilots cover the entire range from sediment in suspension to sediment as building material, embedding ecology, operations as well as socio-economic considerations. This presentation will focus on two of these pilots located in the Netherlands: the Mud Motor and de Kleirijperij (also part of the Eems-Dollard 2050 program). The Mud Motor explored potential for beneficial use of dredge sediments to feed salt marshes, through strategic disposal and optimal use of natural processes. The Kleirijperij studies the technical and financial feasibility of turning dredge sediments into clay-soil for dike construction. During the presentations we will focus on technical results as well as governance challenges and triggers critical for the realization of sustainable beneficial sediment use projects. These pilots and this presentation tight also to the 2017 CEDA and the 2018 PIANC working groups on Beneficial Sediment Use.</p

Beneficial and nature-based sediment use - Experiences from Dutch pilots

The natural sediment cycle is disrupted and impacted by human interventions world-wide, such as dams in rivers, port developments in estuaries, dredging activities for the maintenance of existing ports and waterways, and pollution from industrial activities. Coasts, shores, lakes and rivers suffer from an imbalance in sediment quantity and poor sediment quality. This impacts human industrial activities (e.g. navigation, logistic and tourism), life and safety (e.g. space for living, flood safety, food security and loss of productivity). In addition, shortage of sand cause by excessive sand mining or lack of sand in the environment in many locations of the world brings a special focus on fine and soft sediment, generally considered an unsuitable resource if not a contaminated waste. In line with this world-wide demand, EcoShape - Building with Nature is executing various pilots in the Netherlands and Indonesia to improve knowledge and demonstrate practical nature-based solutions regarding management, use and reuse of (fine and soft) sediments. These pilots are bonded in the EcoShape Living Lab for Mud initiative. These pilots cover the entire range from sediment in suspension to sediment as building material, embedding ecology, operations as well as socio-economic considerations. This presentation will focus on two of these pilots located in the Netherlands: the Mud Motor and de Kleirijperij (also part of the Eems-Dollard 2050 program). The Mud Motor explored potential for beneficial use of dredge sediments to feed salt marshes, through strategic disposal and optimal use of natural processes. The Kleirijperij studies the technical and financial feasibility of turning dredge sediments into clay-soil for dike construction. During the presentations we will focus on technical results as well as governance challenges and triggers critical for the realization of sustainable beneficial sediment use projects. These pilots and this presentation tight also to the 2017 CEDA and the 2018 PIANC working groups on Beneficial Sediment Use.</p