Research

End Pit Lake Reclamation

In northeastern Alberta, the bitumen extraction from the surface-mined oil sand produces approximately 1 million cubic meters of tailings per day. The fluid fine tailings (FFT) is a mixture of water, fine clay, and uncovered hydrocarbons. FFT take years to become consolidated, making the reclamation of FFT difficult to achieve. The end pit lake (EPL) is an attractive option for tailing’s reclamation. The EPL is created by adding FFT, oil sands process affected water (OSPW), and freshwater into a closed mine pit. The EPL is expected to develop into a self-sustaining ecosystem so that the reclamation of tailings can be completed. End Pit Lakes are one of the primary methods used by oil sands companies to manage their mine waste over a long-term and to integrate mine waste back into the surrounding environment. Nevertheless, the application of EPL as a reclamation method have not been practicable in the oil sand field at Northeast Alberta due to unique challenges.

Geotechnical Optimization of Treated Tailings Systems for Aqueous Covers

Previous water capped deposits are either untreated tailings or completely treated tailings. In this study, water capped deposits are optimized by developing a treatment layer on top of untreated tailings. Examples of potential treatment layers include permeable reactive barriers (PRBs), biological mats consisting of algae species, coagulated/flocculated tailings, and weathered tailings crust. The treated tailings systems will be analyzed for PSD, the effect of segregation, compressibility and hydraulic conductivity. These geotechnical parameters will influence and also be influenced by the biogeochemical properties of the treated tailings systems. As such, a primary and a secondary structure is formed during the experiment. The primary structure is what has already been deposited; the secondary structure is the result of the ongoing interactions between the geotechnical and biogeochemistry of water capped deposits. As we are trying to move toward engineered deposits that have a step-change improvement in performance, we need to understand the influence of the secondary structures, as these are the factors that are determining the fluxes of constituents of potential concern in field deposits. This project will optimize water capped deposits for oil sand tailings aquatic reclamation. The key geotechnical and biogeochemical parameters, and their relationships, will be identified to predict the performance of water capped deposits. The objective of the study is to develop criteria that will optimize the geotechnical properties and biogeochemical properties, coupled with an engineered deep deposit, to accelerate the transition of the deposit to a natural ecosystem that sequesters the constituents of potential concern.

Integrity and Long-term Stability of Treated Tailings Systems

The long-term stability and performance of the chemically amended tailings systems are evaluated by conducting laboratory-accelerated ageing experiments. Large scale ageing cells are designed to contain the treated tailings systems and incubated at elevated temperatures, pressures, and methane ebullition rates.

During the ageing experiment, the treated tailings systems are analyzed for particle size, shear strength, compressibility, consolidation rate, and hydraulic conductivity to assess their long-term geotechnical integrity. The concentrations of bitumen, naphtha, naphthenic acids, ions, and metals will be determined in both tailings deposits and expressed pore-water. Illumina sequencing and subsequent bioinformatics analysis is performed to determine the changes in microbial communities and activities in aged tailings deposits. These geotechnical and biogeochemical parameters are used to evaluate the potential long-term chemical flux under test conditions. The aged tailings deposits are further tested under a water capped deposit scenario to understand how the altered geotechnical integrity impacts biogeochemical evolution. The fluxes of constituents of concern across the aged tailings-water cover interface will be quantified and correlated with the geotechnical parameters. Finally, the results from the combined ageing and consolidation test will allow the quick clay potential of the treated tailings to be assessed and understood as the biogeochemistry evolves.

Anaerobic Benzene Degradation

In Alberta, benzene is commonly used as a diluent for bitumen. Benzene is a highly stable and mobile six-carbon ring molecule and is extremely toxic and carcinogenic. Therefore, benzene becomes a significant contaminant in tailing ponds, and its remediation is highly prioritized. The bacterial anaerobic process plays an important role in oil sand tailings bioremediation, but it has been technically proven as problematic to maintain an anoxic culture. The aerobic biodegradation of benzene, therefore, turns into a challenge because the microenvironment is usually depleted in oxygen in the tailings pond.

Our research studies the benzene contaminants of the oil gas industry. It is interested in the bioremediation method that is most cost-effective and non-intrusive to soil properties and biodiversity. Our lab is now studying the samples from tailings ponds and seeking to understand the enzymatic processes and community dynamics of anaerobic benzene degradation. Bottles with clay/sand and media were set up and spiked to 10 mg/L liquid benzene to model the ecosystem. Three different conditions (methanogenesis, nitrate-reduction, and sulfate-reduction) are studied. The bottles are monitored every three weeks to trace benzene degradation. The ultimate research objectives consider the characterization of the putative benzene carboxylase AbcDA, the qualification and quantification of biofilm in benzene-degrading cultures, and the optimization of growth conditions for benzene-metabolizing microbial communities.

Naphthenic Acids Remediation

Large amounts of water are consumed every day in the oil sands industry for bitumen extraction. As a result, vast quantities of oil sands process-affected water (OSPW) are produced and require remediation. OSPW contains various contaminants, while it is considered that Naphthenic Acids (NAs) are the primary cause of toxicity and main contaminant of concern. The oil sands industry is looking for a mediation method that can adequately remove NAs from OSPW in the most cost-effective manner.

Our lab focuses on optimizing the coupling of chemical oxidation and biodegradation for the feasible and efficient remediation of NAs. The strategy of adding chemical oxidants into OSPW had been proven quite successful for NAs removal. However, it has also been realized an expensive process to achieve complete mineralization of NAs by the chemical oxidation method. On the other hand, bioremediation is now being considered as another potential strategy for NAs. The advantage of bioremediation is that it is less intrusive and inexpensive because it utilizes microbial communities that already exist in OSPW and have adapted to using NAs as a substrate. Nevertheless, bioremediation takes a longer time to achieve remarkable results and has less influential to complex NAs. Our lab is developing both a time and cost-effective remediation process by combining the chemical oxidation and biodegradation method. Suitable chemical oxidant must be chosen based on oxidizing abilities and stability. It can break down the recalcitrant NAs into simpler and more bioavailable compounds. In the next stage, the resilient microbe found in OSPW with proven ability to degrade NAs is applied for biodegradation. After the chemical oxidation, the NAs become more accessible for the microorganisms to degrade. Our research will generate fundamental knowledge of this combined remediation technology for the in-situ applications and leads to future environmental research.

Biodegradation of Anionic Polyacrylamide Under Different Redox Conditions in Oil Sands Tailings

Polyacrylamide is a common flocculant used to increase the settling and dewatering rate tailings. Although polyacrylamide is effective for tailings settlement and is widely used in tailings management, little is known about its interactions with oil sands tailings microbial communities and susceptibility to biodegradation in tailings systems. We are therefore investigating how microbial communities respond to the introduction of polyacrylamide and if indigenous oil sand tailings microorganisms are capable of polyacrylamide biodegradation under oxic and anoxic conditions. We are also evaluating how Size Exclusion Chromatography can be used to determine polyacrylamide biodegradation, and monitoring water chemistry to identify potential biodegradation products. Oil sands tailings treated with polyacrylamide will eventually be incorporated into the reclaimed landscape, enforcing the importance of our research in understanding and monitoring these systems.

Past Projects

The Feasibility of Using Enzymes to Accelerate the Dewatering of Oil Sands Tailings (2017 - 2022)

Enzymes are proteins with a catalytic activity that have been previously used as conditioners for enhancing sludge dewaterability. We investigate the possibility of improving the dewatering of oil sands tailings by using various types of enzymes (e.g., lysozyme from chicken egg white). The hypothesis is that the enzyme can promote microbial activity in tailings and increase hydrocarbon degradation, which leads to enhanced biogas production. The transport of the biogases can facilitate the release of water from the tailings by creating pathways for pore-water. Another prospect is that enzymes act as a coagulant aid, and hence enhance the MFT consolidation and dewatering.

Optimizing the Usage of Tubifex to Enhance Densification and Strength of Oil Sands Tailings (2019 - 2021)

Accelerating the dewatering and consolidation process of fluid fine tailings and sediment management is a significant challenge to the oil sands industry in Canada and for the mining and land reclamation industry world-wide. A recent research program carried out at Deltares in The Netherlands, in collaboration with the University of Alberta, showed that adding Tubifex, an earthworm prevalent in Alberta, significantly improves dewatering and strength development of fluid and soft fine tailings, beyond and in addition to polymeric treatment. The mechanism behind this improvement is linked to the network of channels produced by Tubifex. In recent tests, Tubifex-treated fluid fine tailings achieved a solids content 25% (45% vs. 55%) higher than tailings with no Tubifex. As such, this technology has the potential to offer an alternative biological method to improve reclamation and potentially bioremediation of oil sands tailings, on its own, or coupled with other technologies, such as sand capping.

After the project was started, Tubifex, the worm species originally utilized in this project, was declared as a carrier of the whirling disease, which is dangerous for salmon. Therefore the use of a similar but different species in the next tasks of this project was evaluated. The California blackworm (Lumbriculus variegatus) is an aquatic species similar to Tubifex, which does not carry whirling diseases; therefore, it was used for all experiments.

Laboratory studies investigating chemical flux across tailings-cap water zones, simulating an End Pit Lake in the Athabasca oil sands region (2015 - 2019)

The primary research project in our lab was to estimate the feasibility of EPL for tailings reclamation. Therefore, physical, chemical, mineralogical, and molecular microbiological approaches were utilized to investigate biogeochemical and physical processes occurring in water-capped FFT. The first part of the project included monitoring of degradation and flux of chemicals and microbial community analysis. Twelve 50-L mesocolumns containing underlying FFT and overlying water, with a volume ratio of 5:1, were set up to simulate the environmental system for EPL. The mesocolumns are treated under different temperatures, with different carbon sources, and were measured bi-weekly to quantify the COCs flux and methane production across the tailing/water interface. The second part of the project was to research on the chemical and biological mitigation strategies used to reduce the cap water turbidity. The strategies researched in our lab include CO2 addition, nutrient amendment, microbial mat application, chemical coagulants, and cap water dilutions.