Search

Surface mining of oil sands ore in Alberta, Canada has generated fluid fine tailings (FFT) that must be reclaimed. End pit lakes (EPLs), which consist of thick deposits of FFT capped with water, have been proposed for FFT reclamation, and Base Mine Lake (BML) is the first full-scale demonstration EPL. However, FFT particle settling and resuspension contributes to high turbidity in the BML water cap, which may be detrimental to the development of an aquatic ecosystem. This study investigated the effect of Ca and Al treatments on turbidity mitigation. The initial turbidity was reduced from 20 NTU to less than 2 NTU in BML surface water treated with 54 mg/L of Ca or 1.1 mg/L of Al. At a concentration of 1.1 mg/L, Al reduced the initial turbidity to a greater extent, and in a shorter time, than 54 mg/L of Ca. Further, resuspended Al-treated FFT particles were 100–700 nm larger in diameter, and thus resettled faster than the resuspended untreated or Ca-treated FFT particles. The final turbidity values 21 days after resuspension of untreated and 1.7 mg/L Al-treated FFT particles in fresh BML surface water were 20.5 NTU and 2.5 NTU, respectively. Thus, Al treatment may be effective in mitigating turbidity in BML through both Al-induced coagulation and self-weight settling of the resuspended Al-treated FFT particles.

Engineering strategies to reduce greenhouse gases (GHGs) emissions by inhibiting methanogenesis in oil sands tailings have rarely been examined. In this study, we explored the potential impact of chemical treatment (lime) and biological treatment using enzymes (lysozyme and protease) on inhibiting methane emissions from tailings. Overall, treatment with protease 3%, lysozyme 3%, and lime 5000 ppm reduced CH

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.

Oil sands surface mining in Alberta has generated over a billion cubic metres of waste, known as tailings, consisting of sands, silts, clays, and process-affected water that contains toxic organic compounds and chemical constituents. All of these tailings will eventually be reclaimed and integrated into one of two types of mine closure landforms: end pit lakes (EPLs) or terrestrial landforms with a wetland feature. In EPLs, tailings deposits are capped with several metres of water while in terrestrial landforms, tailings are capped with solid materials, such as sand or overburden. Because tailings landforms are relatively new, past research has heavily focused on the geotechnical and biogeochemical characteristics of tailings in temporary storage ponds, referred to as tailings ponds. As such, the geochemical stability of tailings landforms remains largely unknown. This review discusses five mechanisms of geochemical change expected in tailings landforms: consolidation, chemical mass loading via pore water fluxes, biogeochemical cycling, polymer degradation, and surface water and groundwater interactions. Key considerations and knowledge gaps with regard to the long-term geochemical stability of tailings landforms are identified, including salt fluxes and subsequent water quality, bioremediation and biogenic greenhouse gas emissions, and the biogeochemical implications of various tailings treatment methods meant to improve geotechnical properties of tailings, such as flocculant (polyacrylamide) and coagulant (gypsum) addition.

Surface water turbidity from dispersed clay particles can hinder the development of aquatic ecosystems. One of the primary objectives for proposed oil sands end pit lakes is that they support ecological functions and lake-specific wildlife habitat. However, high surface water turbidity has been observed in the Base Mine Lake cap water, the first full-scale demonstration oil sands end pit lake. Our previous study showed that adjusting the solution pH through carbon dioxide addition reduced surface water turbidity in oil sands tailings. Carbonate minerals such as calcite and dolomite were also previously identified in tailings, and thus the goal of this study was to determine the effect of calcite and dolomite dissolution through carbon dioxide mediated pH reduction on turbidity and the stability of suspended clay particles. Calcite dissolution resulted in ���99% reduction of turbidity. The suspended clay particle stability was analyzed using DLVO (Derjaguin-Landau-Verwey-Overbeek) theory with water chemistry data from this column study. An inverse correlation was observed between the amount of dolomite and the energy barrier values on day 42 of the experiment. These results suggest carbon dioxide mediated calcite dissolution changes the water chemistry and is the most promising treatment condition for the settlement of suspended tailings particles.

Surface water turbidity from dispersed clay particles can hinder the development of aquatic ecosystems. One of the primary objectives for proposed oil sands end pit lakes is that they support ecological functions and lake-specific wildlife habitat. However, high surface water turbidity has been observed in the Base Mine Lake cap water, the first full-scale demonstration oil sands end pit lake. Our previous study showed that adjusting the solution pH through carbon dioxide (CO2) addition reduced surface water turbidity in oil sands tailings. Carbonate minerals such as calcite and dolomite were also previously identified in tailings, and thus the goal of this study was to determine the effect of calcite and dolomite dissolution through CO2-mediated pH reduction on turbidity and the stability of suspended clay particles. Calcite dissolution resulted in ∼99% reduction of turbidity. The suspended clay particle stability was analyzed using DLVO (Derjaguin-Landau-Verwey-Overbeek) theory with water chemistry data from this column study. An inverse correlation was observed between the amount of dolomite and the energy barrier values on day 42 of the experiment. These results suggest CO2-mediated calcite dissolution changes the water chemistry and is the most promising treatment condition for the settlement of suspended tailings particles.

Alberta is a major center for oil and gas production, and correspondingly harbors hundreds of unresolved contamination sites by environmental hazards such as benzene (C6 H6 ). Due to its cost-effectiveness, bioremediation has become a promising strategy for C6 H6 removal. Contamination sites typically take on an anaerobic context, which complicates the energetics of contamination sites and is a subject that is scarcely broached in studies of Albertan sediments. This study examines the innate potential for indigenous microbial communities in Albertan sediments to remove C6 H6 in a multitude of reduced conditions. Community profiles of these sediments were analyzed by 16S rRNA gene amplicon sequencing, and removal rates and reaction stoichiometries were observed by gas chromatography and ion chromatography. Organisms belonging to known primary degrader taxa were identified, including Geobacter (iron-reducing), and Peptococcaceae (nitrate-reducing). Furthermore, benzene removal patterns of the cultures were similar to those observed in previously reported microcosms, with lag times between 70 and 168 days and removal rates between 3.27 and 12.70 µM/day. Such information could support a more comprehensive survey of Albertan sediment consortia, which may eventually be utilized in informing future remediation efforts in the province. PRACTITIONER POINTS: ●Clay and sand sediments originating from Northern Alberta could remove benzene under methanogenic, sulfate-reducing, iron-reducing, and nitrate-reducing conditions. ●Degradation profiles were broadly comparable to those of reported cultures from other geographical locales. ●Key degrader taxa observed included Geobacter (Fe3+ -reducing) and Peptococcaceae ( NO3- -reducing). ●Knowledge gained can be the start of a more extensive survey of Albertan sediments. Eventually, this collection of information can be used to generate robust C6 H6 -degrading cultures that can be implemented for bioaugmentation and be implemented in informing remediation strategies in soil and water matrices for priority contamination cases such as leaking underground storage tanks and orphan wells.

Seepage from oil sands tailings ponds (OSTP), which contain toxic naphthenic acids (NAs), can infiltrate into groundwater. Clay sediment layer beneath is a critical barrier for reducing the infiltration of NAs into the sand sediment layer, where groundwater channels reside. Biodegradation has great potential as a strategy for NAs removal, but little is known about NAs biodegradability and potential functional microbes in these pristine sediments. This study investigated the potential for anaerobic biodegradation of NAs by microbial consortia enriched from clay and sand sediments underlying OSTP, amended with either acid extracted organics or Merichem NAs, under nitrate- and sulfate-reducing conditions. Degradation of NAs only be detected after DOC concentration reached to steady state after 163 days. Microbial community analysis shows that different electron acceptors, sediment types, and NAs sources associated with specific microbial taxa and can explain 14.8, 13.9 % and 5% of variation of microbial community structures, respectively. The DOC and methane were the most important geochemical properties for microbial community variations. This study approved the potential capability of indigenous microbial communities from the pristine sediments in NA degradation, demonstrating the barrier function of pristine clay sediments underlying OSTP in prohibiting organic contaminants from entering into groundwater.

Oil sands operations in Alberta, Canada generate large volumes (>840 × 106 m3) of oil sands process-affected water (OSPW) that contains contaminants that are toxic to aquatic life. OSPW is stored in open tailings ponds and leakage from the ponds presents a potential long-term environmental risk. However, the presence of naturally occurring saline water in the oil sands region in Alberta presents a challenge for delineating the impact of OSPW in cases where OSPW is leaked to the environment. Here, we characterize the inorganic chemistry and isotopic variations of boron (δ11B), lithium (δ7Li), and strontium ( e S r S W ) of OSPW from tailings ponds in order to evaluate the source of salinity in OSPW and the potential utilization of these isotope ratios as forensic tracers of OSPW migration in the environment. In addition to generating new data, we compiled published data to build a comprehensive dataset of the geochemical composition of different water sources in the oil sands region of Alberta. OSPW is brackish (TDS ∼ 1800 mgL−1), with elevated chloride (392 ± 184 mg L−1), boron (2.2 ± 0.4 mg L−1), and lithium (0.12 ± 0.11 mg L−1) concentrations relative to the Athabasca River that is used for bitumen extraction. OSPW is characterized by narrow ranges of δ11B (23.7 ± 1.8‰), δ7Li (16.3 ± 1.7‰), and 87Sr/86Sr ratios ( e S r S W =-3.9 ± 19.2). The geochemical and isotope ratios in OSPW reflect mixing of residual, saline formation water from Lower Cretaceous units with fresh surface water that has been modified by interactions with the solid oil sands. The elevated boron and lithium concentrations and δ11B, δ7Li and e S r S W variations we observed are distinct from the compositions of a shallow freshwater aquifer in the area (8.1 ± 5.0‰, 11.3 ± 0.9‰ and 9.7 ± 5.6, respectively) and the local rivers (15.6 ± 4.7‰, 15.1 ± 1.4‰ and 30.3 ± 16.0). However, groundwater and saline springs in the region presents a wider range of geochemical and isotopic values that are not always distinguishable from OSPW. The integration of boron, lithium, and strontium isotopes provides a potential monitoring tool for tracing OSPW release to local freshwater sources.

Phosphorus availability and cycling in microbial communities is a key determinant of bacterial activity. However, identifying organisms critical to P cycling in complex biodegrading consortia has p...

Bacteriological contamination of drinking water wells poses a challenge to many rural areas of First Nations communities in Alberta that rely on wells as the primary drinking water source for large proportions of their populations. Here we reviewed available historical data for the Samson Cree Nation near Maskwacis, Alberta (formerly Hobbema), to identify linkages between various environmental and historical factors and the risk of contamination by Escherichia coli and total coliform bacteria. Increased bacterial counts were found to be associated with a peak in total precipitation and surface water flow following a two to four month lag period. Wells installed by contractors operating at an earlier period in time were also found to be at greater risk than more recent installations. These findings can be used to better characterize the risk of contamination, which will assist in tailoring remedial actions to address chronic or recurring bacteriological presence in wells.

Oil sands tailings have a limited ability to dewater and can also release toxic water, so finding a cost-effective tailings reclamation strategy has been challenging. End pit lakes (EPLs) are being examined as one potential approach to reduce fluid fine tailings (FFT) inventories for the oil sands industry. This study investigated the effect of adding lime (650 to 4000 ppm) on FFT dewatering and improving cap water quality under the simulated EPL scenario. The results illustrated that a high lime dose of 3500 ppm achieved the highest FFT water recovery, decreased the cap water alkalinity at the end of the experiment (after 90 d), and increased the possibility of cation exchange (at day 0). In contrast, the degradation of petroleum hydrocarbons was slightly enhanced at low lime dose of 650 ppm in comparison to high doses. In addition, the 650 ppm dose resulted in minimal change in the microbial cell counts at day 90, compared with high lime doses that resulted in a large reduction in the cell counts. Comparisons of toxicity of the FFT pore water after lime addition exhibited higher toxic effects for lime dosages >1600 ppm. Nevertheless, at all lime doses, low cap water toxicity (i.e.

Accelerating dewatering of fluid fine tailings (FFT) to facilitate land reclamation is a major challenge to the oil sands industry in Canada. A new method was tested, addition of Tubifex to FFT. Tubifex is an indigenous earthworm in Canada. The survival rate tests showed that Tubifex can survive in oil sands tailings and penetrate to 42 cm depth (maximum depth tested). Columns (5 L of FFT) were set-up with tailings alone, Tubifex treated tailings and polymer-Tubifex treated tailings. Test results showed that (a) the final mud–water interface of tailings alone was 26% higher than that of Tubifex treated tailings; (b) solids content of Tubifex treated tailings was 21% more than that of tailings alone; (c) Tubifex was capable to accelerate the dewatering process of both cationic and anionic polymer treated tailings; (d) anionic polymer was superior in facilitating long-term dewatering and its coupled effects with Tubifex were better than the cationic polymer.

The expansion of oil sands has made remediation of oil sands process-affected water (OSPW) critical. As naphthenic acids (NAs) are the primary contributors to toxicity, remediation is required. Bioremediation by native microorganisms is potentially effective, however, toxicity of NAs towards native microorganisms is poorly understood. The aim of this study was to isolate microorganisms from OSPW, assess tolerance to stressors, including naturally sourced NAs and examine exposure effect of NAs on cell membranes. Microorganisms were isolated from OSPW, including the first reported isolation of a fungus (Trichoderma harzianum) and yeast (Rhodotorula mucilaginosa). Isolates tolerated alkaline pH, high salinity, and NA concentrations far exceeding those typical of OSPW indicating toxic effects of OSPW are likely the result of interactions between OSPW components. Comparisons of toxicity determined that OSPW exhibited higher cytotoxicity than NAs. The fungal isolate was able to grow using commercial NAs as its sole carbon source, indicating high resistance to NAs' cytotoxic effects. Future studies will focus on the organisms' ability to degrade NAs, and subsequent effects on toxicity. Characterization of OSPW constituents should be investigated with focus on the synergistic toxic effects of dissolved compounds. A better understanding of OSPW toxicity would enable more effective and targeted bioremediation schemes by native microorganisms.

Critical care medicine is a medical specialty where women remain underrepresented relative to men. The purpose of this study was to explore perceived drivers (i.e., influencing factors) and implications (i.e., associated consequences) of gender inequity in critical care medicine and determine strategies to attract and retain women.Qualitative interview-based study.We recruited participants from the 13 Canadian Universities with adult critical care medicine training programs.We invited all faculty members (clinical and academic) and trainees to participate in a semistructured telephone interview and purposely aimed to recruit two faculty members (one woman and one man) and one trainee from each site. Interviews were transcribed verbatim, and two investigators conducted thematic analysis.Not applicable.Three-hundred seventy-one faculty members (20% women, 80% men) and 105 trainees (28% women, 72% men) were invited to participate, 48 participants were required to achieve saturation. Participants unanimously described critical care medicine as a specialty practiced predominantly by men. Most women described experiences of being personally or professionally impacted by gender inequity in their group. Postulated drivers of the gender gap included institutional and interpersonal factors. Mentorship programs that span institutions, targeted policies to support family planning, and opportunities for modified role descriptions were common strategies suggested to attract and retain women.Participants identified a gender gap in critical care medicine and provided important insight into the impact for personal, professional, and group dynamics. Recommended improvement strategies are feasible, map broadly onto reported drivers and implications, and are applicable to critical care medicine and more broadly throughout medical specialties.

Naphthenic acids (NAs) originate from bitumen and are considered a major contributor to acute toxicity in oil sands process-affected water (OSPW) produced from bitumen extraction processes. To reclaim oil sands tailings and remediate OSPW, in-pit fluid fine tailings can be water-capped as end pit lakes (EPL). Addressing NAs present in OSPW, either through removal, dilution or degradation, is an objective for oil sands reclamation. EPLs can remediate NAs through degradation or dilution or both. To assess and understand degradation potential, Chlorella kessleri and Botryococcus braunii were tested for their tolerance to, and ability to biodegrade, three model NAs (cyclohexanecarboxylic acid, cyclohexaneacetic acid, and cyclohexanebutyric acid). Water sourced from the industry's first EPL, the Base Mine Lake (BML), was used alone as an inoculum or co-cultured with C. kessleri to biodegrade cyclohexanecarboxylic acid and cyclohexanebutyric acid. All cultures metabolized the model compounds via β-oxidation. Biodegradation by the co-culture of C. kessleri and BML inoculum was most effective and rapid: the cyclohexaneacetic acid generated from cyclohexanebutyric acid could be further degraded by the co-culture, while the cyclohexaneacetic acid generated could not be consumed by pure algal cultures or BML inoculum alone. Adding C. kessleri greatly increased the diversity of the microbial community in the BML inoculum; many known hydrocarbon and NA degraders were identified from the 16S rRNA gene sequencing from this co-culture. This more diverse microbial community could have potential for EPL remediation.

Currently, tailings ponds are used to contain oil sands process-affected water (OSPW) and fluid fine tailings (FFT) generated from the Alberta oil sands mining operations. In 2016, the gove...

Laboratory-scale columns were employed to study the effect of oxygen and ionic strength on the transport of Pseudomonas aeruginosa PAO1 in porous media. In anaerobic experiments, cells were grown and transport experiments were conducted in a well-controlled anaerobic chamber. Cell surface electrokinetic potentials were measured and surface elemental composition was analyzed using X-ray photoelectron spectroscopy (XPS). Transport experimental results showed reduced travel distance of PAO1 with increased ionic strength under aerobic and anaerobic conditions, consistent with calculated Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The deposition rates of PAO1 were significantly higher in aerobic than in anaerobic condition at higher ionic strength (10 and 100 mM), although the electrokinetic potentials were similar throughout the tested ionic strength (1, 10, and 100 mM). No difference in PAO1 deposition rate was observed at 1 mM. XPS analysis showed that variation in cell surface composition due to different growth conditions played a primary role in determining the different deposition behaviors.

Biological fixation of CO 2 using microalgae is an effective carbon dioxide capture technology. To make this option economically competitive compared to other CO 2 capture techniques, a better understanding of its dynamic behavior is required. In this study, data generated using a central composite experimental design (CCD) with varying light intensity, CO 2 and phosphate concentration was used to develop a mathematical model that describes the kinetics of algal growth and CO 2 , phosphate, nitrate and ammonium uptake rate of Chlorella kessleri cultivated in oil sands process water (OSPW). The model considers the uncoupling between nutrients uptake and growth and the possibility of luxurious uptake of nutrients. This nonlinear dynamic model was used to determine the optimal CO 2 concentration, phosphate concentration and light intensity for CO 2 uptake and algal growth over a period of time in a batch culture using a multi-objective optimization technique to maximize CO 2 fixation and algal growth simultaneously.

Naphthenic acids (NAs) can be syntrophically metabolized by indigenous microbial communities in pristine sediments beneath oil sands tailings ponds. Syntrophy is an essential determinant of the microbial interactome, however, the interactome network in anaerobic NAs-degrading consortia has not been previously addressed due to complexity and resistance of NAs. To evaluate the impact of electron acceptors on topology of interactome networks, we inferred two microbial interactome networks for anaerobic NAs-degrading consortia under nitrate- and sulfate-reducing conditions. The complexity of the network was higher under sulfate-reducing conditions than nitrate-reducing conditions. Differences in the taxonomic composition between the two modules implies that different potential syntrophic interactions exist in each network. We inferred the presence of the same syntrophic microorganisms, from genera Bellilinea, Longilinea, and Litorilinea, initiating the metabolism in both networks, but within each network, we predicted unique syntrophic associations that have not been reported. Electron acceptor has a large effect on the interactome networks for anaerobic NAs-degrading consortia, offers insight into an unrecognized dimension of these consortia. These results provide a novel approach for exploring potential syntrophic relationships in biodegrading processes to help cost-effectively remove NAs in oil sands tailings ponds.

Accelerating the dewatering of oil sands tailings is a crucial challenge to the oil sands industry. Fresh tailings (15–20% by weight solids) and mature tailings (30–35% by weight solids) de...

The aim of this study is to optimize biological fixation of CO 2 using Chlorella kessleri cultivated in oil sands process water (OSPW). A lab-scale closed raceway photobioreactor was designed and assembled for cultivation of C. kessleri in OSPW. A fed-batch model describing the dynamics of microalgae growth and CO 2 , phosphate and ammonium uptake rate was developed based on batch kinetics identified in our previous study, and was successfully validated against experimental data. A model-based optimization method was used to calculate the optimal feeding strategies for CO 2 , phosphate and light intensity which resulted in a 1.5-fold increase in the final biomass concentration and a 2-fold increase in the average CO 2 uptake rate in 240 h (10 days) compared to the initial fed-batch experiment over 432 h (18 days). Finally, scale-up to large-scale continuous operation was considered, and the optimal hydraulic retention time ( HRT ) and feeding strategy for maximum productivity were estimated.

In this study, the biodegradation of total acid-extractable organics (TAOs), commonly called naphthenic acids (NAs), was investigated. An indigenous microbial culture containing algae and bacteria was taken from the surface of a tailings pond and incubated over the course of 120 days. The influence of light, oxygen and the presence of indigenous algae and bacteria, and a diatom ( Navicula pelliculosa ) on the TAO removal rate were elucidated. The highest biodegradation rate was observed with bacteria growth only (without light exposure) with a half-life ( t 1/2 ) of 203 days. The algae–bacteria consortium enhanced the detoxification process, however, bacterial biomass played the main role in toxicity reduction. Principal component analysis (PCA) conducted on FT-IR spectra, identified functional groups and bonds (representing potential markers for biotransformation of TAOs) as follows: hydroxyl, carboxyl and amide groups along with C H, aryl H, aryl OH and N H bonds.

The influence of solution chemistry on microbial transport was examined using the strictly anaerobic trichloroethene (TCE) bioaugmentation culture KB-1(®). A column was employed to determine transport behaviors and deposition kinetics of three distinct functional species in KB-1(®), Dehalococcoides, Geobacter, and Methanomethylovorans, over a range of ionic strengths under a well-controlled anaerobic condition. A quantitative polymerase chain reaction (qPCR) was utilized to enumerate cell concentration and complementary techniques were implemented to evaluate cell surface electrokinetic potentials. Solution chemistry was found to positively affect the deposition rates, which was consistent with calculated Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies. Retained microbial profiles showed spatially constant colloid deposition rate coefficients, in agreement with classical colloid filtration theory (CFT). It was interesting to note that the three KB-1(®) species displayed similar transport and retention behaviors under the defined experimental conditions despite their different cell electrokinetic properties. A deeper analysis of cell characteristics showed that factors, such as cell size and shape, concentration, and motility were involved in determining adhesion behavior.

Biological fixation of CO 2 using microalgae is an environmentally sustainable option for CO 2 capture. In this study, response surface methodology (RSM) was used to model the CO 2 uptake rate and specific growth rate of Chlorella kessleri , which had been identified previously as a promising strain for CO 2 fixation, cultivated in oil sands process water (OSPW). The quadratic models developed were used to determine the optimal sets of CO 2 concentration, phosphate concentration and light intensity for CO 2 uptake rate and specific growth rate in batch operation. The optimal CO 2 concentration, phosphate concentration and light intensity of 35%, 29 mM and 70 μmol photons m −2 s −1 , respectively, were estimated to maximize the CO 2 uptake rate to 65.03 mg/L/day. Also, the maximum specific growth rate of 0.310 per day was obtained at 22% CO 2 concentration, 29 mM phosphate concentration and 70 μmol photons m −2 s −1 . Finally, a multi-objective optimization technique was used to maximize the CO 2 uptake rate and specific growth rate simultaneously. The optimal Pareto set was found to occur at CO 2 uptake rate of 62.98 mg/L/day and specific growth rate of 0.309 per day at 28% CO 2 , 29 mM phosphate concentration and 70 μmol photons m −2 s −1 light intensity. Thus, each of the optimal conditions correspond to high phosphate concentration and high light intensity in the ranges investigated, while the CO 2 concentration varied between high and intermediate levels in the range investigated.

The Alberta oil sands contain one of the world's largest reserves of oil - over 169 billion barrels of bitumen are economically recoverable with current extraction technologies. Surface mining and subsequent hot water extraction of bitumen from the ore generates about nine cubic meters of raw tailings per cubic meter of oil. Oil sands facilities are required to operate under a policy of zero water discharge, resulting in ponds containing more than one billion cubic meters of tailings, a mixture of sand, fines and process-affected water. Process-affected water contains numerous organic compounds, including naphthenic acids (NAs), which have been identified as the primary source of acute toxicity of process-affected water. Developments in analytical techniques, aerobic biodegradability, and treatment via chemical oxidation (ozone) of NAs are reviewed. The field continues to be challenged by the lack of a cost-effective, accurate analytical technique for NAs or an understanding of all the organic constituents in process-affected water that may be contributing to observed toxicity and thus requiring treatment.

The storage of large volumes of tailings has become an issue for Canada׳s oil sands industry. The use of diluent, along with incomplete bitumen and solvent recovery from the tailings stream, leads to the accumulation of organic compounds within tailings ponds. Volatile organic compounds, reduced sulfur compounds, carbon dioxide, and methane are emitted from tailings outfalls, oily films, bitumen slicks, and mature fine tailings. These emissions are linked to the bitumen extraction and tailings treatment processes, tailings properties (composition, age, residence time), and environmental factors (wind, temperature, rain, and ice cover). Due to limited research in this area, it is difficult to evaluate relationships between emission sources and compounds emitted. To estimate emissions, emission factors based on snapshot measurements, and varying models and assumptions are commonly used. This review presents current knowledge on factors and parameters influencing emission estimates, and challenges pertaining to the development of current emissions factors. Standard emission measurement and calculation methods, vigilant sampling, and increased research are needed to develop a more accurate and representative understanding of emissions from oil sands tailings ponds.

Biological fixation of CO2 using microalgae is a potential CO2 reduction strategy which can be applied to the oil sands operations in Alberta. These operations also produce large amounts of oil sands process water (OSPW), which can act as a growth medium for the microalgae. In this study, three different microalgae: Botryococcus braunii, Chlorella pyrenoidosa and Chlorella kessleri were investigated for their ability to grow in OSPW, and to uptake CO2. Also, the effect of phosphate, nitrate, CO2 concentrations and light intensity were studied using a fractional two-level and a full two-level factorial design. These investigations eliminated Botryococcus braunii as it cannot grow in OSPW, and demonstrated that Chlorella kessleri has a higher CO2 uptake rate than Chlorella pyrenoidosa. Moreover, CO2 concentration, light intensity and phosphate concentration proved to have the strongest effects (in that order) on the growth and CO2 uptake rate of Chlorella kessleri.

In this study, a surrogate of Cryptosporidium parvum oocysts was prepared using Cryptosporidium-sized carboxylated polystyrene microspheres and an alpha-1-acid glycoprotein (AGP). The zeta ...

The long-term storage of oil sands tailings has resulted in the evolution of greenhouse gases (CH 4 and CO 2 ) as a result of residual organics biodegradation. Recent studies have identified black, sulfidic zones below the tailings-water interface, which may be producing toxic sulfur-containing gases. An anaerobic mesocosm study was conducted over an 11-week period to characterize the evolution of CH 4 , CO 2 and reduced sulfur compounds (RSCs) (including H 2 S) in tailings as it relates to naphtha-containing diluent concentrations (0.2, 0.8, and 1.5% w/v) and microbial activity. Our results showed that RSCs were produced first at 0.12 μmol°RSCs/mL MFT (1.5% w/v diluent treatment). RSCs contribution (from highest to lowest) was H 2 S and 2-methylthiophene > 2.5-dimethylthiophene > 3-methylthiophene > thiofuran > butyl mercaptan > carbonyl sulfide, where H 2 S and 2-methylthiophene contributed 81% of the gas produced. CH 4 and CO 2 production occurred after week 5 at 40.7 μmol CH 4 /mL MFT and 5.9 μmol CO 2 /mL MFT (1.5% w/v diluent treatment). The amount of H 2 S and CH 4 generated is correlated to the amount of diluent present and to microbial activity as shown by corresponding increases in sulfate-reducers' Dissimilatory sulfite reductase (DsrAB) gene and methanogens' methyl-coenzyme M reductase (MCR) gene.

The oil sands industry faces significant challenges in developing effective remediation technologies for process-affected water stored in tailings ponds. Naphthenic acids, a complex mixture of cycloaliphatic carboxylic acids, have been of particular concern because they concentrate in tailings ponds and are a component of the acutely toxic fraction of process water. Ozone treatment has been demonstrated as an effective means of rapidly degrading naphthenic acids, reducing process water toxicity, and increasing its biodegradability following seeding with the endogenous process water bacteria. This study is the first to examine subsequent in situ biodegradation following ozone pretreatment. Two aged oil sands process-affected waters from experimental reclamation tailings ponds were ozonated to reduce the dissolved organic carbon, to which naphthenic acids contributed minimally ( −1 ). Treatment with an ozone dose of 50 mg L −1 improved the 84 d biodegradability of remaining dissolved organic carbon during subsequent aerobic incubation (11–13 mg L −1 removed from aged process-affected waters versus 5 mg L −1 when not pretreated with ozone). The ozone-treated indigenous microbial communities were as capable of degrading organic matter as the same community not exposed to ozone. This supports ozonation coupled with biodegradation as an effective and feasible treatment option.

Snow collected from roadways in northern climates is not pristine and may contain sand or gravel, deicing agents, litter, and airborne pollutants. Although fate and transport of contaminants in snowmelt has been studied under laboratory conditions, it is unknown whether the same mechanisms apply to a heterogeneous snow pile. This case study sought to identify and quantify organic species in snow pile meltwater in Edmonton, Canada, and estimate the total potential hydrocarbon loading bound to sediment. Analysis of meltwater and sediment samples revealed that most hydrocarbons were present in sediments, with meltwater containing low concentrations ( C10–C16) and F3 (>C16–C34) fraction hydrocarbons. Sediments showed detectable levels of F2 and F3 hydrocarbons in ∼21% of the samples tested, with concentrations ranging from approximately 600 to 7,800 mg·kg−1, with average F3 concentrations (the main source of hydrocarbons) well below Canadian guidelines for most samples. The estimat...

This review compares the occurrence of pharmaceuticals in Canadian sewage treatment plant (STP) effluents and surface waters (SWs) to those from different countries. The occurrence in Canadian aquatic environments was found to be similar to other countries. The most concentrated drugs in STP effluents were: analgesic drugs, salicylic acid (59.6 μg/L) and naproxen (33.9 μg/L); antibiotics, trimethoprim (3.528 μg/L) and sulphamethoxazole (3.278 μg/L); antidepressants, venlafaxine (0.808 μg/L) and fluoxetine (0.799 μg/L); the antiepileptic and mood-stabilizing drug carbamazepine (3.287 μg/L); a lipid regulator gemfibrozil (2.09 μg/L); and atenolol (a β-blocker) reported at a concentration of 1.68 μg/L. The occurrence of pharmaceuticals in Canadian STPs is likely related to drug consumption and water treatment inefficiencies at the STPs investigated. A similar trend was observed for SWs, but the most concentrated drugs were found at lower concentrations such as salicylic acid (17 μg/L), sulphamethoxazole (0.2...

Cation exchange capacity (CEC) and exchangeable cation composition are important properties in defining water–sediment interactions in contaminant transport scenarios, such as the seepage of process-affected water from oil sands tailings impoundments. At present, detailed characterization of these properties has been overlooked in the surficial Pleistocene sediments of the Athabasca Oil Sands region in Canada. Although a great variety of methods for determining CEC exist and continue to be developed, there is a deficiency in detailed comparisons amongst these methods in the literature, and consequently uncertainty still remains as to which extractants/methods are most suitable for use with sediments containing partially soluble carbonate salts. The present study (1) conducts an up-to-date evaluation of several distinct methods for their suitability in characterizing cation exchange properties in mildly calcareous sediments; using them to (2) evaluate the sorptive capacity and easily displaceable cations of mildly calcareous, surficial sediments near Fort McMurray, Alberta. Four conceptually different CEC methods were chosen: (a) a summation method (Lithium Chloride extractant); (b) a method that displaces an index cation after intermediary washes (Sodium Acetate–Ammonium Acetate); (c) a method using a high affinity cation complex (Silver Thiourea); and (d) a titration method using an organic cationic dye (Methylene Blue). Exchangeable cations were characterized using the Lithium Chloride and Silver Thiourea methods. Analysis suggests that the Methylene Blue test is least impacted by the presence of carbonate mineral phases. Results from field sediments suggest that the exchangeable cations, in decreasing abundance, consist of Ca > Mg > K > NH 4 > Na; while the CEC was found to be 4.7 ± 2.7 meq 100 g −1 in the clay-rich glacial till, 0.7 ± 0.0 meq 100 g −1 in the underlying sand and 4.1 ± 2.3 meq 100 g −1 in the till-sand transition zone.

In Canada, the Athabasca oil sands deposits are a source of bitumen-derived contaminants, reaching the aquatic environment via various natural and anthropogenic pathways. The ecological effects of these contaminants are under debate. To quantify the effects of bitumen-derived contaminants we monitored the aquatic exposure of polycyclic aromatic hydrocarbons (PAHs), metals, and naphthenic acids as well as the invertebrate community in the Athabasca River and its tributaries. PAH concentrations over 3 consecutive years were related to discharge and were highest in the year with high autumn rainfall. In the year with the highest PAH concentrations, these were linked with adverse effects on the aquatic invertebrate communities. We observed relative effects of the composition and concentration of contaminants on the invertebrate fauna. This is reflected by the composition and abundance of invertebrate species via the use of the species' traits “physiological sensitivity” and “generation time”. Applying the SPEAR approach we observed alterations of community structure in terms of an increased physiological sensitivity and a decrease of generation time for the average species. These effects were apparent at concentrations 100 times below the acute sensitivity of the standard test organism Daphnia magna . To rapidly identify oil sands related effects in the field we designed a biological indicator system, SPEAR oil , applicable for future routine monitoring.

Municipal stormwater retention ponds are a means of managing stormwater in urban settings. Numerous contaminants collect in stormwater retention ponds, creating problems such as odor. Because of the complex and variable nature of stormwater quality, a comprehensive study involving both a field study and a laboratory study were accomplished. These two components used a multidisciplinary approach, focused on both water chemistry and microbiological methods to analyze the existing conditions that encourage sulfide production. The field study compared two stormwater retention ponds in terms of water quality and sediment microbial communities in Edmonton, Canada to determine methods to reduce sulfate levels, which are believed to stimulate generation of the toxic hydrogen sulfide. The field study comparison was followed by laboratory studies focused on methods of suppressing sulfide production. Nitrate amendments were found to be effective in suppressing sulfate production; however, the addition of a c...

Remediation of a contaminated site to site-specific cleanup standard requires a good understanding of the geochemical characteristics of the site. In this study, the groundwater hydrochemical characteristics of a fuel-contaminated mine site in the Northwest Territories (Canada) was evaluated to understand the active geochemical processes and assess the groundwater quality in comparison to guidelines for the protection of freshwater aquatic life. Groundwater samples were taken from installed monitoring wells across the site and analyzed by field and laboratory methods for dissolved metals; ions; and benzene, toulene, ethylbenzene, and xylenes (BTEX) organic constituents. The results showed that the groundwater is Ca-SO4 type because of ubiquitous occurrence of gypsum dissolution and carbonate weathering. The last sampling at the site showed that the BTEX constituents of interest were above the guideline limits in some locations, but other geochemical indicators showed biodegradation is occurring at...

The accumulation of organic contaminants in process-affected (PA) water represents an environmental liability for oil sands operators. Oil sands coke is a promising adsorbent for removing dissolved organic carbon (DOC), which includes toxic acid-extractable oil sands tailings organics (AEOSTO) found in PA water. The ability of raw and activated delayed and fluid coke to remove DOC and AEOSTO from PA water was assessed. Treatment with 5 g/L of activated delayed and fluid coke removed 91% of DOC and 92% of AEOSTO at levels of 36 mg/L and 60 mg/L, respectively. Heavy metal leaching of vanadium at 5.9 mg/L was observed for a 5 g/L application of activated delayed coke, representing a challenge to the approach. Microtox testing indicated that higher carbon doses of activated cokes were effective in reducing toxic the biological response caused by organic compounds; however, exposure to heavy metals increased the toxic effect with time. The proposed methodology should be coupled with an inorganic t...

Several million tonnes of oil sands coke are generated each year in Alberta, Canada as a by-product of bitumen upgrading. Due to its high carbon content, oil sands coke can be a suitable precursor for the preparation of activated carbon. In this study, delayed and fluid oil sands coke were physically activated in a muffle furnace under select conditions of activation time (2–6 h), temperature (800–900 °C), steam rate (0.3–0.5 mL/min), and activation atmosphere (CO2, CO2 + steam, and N2 + steam). The activated products were characterized using thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, nitrogen adsorption, iodine and methylene blue tests. An increase in activation time and temperature resulted in higher surface areas in both delayed and fluid coke due to an enhanced etching of pores. An increase in steam rate led to the production of the highest specific surface area (577 m2/g) and iodine number (670 mg/g) within delayed coke; whereas, a lower steam rate resulted in the production of the highest specific surface area (533 m2/g) and iodine number (530 mg/g) in activated fluid coke samples.

In Northern Alberta, the placement of out-of-pit oil sands tailings ponds atop natural buried sand channels is becoming increasingly common. Preliminary modeling of such a site suggests that process-affected (PA) pond water will infiltrate through the underlying clay till aquitard, reaching the sand channel. However, the impact of seepage upon native sediments and groundwater resources is not known. The goal of this study is to investigate the role of adsorption and ion exchange reactions in the clay till and their effect on the attenuation or release of inorganic species. This was evaluated using batch sorption experiments (traditional and a recent modification using less disturbed sediment samples) and geochemical modeling with PHREEQC. The results show that clay till sediments have the capacity to mitigate the high concentrations of ingressing sodium (600 mg L −1 ), with linear sorption partitioning coefficients (K d ) of 0.45 L kg −1 . Ion exchange theory was required to account for all other cation behaviour, precluding the calculation of such coefficients for other species. Qualitative evidence suggests that chloride will behave conservatively, with high concentrations remaining in solution (375 mg L −1 ). As a whole, system behaviour was found to be controlled by a combination of competitive ion exchange, dissolution and precipitation reactions. Observations, supported by PHREEQC simulations, suggest that the influx of PA water will induce the dissolution of pre-existing sulphate salts. Sodium present in the process-affected water will exchange with sediment-bound calcium and magnesium, increasing the divalent ions' pore fluid concentrations, and leading to the precipitation of a calcium–magnesium carbonate mineral phase. Thus, in similar tailings pond settings, particularly if the glacial till coverage is thin or altogether absent, it is reasonable to expect that high concentrations of sodium and chloride will remain in solution, while sulphate concentrations will exceed those of the ingressing plume (150 mg L −1 ).

The impact of cold temperatures on natural attenuation rates is poorly understood and compounded by the lack of published data, particularly under field conditions. This paper presents a collection of data from monitoring and remediation projects completed at cold temperatures. The data set was compiled from 55 studies under anaerobic conditions (46 field and nine laboratory) from sites where groundwater temperatures are typically less than 15 °C. By normalizing the data to +5 and +10 °C, the scatter in rates for BTEX degradation in groundwater was reduced by 33% to 66%. In an attempt to address the paucity of data on natural attenuation rates under cold temperatures, this study has compiled and normalized 101 anaerobic BTEX natural attenuation rates. Eleven of the 55 studies and 43 of the 101 rates presented in this study have not been previously published. Additionally, this study has compiled, for each site, relevant contaminant and hydrogeological information that can be reviewed to choose appropriate rates for preliminary site analysis.

Hydrocarbon-contaminated soil and groundwater at oil and gas production sites may be additionally impacted by salts due to release of produced waters. However, little is known about the effect of salt on the in-situ biodegradation of hydrocarbons by terrestrial microbes, especially at low temperatures. To study this effect, we prepared a groundwater-soil slurry from two sites in Canada: a former flare pit site contaminated with flare pit residue (Site A), and a natural gas processing facility contaminated with natural gas condensate (Site B). The slurry with its indigenous microbes was amended with radiolabeled hydrocarbons dissolved in free product plus nutrients and/or NaCl, and incubated in aerobic biometer flasks with gyrotory shaking at either 25 or 10 degrees C for up to 5 weeks. Cumulative production of (14)CO(2) was measured and the lag time, rate and extent of mineralization were calculated. For Site A, concentrations of NaClor=1% (w/v) delayed the onset of mineralization of both (14)C-hexadecane and (14)C-phenanthrene under nutrient-amended conditions, but once biodegradation began the degradation rates were similar over the range of salt concentrations tested (0-5% NaCl). For Site B, increasing concentrations of NaClor=1% (w/v) increased the lag time and decreased the rate and extent of mineralization of aliphatic and aromatic substrates. Of particular interest is the observation that low concentrations of salt (or=1% NaCl) slightly stimulated mineralization in some cases.