Oil Sands Tailings Research Articles

Kemira may sell oil chemicals unit

Kemira says it has begun a strategic review of its oil and gas chemical activities, including a potential sale of the business. The unit provides chemicals for enhanced oil recovery and the treatment of oil sand tailings. It had sales of about $412 million in 2022. Meanwhile, Clariant has completed the sale of North American Land Oil—its oilfield chemical technologies and services firm—to the Indian specialty chemical firm Dorf Ketal for $14.5 million. The Clariant business generated $115 million in sales last year.

Enhanced accumulation of bitumen residue in a highly concentrated tailings flow by microbubbles from in-situ catalytic decomposition of hydrogen peroxide

The massive volume of oil sands tailings has been one of the most challenging environmental issues. In this work, we experimentally explore a simple and effective approach to bitumen residue separation from a highly concentrated slurry flow of the artificial oil sands tailings. By utilizing microbubbles from in-situ catalytic decomposition of H2O2 at low concentrations, bitumen aggregation is enhanced on the top part of the hydrotransport pipeline. The microscopic image analysis revealed the in-situ formation of microbubbles and confirmed that magnetic particles present in the slurries contributed to the fast release of the gas products and bubble formation from hydrogen peroxide decomposition. A high-speed camera was applied to capture images of the tailings flow in the pipeline through a transparent view window. A large number of tiny bubbles were identified post to the injection of H2O2 to the slurry flow. More than 70 % bitumen could be recovered from a lab-scale pipeline loop within 30 mins after H2O2 injection. The bitumen recovery efficiency from the collected froth was quantitatively compared under seven conditions with varied dosages, the concentration of H2O2, and the amount of magnetic solids in the slurries. Our results confirmed that the total dosage of H2O2 is the dominant factor in in-situ microbubble formation for enhanced bitumen aggregation in the flow. Importantly, microbubbles were generated rapidly in the real mature fine tailings. The results from our study provide insights into the preferential distribution of oil residue in the flow during hydrotransport without the requirement for an additional device. Removal of oily residues from concentrated slurries may bring economical and environmental advantages.

Ageing/thixotropy effects on strength and compressibility in Leda clay and polymer-amended clayey tailings

Evidence of ageing has been reported in natural deposits of sedimentary clays, dredged sediments, and in clay-rich oil sands tailings, and such time-dependent behaviour has been observed to influence their long-term settlement and strength development characteristics. The ageing phenomenon can, therefore, have important implications for the reclamation of such deposits. This research investigated ageing in polymer-amended tailings and Leda clay monitoring relatively small (10 cm high) laboratory samples for over 100 days. Both tailings and natural clay were found to develop increased strength, sensitivity, and higher pre-consolidation pressure and reduced compressibility. The correlation between fall cone shear strengths and pre-consolidation pressures was strong for both the natural clay and the clayey tailings, though this ratio was different in the tailings and the clay. The Leda clay appeared to reabsorb some of its bleed water, which was found to be due to the transition of some free water to absorbed water after 80 days. Using a concept developed from ageing experiments in artificial clays, it was found that shear strengths measured after an “early equilibrium state” correlated strongly with shear strengths measured near the end of ageing. This is promising for quantifying the potential for ageing on compressibility without having to resort to year-long experiments.

A Comprehensive Review of Large Strain Consolidation Testing for Application in Oil Sands Mine Tailings

Oil sand tailings are a mixture of sand, fines, water, and a residual amount of un-extracted bitumen in varying proportions. Tailings management is highly dependent on the consolidation behavior of the tailings. Although a great deal of work on this sector has been performed to study the consolidation behavior of oil sands tailings, it continues to play a critical role in quantifying the long-term geotechnical stability of tailings storage facilities. A review of large strain consolidation testing that exists, whether in the industry or in academia, has been compiled and presented in this manuscript to illustrate the advantages and drawbacks of measuring consolidation behavior of tailings using these tests. For oil sands mine tailings, it has been concluded that the conventional oedometer consolidation test can result in significant errors in quantifying the consolidation behavior. Conversely, testing procedures such as multi-step loading large strain consolidation tests, large slurry consolidometer tests, centrifuge testing, and seepage induced consolidation tests are widely employed to quantify the consolidation behavior of oil sands tailings.

One-dimensional large strain electroosmotic consolidation of ultra-soft geomaterials

Electrokinetic (EK) consolidation has been proven to effectively consolidate ultra-soft geomaterials, such as coal washeries, mine tailings, oil sands tailings and so on. The conventional consolidation model based on the small strain theory encountered difficulties with these geomaterials due to continuous changes in material properties during consolidation. This research developed a one-dimensional large strain EK (LSEK-1D) consolidation model for ultra-soft geomaterials. The model is validated using experimental laboratory results regarding settlements and times on mature fine oil sand tailings (MFT), a major environmental challenge for the oil industry in Northern Alberta, Canada. Moreover, the effects of initial sample heights and applied current densities on consolidation times are evaluated. The experimental data on consolidation times of MFT is consistent with the LSEK-1D model. The LSEK-1D model was used to find the scale effect of drainage path on the EK consolidation behaviour of MFT. The model can also be used for other ultra-soft geomaterials and to facilitate the geotechnical engineering design for EK application.

The filtration of aqueous clay mineral suspension in the presence of bitumen

Typical mine tailings can be dewatered by filter press to filter cakes containing >=85 wt% solids that are ready for reclamation, but Alberta oil sands tailings could only reach about 60 wt% solids using the same technology, even when the dominant particle sizes are similar. In this work, the effects of residual bitumen, one of the distinguishing features of oil sands tailings, were investigated. The residual bitumen in the oil sands tailings exists in the forms of bulk bitumen, emulsified bitumen, and adsorbed bitumen. The roles of the three forms of bitumen were investigated in the filtration of primarily a model mineral kaolinite mineral slurry supplemented by rutile, quartz and montmorillonite slurries. Generally, bulk bitumen was found not to affect filtration significantly, emulsified bitumen facilitated filtration possibly by mopping the ultrafine particles, while bitumen adsorbed on mineral surfaces had more complex effects: a thin bitumen coating improved filtration because of the induced surface hydrophobicity, while a thick bitumen coating impeded filtration due to its mobile and deformable nature. The poor filterability of oil sands tailings may be partly caused by the mobile and deformable bitumen coating on the sands/clay mineral surfaces. This study elucidated the effects of a third deformable organic phase on the filtration of an aqueous mineral slurry, providing insights for solid–liquid separation in the presence of a mobile third phase.

Chemical communication in wood frog (Rana sylvatica) tadpoles is influenced by early-life exposure to naphthenic acid fraction compounds

Environmental pollutants can disrupt chemical communication between aquatic organisms by interfering with the production, transmission, and/or detection of, as well as responses to, chemical cues. Here, we test the hypothesis that early-life exposure to naphthenic acid fraction compounds (NAFCs) from oil sands tailings disrupts antipredator-associated chemical communication in larval amphibians. Wild adult wood frogs (Rana sylvatica) captured during their natural breeding period were combined (1 female:2 males) in six replicate mesocosms filled with either uncontaminated lakewater or with NAFCs isolated from an active tailings pond in Alberta, Canada, at nominal 5 mg/L concentrations. Egg clutches were incubated and tadpoles maintained in their respective mesocosms for ∼40 days post-hatch. Tadpoles (Gosner stage 25-31) were then transferred individually to trial arenas filled with uncontaminated water and exposed to one of six chemical alarm cue (AC) stimuli solutions following a 3 × 2 × 2 design (3 AC types × 2 stimulus carriers × 2 rearing exposure groups). Relative to control tadpoles, NAFC-exposed tadpoles demonstrated higher baseline activity levels (line crosses and direction changes) when introduced to uncontaminated water. Antipredator responses differed in graded fashion with AC type, with control ACs eliciting the greatest latency to resume activity, water the least, and NAFC-exposed ACs intermediate. Pre- to post-stimulus difference scores were non-significant in control tadpoles, while NAFC-exposed tadpoles demonstrated significantly greater variation. While this suggests that exposure to NAFCs from fertilization through hatching may have interfered with AC production, it is unclear whether the quality or quantity of cues was affected. There was also no clear evidence that NAFC carrier water interfered with ACs or the alarm response in unexposed control tadpoles. These results emphasize the importance of understanding how behavioral and physiological effects of early-life NAFC exposure on critical antipredator responses may persist across life history stages.

Application of Tempe Cell to Measure Soil Water Characteristic Curve along with Geotechnical Properties of Oil Sands Tailings

The traditional Tempe cell can be used to adequately determine the soil water characteristic curve (SWCC) for soils that do not undergo significant volume change as matric suction is increased, such as coarse-grained material such as sand with a low air entry value (AEV) (<500 kPa). When soils undergo substantial volume change as soil suction increases, such as fine-grained silts, clays, and oil sands tailings material, the soils need to be tested with distinctly different methods involving two apparatuses when using the Tempe cell. A single-step Tempe cell technique was developed and tested to measure the geotechnical and unsaturated properties of oil sands tailings samples. A series of nine Tempe cells were simultaneously used to measure the geotechnical and unsaturated soil properties of untreated fluid fine tailings (FFT) and treated flocculated centrifuged tailings (FCT). The results of the single-step Tempe cell technique provide several useful engineering functions relating matric suction to water content (SWCC), void ratio (volume change), solids content, and undrained shear strength. Both the traditional and single-step Tempe cell techniques yield comparable SWCC results, but the single-step Tempe cell yields result about three times faster than the traditional Tempe cell. The geotechnical results indicate that both the solids content and undrained shear strength of the FCT are greater than those of the untreated FFT and this indicates that flocculation and centrifugation increase solids content and undrained shear strength of the treated samples. Furthermore, the results indicate that the FFT starts at higher fine void ratio than the FCT and loses more water (volume change) at matric suctions lower than 7 kPa. Beyond 7 kPa, the compressions of both samples become the same. The single-step Tempe cell technique is, however, labor-intensive. The number of Tempe cell can be reduced to six depending on the starting load of the test. The use of the single-step Tempe cell technique in providing fast estimates of SWCC and geotechnical properties for oil sands tailings will be attractive to practitioners who intend to incorporate matric suction in oil sands geotechnical engineering problems.

Computational fluid dynamics investigation of bitumen residues in oil sands tailings transport in an industrial horizontal pipe

Pipeline transport is commonly used in the oil sand industry to convey crushed oil sand ores and tailings. Bitumen residues in the oil sand tailings can be a threat to the environment that separating them from tailings before disposal is crucial. However, low bitumen concentration in the tailing slurry and the complex transport characteristics of the four-phase mixture make the process difficult. This study establishes an Eulerian–Eulerian (E–E) computational fluid dynamics model for an industrial-scale oil sand tailings pipeline. A comprehensive sensitivity analysis was conducted on the selection of carrier-solid and solid-bitumen drag models. The combination of small and large particle sizes (i.e., 75 and 700 μm) and bitumen droplet size (i.e., 400 μm) provided good agreement with field data in velocity profiles and pressure drop. The validated model was subsequently extended to investigate the influence of the secondary phase (i.e., bitumen droplets and bubbles) on flow characteristics in a tailing pipeline. The investigation covered a range of bitumen droplet size (100–400 μm), bitumen fraction (0.0025–0.1), bubble size (5–1000 μm), and bubble fraction (0.0025–0.3) and their influences on the velocity, solids, and bitumen distribution are revealed. For an optimum bubble size of 500 μm, a maximum recovery of 59% from the top 50% and 83% from the top 75% of the pipe cross section was obtained. The present study demonstrates the preferential distribution of bitumen and provides valuable insight into bitumen recovery from an industrial-scale tailing pipeline.

Root hypoxia aggravates the effects of saline tailings water on the growth and physiology of woody plants

AimsOil sands mining in the boreal forest produces large volumes of liquid tailings. Forestry research has generally focused on the thickness and composition of the soil layers to be placed on top of the tailings during reclamation. However, tailings release water, which may seep into the root zone and affect plants. Furthermore, the interactions and combined effects of root hypoxia and root substrate chemistry on plant responses are poorly understood.MethodsThe effects of the aqueous phase of novel tailings (Non-Segregating Tailings—NST) were studied under well-aerated and hypoxic conditions in three relatively waterlogging tolerant tree species [tamarack (Larix laricina), black spruce (Picea mariana), and balsam poplar (Populus balsamifera)] and three relatively sensitive tree species [lodgepole pine (Pinus contorta), jack pine (Pinus banksiana), and aspen (Populus tremuloides)] by growing them in hydroponic solutions in a controlled environment.ResultsRoot hypoxic conditions further reduced the survival, growth, and physiology of plants exposed to NST. Our results confirm that NST water produces the same deleterious effects in plants as previously reported in the amalgamated oil sands tailings. Root hypoxia inhibited salt sequestration in trembling aspen and may have inhibited an osmoregulative mechanism in black spruce needles.ConclusionsOur results highlight the potential impact of water seepage from buried tailings on reclamation success. Furthermore, hypoxic conditions can aggravate these effects by inhibiting salt stress mechanisms. We suggest that the preparation of reclamation sites impacted by tailings water should involve efforts to enhance soil aeration to minimize the detrimental effects on plants.

Mitigating methane emission from oil sands tailings using enzymatic and lime treatments

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 CH4 production (by 52%, 28%, and 25%, respectively) and were weakly associated with the archaeal abundance. Enzymes treatment resulted in a higher reduction in CH4 production compared with lime treatment. A 3% lysozyme treatment suppressed CH4 production (the change in methane was 0.48 mmol) and reduced the degradation of hexane throughout the experiment. Similarly, 3% protease suppressed CH4 production throughout the experiment (the change in methane was 0.78 mmol), which could be attributed to the pH reduction to pH 4.9 at week 23 resulting from the formation of volatile fatty acids. Another possible mechanism could be the formation of toxic compounds, such as high nitrogen content, after protease treatment that inhibited the microbial community. The toxicity effect to Vibrio fischeri was greater with lysozyme 3% and protease 3% treatment than with lime treatment (124 TU and 76 TU, respectively). Lime treatment resulted in the highest reduction in 16S rRNA gene copies from 5.7 × 106 cells g−1 (control) to 2.7 × 105, 1.71 × 105, and 1.4 × 105 cells g−1 for 1600, 3500, and 5000 ppm treatments, respectively. This study supports further work to examine and determine the optimum conditions (e.g., enzyme and lime dosages) for CH4 inhibition.

Understanding the evolution of oil sands tailings deposits using tritium-helium dating and noble gases

Oil sands tailings are deposited in tailings ponds to allow fines to settle over time. Knowledge of the age of tailings allows for an improved determination of the settling rates of tailings as well as an understanding of geochemical processes within the tailings ponds. In this study we tested the use of the tritium (3H) – helium (3He) age dating method to date pore water of oil sands tailings deposits. This method exploits the decay of naturally occurring 3H and its radioactive daughter product 3He to calculate the ages of tailings. Samples were collected from four oil sands tailings ponds. Many of the samples have noble gas concentrations that were below the air equilibrated water concentrations and some samples were supersaturated in methane (CH4). The concentrations are interpreted to be lower than expected as a result of stripping by the production of CH4. When samples supersaturated in CH4 are excluded, the calculated ages of Pond A samples ranged from 1.5 ± 0.1 to 32.0 ± 0.9 years, Pond B ranged from 5.3 ± 0.3 to 23.0 ± 0.8 years, Pond C ranged from 0 ± 0 to 6.5 ± 0.3 years, and Pond D ranged from 16.6 ± 0.6 to 27.3 ± 0.8. The tailings samples obtained from Pond A, Pond C and Pond D show a general trend of increasing tailings age with depth.

The last 25 years of research on bioflocculants for kaolin flocculation with recent trends and technical challenges for the future.

The generation of kaolin-containing wastewater is an inevitable consequence in a number of industries including mining, wastewater treatment, and bitumen processing. In some cases, the production of kaolin tailings waste during the production of bitumen or phosphate is as high as 3 times greater than the actual produced product. The existing inventory of nearly five billion barrels of oil sands tailings alone represents a massive storage and reclamation challenge, as well as a significant economic and environmental liability. Current reclamation options like inorganic coagulants and organic synthetic polymers may settle kaolin effectively, but may themselves pose an additional environmental hazard. Bioflocculants are an emerging alternative, given the inherent safety and biodegradability of their bio-based compositions. This review summarizes the different research attempts towards a better bioflocculant of kaolin, with a focus on the bioflocculant source, composition, and effective flocculating conditions. Bacillus bacteria were the most prevalent single species for bioflocculant production, with wastewater also hosting a large number of bioflocculant-producing microorganisms while serving as an inexpensive nutrient. Effective kaolin flocculation could be obtained over a broad range of pH values (1-12) and temperatures (5-95°C). Uronic acid and glutamic acid were predominant sugars and amino acids, respectively, in a number of effective bioflocculants, potentially due to their structural and charge similarities to effective synthetic polymers like polyacrylamide. Overall, these results demonstrate that bioflocculants can be produced from a wide range of microorganisms, can be composed of polysaccharides, protein or glycoproteins and can serve as effective treatment options for kaolin. In some cases, the next obstacle to their wide-spread application is scaling to industrially relevant volumes and their deployment strategies.

A real time in situ light-scattering technique for tailings solids content measurement: Near-infrared versus visible wavelengths

Optical scattering can be potentially used to develop an effective solids content measurement tool for tailings ponds monitoring and management. This bench-scale study investigated suitable laser wavelengths in both visible (405, 520 and 658 nm) and near infrared (980, 1310 and 1550 nm) ranges for real time in situ application in oil sands tailings. In general, the near infrared wavelengths demonstrated higher sensitivity over the entire test range compared to the visible wavelengths. Furthermore, residual bitumen in oil sands tailings tended to absorb the visible wavelengths, which interfered with the scattering light signals, leading to inaccurate measurements. Due to a sufficiently strong water absorption, the 1550 nm wavelength in particular showed an almost linear sensitivity of the light scattering with the change in solids concentration with a 1.5% accuracy and was able to overcome the effects of the variation in the physical and chemical properties of the samples including particle size distributions. Conveniently, the absorption was not strong enough to generate noise in the measurement caused by atmospheric moisture. The 1550 nm wavelength was identified as a promising candidate for the light scattering-based solids content analyzer for real time in situ tailings ponds monitoring. • Light scattering technique for real time in situ solids content measurement. • Investigate wavelengths from visible to near infrared. • 1550 nm wavelength demonstrated sensitivity to better than 2 percent level. • 1550 nm wavelength mitigates bitumen fouling effects in oil sands tailing applications.

Aerobic degradation of anionic polyacrylamide in oil sands tailings: Impact factor, degradation effect, and mechanism

An investigation was carried out to study the degradation of anionic polyacrylamide (A-PAM) under different temperature and microorganism conditions as well as to assess its effects on water chemistry and toxicity in oil sands tailings. The maximum removal efficiency of A-PAM was 41.0 % in tailings water with augmented microorganisms at 20 °C. No acrylamide (AMD) monomer was released during the A-PAM degradation, while residual AMD, from the manufacturing process to make A-PAM, was completely removed within 4 weeks. Both temperature and microorganisms showed significant effects (p < 0.05) on the degradation of A-PAM and residual AMD. Gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) analyses showed that biodegradation could be the active pathway for A-PAM degradation in oil sands tailings. These analyses also indicated that macromolecular A-PAM was degraded into lower molecular weight organic compounds. No remarkable changes of the total concentration of naphthenic acids (NAs) were observed in A-PAM treated tailings water. However, low concentrations of fatty acids (<2.5 mg/L), which fit the NAs formula, were detected in pure polymer solution, indicating that A-PAM degradation would not affect the total concentration of NAs in tailings water but affect their distribution. Our results also showed that total organic carbon (TOC) and chemical oxygen demand (COD) could be used as indicators of A-PAM degradation in tailings water due to their strong linear correlations (R2 > 0.90). Only slight increases in zeta potential and pH were found during A-PAM degradation. Limited effect on acute toxicity and no genotoxicity were found in A-PAM treated tailings water. Furthermore, the results suggest that A-PAM undergoes hydrolysis of amide groups by amidase enzymes, releasing ammonia and smaller molecules like organic acids. This research provides valuable information regarding the stability and impacts of A-PAM and thus will be beneficial for the management of oil sands tailings in long period of time.

Undrained shearing behaviour of oil sands tailings

The instability of coarse oil sands tailings (CST) is investigated in this study by conducting a series of monotonic direct simple shear tests. Laboratory specimens were prepared using moist-tamping, dry deposition, and slurry deposition techniques to investigate the effect of sample reconstitution method and tailings fabric on CST's instability behaviour. CST specimens were then subjected to constant volume (CV), and constant vertical stress (drained) shearing at three different consolidated relative densities corresponding to loose, medium-dense, and dense conditions. The effects of consolidation vertical stress and void ratio on the instability and post-liquefaction strength of the CST specimens were examined. Shear wave velocity (VS) of the specimens were also measured using a pair of bender elements attached to the top and bottom caps of the simple shearing apparatus. The VS measurements were subsequently used to establish practical relationships with undrained strength ratios and yield friction angle of CST.

Cation Exchange in Smectites as a New Approach to Mineral Carbonation

Mineral carbonation of alkaline mine residues is a carbon dioxide removal (CDR) strategy that can be employed by the mining industry. Here, we describe the mineralogy and reactivity of processed kimberlites and kimberlite ore from Venetia (South Africa) and Gahcho Kué (Canada) diamond mines, which are smectite-rich (2.3–44.1 wt.%). Whereas, serpentines, olivines, hydrotalcites and brucite have been traditionally used for mineral carbonation, little is known about the reactivity of smectites to CO2. The smectite from both mines is distributed as a fine-matrix and is saponite, Mx/mm+Mg3(AlxSi4−x)O10(OH)2·nH2O, where the layer charge deficiency is balanced by labile, hydrated interlayer cations (Mm+). A positive correlation between cation exchange capacity and saponite content indicates that smectite is the most reactive phase within these ultramafic rocks and that it can be used as a source of labile Mg2+ and Ca2+ for carbonation reactions. Our work shows that smectites provide the fast reactivity of kimberlite to CO2 in the absence of the highly reactive mineral brucite [Mg(OH)2]. It opens up the possibility of using other, previously inaccessible rock types for mineral carbonation including tailings from smectite-rich sediment-hosted metal deposits and oil sands tailings. We present a decision tree for accelerated mineral carbonation at mines based on this revised understanding of mineralogical controls on carbonation potential.

Understanding Willow Transcriptional Response in the Context of Oil Sands Tailings Reclamation.

One of the reclamation objectives for treated oil sands tailings (OST) is to establish boreal forest communities that can integrate with the surrounding area. Hence, selection of appropriate soil reclamation cover designs and plant species for revegetation are important aspects of tailings landform reclamation and closure. Research and monitoring of the long term and immediate impacts of capped OST on the growth and survival of native boreal plant species are currently underway. However, plant responses to OST-associated toxicity are not well known at the molecular level. Using RNA sequencing, we examined the effects of three types of OST on the willow transcriptome under different capping strategies. The transcriptomic data showed that some genes respond universally and others in a specific manner to different types of OST. Among the dominant and shared upregulated genes, we found some encoding protein detoxification (PD), Cytochrome P450 (CYPs), glutathione S-transferase regulatory process (GST), UDP-glycosyltransferase (UGT), and ABC transporter and regulatory process associated proteins. Moreover, genes encoding several stress-responsive transcription factors (bZIP, BHLH, ERF, MYB, NAC, WRKY) were upregulated with OST-exposure, while high numbers of transcripts related to photosynthetic activity and chloroplast structure and function were downregulated. Overall, the expression of 40 genes was found consistent across all tailings types and capping strategies. The qPCR analysis of a subset of these shared genes suggested that they could reliably distinguish plants exposed to different OST associated stress. Our results indicated that it is possible to develop OST stress exposure biosensors merely based on changes in the level of expression of a relatively small set of genes. The outcomes of this study will further guide optimization of OST capping and revegetation technology by using knowledge based plant stress adaptation strategies.

Fathead Minnows Exposed to Organic Compounds from Oil Sands Tailings as Embryos Have Reduced Survival, Impaired Development, and Altered Behaviors That Persist into Larval Stages.

Our study evaluated whether exposure to naphthenic acid fraction compounds (NAFCs) extracted from oil sands process–affected waters (OSPW) has adverse effects on fish embryos that persist into later life. We exposed fathead minnow (Pimephales promelas) embryos to concentrations of NAFCs found in OSPW (2.5–54 mg/L) for 7 days (1 day postfertilization to hatch), then raised surviving larvae in outdoor mesocosms of uncontaminated lake water for 1 month. Embryos exposed to NAFCs were more likely to exhibit malformations (by up to 8‐fold) and had slower heart rates (by up to 24%) compared to controls. Fish raised in uncontaminated lake water following exposure to NAFCs as embryos, were 2.5‐fold less likely to survive during the larval stage than control fish. These fish also showed up to a 45% decrease in swim activity and a 36% increase in swim burst events during behavioral tests relative to controls. We conclude that exposure to NAFCs during the embryonic stage can have lasting effects on fish survival, physiology, and behavior that persist at least through the larval stage. These findings of delayed mortalities and persistent sublethal effects of embryonic NAFC exposure are relevant to informing the development of regulations on treated OSPW releases from mining operations. Environ Toxicol Chem 2022;41:1319–1332. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Enhanced Settling and Dewatering of Oil Sands Mature Fine Tailings with Titanomagnetite Nanoparticles Grafted with Polyacrylamide and Lauryl Sulfate

In this study, a three-in-one nanoflocculent that consists of nanoparticles of titanomagnetite (NTM) grafted with multiple segments of hydrophobically modified chains of polyacrylamide (PAM) with sodium laurel sulfate (SLS) was developed for enhanced settling and dewatering of oil sands mature fine tailings (MFT). The existence of NTM allowed more than one segment to graft/functionalize (i.e., hydrophobic and hydrophilic) on the same surface. This three-in-one nanoflocculent not only provides better exposure for the functionalized species, but it also increases the nanoflocculant specific gravity and dispersibility for better interactions. The NTM was initially synthesized by the coprecipitation method and subsequently grafted with PAM and SLS at room conditions. The flocculation and dewatering performance of the as-synthesized nanoflocculants was evaluated using the initial settling rate (ISR), supernatant turbidity, sludge volume index, capillary suction time (CST), and specific resistance to filtration (SRF). Flocculation of the MFT suspension using the novel optimized nanoflocculants at 3000 ppm had 15 times faster ISR, and the supernatant turbidity, CST, and SRF had stronger outcomes than the traditionally used 20,000 ppm commercial anionic PAM. This study demonstrates the potential of designing nanoflocculants to effectively enhance settling and dewatering of oil sands tailings, while reducing the required amount of coagulants.