Tailings Pond Water Research Articles

The Use of Stable Isotopes (13C/12C and 15N/14N) to Trace Exposure to Oil Sands Processed Material in the Alberta Oil Sands Region

Various oil sands reclamation strategies incorporate oil sands processed material (OSPM) such as mature fine tailings (MFT), engineered tailings (consolidated tailings, CT), and tailings pond water (TPW) into reclamation components that need to develop into viable aquatic ecosystems. The OSPM will contain elevated salinity and organics such as naphthenic acids (NA) and polycyclic aromatic compounds (PAC) that can be chronically toxic to aquatic organisms depending upon levels and age. Due to the complexity of the chemical mixtures, analysis of these compounds in exposed organisms can be challenging. In this study, the stable carbon and nitrogen isotope signatures of selected invertebrates from various types of oil sands reclamation sites were analyzed to determine whether stable isotopes can be used to trace the exposure of aquatic organisms to organic constituents of OSPM. In a series of experimental reclamation ponds of similar age and size, there were trends of 13C depletion and 15N enrichment for benthic invertebrates along a gradient of increased levels of MFT and/or TPW. A survey of 16 sites revealed high δ15N values for invertebrates in aquatic systems containing MFT and CT (gypsum-treated mixes of MFT and tailings sand), which was attributed to the presence of NH4 +, a process by-product in OSPM. Findings of this study indicate a potential for the use of stable nitrogen isotopes to define exposure of biota to OSPM during environmental effects monitoring programs both in surface waters and in cases where groundwater seepage containing oil sands processed water enters surface receiving environments in the region.

Process water treatment in Canada’s oil sands industry: I. Target pollutants and treatment objectives

Process water treatment has become a critical issue for Canada’s oil sands industry. Continuous recycling of tailings pond water (TPW) has contributed to a decline in water quality that has consequences for bitumen recovery, water consumption, and reclamation efforts. Potential roles for water treatment were assessed through a review of process water quality and toxicity data from two long-term oil sands operations. Target pollutants were identified according to exceedances of environmental and industrial water quality guidelines. From 1980 to 2001, the salinity of TPW increased at a rate of 75 mg/L per year. Recent increases in hardness, sulphate, chloride, and ammonia have raised concerns over scaling and corrosion. Naphthenic acids released during bitumen extraction are the primary source of toxicity in TPW. Biodegradation of naphthenic acids has been demonstrated in pond experiments;; however, recalcitrant compounds may contribute to chronic toxicity in reclaimed environments. Water treatment objectives established in this review provide benchmarks for the selection of candidate water treatment technologies.

Phytotoxicity of oil sands naphthenic acids and dissipation from systems planted with emergent aquatic macrophytes

Differences in dissipation and phytotoxicity were measured for two naphthenic acid mixtures in hydroponically grown emergent macrophytes (Typha latifolia, Phragmites australis, and Scirpus acutus). One of the naphthenic acid (NA) mixtures was extracted from tailings pond water of an oil sands operation in Fort McMurray, Alberta, Canada. The other mixture was a commercially available NA mixture. While the oil sands NA mixture was less phytotoxic to wetland plants compared to the commercially available NA mixture, they were not sequestered by wetland plants like their commercial NA counterparts. The small loss of commercial NAs from the spiked hydroponic system appeared to be selective and dependant on the specific NA compound. The results of this study indicate that plants alone may not mitigate NAs from oil sands tailings pond water. In addition, caution should be taken when making predictions on the environmental fate of oil sands naphthenic acids when using commercial NAs as surrogates.

Diethylaminoethyl-cellulose clean-up of a large volume naphthenic acid extract

The Athabasca oil sands of Alberta, Canada contain an estimated 174 billion barrels of bitumen. During oil sands refining processes, an extraction tailings mixture is produced that has been reported as toxic to aquatic organisms and is therefore collected in settling ponds on site. Investigation into the toxicity of these tailings pond waters has identified naphthenic acids (NAs) and their sodium salts as the major toxic components, and a multi-year study has been initiated to identify the principal toxic components within NA mixtures. Future toxicity studies require a large volume of a NA mixture, however, a well-defined bulk extraction technique is not available. This study investigated the use of a weak anion exchanger, diethylaminoethyl-cellulose (DEAE-cellulose), to remove humic-like material present after collecting the organic acid fraction of oil sands tailings pond water. The NA extraction and clean-up procedure proved to be a fast and efficient method to process large volumes of tailings pond water, providing an extraction efficiency of 41.2%. The resulting concentrated NA solution had a composition that differed somewhat from oil sands fresh tailings, with a reduction in the abundance of lower molecular weight NAs being the most significant difference. This reduction was mainly due to the initial acidification of tailings pond water. The DEAE-cellulose treatment had only a minor effect on the NA concentration, no noticeable effect on the NA fingerprint, and no significant effect on the mixture toxicity towards Vibrio fischeri.

Mass spectrometric and toxicological assays of Athabasca oil sands naphthenic acids

This work concerns the analysis of model naphthenic acids and authentic naphthenic acids from the tailings ponds of the Athabasca tar sands. A first objective was to compare atmospheric pressure chemical ionization mass spectrometry (APCI–MS) with the previously studied electrospray mass spectrometry (ESI–MS) in this analysis. APCI–MS had a wider range of quantitation than ESI–MS, but its detection limit was poorer and model compounds showed greater variation in calibration sensitivity. A second objective was fractionation of naphthenic acids from tailings pond water and analysis by the Microtox ® toxicity assay. Fractionation on the basis of solubility gave fractions that did not differ significantly either in their congener distribution by ESI–MS or in their response to the Microtox assay. When partial separation was achieved by anion exchange chromatography, fractions with a higher proportion of multi-ring structures exhibited lower toxic potency. This finding is consistent with field observations that indicate that the toxic potency of tailings ponds water declines as the samples age—multi-ring structures are more highly branched and therefore more resistant to microbial degradation.

In Situ Bioremediation of Naphthenic Acids Contaminated Tailing Pond Waters in the Athabasca Oil Sands Region—Demonstrated Field Studies and Plausible Options: A Review

Currently, there are three industrial plants that recover oil from the lower Athabasca oil sands area, and there are plans in the future for several additional mines. The extraction procedures produce large volumes of slurry wastes contaminated with naphthenic acids (NAs). Because of a “zero discharge” policy the oil sands companies do not release any extraction wastes from their leases. The process-affected waters and fluid tailings contaminated with NAs are contained on-site primarily in large settling ponds. These fluid wastes from the tailing ponds can be acutely and chronically toxic to aquatic organisms, and NAs have been associated with this toxicity. The huge tailings containment area must ultimately be reclaimed, and this is of major concern to the oil sands industry. Some reclamation options have been investigated by both pioneering industries (Syncrude Energy Inc. and Suncor Inc.) with mixed results. The bioremediation techniques have limited success to date in biodegrading NAs to levels below 19 mg/L. Some tailing pond waters have been stored for more than 10 years, and it appears that the remaining high molecular weight NAs are refractory to the natural biodegradation process in the ponds. Some plausible options to further degrade the NAs in the tailings pond water include: bioaugmentation with bacteria selected to degrade the more refractory classes of NAs; the use of attachment materials such as clays to concentrate both the NA and the NA-degrading bacteria in their surfaces and/or pores; synergistic association between algae and bacteria consortia to promote efficient aerobic degradation; and biostimulation with nutrients to promote the growth and activity of the microorganisms.

Spray freezing treatment of water from oil sands tailing ponds

Tailings pond water produced from the extraction of bitumen from the oil sands in Northern Alberta, Canada, was treated using the spray freezing process. The wastewater was frozen by spraying at –10°C and –24°C ambient temperatures. The effect of the degree of freezing (i.e., freezing with and without runoff generation) of the sprayed water on the treatment efficiency, the concentration, and distribution of the impurities within the ice columns was examined. When the sprayed water only partially froze (i.e., freezing with runoff formation), the treatment efficiency (measured by reduction in COD, TOC, conductivity, Cl–, SO42– concentrations) was higher and larger volumes of high quality meltwater was obtained. Reduction of toxicity (Microtox) in meltwater, and the relationship between the overall impurity removal and toxicity reduction was also examined in this study. The decay coefficients were determined for prediction of meltwater impurity concentrations using mathematical models.Key words: spray freezing, wastewater treatment, oil sands tailings pond, toxicity reduction.

Isolation and characterization of naphthenic acids from Athabasca oil sands tailings pond water.

A laboratory bench procedure was developed to efficiently extract naphthenic acids from bulk volumes of Athabasca oil sands tailings pond water (TPW) for use in mammalian oral toxicity testing. This solvent-based procedure involved low solvent losses and a good extraction yield with low levels of impurities. Importantly, labour-intensive centrifugation of source water to remove solids was avoided, allowing processing of much larger volumes of water compared with previous protocols. Naphthenic acids, present at an estimated concentration of 81 mg/l, were procured from 515.5 l of TPW at an overall extraction efficiency of approximately 85%. By using distillation to recover and recycle solvent, a high solvent:water ratio was maintained while actual solvent consumption was limited to 70 ml per liter of water processed. Electrospray ionization mass spectrometry suggested a highly heterogeneous naphthenic acid mixture that exhibited nearly identical proportions of monocyclic, polycyclic, and acyclic acids with molecular weights primarily between 220 and 360. Biphenyls, naphthalenes, and phenanthrene/anthracene were the most prominent impurities detected, but their levels were low (< or = 13 microg/l) even in a concentrated solution of the naphthenic acids (8549 mg/l). Naphthenic acids stored at 4 degrees C at this concentration were stable, exhibiting no significant change in concentration over a 10-month period. This bulk isolation procedure should be useful to others needing to process large volumes of tailings or other source water for the purpose of procuring moderate amounts of naphthenic acids.

Acute and Subchronic Mammalian Toxicity of Naphthenic Acids from Oil Sands Tailings

Naphthenic acids are the most significant environmental contaminants resulting from petroleum extraction from oil sands deposits. In this study, a mixture of naphthenic acids isolated from Athabasca oil sands (AOS) tailings pond water was used in acute and subchronic toxicity tests with rodents, in order to assess potential risks posed to terrestrial wildlife. Dosages were chosen to bracket worst-case environmental exposure scenarios. In acute tests, adult female Wistar rats were given single po dosages of naphthenic acids at either 3, 30, or 300 mg per kg body weight (mg/kg), while adult male rats received 300 mg/kg. Food consumption was temporarily suppressed in the high-dose groups of both sexes. Following euthanasia 14 days later, histopathology revealed a significant incidence of pericholangitis in the high-dose group of both sexes, suggesting hepatotoxicity as an acute effect. Other histological lesions included brain hemorrhage in high-dose males, and cardiac periarteriolar necrosis and fibrosis in female rats. In subchronic tests, naphthenic acids were po administered to female Wistar rats at 0.6, 6, or 60 mg/kg, 5 days per week for 90 days. Results again suggested the liver as a potential target organ. The relative liver weight in the high-dose group was 35% higher than in controls. Biochemical analysis revealed elevated blood amylase (30% above controls) and hypocholesterolemia (43% below controls) in high-dose rats. Excessive hepatic glycogen accumulation was observed in 42% of animals in this group. These results indicate that, under worst-case exposure conditions, acute toxicity is unlikely in wild mammals exposed to naphthenic acids in AOS tailings pond water, but repeated exposure may have adverse health effects.

Reproductive, immune, and physiological end points in tree swallows on reclaimed oil sands mine sites

AbstractWild nestling tree swallows (Tachycineta bicolor) inhabiting reclaimed wetlands receiving tailings or water from mine tailings ponds on oil sands mine sites were the subjects in a multiyear study to determine the ecological viability of these areas. Spanning two field seasons, immune function, reproductive performance (clutch size and mass, hatching success), nestling growth and survival, and diet of tree swallows were examined on six wetlands. One aspect of immune function, the T‐lymphocyte proliferative response, was assessed in vivo using a phytohemagglutinin skin test. Hepatic ethoxyresorufin‐O ‐deethylase (EROD) activityprovided a biomarker of exposure to oil sands contaminants in the tree swallow nestlings. Results show that there were no differences among reclaimed wetland sites for tree swallow reproductive success, nestling growth rate, and immune response that could be attributed to tailings or tailings pond water additions. Increased EROD activity confirmed the presence of xenobiotics in the diets of nestlings from two sites, while the main reference site was relatively free of EROD‐inducing compounds. Dietary analyses showed that 84% of the food items of the tree swallow nestlings were of aquatic origin, likely from the local wetlands, and thus would be expected to provide a good reflection of biological effects of any mining‐related contaminants accumulating through the food chain.

Growth of fathead minnows in oilsand‐processed wastewater in laboratory and field

AbstractTwo waste products of Syncrude Canada Ltd. (SCL) oilsands mine are mature fine tailings (MFT), a toxic aqueous suspension of particles, organic acids, bitumen, and metals, and tailings pond water (TPW), a saline solution containing organic and inorganic contaminants. The chemical profiles of MFT interstitial water and TPW are very similar. Syncrude Canada has proposed disposing of MFT in constructed lakes, which would be lined with MFT and capped with clean water. As the MFT consolidates, MFT‐associated water would be released into the overlying watercap. Prototype ponds support fathead minnows (Pimephales promelas), but the long‐term viability of these populations is unknown. This study attempts to determine if exposure to MFT and TPW, a related waste product, affected growth of fathead minnow larvae in the laboratory and field. Laboratory larval growth bioassays (7 and 56 d) on whole effluent from numerous prototype ponds yielded no significant differences in dry weight, but one 7‐d bioassay showed reduced survival in two SCL sites. A 56‐d growth bioassay showed significant increases in length of fish exposed to SCL wastewater at 7 d but not at 28 or 56 d. Larvae exposed as embryos and then introduced into field mesocosms did display significant differences in dry weight. In this instance, fish exposed to wastewater were significantly larger during the laboratory portion of the test (initial), but after 21 d in a field mesocosm (final), they were similar in size or smaller than fish growing in nonprocessed water.

Residuary Toxic Elements And PAHs in Sediments of the Zbiornik Gilow Tailings Pond and Zimmica Stream from Lubin District, Southwest Poland

Eight selected elements (As, Cd, Co, Cu, Pb, Zn, Cr and Ni) were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) in five samples from the tailings pond (Zbiornik Gilow) and waste water stream (Zimmica) in the Kupferschiefer mining district in Southwest Poland. Waste water from mining and concentration plants was discharged into Zbiornik Gilow pond for 30 years before 1989. Below Zbiornik Gilow the water flows through Zimmica stream, and then discharges into the River Odra. The analytic results indicate that the contamination of As, Cd, Co, Cu, Pb and Zn has spread out over 5 km, and the contamination by Ni and Cr extends for 1.5 km along the Zimmica stream although the stream has been abandoned since 1989. These elements could still be toxic for plants, animals and humans. Polycyclic aromatic hydrocarbons (PAHs) were determined by GC and GC/MS. The results of the sediment samples show a contamination of PAHs only in trace contents.

Distribution of selected elements and PAH in freshly deposited sediments of waste water streams from Lubin district, Southwest Poland

Nine selected elements (Cu, Pb, As, Zn, Co, Ni, Cr, Cd and Fe) were determined by inductively coupled plasma atomic emission spectroscopy in 15 samples from the tailings pond (Zelazny Most) and waste water streams (Moskorzynke and Rudna) in the Kupferschiefer mining district in Southwest Poland. Waste water from mining and industry enter the Zelazny Most pond. The water then flows through Moskorzynke and Rudna streams, and discharges into the River Odra. The analytic results indicate that the contamination with Cu, Pb, Zn, As, Co, Cd and Fe extend about 6 km along the streams in contrast to the non‐polluted samples close the River Odra. Their concentrations reach a level, which could be toxic for plants, animals and humans. The contamination with Ni and Cr continued at least 20 km along Rudna stream. Besides mechanical transport, redox conditions and Corg contents also played an important role for trace element and Fe contamination in Rudna stream. The samples with high Corg contents have also high contents of trace metals. In Moskorzynke stream the element contamination was mainly caused by mechanical transport of particles. Polyaromatic hydrocarbon (PAH), which is abundant in Kupferschiefer, is toxic for animals and humans. The PAH concentration in the stream sediments was determined by GC and GC/MS. The results indicate that the contamination of PAH reaches 6 and 17 mg kg−1 in samples TP1 and RS6, respectively. In the other samples, the PAH contents are lower than 3 mg kg−1. Some PAH could be solved by waste water in the tailings pond and migrated to the stream sediments. Some PAH might be contained in particles which were transported mechanically from the tailings pond into stream sediments.

Factors that affect the degradation of naphthenic acids in oil sands wastewater by indigenous microbial communities

AbstractThe acute toxicity of wastewater generated during the extraction of bitumen from oil sands is believed to be due to naphthenic acids (NAs). To determine the factors that affect the rate of degradation of representative NAs in microcosms containing wastewater and the acute toxicity of treated and untreated wastewater, the effects of temperature, dissolved oxygen concentration, and phosphate addition on the rate of 14CO2 release from two representative naphthenic acid substrates, (linear) U‐14C‐palmitic acid (PA) and (bicyclic) decahydro‐2‐naphthoic acid‐8‐14C (DHNA), were monitored. Tailings pond water (TPW) contained microorganisms well adapted to mineralizing both PA and DHNA: PA was degraded more quickly (10–15% in 4 weeks) compared to DHNA (2–4% in 8 weeks). On addition of phosphate, the rate of NA degradation increased up to twofold in the first 4 weeks, with a concurrent increase in the rate of oxygen consumption by oil sands TPW. The degradation rate then declined to levels equivalent to those measured in flasks without phosphate. The observed plateau was not due to phosphate limitation. Decreases in either the dissolved oxygen concentration or the temperature reduced the rate. Phosphate addition also significantly decreased the acute toxicity of TPW to fathead minnows. In contrast, Microtox® analyses showed no reduction in the toxicity of treated or untreated TPW after incubation for up to 8 weeks at 15°C.

Description of Two Treatment Methods for Detoxifying Oil Sands Tailings Pond Water

Abstract Large quantities of toxic wastewater are produced in the processing of oil sands. The toxicity appears to be due primarily to polar organic carboxylic acids (naphthenic acids). These surfactants occur naturally in oil sands and are released during the caustic hot-water extraction process. Relatively high concentrations of suspended particulate matter, bitumen, and dissolved solids, as well as low dissolved oxygen levels, may also contribute to the toxicity of the water. Tailings pond water can be detoxified by rapid chemical treatments which involve coagulation at a pH between 4.5 - 5.0, followed by flocculation with an anionic polyelectrolyte. This method has been successfully scaled up to large batch and flowthrough systems under field conditions. A second treatment method involves the storage of tailings pond water in shallow, well aerated pits for 1 - 2 years, during which period natural processes result in a significant improvement in water quality. Bioassays with bacteria (Beckman Microtox), trout and Daphnia indicate that both treatment met hods result in removal of acute toxicity ( EC50 and LC50 greater than 100%). Ten-week tests with multi-species, simulated pond “ecosystems” in 10 m3 outdoor pooIs indicate some chronic effects remain after treatment. However, these effects are not considered to be limiting to the environmental acceptability of the treated waters.