Oil Sands Steam-Assisted Gravity Drainage Process Water Sample

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Oil Sands SAGD Process Water Sample Aging during Long-Term Storage Matthew A. Petersen, Claire S Henderson, Anthony Yu-Chung Ku, Annie Q Sun, and David J Pernitsky Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/ef502444z • Publication Date (Web): 03 Feb 2015 Downloaded from http://pubs.acs.org on February 18, 2015

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Oil Sands SAGD Process Water Sample Aging during Long-Term Storage Matthew A. Petersen*,1, Claire S. Henderson1, Anthony Y. Ku1, Annie Q. Sun2, and David J. Pernitsky2 1

GE Global Research, 1 Research Circle, Niskayuna, NY 12309, USA

2

Suncor Energy Inc., 150−6 Ave. SW, Calgary, Canada, T2P 3E3

Corresponding Author E-Mail: [email protected] O: +1 518 387 7054 F: +1 518 387 6972

KEYWORDS aging, steam assisted gravity drainage, SAGD, water, water treatment

ACS Paragon Plus Environment

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ABSTRACT Technology development activities are routinely performed using process water samples collected and stored for several months while tests are being conducted. The results of the technology development activities are highly correlated to the water composition and properties. Processes such as atmospheric oxygen contamination, microbiological activity, and UV oxidation have the potential to act on a sample during long-term storage and modify the properties that may be relevant to technology development testing. These changes are referred to as “aging.” Process water samples collected from a steam assisted gravity drainage (SAGD) bitumen production plant were subjected to different storage conditions and monitored for nearly five months. The sample organic composition and physical characteristics of the water were found to be highly dependent on storage conditions, particularly atmospheric oxygen exposure. Oxygen exposure appeared to drive abiotic polymerization and precipitation of phenolic species, and promote aerobic microbiological activity. These results highlight the importance of excluding oxygen from the sample matrix during collection and storage activities. Sample aging must be accounted for in technology development testing activities.


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Introduction The steam assisted gravity drainage (SAGD) process is widely used for in-situ bitumen extraction in the northern Alberta Oilsands.1 In this process, steam is injected into the bitumencontaining formation to heat the bitumen to reduce its viscosity and allow it to flow to collection wells. At the surface, the bitumen is separated from the produced water, which consists of condensed steam and formation water. Typically, 80 to 90% of the produced water is treated and recycled as boiler feed water for steam generation. A significant amount of research and development is currently underway in the oil sands industry to improve boiler water treatment processes to allow higher levels of water recycle and to reduce the energy associated with water treatment and steam generation. Because of the costs and complexities of conducting technology evaluation tests at remotely located, operating SAGD facilities, technology development for water treatment systems is typically performed offsite using process water samples collected from operating systems that may be stored for several months while tests are being conducted. The results of the development and scale-up activities are strongly dependent on the composition and properties of the stored samples. Two primary risks exist that could limit the applicability of offline development testing due to unrepresentative sample water quality: a) changes in produced water quality or treatment-process variability; and b) systemic changes in sample water quality during storage. The latter risk is the focus of the research presented in this paper using a SAGD plant as the sample water source and process template. A conceptual SAGD plant process flow diagram has been previously presented.2 Primary separation processes are conducted at temperatures up to 160°C and pressures of up to 9 bar. Other water treatment processes are conducted at temperatures up to 95°C and atmospheric pressures. As mentioned above, the chemical characteristics of a sample collected from any


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point in the process are a function of the composition of the initial produced water and upstream unit operations. Consequently, the nature, extent, and kinetics of changes in the chemical properties of a sample during storage may be different depending on the sample location in the SAGD process. Understanding the nature and extent of sample aging is critical to interpreting the results of offsite treatability tests using stored water samples. Several processes may act to age a produced water sample during, or after, sample collection. Samples collected from SAGD plants that operate at elevated temperatures and pressures are often stored at ambient conditions. Initial depressurization and cooling can lead to the loss of volatile components and promote the onset of temperature and pressure related solids precipitation.3, 4 Transitioning from a turbulent to quiescent shear environment may impact physicochemical properties of the system such as emulsion droplet size.5 Over time under quiescent conditions, gravity forces acting on suspended particles in the sample can separate out specific components through sedimentation or flotation processes.6-8 In addition to these factors, the storage container can have an impact on sample aging. Gas headspace in contact with the sample that has a higher CO2 partial pressure will induce pH changes as a result of carbonate reequilibration.9 Storage container material incompatibility may also influence sample conditions over time.10 Over longer timeframes, chemical and biochemical processes may affect the chemical composition of the sample. Samples collected from bitumen surface mining processes have exhibited substantial changes in water processability as a result of atmospheric oxygen contamination and subsequent oxidation of the sample organics.11, 12 In addition to promoting abiotic mechanisms, oxygen contamination has the potential to support aerobic microbial activity. This process would alter the organic composition by enriching the sample with


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biologically recalcitrant species and metabolites.13, 14 Even in the absence of oxygen, nitrate- and sulfate-reducing anaerobic activity may not completely be arrested.15 Depending on storage and use conditions, photooxidation of the organics may also occur over time.16 The objective of this research was to evaluate physicochemical and composition aging in SAGD process water samples over time under conditions representative of a long-term storage environment. The changes in SAGD process water sample characteristics were tracked over time using a variety of analytical techniques in order to evaluate a broad range of potential aging effects. The results of this study may be used to inform best practices for sample handling and storage, and provides a context to practitioners for interpreting testing results. Materials and Methods Process water sample. The process water used in this study was collected at a SAGD plant in northern Alberta from the effluent of the skim tank prior to the deoiling section of the process. The dissolved and total organic carbon of the process water samples was 333 mg/L and 381 mg/L, respectively (SM5310B), and total oil & grease was 49 mg/L (SM5520B). These measurements were consistent with the sampling containing suspended colloidal oil. The sample was collected in an epoxy-lined 45-gal steel drum. The drum was filled completely, capped while the fluid was still hot, and shipped from the plant site to the GE Global Research Center (GRC) in Niskayuna, NY. Once on site the water was transferred from the storage drum to 10-L glass containers. The containers were purged with nitrogen during liquid transfer in order to keep the headspace inside the bottles uniform and oxygen free until the experiment was started. After approximately 10 L of water was transferred to a container it was immediately capped with a Teflon-faced screwcap that contained ports for water collection and headspace


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flushing (Figure 1). The cap was taped to the bottle with electrical tape to prevent it from loosening during handling throughout the experiment. Study design. The parameters controlled during the test were storage temperature, the presence of oxygen in the bottle headspace, and exposure to UV light (sunlight). Each parameter was hypothesized to influence different aging mechanisms. The parameter ranges were selected to reflect conditions that are expected to be used for long-term archival storage of water. The six storage conditions used in the study are summarized in Table 1. The aging study was conducted for 20 weeks. The two temperature levels were controlled by storing the cold containers in a temperature-controlled cold room, and the room temperature containers on a lab bench. The ambient temperature for each condition was recorded during the experiment using an OM-63 temperature data logger (Omega Engineering Inc., Stamford, CT). Oxygen exposure to the sample fluid was managed by flushing the bottle headspace with either air or nitrogen. The headspace of each bottle was flushed for approximately 10 to 15 minutes once a week during the study. Gas was not bubbled through sample liquid in the container during headspace flushing. Dissolved oxygen was monitored in the sample water to quantify the effects of headspace flushing. Sample exposure to UV light was controlled by using either amber or clear glass bottles. The amber bottles prevented sample exposure to light at wavelengths up to 500 nm during storage. Clear glass bottles were stored in front of an eastern exposure window to allow for sunlight penetration into the sample. Water samples were collected from the containers while the headspace was being purged. During the headspace purge, water was collected from the container using a peristaltic pump attached to the liquid sample ports. In between sampling events, pinch valves were used to close


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the access ports and maintain the container headspace atmosphere. The liquid in the container was not homogenized during the study. Analytical methods. Several properties were tracked at different frequencies over the course of the study. The more frequently monitored parameters were pH, oxidation-reduction potential (ORP), specific conductivity (SC), and dissolved oxygen (DO). Each of these measurements was conducted on a single aliquot of water collected from the storage containers. Turbidity and particle size distribution (PSD) were collected at less frequent intervals. Analytical method details to measure these parameters, and inorganic species concentrations, are included in the supplemental information. The organic composition of the water was evaluated using species-specific and nonspecific methods. The nonspecific methods used were total organic carbon (TOC) and chemical oxygen demand (COD). A detailed description of the nonspecific analytical methods is included in the supplemental information. More compound specific analyses were conducted using UV/Vis and IR absorption. Absorption of UV/Vis light from 230 to 400 nm was performed on samples in a 1-cm quartz cuvette on a Shimadzu UV-2501 PC spectrophotometer. Samples were filtered with a 0.1-µm anodic aluminum oxide (AAO) ceramic filter prior to analysis to remove any interference from suspended solids. IR absorption analysis was conducted on organic residue extracted from the samples with ACS grade trichloroethene (Fisher). The organic solvent extract was dried on a KBr plate over a nitrogen stream. IR spectra were obtained using a Hyperion 3000 IR microscope (Bruker Optics, Billerica, MA) attached to a Bruker Optics Vertex 70 FTIR. A total of 64 interferograms were collected prior to performing the Fourier transform.


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Volatile fatty acids were measured at the end of the study as a gauge of microbial activity in the sample containers. Acetate, propionate, isobutyrate, and n-butyrate analysis was performed by ion-exclusion chromatography. The analysis was conducted on an Agilent 1100 series HPLC (Agilent, Santa Clara, CA) in combination with an Agilent 1100 diode-array UV detector set to 210 nm. A Bio-Rad Aminex HPX-87H 300 x 7.8 mm Ion-Exclusion column was used for the analysis. A 50 µL sample was introduced into the column that was operated isocratically at a flowrate of 0.75 mL/min using a 3 mM sulfuric acid solution in HPLC grade water as the solvent. Two-dimensional gas chromatography with mass spectrometry detection (2DGC-MS) was utilized to provide a greater level of resolution on the organic mixture composition in the water. A full description of the analytical method, and means for general data interpretation may be found in Petersen and Grade.2 Two different sample preparation methods were performed to provide complementary data sets and broaden the perspective of compounds amenable to analysis by gas chromatography. The samples were prepared by first acidifying them to pH ≈ 2 by addition of 1:1 HCl (approx. 10 mL per 1-L sample). The analytes were extracted from the acidified water by a batch liquid-liquid extraction using methylene chloride. Five sequential batch extractions were performed with 100 mL of solvent for each repetition. The five 100-mL portions of methylene chloride were combined and reduced to 10 mL on a rotary evaporator. An aliquot of the concentrated methylene chloride extract was derivatized in order to stabilize compounds containing acidic functional groups using an N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) silylation kit.


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Populations for two functionally differentiated bacteria in the sample containers were assayed during the experiment. A detailed assay description is included in the supplemental information. Results and Discussion Maintenance of storage conditions. Although the process water was not stored under controlled conditions during transport from the plant site to the GRC, two observations indicated that the sample integrity had not substantially deteriorated in the drum during transport. First, a vacuum had formed in the drum headspace as a result of the sample temperature cooling from process to ambient conditions, and the vacuum remained intact until the bungs were opened. Second, the sample had not developed a substantial amount of turbidity and the color was still similar to that of the freshly collected water (light yellow). These phenomena were reported on in a previous study following water exposure to oxygen.17 The average temperature during the study of the cold bottles and room temperature bottles was 6.1°C. and 21.3°C, respectively. Minor temperature excursions from these intervals were observed during sample events due to two short-term building system events. Container 21NC was accidently broken on week 4 of the study. A backup sample stored at conditions identical to container 21ND was used to replace the broken 21NC container. The backup container was initially filled when the water was transferred from the shipment drum to the glass containers. The backup container was deemed suitable for the rest of the study, because there were no significant changes observed between the 21NC and 21ND samples at week 4. DO was measured at the plant site within an hour of sample collection, and also monitored weekly in the sample water from all six containers. DO levels measured within an hour of


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sample collection were approximately 1 mg/L. The results of weekly DO monitoring in the study are presented in Figure 2. Probe availability limitations prevented DO measurements from being conducted until week 6 of the study. The DO increased until week8, when concentrations appeared to remain more constant. This would indicated that oxygen consumption in the samples had slowed compared to near the beginning the study when DO concentrations were near 1 mg/L. The DO concentration in containers with nitrogen-purged headspaces remained relatively low at slightly less than 2 mg/L. The sample water in air-purged containers had a much higher DO concentration between 6 and 8 mg/L throughout much of the study. There was negligible difference in the DO between the three nitrogen-purged containers. However, the DO in container 6AD stored in the cold room was approximately 2 mg/L greater than the concentration in the two air-purged containers stored at room temperature, likely due to the temperature dependent solubility differences. The measured values were proportional to the aqueous solubility limit of oxygen at 21°C and 6°C and atmospheric oxygen partial pressure ( 8.9 mg/L and 12.5 mg/L, respectively). The color of the nitrogen purged containers changed to dark brown by week 2 of the study, which is consistent with observations of a previous study on impact of oxygen exposure on treatment technology evaluation (Figure 1).17 The temperature and DO data demonstrated that the storage conditions were maintained and differentiated according to the experimental plan described. The subsequent data presentation and discussion will focus on the impact of these storage conditions on sample aging.


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Organic composition changes. TOC and COD measurements conducted over time are presented in Figure 3. Neither parameter substantially changed during the study. Additionally, TOC and COD values did not clearly diverge among the storage conditions. These results suggest that these parameters may not be appropriate metrics to evaluate sample aging, and that more specific methods are required to discern changes in water characteristics. Samples were analyzed by UV and IR absorption spectrophotometry over the course of the study to assess how the principle functional groups present in the mixture of organic species were affected during the aging processes. Undiluted samples strongly absorbed short wavelength UV light, essentially eliminating any transmission through the 1-cm path length quartz cuvette. The shoulder of the UV peak became resolvable at wavelengths greater than approximately 300 nm in all samples analyzed. Therefore, absorbance at 330 nm was used as a representative wavelength for the presence of UV absorbing species. The UV absorption data presented in Figure 4 are from 0.1-µm filtered samples. A clear differentiation developed over time in the UV absorbance data between the air-purged and nitrogen-purged containers, with the absorbance in the air-purged containers steadily increasing over the course of the study. The increase in absorbance seen for the air-purged containers suggests that the nature of the dissolved organics changed, possibly via the dominant UV absorbing species becoming more highly substituted over time. For example, it has been reported that substitution of hydroxyl groups (-OH) onto aromatic or conjugated diene molecules alters the absorption response and the wavelength of maximum absorbance depending on the structure of the conjugated species.18 Based on the similar results seen between filtered and unfiltered UV absorbance results, the increases in absorption were not attributable to the formation of light-scattering precipitates. Also, based on the constant TOC results shown in


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Figure 3, UV absorption increases were not attributable to increases in the concentration of dissolved organics. IR absorption analysis was carried out on dried residue from the solvent extraction. Spectra were collected in weeks 5, 10, and 15 of the study, and are presented in Figure S1 in the Supporting Information. The principal peak observed at 2925 cm-1 corresponds to absorption of a methylene C-H bond stretching vibration. This peak was used as an internal standard for each individual sample to compare the relative compositions between the storage conditions and points in time. This absorption peak has historically been used for oil-in-water concentrations as determined by solvent extraction and IR detection.19 IR spectra from the room temperature and sunlight-exposed containers were more enriched in oxygenated functionalities compared to the cold and dark containers. The 6ND and 21AC containers represent the most extreme differences in storage conditions. Normalized Spectra these two samples are shown in Figure S2. Carboxylated aromatics were more strongly evident the 21AC container, which as mentioned above, could account for the differences in UV absorbance observed between the air-purged versus nitrogen-purged containers. Although oxygen functionalities were present in both air-purged and nitrogen-purged samples, a time lag occurred for the appearances of certain peaks between the two groups. For example, at week 15 a large peak at 1538 cm-1 was detected for the 21ND sample. The same peak was noted in the 21AD container, but at week 10 of the study. This suggests that the nitrogen purging did not completely eliminate oxygenation of the organic content, but may have decreased the aging process kinetics. This is consistent with the visual observation of the sample fluid darkening over time, which occurred at a much faster pace in the air-purged containers compared to the


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nitrogen-purged conditions. Overall, evaluation of the IR spectra between the different storage conditions largely supported the conclusions drawn from the divergence in UV absorption between air-purged and nitrogen-purged containers. Carboxylated and hydroxylated compounds were thought to be one of the important organic fractions susceptible to sample aging. The BSTFA-derivatization 2DGCMS analysis specifically targets these types of compounds. In order to easily compare multiple samples one-dimensional chromatograms were reconstructed from the two-dimensional data. The one-dimensional chromatograms from multiple samples are stacked for visual inspection of differences between the samples in Figure 5. The reconstructed one-dimensional data shown in Figure 5 are ionspecific chromatograms for the ion fragments attributable to the BSTFA-derivatized carboxyl and hydroxyl groups (m/z 45+73+75+117). The primary difference between the chromatograms was a deficiency of peaks in the air-purged, room temperature containers. The deficiency was most apparent for peaks eluting at residence times greater than 1800 s. These results indicated that acids and other compounds with labile protons were susceptible to oxygen induced aging processes. At the same residence times noted, the cold room, air-purged container (6AD) contained some of the peaks, but at decreased intensities compared to the nitrogen-purged peaks. This suggests that aging kinetics may be temperature controlled. The benefits of low temperature storage did not appear to be as significant as the nitrogen purge. The select ion two-dimensional chromatograms for samples 21AC and 6ND are shown in Figure 6. The circled areas in the chromatograms denote the region where catechols and alkyl catechols elute within the two-dimensional chromatographic space. Their absence from the 21AC sample


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suggests that they were transformed during sample aging, but were conserved in the 6ND storage conditions. The 1st dimension residence times for this class of compounds corresponds to the region noted in Figure 5 where peak deficiencies were noted for all air-purged samples relative to nitrogen-purged samples. Analysis of underivatized samples highlighted other differences in composition between the airpurged and nitrogen-purged storage conditions. Thiophene and alkylthiophene were the only major compounds not present in the room temperature air-purged samples that were detected in the nitrogen-purged samples (Figure S3 in Supporting Information). In a complementary study air bubbled through a fresh process water sample led to loss of thiophene and (alkyl)benzene species.17 The loss of heterocyclic and aromatic compounds may be through a coprecipitationtype mechanism with polymerized phenolics.20 Samples were collected for analysis of volatile fatty acids (VFA) in week 20 of the study. Concentrations of acetate, propionate, and butyrate are presented in Figure 7. VFA concentrations were consistently greater in the air-purged samples compared to the nitrogenpurged samples. Their presence has been used as an indicator of fermentation processes occurring in biologically active systems.21 VFA analysis was not conducted at the beginning of the study. Therefore, no conclusions could be drawn with respect as to whether the fermentation potentially occurred during storage or in situ. VFA utilization by anaerobic bacteria as an electron donor for sulfate reduction may partially explain the smaller concentrations observed in the nitrogen-purged containers. The occurrence of sulfate reduction was further supported by smaller sulfate concentrations observed in the nitrogen-purged study containers near the end of the study (Table 2).


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Physicochemical changes. Turbidity and particle size data provided quantitative information on the behavior of suspended solids in the containers over time (Figure S4). The initial turbidity of the sample water ( not shown in Figure S4A) was very low, at less than 10 NTU. Turbidity developed in the sample water through the first 2 to 6 weeks of the study. Trends in both turbidity and effective particle diameter were compared according to storage temperature. The containers stored in a cold room maintained a much higher turbidity and exhibited nearly twice the effective particle diameter compared to the water stored at room temperature. Under all conditions turbidity decreased over time from early maximum values of 100 to 400 NTU down to less than 50 NTU for the room temperature containers and 150 NTU for the cold room containers. The containers were not regularly mixed during the study, or immediately prior to sampling. Large, loose precipitates that were not apparent when the containers were initially filled were observed at the bottom of the containers in the later weeks of the study. This suggests that aging processes included sedimentation of slow-settling suspended solids, and/or precipitation of initially dissolved materials. Once particles were formed the settling rate appeared to be governed by the containers storage temperature. The rate of turbidity decline appeared to be inversely proportional to water temperature, and viscosity, which is consistent with stokes law.6 Redox state and inorganic changes. The pH and ORP were used to gauge the overall redox state of the water stored in the containers. These parameters were hypothesized to shift during sample aging as a result of such processes as microbial activity and equilibration with atmospheric CO2 partial pressure. The pH and ORP correlated most strongly with the air-purged and nitrogen-purged containers, but was relatively insensitive to the other test parameters. Data from these measurements are shown in Figure 8.


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The SC was not different between the storage conditions evaluated through the study (Figure 8C). The gradual increase in SC over time from approximately 0.7 to 0.85 mS/cm suggested a negligible loss of dissociable transformation products throughout the aging process (e.g., formation and subsequent volatilization of VFAs). The outliers measured in 21ND at week 7 and 6AD at week 9 did not appear to coincide with any other physicochemical changes, and were assumed to be the result of measurement and sampling variability from the potentially nonuniform conditions in the storage containers. The concentrations of inorganic species and metals were sampled at the end of the study. No substantial differences in major cations and metals were observed between any of the storage conditions at the end of the study (Table S1 in Supporting Information). The total cation and metals concentrations were similar to the dissolved concentrations, indicating that the suspended solids greater than 200 nm in diameter did not contain significant amounts of inorganic constituents. Dissolved silica was measured at the beginning of the study, in week 8, and in week 15. The concentration declined from the initial level of approximately 205 mg/L of molybdate reactive silica (Figure 9). By week 15 of the study the dissolved silica concentration 6AD, 6ND, and 21AD containers was substantially less than the in the other containers. Temperature related solubility decreases may have contributed to the different dissolved silica concentrations between the two storage temperatures.22 The silica concentration in the 21AD container was lower than in the other containers stored at room temperature near the end of the test. A mechanistic explanation for this observation was beyond the scope of this study.


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In general, the pH in the air-purged containers was lower and the ORP was higher than the nitrogen-purged containers. The more oxidized condition supported in the air-purged conditions are reflected in the organic mixture data previously discussed. The two groups of containers (airand nitrogen-purged) trended over time towards a more oxidized state relative to the beginning of the study. This trend was potentially a result of oxygen contamination through the bottle caps, or within the nitrogen used to purge the bottle headspaces. The redox state in the nitrogen-purged containers later in the study was not indicative of a strongly reducing environment. Instead, based on the ORP level, they had transitioned from a sulfate-reducing to iron-reducing conditions by the end of the study. A time lag in this transition was observed for the 6ND container that was stored in the cold room. This suggests that cold storage may substantially decrease the rate of this transition. The initial ORP in the nitrogen-purged bottles was indicative of sulfate reducing conditions. However, over time and under air-purged conditions the redox conditions were consistent with oxidized conditions. These would be expected where an oxic environment may encounter a previously reduced, sulfide rich environment. This data suggest a very complex and dynamic redox environment in the storage bottles that may impact sample characteristics by different mechanisms over time. Aging mechanistic drivers. Air-purging the container headspace introduced and maintained dissolved oxygen in the sample water. The substantial differences in appearance between the air and nitrogen headspaces samples, even early on in the study, supported oxygen induced sample aging. The primary aging mechanism related to oxygen exposure may be due to the phenol and catechol compounds present in the water samples. These compounds are susceptible to oxidation


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via reaction with molecular oxygen.23-25 Initial products from these reactions are benzoquinones and hydroquinones. One potential product of this process, o-benzoquinone, is well known to undergo polymerization reactions that lead to brown precipitates.25, 26 These types of precipitates are routinely observed in the highly aged, oxygenated samples encountered in this study. As illustrated in Figure 6 there was a clear absence of catechol compounds found in the airpurged samples. The compounds were present, but at lowered concentrations in the air-purged container stored at cold temperatures. This provides evidence for the occurrence of the proposed mechanism shown in Figure 10. Catechol may be present initially in the sample, and may also form over time through aerobic microbial conversion of aromatic and phenol parent compounds.27 This process may contribute a substantial impact on sample aging due to the large relative concentration of phenol and singlering aromatics present in the water. Aerobic bacteria and sulfate reducing bacteria (SRB) populations were assayed during the study. These two bacteria types were selected for monitoring due to the storage conditions used in the study, the presence of sulfate in the source water, and the potential for atmospheric contamination while transferring the water. A test performed on water collected from the shipment drum immediately after all of the study containers will filled indicated that heterotrophic aerobic bacteria (HAB) were not substantially present (< 7 × 103 cfu/mL), and a general anaerobic consortium was present at a population of approximately 1.8 × 103 cfu/mL. By week 5 a clear distinction between container storage temperature and headspace was apparent. Images from the activity tests conducted in week 5 and 15 are shown in Figure S5 in the Supporting Information.


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Activity in containers 6AD and 6ND was noticeably lower than in the other containers based on the relatively slow rate of color change used to indicate the test results. The results of the BART test indicated that a strong population (> 7 × 106 cfu/mL) of HAB were present at week 5 in all of the room temperature air-purged containers, and present to a lesser degree in the nitrogenpurged containers (≈ 5 × 105 cfu/mL). The population in container 6ND was approximately 5 × 104 cfu/mL. The SRB tests showed that populations at week 5 were approximately 7 × 105 cfu/mL except for the 6ND container, which had an SRB concentration of approximately 5 × 103 cfu/mL. By week 15 the assays indicated bacteria populations were in excess of the HAB and SRB test limits in all of the room temperature containers, 7 × 106 cfu/mL and 7 × 105 cfu/mL, respectively. Both containers stored at 4°C were interpreted to be at the same or less concentrations of HAB and SRB. However, a lag in color development for these conditions was still observed at this point in the study. A darker color developed in the HAB and SRB BART assays for both the 21AD and 21AC conditions suggesting that both functional classes of bacteria were active in the containers. The results of the SRB assays indicated the presence of SRB consortium activity in the nitrogenpurged containers. The air-purged bottles contained a more complex consortium with SRBs present within that population. The indications of a mixed functionally aerobic-anaerobic population may have been due to stratified conditions developing within the quiescent containers, with aerobic/oxidized conditions near the headspace contact, and transitions to more anaerobic/reduced conditions with liquid depth.


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Although the nitrogen-purged containers were designed to minimize oxygen contamination, dissolved oxygen in the nitrogen-purged containers remained at concentrations greater than 1 mg/L, which is large enough to support some aerobic microbial activity, though the data suggests a lower level of activity compared to the air-purged bottles. Based on the results of this study, photooxidation did not appear to be a significant aging process compared to oxygen contamination and microbial activity. None of the water quality parameters indicated a different behavior for the clear containers relative to the amber containers. However, mitigating UV light exposure by using amber glass bottles is simple to institute, and has a smaller implementation risk, compared to methods that address the other hypothesized mechanisms.

Conclusions Aging of SAGD process water collected from the skim tank effluent was observed under a variety of long-term storage conditions over the course of approximately four months of observation period. Aging was primarily realized as changes in certain physiochemical properties, such as particulate formation with sedimentation, and specific organic components, such as catechols, within the overall mixture. Some nonspecific sample parameters were insensitive to the extent of sample aging induced in the study, particularly TOC and COD. These results illustrate that subtle changes in sample characteristics that may occur during sample aging may not be easily resolved using nonspecific analytical techniques. Sample oxygen exposure appeared to be the critical parameter that impacted aging based on the extent of sample characteristic changes observed in the study. The aging transformations observed may be


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attributed to biotic and abiotic processes. Storage temperature had the effect of mitigating some of the effects, potentially by arresting microbial growth or retarding chemical reaction kinetics. Lowering the storage temperature to 4°C did not eliminate the aging process from occurring. However, cold storage appears to be an appropriate best practice for process water sample handling. The results suggest that reducing or eliminating oxygen exposure to the sample is crucial for preserving sample integrity over a period of time that may be relevant to treatment technology testing. The sample organic composition changes observed in this study may present a substantial impact to the results of offline treatment technology evaluation. Samples collected at different locations within the SAGD process (e.g., skim tank inlet, boiler feed water) would likely have different composition profiles and consequently the aging risk would be different than the sample used in the present study. Mapping results of offline laboratory testing with aging-affected process water to plant conditions remains a substantial challenge for research and development activities.

ACKNOWLEDGMENT This work was performed as part of a jointly funded effort between The General Electric Company and Suncor Energy Inc. The project team gratefully acknowledges assistance in sample analysis from Hans Grade, Margaret Semon, Eric Telfeyan, Denise Anderson, and Rob Davis from General Electric.


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Table 1. Summary of sample container storage conditions.

Container code

Temperature

Headspace

UV exposure

6AD

6.1°C

Air

No

6ND

6.1°C

N2

No

21AD

21.3°C

Air

No

21ND

21.2°C

N2

No

21AC

21.3°C

Air

Yes (sunlight)

21NC

21.3°C

N2

Yes (sunlight)


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Table 2. Concentration of anions from samples collected in week 15 of the study. All concentrations appear in ppm.

Species concentration 6AD (ppm)

6ND

21AD

21ND

21AC

21NC

Chloride

97

94

96

96

96

96

Nitrate

< 2.8

< 2.8

< 2.8

< 2.8

< 2.8

< 2.8

Sulfate

58

53

68

55

76

60

Phosphate

< 6.8

< 6.8

< 6.8

< 6.8

< 6.8

< 6.8

Containers


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REFERENCES 1. Butler, R. M., Horizontal wells for the recovery of oil, gas and bitumen. Petroleum Society Monograph of Canada Institute of Mining, 1994; Vol. 2, pp 169-199. 2.

Petersen, M. A.; Grade, H. Ind. Eng. Chem. Res. 2011, 50, 12217-12224.

3. Joshi, N. B.; Mullins, O. C.; Jamaluddin, A.; Creek, J.; McFadden, J. Energy Fuels 2001, 15, 979-986. 4.

Hirchberg, A.; deJong, L. N. J.; Schipper, B. A.; Meijer, J. G. SPE J. 1984, 24, 283-293.

5.

Walstra, P. Chem. Eng. Sci. 1993, 48, 333-349.

6. Bird, R. B.; Stewart, W. E.; Lightfoot, E. N., Transport Phenomena. 2nd Edition ed.; John Wiley & Sons, Inc.: New York, 2002. 7.

Eckert, W. F.; Masliyah, J. H.; Gray, M. R.; Fedorak, P. M. AIChE J. 1996, 42, 960-972.

8. Poindexter, M. K.; Chuai, S.; Marble, R. A.; Marsh, S. C. Energy Fuels 2005, 19, 13461352. 9. Arla, D.; Sinquin, A.; Palermo, T.; Hurtevent, C.; Graciaa, A.; Dicharry, C. Energy Fuels 2007, 21, 1337-1342. 10. Keith, L. H., Environmental sampling and analysis: A practical guide. CRC Press: Boca Raton, 1991. 11.

Schramm, L. L.; Smith, R. G. AOSTRA J. Res. 1987, 3, 195-214.

12.

Schramm, L. L.; Smith, R. G. AOSTRA J. Res. 1987, 3, 215-224.

13. Scott, A. C.; Mackinnon, M. D.; Fedorak, P. M. Environ. Sci. Technol. 2005, 39, 83888394. 14.

Erstad, K.; Hvidsten, I. V.; Askvik, K. M.; Barth, T. Energy Fuels 2009, 23, 4068-4076.

15. Bordenave, S.; Kostenko, V.; Dutkoski, M.; Grigoryan, A.; Martinuzzi, R. J.; Voordouw, G. Chemosphere 2010, 81, 663-668. 16. Garrett, R. M.; Pickering, I. J.; Haith, C. E.; Prince, R. C. Environ. Sci. Technol. 1998, 32, 3719-3723. 17. Ku, A. Y.; Henderson, C. S.; Petersen, M. A.; Pernitsky, D. J.; Sun, A. Q. Ind. Eng. Chem. Res. 2012, 51, 7170–7176. 18. Brown, D. W.; Floyd, A. J.; Sainsbury, M., Organic Spectroscopy. John Wiley & Sons: Chichester, 1998.


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19. ASTM D3921, Standard Test Method for Oil and Grease and Petroleum Hydrocarbons in Water. In 2011; Vol. D3921 - 96(2011). 20.

Wilberg, K. Q.; Nunes, D. G.; Rubio, J. Braz. J. Chem. Eng. 2000, 17, 907-913.

21. Rittmann, B. E.; McCarty, P. L., Environmental Biotechnology: Principles and applications. McGraw-Hill: Boston, 2001. 22. Iler, R. K., Chemistry of Silica - Solubility, Polymerization, Colloid and Surface Properties and Biochemistry. John Wiley & Sons: New York, 1979. 23.

Devlin, H. R.; Harris, I. J. Ind. Eng. Chem. Res. Fundam. 1984, 23, 387-392.

24.

Sadana, A.; Katzer, J. R. Ind. Eng. Chem. Res. Fundam. 1974, 13, 127-134.

25.

Colarieti, M. L.; Toscano, G.; Greco Jr, G. Water Res. 2002, 36, 3015-3022.

26.

Pierpoint, W. S. Biochem. J. 1969, 112, 609-616.

27.

Sanier, R. Y.; Ornston, L. M. Adv. Microb. Physiol. 1973, 9, 89-151.


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Figure 1. Image of 21AC (left) and 21NC (right) storage containers in week 2 of the study. Image reprinted (adapted) with permission from A. Y. Ku, C. S. Henderson, M. A. Petersen, D. J. Pernitsky, and A. Q. Sun. Industrial & Engineering Chemistry Research 2012. 51 (21), 7170-7176. Copyright 2012 American Chemical Society. 119x115mm (150 x 150 DPI)


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Figure 2. Dissolved oxygen concentration in sample water. 118x112mm (150 x 150 DPI)


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Figure 3. TOC (A) and COD (B) concentrations in sample water over time. 167x228mm (150 x 150 DPI)


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Figure 4. Light absorbance at 330 nm wavelength of undiluted water samples passed through a 0.1-µm membrane filter. 115x112mm (150 x 150 DPI)


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Figure 5. Reconstructed one-dimensional chromatograms of the BSTFA-derivatized carboxyl- and hydroxylfunctional groups (m/z 45+73+75+117) from week 4 samples. Boxed areas highlights regions where the samples are substantially differentiated. 153x108mm (150 x 150 DPI)


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Figure 6. 2DGCMS data from the BSTFA-derivatized extract from sample 21AC (A) and 6ND (B) collected in week 4 of the study. The data presented is total ion chromatogram. Each black dot represents a unique compound identified in the sample. Circled regions denote areas where catechols are eluted. 152x128mm (150 x 150 DPI)


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Figure 7. Volatile fatty acid concentrations in the containers in week 20 of the aging study. 265x230mm (150 x 150 DPI)


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Figure 8. Sample water pH (A), ORP (B), and specific conductivity (C) over time. 157x233mm (150 x 150 DPI)


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Figure 9. Dissolved silica measured as molybdate reactive silica over time. 120x112mm (150 x 150 DPI)


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Figure 10. Reaction pathway of phenol and catechol with dissolved oxygen to form hydroquinone and catechol products. o-Benzoquinone may polymerize or form brown-colored precipitates. The dashed line denotes the potential production of catechol from phenol via aerobic microbial pathways. 66x38mm (300 x 300 DPI)


Oil Sands Steam-Assisted Gravity Drainage Process Water Sample

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