Aerobic biodegradation of cycloalkanes in non-aqueous extracted oil sands tailings.

Management of growing volumes of fluid fine tailings (FFT) is a significant challenge for oil sands industry. A potential alternative non-aqueous solvent extraction (NAE) process uses cycloalkane solvent such as cyclohexane or cyclopentane with very little water and generates smaller volumes of 'dry' solids (NAES) with residual solvent. Here we investigate remediation of NAES in a simulated bench-scale upland reclamation scenario. In the first study, microcosms with nutrient medium plus FFT as inoculum were amended with cyclohexane and incubated for ∼1 year, monitoring for cyclohexane biodegradation under aerobic conditions. Biodegradation of cyclohexane occurred under aerobic conditions with no metabolic intermediates detected. A second study using NAES mixed with FFT spiked with cyclohexane and cyclopentane, with or without additional nutrients (nitrogen and phosphorus), showed complete and rapid aerobic biodegradation of both cycloalkanes in NAES inoculated with FFT and supplemented with nutrients. 16S rRNA gene sequencing revealed dominance of Rhodoferax and members of Burkholderiaceae during aerobic cyclohexane biodegradation in FFT, and Hydrogenophaga, Acidovorax, Defluviimonas and members of Porticoccaceae during aerobic biodegradation of cyclohexane and cyclopentane in NAES inoculated with FFT and supplemented with nutrients. The findings indicate that biodegradation of cycloalkanes from NAES is possible under aerobic condition, which will contribute to the successful reclamation of oil sands tailings for land closure.

Biodegradation in oil sands process-affected water: A comprehensive laboratory analysis of the in situ biodegradation of dissolved organic acids.

Oil sands process-affected water (OSPW) is a by-product of the extraction of bitumen, and volumes of OSPW have accumulated across the Alberta oil sands region due to the governments zero-discharge policy. Some dissolved organics in OSPW, including toxic naphthenic acids (NAs), can be biodegraded in oxic conditions, thereby reducing the toxicity of OSPW. While there has been much focus on degradation of NAs, the biodegradation of other dissolved organic chemicals by endogenous organisms remains understudied. Here, using the HPLC-ultrahigh resolution Orbitrap mass spectrometry, we examined the microbial biodegradation of dissolved organic acids in OSPW. Non-targeted analysis enabled the estimation of biodegradation rates for unique heteroatomic chemical classes detected in negative ion mode. The microcosm experiments were conducted with and without nutrient supplementation, and the changes in the microbial community over time were investigated. Without added nutrients, internal standard-adjusted intensities of all organics, including NAs, were largely unchanged. The addition of nutrients increased the biodegradation rate of O2- and SO2- chemical classes. While anoxic biodegradation can occur in tailings ponds and end pit lakes, microbial community analyses confirmed that the presence of oxygen stimulated biodegradation of the OSPW samples studied. We detected several aerobic hydrocarbon-degrading microbes (e.g., Pseudomonas and Brevundimonas), and microbes capable of degrading sulfur-containing hydrocarbons (e.g., Microbacterium). Microbial community diversity decreased over time with nutrient addition. Overall, the results from this study indicate that toxic dissolved organics beyond NAs can be biodegraded by endogenous organisms in OSPW, but reaffirms that biological treatment strategies require careful consideration of how nutrients and dissolved oxygen may impact efficacy.

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.

Biofilms for Turbidity Mitigation in Oil Sands End Pit Lakes.

End pit lakes (EPLs) have been proposed as a method of reclaiming oil sands fluid fine tailings (FFT), which consist primarily of process-affected water and clay- and silt-sized particles. Base Mine Lake (BML) is the first full-scale demonstration EPL and contains thick deposits of FFT capped with water. Because of the fine-grained nature of FFT, turbidity generation and mitigation in BML are issues that may be detrimental to the development of an aquatic ecosystem in the water cap. Laboratory mixing experiments were conducted to investigate the effect of mudline biofilms made up of microbial communities indigenous to FFT on mitigating turbidity in EPLs. Four mixing speeds were tested (80, 120, 160, and 200 rpm), all of which are above the threshold velocity required to initiate erosion of FFT in BML. These mixing speeds were selected to evaluate (i) the effectiveness of biofilms in mitigating turbidity and (ii) the mixing speed required to 'break' the biofilms. The impact of biofilm age (10 weeks versus 20 weeks old) on turbidity mitigation was also evaluated. Diverse microbial communities in the biofilms included photoautotrophs, namely cyanobacteria and Chlorophyta (green algae), as well as a number of heterotrophs such as Gammaproteobacteria, Desulfobulbia, and Anaerolineae. Biofilms reduced surface water turbidity by up to 99%, depending on the biofilm age and mixing speed. Lifting and layering in the older biofilms resulted in weaker attachment to the FFT; as such, younger biofilms performed better than older biofilms. However, older biofilms still reduced turbidity by 69% to 95%, depending on the mixing speed. These results indicate that biostabilization is a promising mechanism for turbidity mitigation in EPLs.

Persulfate Oxidation Coupled with Biodegradation by Pseudomonas fluorescens Enhances Naphthenic Acid Remediation and Toxicity Reduction.

The extraction of bitumen from the Albertan oilsands produces large amounts of oil sands process-affected water (OSPW) that requires remediation. Classical naphthenic acids (NAs), a complex mixture of organic compounds containing O2- species, are present in the acid extractable organic fraction of OSPW and are a primary cause of acute toxicity. A potential remediation strategy is combining chemical oxidation and biodegradation. Persulfate as an oxidant is advantageous, as it is powerful, economical, and less harmful towards microorganisms. This is the first study to examine persulfate oxidation coupled to biodegradation for NA remediation. Merichem NAs were reacted with 100, 250, 500, and 1000 mg/L of unactivated persulfate at 21 °C and 500 and 1000 mg/L of activated persulfate at 30 °C, then inoculated with Pseudomonas fluorescens LP6a after 2 months. At 21 °C, the coupled treatment removed 52.8-98.9% of Merichem NAs, while 30 °C saw increased removals of 99.4-99.7%. Coupling persulfate oxidation with biodegradation improved removal of Merichem NAs and chemical oxidation demand by up to 1.8× and 6.7×, respectively, and microbial viability was enhanced up to 4.6×. Acute toxicity towards Vibrio fischeri was negatively impacted by synergistic interactions between the persulfate and Merichem NAs; however, it was ultimately reduced by 74.5-100%. This study supports that persulfate oxidation coupled to biodegradation is an effective and feasible treatment to remove NAs and reduce toxicity.

The role of carbonate mineral dissolution in turbidity reduction in an oil sands end pit lake.

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

Indigenous microbial communities in Albertan sediments are capable of anaerobic benzene biodegradation under methanogenic, sulfate-reducing, nitrate-reducing, and iron-reducing redox conditions.

Alberta is a major center for oil and gas production, and correspondingly harbors hundreds of unresolved contamination sites by environmental hazards such as benzene (C6 H6 ). Due to its cost-effectiveness, bioremediation has become a promising strategy for C6 H6 removal. Contamination sites typically take on an anaerobic context, which complicates the energetics of contamination sites and is a subject that is scarcely broached in studies of Albertan sediments. This study examines the innate potential for indigenous microbial communities in Albertan sediments to remove C6 H6 in a multitude of reduced conditions. Community profiles of these sediments were analyzed by 16S rRNA gene amplicon sequencing, and removal rates and reaction stoichiometries were observed by gas chromatography and ion chromatography. Organisms belonging to known primary degrader taxa were identified, including Geobacter (iron-reducing), and Peptococcaceae (nitrate-reducing). Furthermore, benzene removal patterns of the cultures were similar to those observed in previously reported microcosms, with lag times between 70 and 168 days and removal rates between 3.27 and 12.70 µM/day. Such information could support a more comprehensive survey of Albertan sediment consortia, which may eventually be utilized in informing future remediation efforts in the province. PRACTITIONER POINTS: ●Clay and sand sediments originating from Northern Alberta could remove benzene under methanogenic, sulfate-reducing, iron-reducing, and nitrate-reducing conditions. ●Degradation profiles were broadly comparable to those of reported cultures from other geographical locales. ●Key degrader taxa observed included Geobacter (Fe3+ -reducing) and Peptococcaceae ( NO 3 - -reducing). ●Knowledge gained can be the start of a more extensive survey of Albertan sediments. Eventually, this collection of information can be used to generate robust C6 H6 -degrading cultures that can be implemented for bioaugmentation and be implemented in informing remediation strategies in soil and water matrices for priority contamination cases such as leaking underground storage tanks and orphan wells.

Oil sands process affected water sourced Trichoderma harzianum demonstrates capacity for mycoremediation of naphthenic acid fraction compounds.

Development of Alberta's oil sands requires large volumes of water, leading to the abundance of oil sands process affected water (OSPW) that must be remediated prior to discharge or reuse. OSPW contains a variety of dissolved organic compounds, however naphthenic acids (NAs) have been found to contribute significantly to the toxicity of OSPW. A fungus, Trichoderma harzianum, isolated directly from OSPW, has previously demonstrated a high tolerance and capacity for growth in the presence of commercial NAs. This study conducted microcosm experiments to elucidate and characterize the capacity of T. harzianum to degrade labile commercial NAs (Merichem), and OSPW-sourced naphthenic acid fraction compounds (NAFCs). Additionally, two model NA compounds, the simple single ring cyclohexane carboxylic acid (CHCA) and complex diamondoid 1-adamanatane carboxylic acid (ADA), were utilized to determine the influence of NA structure on degradation. T. harzianum degraded 14% of CHCA, 13% of ADA, and 23-47% of Merichem NAs. Additionally, Orbitrap mass spectrometry revealed a large change in Z-series within NAFCs. This removal and shift in composition correlated to a 59% and 52% drop in toxicity as per Microtox, for Merichem NAs and NAFCs respectively. This proof of concept experiment confirms that the fungal species T. harzianum can contribute to the biodegradation of complex dissolved organics found in OSPW, including cyclic and diamondoid structures.

Potential syntrophic associations in anaerobic naphthenic acids biodegrading consortia inferred with microbial interactome networks.

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

Naphthenic acid anaerobic biodegrading consortia enriched from pristine sediments underlying oil sands tailings ponds.

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

Tolerance and cytotoxicity of naphthenic acids on microorganisms isolated from oil sands process-affected water.

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

Model naphthenic acids removal by microalgae and Base Mine Lake cap water microbial inoculum.

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

Toward Gender Equity in Critical Care Medicine: A Qualitative Study of Perceived Drivers, Implications, and Strategies.

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

Indigenous microorganisms residing in oil sands tailings biodegrade residual bitumen.

The purpose of this study was to determine the capacity of indigenous microbes in tailings to degrade bitumen aerobically, and if acetate biostimulation further improved degradation. Fluid fine tailings, from Base Mine Lake (BML), were used as microbial inocula, and bitumen in the tailings served as a potential carbon source during the experiment. The tailings were capped with 0.22 µm-filtered BML surface water with or without BML bitumen and acetate addition and incubated for 100 days at 20 °C. CO2 production and petroleum hydrocarbon reductions (50-70% for the biostimulation treatment) in the tailings were observed. DNA was extracted directly from the tailings, and increased bacterial density was observed by qPCR targeting the rpoB gene in the biostimulated group. 16 S rRNA sequencing was used to determine microbial composition profiles in each treatment group. The microbial communities indigenous to the tailings shifted after the bitumen was added. Acidovorax, Rhodoferax, Pseudomonas and Pseudoxanthomonas spp. significantly increased compared to the original microbial community and demonstrated tolerance to bitumen-based toxicity. The first three genera showed more potential for biostimulation treatment with acetate and may be important bitumen/hydrocarbon-degraders in an oil sands end pit lake environment.

Who Is the Rock Miner and Who Is the Hunter? The Use of Heavy-Oxygen Labeled Phosphate (P18O4) to Differentiate between C and P Fluxes in a Benzene-Degrading Consortium.

Phosphorus availability and cycling in microbial communities is a key determinant of bacterial activity. However, identifying organisms critical to P cycling in complex biodegrading consortia has proven elusive. Here we assess a new DNA stable isotope probing (SIP) technique using heavy oxygen-labeled phosphate (P18O4) and its effectiveness in pure cultures and a nitrate-reducing benzene-degrading consortium. First, we successfully labeled pure cultures of Gram-positive Micrococcus luteus and Gram-negative Bradyrhizobium elkanii and separated isotopically light and heavy DNA in pure cultures using centrifugal analyses. Second, using high-throughput amplicon sequencing of 16S rRNA genes to characterize active bacterial taxa (13C-labeled), we found taxa like Betaproteobacteria were key in denitrifying benzene degradation and that other degrading (nonhydrocarbon) inactive taxa (P18O4-labeled) like Staphylococcus and Corynebacterium may promote degradation through production of secondary metabolites (i.e., "helper" or "rock miner" bacteria). Overall, we successfully separated active and inactive taxa in contaminated soils, demonstrating the utility of P18O4-DNA SIP for identifying actively growing bacterial taxa. We also identified potential "miner" bacteria that choreograph hydrocarbon degradation by other microbes (i.e., the "hunters") without directly degrading contaminants themselves. Thus, while several taxa degrade benzene under denitrifying conditions, microbial benzene degradation may be enhanced by both direct degraders and miner bacteria.

Effect of naphtha diluent on greenhouse gases and reduced sulfur compounds emissions from oil sands tailings.

The long-term storage of oil sands tailings has resulted in the evolution of greenhouse gases (CH4 and CO2) as a result of residual organics biodegradation. Recent studies have identified black, sulfidic zones below the tailings-water interface, which may be producing toxic sulfur-containing gases. An anaerobic mesocosm study was conducted over an 11-week period to characterize the evolution of CH4, CO2 and reduced sulfur compounds (RSCs) (including H2S) in tailings as it relates to naphtha-containing diluent concentrations (0.2, 0.8, and 1.5% w/v) and microbial activity. Our results showed that RSCs were produced first at 0.12µmol°RSCs/mL MFT (1.5% w/v diluent treatment). RSCs contribution (from highest to lowest) was H2S and 2-methylthiophene>2.5-dimethylthiophene>3-methylthiophene>thiofuran>butyl mercaptan>carbonyl sulfide, where H2S and 2-methylthiophene contributed 81% of the gas produced. CH4 and CO2 production occurred after week 5 at 40.7µmolCH4/mL MFT and 5.9µmolCO2/mL MFT (1.5% w/v diluent treatment). The amount of H2S and CH4 generated is correlated to the amount of diluent present and to microbial activity as shown by corresponding increases in sulfate-reducers' Dissimilatory sulfite reductase (DsrAB) gene and methanogens' methyl-coenzyme M reductase (MCR) gene.

Stream invertebrate community structure at Canadian oil sands development is linked to concentration of bitumen-derived contaminants.

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

Optimization of CO2 fixation by Chlorella kessleri cultivated in a closed raceway photo-bioreactor.

The aim of this study is to optimize biological fixation of CO2 using Chlorella kessleri cultivated in oil sands process water (OSPW). A lab-scale closed raceway photobioreactor was designed and assembled for cultivation of C. kessleri in OSPW. A fed-batch model describing the dynamics of microalgae growth and CO2, phosphate and ammonium uptake rate was developed based on batch kinetics identified in our previous study, and was successfully validated against experimental data. A model-based optimization method was used to calculate the optimal feeding strategies for CO2, phosphate and light intensity which resulted in a 1.5-fold increase in the final biomass concentration and a 2-fold increase in the average CO2 uptake rate in 240 h (10 days) compared to the initial fed-batch experiment over 432 h (18 days). Finally, scale-up to large-scale continuous operation was considered, and the optimal hydraulic retention time (HRT) and feeding strategy for maximum productivity were estimated.

Retention and transport of an anaerobic trichloroethene dechlorinating microbial culture in anaerobic porous media.

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

In situ biodegradation of naphthenic acids in oil sands tailings pond water using indigenous algae-bacteria consortium.

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