mesocosm-scale-constructed-wetland-design-for-wastewater-treatment

Mesocosm-Scale Constructed Wetland Design for Wastewater Treatment

Oil sands process-affected water (OSPW), a by-product of bitumen extraction through surface mining in Alberta, Canada, contains various constituents of ...

collecting-processing-drone-based-remotely-sensed-data-for-use-forest

Collecting and Processing Drone-based Remotely Sensed Data for Use in Forest Recovery Monitoring

Remote sensing (RS) technologies, particularly light detection and ranging (LiDAR) and multispectral (MS) imagery, provide broad-scale vegetation ...

Natural Resources Canada, Canadian Forest Service

Northern Forestry Centre

Bitumen extraction from surface-mined oil sands deposits results in the accumulation of large volumes of oil sands process-affected water (OSPW). Naphthenic acids (NAs) are primary contributors to OSPW toxicity and have been a focal point for the development of OSPW remediation strategies. Phytoremediation is an approach that utilizes plants and their associated microbes to remediate contaminants from soil and groundwater. While previous evidence has indicated a role for phytoremediation in OSPW treatment through the transformation and degradation of NAs, there are no reports that demonstrate the direct uptake of NAs into plant tissue. Using NAs labelled with C radioisotopes (C-NAs) paired with whole-plant autoradiography, we show that NAs representing aliphatic (linear), single-ring, and diamondoid compounds were effectively removed from hydroponic solution and OSPW-treated soil by sandbar willow (Salix interior) and slender wheatgrass (Elymus trachycaulus) and their associated microbiomes. The NA-derived C label accumulated in root and shoot tissues of both plant species and was concentrated in vascular tissue and rapidly growing sink tissues, indicating that C-NAs or their metabolic derivatives were incorporated into physiological processes within the plants. Slender wheatgrass seedlings grown under axenic (sterile) hydroponic and soil conditions also effectively removed all C-NAs, including a highly stable diamondoid NA, demonstrating that plants can directly take up simple and complex NAs without the assistance of microbes. Furthermore, root and shoot tissue fractionation into major biomolecule groups suggests that NA-derived carbon is allocated toward biomolecule synthesis rapidly after NA treatment. These findings provide evidence of plant-mediated uptake of NAs and support a direct role for plants and their associated microbes in the development of future large-scale OSPW phytoremediation strategies.

Detection of naphthenic acid uptake into root and shoot tissues indicates a direct role for plants in the remediation of oil sands process-affected water.

Surface oil sands mining and extraction in northern Alberta's Athabasca oil sands region produce large volumes of oil sands process-affected water (OSPW). OSPW is a complex mixture containing major contaminant classes including trace metals, polycyclic aromatic hydrocarbons, and naphthenic acid fraction compounds (NAFCs). Naphthenic acids (NAs) are the primary organic toxicants in OSPW, and reducing their concentrations is a priority for oil sands companies. Previous evidence has shown that constructed wetland treatment systems (CWTSs) are capable of reducing the concentration of NAs and the toxicity of OSPW through bioremediation. In this study, we constructed greenhouse mesocosms with OSPW or lab process water (LPW) (i.e., water designed to mimic OSPW minus the NAFC content) with three treatments: (1) OSPW planted with Carex aquatilis; (2) OSPW, no plants; and (3) LPW, no plants. The OSPW-C. aquatilis treatment saw a significant reduction in NAFC concentrations in comparison to OSPW, no plant treatments, but both changed the distribution of the NAFCs in similar ways. Upon completion of the study, treatments with OSPW saw fewer high-molecular-weight NAs and an increase in the abundance of O- and O-containing formulae. Results from this study provide invaluable information on how constructed wetlands can be used in future remediation of OSPW in a way that previous studies were unable to achieve due to uncontrollable environmental factors in field experiments and the active, high-energy processes used in CWTSs pilot studies.

Evaluating the attenuation of naphthenic acids in constructed wetland mesocosms planted with Carex aquatilis.

In Alberta's Athabasca oil sands region (AOSR), over 1.25 billion m of tailings waste from the bitumen extraction process are stored in tailings ponds. Fugitive emissions associated with residual hydrocarbons in tailings ponds pose an environmental concern and include greenhouse gases (GHGs), reduced sulphur compounds (RSCs), and volatile organic compounds (VOCs). Froth treatment tailings (FTT) are a specific type of tailings waste stream from the bitumen froth treatment process that contains bioavailable diluent: either naphtha or paraffins. Tailings ponds that receive FTT are associated with the highest levels of biogenic gas production, as diverse microbial communities biodegrade the residual diluent. In this review, current literature regarding the composition, chemical analysis, and microbial degradation of FTT and its constituents is presented in order to provide a more complete understanding of the complex chemistry and biological processes related to fugitive emissions from tailings ponds receiving FTT. Characterizing the composition and biodegradation of FTT is important from an environmental perspective to better predict emissions from tailings ponds and guide tailings pond management decisions.

A Deep Look into the Microbiology and Chemistry of Froth Treatment Tailings: A Review.

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

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

Froth treatment tailings are one type of waste stream generated during the extraction of surface-mined oil sands bitumen. To remove water and solids from bitumen froth recovered during the water-based extraction process, hydrocarbon diluent is added, and settling and/or centrifugation are applied to the diluted bitumen froth, producing diluted bitumen and froth treatment tailings. While recovery processes are in place to remove and recycle the diluent from froth treatment tailings, some residual diluent can remain. Since tailings are stored in outdoor ponds, the residual diluent can have implications for methanogenic microbial processes and resulting greenhouse gas emissions. This work presents a methodology to accurately extract and quantify diluent hydrocarbons from froth treatment tailings using gas chromatography. A cold-start temperature program is used to separate diluent hydrocarbons from any residual bitumen in the sample, and diluent is quantified using commercial standards as well as unprocessed diluent. A series of extraction parameters were tested and results from multiple conditions are shown with a rationale for the selected optimized parameters. Quantification of diluent in tailings samples is demonstrated from 60 to 5329 μg/g, and results from quality control standards show an average diluent recovery of 100 ± 10%.

An optimized extraction and gas chromatography analysis method for the quantification of diluent hydrocarbons in froth treatment tailings.

The oil sands mining operations in Alberta have produced billions of m of tailings which must be reclaimed and integrated into various mine closure landforms, including terrestrial landforms. Microorganisms play a central role in nutrient cycling during the reclamation of disturbed landscapes, contributing to successful vegetation restoration and long-term sustainability. However, microbial community succession and response in reconstructed and revegetated tailings remain largely unexplored. This study aimed to monitor the structural and functional responses of microbial communities in tailings subjected to different capping and vegetation strategies over two growing seasons (GS). To achieve this, a column-based greenhouse experiment was conducted to investigate microbial communities in tailings that were capped with a layer (10 or 30 cm) of peat-mineral mix (PMM) and planted with either upland or wetland communities. DNA metabarcoding analysis of the bacterial 16S rRNA gene and fungal ITS2 region as well as shotgun metagenomics were used to asses the impact of treatments on microbial taxonomy and functions, respectively. Results showed that tailings microbial diversity and community composition changed considerably after two GS compared to baseline samples, while communities in the PMM capping layer were much more stable. Likewise, several microbial functions were significantly enriched in tailings after two GS. Interestingly, the impact of capping on bacterial communities in tailings varied depending on the plant community, leading to a higher number of differentially abundant taxa and to a decrease in Shannon diversity and evenness in the upland treatment but not in the wetland treatment. Moreover, while capping in the presence of wetland vegetation increased the energy-related metabolic functions (carbon, nitrogen, and sulfur), these functions were depleted by capping in the upland treatment. Fungi represented a small proportion of the microbial community in tailings, but the relative abundance of several taxa changed over time, while the capping treatments favored the growth of some beneficial taxa, notably the root endophyte , in both upland and wetland columns. The results suggest that selecting the right combination of capping material and vegetation type may contribute to improve below-ground microbial processes and sustain plant growth in harsh environments such as oil sands tailings.

Microbial community structural and functional differentiation in capped thickened oil sands tailings planted with native boreal species.

Surface mining and bitumen extraction in Alberta's oil sands generates various tailings waste streams as by-products. Among these tailings, froth treatment tailings (FTT), originating from the froth treatment process, are particularly complex due to high levels of iron sulfide minerals (i.e. pyrite) with acid mine drainage (AMD) potential. Paraffinic FTT that are passed through a Tailings Solvent Recovery Unit (TSRU) to recover residual solvent are referred to as TSRU tailings. This study evaluated the ability of TSRU tailings to support upland and wetland vegetation under various thin capping designs using peat mineral soil mix (PMM) and coarse sand tailings (CST). A 30 cm PMM cover cap successfully supported upland and wetland vegetation for three years, while a thicker, multi-layer cap of 30 cm PMM above 20 cm of CST further improved plant survival and growth. The cap was found to effectively act as a barrier, protecting the vegetation from the adverse effects of pyrite oxidation in the TSRU tailings. While the TSRU tailings acidified (pH ≤ 2) under all capping treatments, the thickest cap (30 cm PMM/20 cm CST) delayed acidification by one year. TSRU and CST had low microbial biomass and diversity, with bacterial communities mostly composed of sulfur oxidizers and acidophilic taxa. In contrast, the PMM layer maintained a higher microbial biomass, diversity, and stability across all treatments, highlighting its potential to enhance plant-microbe interactions and improve the reclamation success of TSRU tailings.

ArticleTotal : 2	Year
Publication title Cited by 2	2025
Publication title Cited by 1	2025

Article	Year
Detection of naphthenic acid uptake into root and shoot tissues indicates a direct role for plants in the remediation of oil sands process-affected water. The Science of the total environment\| PubMed ID: 34328940	2021
Evaluating the attenuation of naphthenic acids in constructed wetland mesocosms planted with Carex aquatilis. Environmental monitoring and assessment\| PubMed ID: 37725196	2023
A Deep Look into the Microbiology and Chemistry of Froth Treatment Tailings: A Review. Microorganisms\| PubMed ID: 34069522	2021
Understanding Willow Transcriptional Response in the Context of Oil Sands Tailings Reclamation. Frontiers in plant science\| PubMed ID: 35574135	2022
An optimized extraction and gas chromatography analysis method for the quantification of diluent hydrocarbons in froth treatment tailings. Journal of separation science\| PubMed ID: 37449340	2023
Microbial community structural and functional differentiation in capped thickened oil sands tailings planted with native boreal species. Frontiers in microbiology\| PubMed ID: 37465026	2023
Evaluation of boreal plant and microbe communities on tailings solvent recovery unit (TSRU) tailings: A meso-scale greenhouse study. Chemosphere\| PubMed ID: 40886592	2025

Dani Degenhardt

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