Harnessing Nature-Based Solutions for Industrial Wastewater Remediation: Optimizing Constructed Wetlands for Treating Oil Sands Wastewater

The management of industrial wastewaters represents a global water quality challenge that requires sustainable, low-energy solutions capable of restoring ecological function while reducing contaminant loads. In Alberta, Canada, bitumen extraction from the Athabasca oil sands, one of the largest hydrocarbon reserves in the world, has generated over 1.4 billion m³ of liquid tailings and 400 million m³ of oil sands process-affected water (OSPW), currently stored in large on-site tailings ponds. OSPW exhibits acute and chronic toxicity to aquatic organisms and contains salts, metals, and complex organic contaminants, including naphthenic acids (NAs), a persistent and toxic group derived from bitumen extraction. Given the immense volume of OSPW requiring treatment, scalable and cost-effective remediation strategies are urgently needed. Constructed wetland treatment systems (CWTS) offer a promising, nature-based solution that harnesses plant–microbe–substrate interactions to degrade, transform, and sequester contaminants. Optimizing CWTS for OSPW treatment requires a detailed understanding of their functional mechanisms.

The Genomics Research for Optimization of Constructed Treatment Wetlands for Water Remediation (GROW) project is a multi-stakeholder collaboration among academia, government, and industry that advances both the scientific foundation and applied design of CWTS for OSPW remediation. Using mesocosm and pilot-scale wetland systems, the project integrates insights from molecular biology, wetland ecology, and engineering to elucidate treatment processes and enhance system performance. Here, we present results from a mesocosm-scale experiment evaluating the influence of plant species and system complexity on NA attenuation. Treatments included water-only (OSPW) controls, unplanted substrate systems, and planted systems with Carex aquatilis, Typha latifolia, or a combination of both plants, enabling isolation of plant-mediated, microbial, and abiotic processes. All planted mesocosms showed high survival and robust growth, achieving 46-48% NA removal over 87 days, compared to 19% in unplanted and 6% in water-only controls. Isotopic analyses confirmed preferential removal of bitumen-derived NAs and indicated active biological and biogeochemical processing. Fathead minnow embryo assays generally corroborated chemical analyses, showing the highest toxicity reduction in planted treatments, though some decreases occurred in water-only systems despite the insignificant NA removal. 

These results provide a holistic view of CWTS function, integrating plant physiology, chemical fate, isotopic evidence, and ecotoxicology. The findings demonstrate the potential of CWTS to substantially reduce OSPW toxicity and inform design and management strategies. Beyond efficacy, the GROW project establishes a framework for integrating nature-based solutions to address large-scale water quality challenges. The principles and tools developed have broad applicability to other industrial and municipal wastewater contexts, supporting sustainable water management worldwide.