#FEMSmicroBlog: Microorganisms can help clean industrial wastewater contaminated with naphthenic acids
Microorganisms carry a myriad of genes involved in metabolic processes that are essential to ecosystem functioning and maintaining life on Earth. Some microorganisms have particularly interesting metabolic capabilities, such as the degradation of pollutants and toxic compounds, as explained in the review “Microbial degradation of naphthenic acids using constructed wetland treatment systems: metabolic and genomic insights for improved bioremediation of process-affected water” in FEMS Microbiology Ecology. In this #FEMSmicroBlog, Paula Reis explores how microorganisms represent a sustainable, low-energy, and potentially cost-effective strategy for reducing toxicity in contaminated environments. #FascinatingMicrobes
The problem of industrial wastewater containing naphthenic acid
Mining of oil sands generates large volumes of industrial wastewater containing naphthenic acids. These naturally occurring compounds demonstrate toxicity toward aquatic organisms. Hence, their transformation into less toxic compounds in a sustainable fashion is the focus of ongoing research.
Previous studies have shown that some bacterial species are able to metabolise naphthenic acids, leaving them completely or nearly completely degraded or transformed. This microbial naphthenic acid degradation ability has great potential as a sustainable bioremediation approach for water affected by oil sands processes.
One method for the bioremediation of industrial wastewater is the constructed wetland treatment system. Such an engineered system is designed to mimic the natural processes of wetlands as it combines different physical, chemical, and biological processes, including microbial and plant-mediated transformation.
So far, small or medium-scale studies conducted in the lab and in a field pilot within a constructed wetland have shown promising results. In such a constructed wetland treatment system, over time, the concentrations of specific naphthenic acids and other contaminants were significantly reduced by 7% to up to 83%.
Despite the potential of constructed wetland treatment systems for cleaning industrial wastewater containing naphthenic acid, many challenges need to be overcome for efficient remediation. For example, variable field conditions, such as oxygen availability or temperature, can affect microbial composition, growth, and activity, and in turn impact the rate of naphthenic acid degradation. Also, due to their diverse chemical compositions, some naphthenic acids are more difficult to degrade than others.
Microbial metabolic pathways for naphthenic acid degradation
The review “Microbial degradation of naphthenic acids using constructed wetland treatment systems: metabolic and genomic insights for improved bioremediation of process-affected water” in FEMS Microbiology Ecology summarizes the current knowledge on how microorganisms in such treatment systems can provide solutions for optimized bioremediation of industrial wastewater.
The review discusses the microorganisms known to degrade naphthenic acids in the laboratory, such as Pseudomonas putida, Rhodococcus aetherivorans, Alcaligenes sp., and Arthrobacter sp. It further dives deep into the various microbial genes and metabolic pathways as they depend on the species, the environmental conditions, and the chemical structure of the naphthenic acid molecule.
In constructed wetland treatment systems, plants also play important roles in bioremediation as they interact with microorganisms in the sediments, mostly near their roots. For example, plant roots oxygenate the sediments while compounds released by the plant can stimulate microbial naphthenic acid degradation.
Improving microbial bioremediation of naphthenic acids
Scientists continue to identify and characterize more genes and enzymes that microorganisms use to degrade naphthenic acids. With that, they can then develop tools to track the DNA of naphthenic acid-degrading microorganisms in the environment.
These tools could be used to predict and monitor the potential for microbial naphthenic acid degradation under different environmental conditions, naphthenic acid concentrations and compositions, constructed wetland treatment system configurations, plant compositions, and other factors. This review discusses that such tools, together with complementary approaches, may allow for better monitoring, management, and efficiency of constructed wetland treatment systems.
- Read the article “Microbial degradation of naphthenic acids using constructed wetland treatment systems: metabolic and genomic insights for improved bioremediation of process-affected water” by Reis et al. in FEMS Microbiology Ecology (2023).
Paula Reis is a postdoctoral fellow at the University of Waterloo, Ontario, Canada. She is a microbial ecologist and biogeochemist interested in how microorganisms affect biogeochemical cycles. With a focus on the aquatic environment, her research investigates the links between microbial dynamics and carbon cycling, greenhouse gases, and the degradation of contaminants in water.
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The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.
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