Bioremediation cleans up contaminated environments using live organisms like microbes, plants and fungi to nullify pollutants in soil, water and air. It's famously used in the Exxon Valdez oil spill of 1989 and ever after.
Industrial waste, oil spills, and agricultural runoff send toxins into the environment. Bioremediation uses the natural ability of these organisms to break down, transform or remove harmful pollutants.
This can happen in various ways, such as bioaugmentation, whereby specific microbes are added to speed up breakdown of pollutants. Phytoremediation uses plants to absorb or detoxify contaminants.
It's usually not a fast process especially when heavy metals are involved. It can take several months. Bacterial engineering hopes to speed up operations. Bioremediation has been used many times successfully.
How Bioremediation Works
The science behind bioremediation concerns the metabolic pathways of the organisms. Microbes, for instance, use pollutants like oil, pesticides, and even heavy metals as a food source.
They consume the contaminants and break them down through enzymatic reactions. The results are less harmful compounds like water, carbon dioxide and simpler organic molecules.
Bioremediation picks up as an option after the Exxon Valdez spill off Alaska in 1989. Fertilizers were applied to enhance growth of native microbial populations, reducing oil and helping affected coastlines recover naturally.
Methods of Bioremediation
In-situ bioremediation
This involves treating the contamination directly at the site, without excavating or removing the polluted material. This can be done by:
Biostimulation: Adding nutrients like nitrogen, phosphorus, or oxygen to stimulate the growth and activity of existing microbes capable of degrading the pollutants.
Bioaugmentation: Introducing specific strains of microorganisms known for their exceptional ability to break down specific contaminants.
This is used during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. As in the Valdez crisis, scientists introduce nutrients into the water to stimulate native bacteria.
The bacteria enthusiastically get to work and metabolize hydrocarbons. Their action reduces oil and speeds up the recovery process.
Ex-situ bioremediation
Excavating the contaminated soil or pumping the contaminated water and treating it elsewhere. This enables greater control and optimization of the process, often in bioreactors or landfarms.
This method allows improved monitoring and manipulation of conditions to promote microbial activity. Techniques include biopiles and landfarming, where soil is spread out and treated.
Remediation of a soil contaminated site at former General Motors plant in Tonawanda, New York in 2020 is successful. Soil is excavated, treated in a biopile, and returned to the environment after microbes break down toxins. The city calculates cost at over $7,000,000 US.
Phytoremediation
Phytoremediation uses plants to absorb or stabilize contaminants from the soil or water. Certain species can uptake heavy metals through their root systems, degrade pollutants, or stabilize hazardous materials.
For example, sunflowers have been effectively used to extract lead from contaminated urban soils. Sunflower phytoremediation reduces lead concentration by over 60% in a few months.
Sunflowers were famously used to remove radioactive contaminants like cesium and strontium from soil near the Chernobyl nuclear disaster site.
Sunflowers absorb heavy metals like lead, arsenic and cadmium from soil.
Unfortunately these can end up in seeds. Recent consumer tests in White Plains, New York USA, find disturbing heavy metal levels in sunflower seeds and products.
In India, researchers also use hyperaccumulator plants to absorb toxic metals like arsenic and cadmium from agricultural lands. The plants detoxify soil and give insight into mitigating future contamination.
Bioremediation of Pesticides in Agriculture
Pesticides and fertilizers in agricultural runoff can contaminate waterways and destroy aquatic life each in their own ways. Pesticides introduce toxins and fertilizers can cause massive algal over-blooms.
Bioremediation using microorganisms treats contaminated waters. This helps break down pesticides into less toxic forms before they reach ecosystems and reduce excess nutrients and/or toxins in algal blooms.
Landfill Leachate
Landfills generate leachate, a harmful liquid, when waste decomposes. Bioremediation includes using bacteria or micro-algae in bioreactors to decompose the complex organic compounds found in leachate.
Facts About Bioremediation
Plastic-Reducing Microbes: Scientists recently discover bacteria and fungi able to degrade various types of plastic including polyethylene terephthalate (PET), a common plastic used in bottles and packaging.
Enzymes: Specific enzymes produced by microbes can target and break down complex pollutants. Scientists try to isolate the enzymes and recreate them synthetically.
Microbial Efficiency: Some microbes can metabolize pollutants at faster rates, with some able to break down complex hydrocarbons within weeks under optimal conditions.
Fungi: Some fungi, through a method called mycoremediation, can digest and neutralize pollutants, using enzymes to break down substances.
Bioremediation technologies include phytoremediation, bioventing, bioattenuation, biosparging, composting (such as biopiles and windrows), and landfarming. Other remediation methods are thermal desorption, vitrification, air stripping, bioleaching, rhizofiltration, and soil washing.
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