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Bioremediation
Bacteria That Clean Pollution
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Bioremediation is the use of living organisms to reduce, remove, or transform pollution in soil, water, and sediments. Bacteria, fungi, and plants can turn some toxic chemicals into less harmful substances or trap them so they can be removed. This matters because many polluted sites are too large or fragile for harsh cleanup methods. Bioremediation can be slower than excavation or chemical treatment, but it can be cheaper and less damaging to ecosystems.
Oil-eating bacteria such as Alcanivorax can break hydrocarbons into smaller molecules and eventually into carbon dioxide, water, and biomass when oxygen and nutrients are available. Plants can take up or stabilize some heavy metals through phytoremediation, while fungi can bind metals and digest complex organic pollutants using powerful enzymes. Some tools are used in situ, meaning at the polluted site, while others are ex situ, meaning contaminated soil or water is removed for treatment elsewhere. Real events such as the Exxon Valdez and Deepwater Horizon oil spills showed that natural and assisted microbial activity can play an important role in large-scale cleanup.
Key Facts
- Bioremediation uses living organisms to clean pollution from soil, water, or sediment.
- Hydrocarbon biodegradation can be summarized as hydrocarbons + O2 -> CO2 + H2O + biomass.
- Alcanivorax bacteria become abundant in oil-contaminated seawater when nitrogen and phosphorus nutrients are available.
- Phytoremediation uses plants to absorb, stabilize, or transform pollutants such as lead, cadmium, and arsenic.
- In situ treatment happens at the contaminated site, while ex situ treatment removes material for treatment in a bioreactor, compost pile, or treatment bed.
- Engineered E. coli can be designed as biosensors that produce a signal when arsenic or other contaminants are present.
Vocabulary
- Bioremediation
- Bioremediation is the use of living organisms to break down, remove, or immobilize pollutants in the environment.
- Hydrocarbon
- A hydrocarbon is a molecule made mostly of hydrogen and carbon, such as many compounds found in crude oil and gasoline.
- Phytoremediation
- Phytoremediation is the use of plants to absorb, store, stabilize, or transform contaminants in soil or water.
- Biosensor
- A biosensor is a living system or biological molecule used to detect a chemical and produce a measurable signal.
- In situ
- In situ means treatment is done in the original location without digging up or moving the contaminated material.
Common Mistakes to Avoid
- Assuming bacteria make pollution disappear instantly is wrong because microbial cleanup depends on time, temperature, oxygen, nutrients, and pollutant type.
- Treating all pollutants the same is wrong because oil hydrocarbons can often be broken down, while heavy metals cannot be destroyed and must be removed, stabilized, or transformed.
- Adding too many nutrients during oil cleanup is wrong because excess nitrogen and phosphorus can cause algal blooms and reduce water quality.
- Calling phytoremediation a quick fix is wrong because plants usually need many growing cycles and may create contaminated plant material that must be handled safely.
Practice Questions
- 1 An oil spill contains 1200 kg of biodegradable hydrocarbons. If bacteria break down 35% of the hydrocarbons in the first month, how many kilograms remain after one month?
- 2 A treatment wetland removes 18 mg of dissolved metal from each liter of water. If 2500 L of water pass through the wetland, how many grams of metal are removed?
- 3 A shoreline has oil-contaminated sand, low oxygen below the surface, and very little nitrogen. Explain whether in situ bioremediation would likely work well without assistance, and name two changes that could improve it.