Last reviewed 4 Nov 2026 · 3 min read
1. Principle
DefinitionBioremediation
The use of living organisms — mainly bacteria and fungi, and also plants — to degrade, transform or remove pollutants from soil, water or sediment, converting them into harmless products such as CO₂, water, biomass and salts.
- Microbes use organic pollutants (oil, pesticides, solvents) as a source of carbon and energy.
- Metals cannot be destroyed; organisms can change their form (e.g. reduce toxic Cr(VI) to less toxic Cr(III)), immobilise them or take them up.
- Aerobic processes (with oxygen) are faster for petroleum hydrocarbons; anaerobic processes are useful for chlorinated solvents and some pesticides.
2. Strategies
| Strategy | Meaning |
|---|---|
| Natural attenuation | Allowing native microbes to degrade pollutants, with monitoring |
| Biostimulation | Adding nutrients (N, P), oxygen or moisture to stimulate native microbes |
| Bioaugmentation | Adding specially selected or cultured microbes to the site |
3. Techniques
In-situ (treated in place)
| Technique | How |
|---|---|
| Bioventing | Low-rate air injection into the unsaturated zone to supply oxygen |
| Biosparging | Air injected below the water table into saturated soil/groundwater |
| Bioslurping | Combines vacuum extraction of free product (oil) with bioventing |
| Permeable reactive barriers (biological) | Groundwater flows through a zone that supports degradation |
Ex-situ (excavated or pumped out first)
| Technique | How |
|---|---|
| Landfarming | Contaminated soil spread in thin layers and periodically tilled to aerate |
| Composting | Soil mixed with organic bulking agents; heat and microbes degrade pollutants |
| Biopiles | Heaped soil with aeration pipes, nutrients and moisture control |
| Bioreactors (slurry-phase) | Soil or water treated in a tank — best control, highest cost |