Enhanced Bioremediation - Soil, Sediment, Bedrock and Sludge (Université d’Aberdeen)
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This document explains enhanced bioremediation as a method for cleaning contaminated soils, sediments, bedrock, and sludge. The process involves delivering water-based solutions with nutrients, oxygen, or microbial inoculants into the contaminated area to support the activity of microbes that break down organic pollutants into less toxic substances. Aerobic bioremediation occurs in the presence of oxygen, leading microbes to convert contaminants into carbon dioxide, water, and microbial biomass. It is commonly applied using spray irrigation for shallow soils or injection wells for deeper contamination, although low temperatures can slow the process unless heat blankets are used.
In anaerobic conditions, microorganisms degrade contaminants into methane, carbon dioxide, hydrogen, or sulfides, but some hazardous compounds like vinyl chloride can form as intermediate products, which may require subsequent aerobic treatment for complete breakdown. White rot fungi, which produce lignin-degrading enzymes, have been studied for their ability to degrade pollutants such as TNT, especially in nitrogen-limited environments, though full-scale applications are still experimental due to challenges like microbial competition and chemical sorption.
Enhanced bioremediation is effective for soils, sludge, and groundwater contaminated with petroleum hydrocarbons, pesticides, wood preservatives, and other organics. It can target specific contaminant groups such as PAHs, SVOCs, and BTEX, often with lower costs and minimal site disturbance compared to thermal or chemical treatments. It is particularly useful for low-level residual contamination and can be combined with source removal.
Limitations include a reduced effectiveness in soils with poor contact between microbes and contaminants, heterogeneous or layered soils, and high concentrations of metals or chlorinated organics that inhibit microbial activity. Low temperatures, high concentrations of certain chemicals, or long chain hydrocarbons may also hinder remediation.
Accurate assessment of contaminant properties, soil characteristics, and microbial activity is necessary before undertaking bioremediation. Treatability tests help determine feasibility and expected timelines, which can range from months to years. Benefits include lower costs, less site disturbance, and simultaneous treatment of soil and groundwater, though the process is slower and less predictable than other methods.
The cost typically ranges from £25 to £75 per cubic meter, influenced by soil type, contamination level, and amendments used. Overall, bioremediation is a valuable and environmentally friendly option for organic contaminant cleanup, especially where source removal is already underway or residual contamination remains.
Enhanced Bioremediation - Soil, Sediment, Bedrock and Sludge (Université d’Aberdeen) (en)
Number of pages: 3
Key takeaways
- Enhanced bioremediation effectively degrades organic contaminants in soils and groundwater
- The process utilizes indigenous or inoculated microorganisms, with treatments including nutrient addition, oxygen supply, and moisture management to promote biological degradation, making it suitable for low-level residual contamination.
- In situ bioremediation offers cost and environmental advantages but requires longer treatment times
- Since contaminated soil is not excavated, in situ methods reduce site disturbance and transportation costs; however, benefits are counterbalanced by extended remediation durations, often spanning years, and variability in treatment efficacy.
- Low temperatures and certain soil conditions can impede bioremediation progress
- Factors such as low soil temperature, clay or layered soils, and high concentrations of heavy metals or chlorinated organics can slow microbial activity or hinder contaminant contact with microbes, limiting effectiveness.
- White rot fungus can degrade persistent organo-pollutants but faces limitations at full scale
- Although effective in laboratory settings, field application is challenged by competition with native microbes, toxicity, and chemical sorption; success in degrading compounds like TNT using this method has yet to be proven at full scale.
- Bioremediation's scope is primarily limited to organic contaminants; inorganic contaminants require different approaches
- While bioremediation can alter valence states or immobilize inorganics, it cannot directly decompose inorganic pollutants, necessitating complementary methods for inorganic contamination.
- Cost of enhanced bioremediation ranges from £25 to £75 per cubic meter, influenced by site-specific factors
- Costs depend on soil type, contamination levels, and amendments used, making this method relatively inexpensive compared to thermal or chemical treatments, especially for low to moderate contamination levels.
Sources
- Enhanced Bioremediation - Soil, Sediment, Bedrock and Sludge (Université d’Aberdeen) - - https://www.abdn.ac.uk/remediation-dst/documents/enhanced_bioremediation.pdf
