This website focuses mainly on the many benefits of using bioremediation to clean contaminating chemicals from the environment, but this does not mean that that bioremediation does not have limitations or that there are no alternatives.
For example, there are currently limited applications for bioremediation due to strict government regulation on drinking water standards. Microorganisms capable of bioremediation need a certain amount of the contaminant to survive. If the concentration of the contaminant is reduced to a certain level, then microorganism generation will be outweighed by their death rate and the microorganism population will disappear. Most of the time, this threshold level of contaminant is higher than the drinking water standard, nullifying the applicability of bioremediation.
However, as scientists begin to recognize the relative unimportance of safe drinking water contaminant levels in every location, bioremediation will gain support as a cheap and efficient way to remove the contaminant to a level at which risk would be insignificant. If contaminated water were to leak out into the system after being bioremediated, it would quickly become diluted to concentrations equal to or less than drinking water standards.
Additionally, industries are reluctant to embrace new technologies such as bioremediation. But as our knowledge increases in the field, these industries will be more likely to invest in the promising capabilities of bioremediation. Top
- Cost effective, because contaminants can be treated in situ.
- Capitalizes on a natural processes that occurs anyway.
- Can be used to treat dispersed contaminants in the environment.
- Minimizes disturbance to the environment and danger to workers.
- Can mineralize contaminants completely and eliminate the need for disposal.
For bioremediation success stories click the Examples link for any of the contaminants listed. Top
Failures:
- Most failures at bioremediation are due to failure of introduced organisms to thrive in the natural environment or a failure to access the contaminant. This could be due to:
- Lack of nutrients
- Predation or parasitism
- Competition
- Immobility of introduced bacteria
- Contaminant concentrations below threshold for organism survival
- Organisms may feed on alternative substrates
A Few examples of failed bioremediation attempts (which can be costly):
- Inoculation of soil with aliphatic hydrocarbon degrading bacteria did not enhance degradation of fuel oil
- A Pseudomonas sp. shown in lab cultures to degrade 1,4-dichlorophenol failed to degrade the compound when added to surface soils
(source: Watwood, Maribeth 2003)
Site Specificity:
- Each new site represents a different set of conditions, and what works in the lab may not translate to the field.
- Laboratory experiments can be carefully controlled, but these optimal conditions may not be possible at the site and may misrepresent possibility for success in the field
Fears:
- introducing “foreign” microorganisms to field sites could have unforeseen consequences on the ecosystem
- Concerns about genetically modified organisms used for bioremediation are basically the same as concerns about using GMO’s in general. There is worry about
- Horizontal gene transfer
- Creation of new pathogens
- Possibility of mutations that allow the organism to become invasive.
Hydrocarbons
Burning off oil spills at sea. Has several drawbacks: the ignition of the oil; maintaining combustion of the slick; the generation of large quantities of smoke; the formation and possible sinking of extremely viscous and dense residues; and safety concerns .
Halogenated Organics
- Soil vapor extraction procedures can be used to remove contaminants from the soil ex situ. Scrubbers have been developed to oxidize halogenated carbons through chemical processes into H2O, CO2 and hydrochloric acid (HCI). ThermoxTM uses thermal and catalytic oxidation for the control of halogenated VOC's. Drawbacks: uses expensive equipment, releases HCl which must be dealt with, requires high temperatures.
- Chlorinated solvents at a submarine base in King's Bay Georgia were chemically remediated in situ using Fenton's reagant, a hydrogen peroxide and iron catalyst that oxidizes PCE and TCE. (source: USGS)
Nonchlorinated Pesticides and Herbicides
Properly containing pesticides and herbicides is the best strategy for preventing environmental contamination. Proper waste disposal of obsolete chemicals can prevent widespread contamination which is much more difficult to remediate. “Forgotten” chemical stocks in third world countries can present a major health hazard.
see Cleaning Up the Pesticides Nobody Wants for more information.
Metals
Toxic metal contaminants can be isolated or immobilized through chemical processes.
For details see Remediation of Toxic Metals (Evanko and Dzomback, 1997)
Website designed by:
Edward Burgess, Libby Howard, Michelle Savard, and Jackie Zider