From: Public Services and Procurement Canada
Bioaugmentation is an in situ bioremediation technique that consists of adding indigenous or exogenous (non-indigenous) microorganisms to contaminated soil or groundwater to enhance or supersede the existing microbial population. The microbial strain or consortium is introduced into the contaminated zone to improve contaminant biodegradation, which may be under aerobic (for example: diesel biodegradation) or anaerobic (for example: chlorinated solvent transformation) conditions. Biological activity may degrade contaminants, reduce their mobility and/or their toxicity.
Microbial consortia are prepared in laboratories, from contaminated soil and/or groundwater samples collected from the contaminated site, or from other sites where efficient biodegradation of the targeted contaminants is occurring. Cultures of microorganisms with known degradation capacities can also be used. The microorganisms from soil or groundwater samples can be isolated using a selective growth medium. Then the microorganisms are grown to high concentrations in a nutrient medium to obtain an inoculum. Once introduced into the subsurface, microorganisms must acclimatize, especially for exogenous microorganisms, to the geochemical conditions in the subsurface, before multiplying.
In Canada, the injection of non-indigenous microorganisms into the environment is regulated by a federal agency, and must follow the 1999 Canadian Environmental Protection Act (CEPA 1999). The microorganisms must be registered on the Domestic Substances List (DSL) in order to be considered for the bioaugmentation remediation technique; few cultures are approved for use in Canada.
Bioaugmentation projects may include:
Microorganisms are normally introduced into shallow contaminated soil by surface spraying and into deep contaminated soil or groundwater by injection through injection wells. In specific cases, nutrients, electron donors (substrate) and/or electron acceptors, are also introduced below the water table to induce the destruction or transformation of contaminants of concern by enhancing the microbial degradation activity.
Issues with bioaugmentation are the distribution of treatment media in the subsurface and the selection adapted and efficient bacterial strains or bacterial consortium able to treat the targeted contaminants.
Bioaugmentation has seen extensive application for aerobically degradable fuel compounds and for anaerobically reduced chlorinated solvents.
Injected materials vary widely according to contaminants, general groundwater composition and practitioners. The amendments to support microbial growth are similar to other aerobic or anaerobic bioremediation projects such as the nutrients and electron donor or acceptor substrates.
On-site storage is primarily a function of the compounds being applied to the groundwater systems and the manner of application. Projects using periodic injections of material may bring materials to the site on an as-needed basis and avoid on-site storage.
Notes:
Tests examining the effect of temperature change on hydraulic conductivity and establishing the zone of freezing with a pilot scale tubing system are recommended to properly design the full-scale containment system.
In situ bioaugmentation, is potentially applicable to remote northern sites where impediments to material transport and injection equipment mobilization can be overcome. Cold temperatures can hamper biodegradation and microbial activity may only occur during the summer months, thus treatment time may take several years. Microbial activity may be possible in deep soil as temperatures (below permafrost) are relatively constant over the course of the year.
Follow-up monitoring may be required to verify that the remediation objectives as well as applicable regulations are met once the groundwater system normalizes; after stimulation is withdrawn and excess biomass dies off.
Biodegradation of certain aliphatic chlorinated hydrocarbons could produce by-products or metabolites that are more toxic than the parent compound. In the case of (anaerobic) reductive dechlorination, the formation of chloroethane or vinyl chloride may warrant the use of an aerobic biostimulation step. Similar issues with toxic intermediates may occur in the degradation of some explosives and pesticides. Laboratory or pilot scale studies, as well as strict control of injected materials is typically required.
Bioaugmentation requires no secondary treatment.
Application examples are available at these addresses:
The treatment time for the remediation of a contaminated site by bioaugmentation varies according to contaminant type and concentration, the effectiveness of the bacterial population and the physical and chemical properties of the site.
Unavailable for this fact sheet
Composed by : Magalie Turgeon, National Research Council
Updated by : Karine Drouin, M.Sc., National Research Council
Updated Date : April 1, 2008
Latest update provided by : Marianne Brien, P.Eng., Christian Gosselin, P.Eng., M.Eng., Golder Associés Ltée
Updated Date : March 22, 2019
