From: Public Services and Procurement Canada
Enhanced aerobic bioremediation is an in situ technique mainly used or the treatment of soil and/or groundwater contaminated with petroleum hydrocarbons, and non-halogenated volatile or semi-volatile organic compounds.
Aerobic biodegradation is a well know and proven technology with many modes of operation. The main advantage of this approach is the low cost while the main disadvantage is the long time frame sometimes required. This technique consists of providing oxygen (electron acceptor), nutrients, and/or other necessary compounds required to accelerate natural biodegradation of the contaminant by indigenous aerobic bacteria. Oxygen, which is often the primary factor limiting the growth of aerobic bacteria, can be added to the contaminated area using air or oxygen injection systems such as forced air injection, injection of oxygen saturated water, by the addition of chemical oxidants such as hydrogen peroxide, or by the addition of oxygen release compounds (ORC). Nutrients may be incorporated to the contaminated area in a dissolved (soluble commercial fertilizer), or gaseous form.
Enhanced aerobic bioremediation projects may include:
Nutrients and oxygen are introduced in the contaminated media to induce the destruction or transformation of contaminants of concern. The microbial population adapts to the new chemical and geochemical conditions, multiplying and acclimatizing. When contaminant concentrations reach treatment objectives, stimulating measures are withdrawn.
The primary issue with aerobic bioremediation is the distribution of treatment media in the subsurface and ensuring adequate environment for microbial growth.
Reagents are typically introduced in the saturated or unsaturated zone through injection or extraction wells. Trenches, sparging systems, infiltration galleries, in-well diffusers, groundwater pumping and re-injection, and other equipment may also be used.
Although it is not applicable to metal remediation, several approaches at the experimental stages have been used to reduce dissolved metals concentrations through biologically mediated sorption, sequestration or precipitation (particularly the formation of metal sulphides) by changing the valence state of metals; the long-term fate of metals in these systems and relative benefits of alternative approaches is the subject of ongoing research.
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 aerobic bioremediation 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 monocyclic aromatic hydrocarbons and petroleum hydrocarbons doesn’t usually generate any deleterious secondary by-products or metabolites. Issues with toxic intermediates may occur in the degradation of some explosives and pesticides. Limitations and Adverse Impacts of the Technology
Application examples are available at these addresses:
In situ aerobic bioremediation is a widely proven technology. This technology is often less expensive and results in fewer disturbances to the environment or site activities compared to ex situ technologies requiring excavation. The treatment time for complete remediation with aerobic bioremediation varies according to the type and concentration of contaminants, the microbiological population and activity, and the physical and chemical conditions of the contaminated 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
