Public Services and Procurement Canada
In situ hydrogen peroxide oxidation treatment refers to the injection of liquid hydrogen peroxide into a contaminated soil and/or aquifer in order to convert contaminants into non-toxic compounds, mainly water vapour and carbon dioxide.
The hydrogen peroxide oxidation reaction is relatively slow and this technique alone is not enough to thoroughly degrade organic compounds. However, when combined with a catalyst such as ferrous iron (Fe2+), the hydrogen peroxide oxidation potential is increased substantially. Hydroxyl radicals (OH?) produced from the decomposition of hydrogen peroxide due to ferrous iron are highly reactive, non-specific oxidants. The catalyst can be part of the soil matrix or added as a solution.
The hydrogen peroxide oxidation reaction combined with a catalyst ferrous iron at a pH between 2.5 and 3.5 is known as the “Fenton reaction.” Fenton’s reaction is pH dependent, that is, hydroxyl radical production is more effective under acidic conditions than in alkaline environments. However, stabilizers are currently being developed to improve the effectiveness of oxidation at higher pHs.
Hydrogen peroxide oxidation is suitable for a wide range of contaminants such as petroleum hydrocarbons, phenolic compounds, TCA, PCE, TCE, DCE, VC, BTEX, chlorobenzene, 1,4-dioxane, MTBE and tert-butylalcohol (TBA).
In situ chemical oxidation (ISCO) with hydrogen peroxide consists of injecting a solution of hydrogen peroxide in the soils and/or groundwater using injection wells, infiltration trenches, soil mixing or, is used to bring a strong oxidant in contact with the contaminant. The objective is to bring the oxidant in contact with contaminants. For halogenated compounds intermediate compounds may be formed. Multiple injection events (usually two or three) are often required. The primary issue in chemical oxidation is the distribution of treatment media in the subsurface.
Implementation of hydrogen peroxide oxidation projects may include:
Hydrogen peroxide may also be added as sludge (calcium peroxide) when a longer reaction time is required, for example in low permeability formations, to allow for more uniform distribution.
On-site treatment trials will establish the efficiency of the technology and the parameters that influence the treatment time and cost (e.g. residence time, pump flow rate, requirements for pre-treatment, etc.).
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 chemical oxidation (ISCO) is potentially applicable to remote northern sites, however, significant impediments to material transport and injection equipment mobilization must be overcome. Given the high cost of mobilizing reagents and equipment, ISCO may be pursued on a one-time basis with the objective of reducing concentrations to levels amendable to monitor natural attenuation or another alternative. Northern applications require climate-appropriate design, including consideration of permafrost and of seasonal changes in ground conditions.
Contaminant rebound in groundwater frequently observed following ISCO treatment necessitates multiple treatment campaigns.
The chemical reaction that occurs with the application of this technique releases significant quantities of dissolved oxygen, which can improve biodegradation and natural attenuation.
By-product formation can be a concern if complete reaction cannot be obtained; benchtop and/or pilot testing, as well as strict quality control for injected materials, is typically required.
Oxidation products are usually (but not always) less toxic, more mobile and more biodegradable than parent compounds. For example, MTBE may degrade into acetone of tert butyl formate. Petroleum hydrocarbons may generate acetone or alcohols. Explosives (RDX and HMX) may create elevated levels of nitrate.
Compared to other oxidants, hydrogen peroxide has a low potential to generate by-products.
Application examples are available at these websites:
Unavailable for this fact sheet
Composed by : Serge Delisle, Eng. M.Sc., National Research Council
Updated by : Karine Drouin, M.Sc., National Research Council
Updated Date : March 1, 2009
Latest update provided by : Marianne Brien, P.Eng., Christian Gosselin, P.Eng., M.Eng., Golder Associés Ltée
Updated Date : March 22, 2019