From: Public Services and Procurement Canada
Ex situ chemical oxidation using permanganate requires excavation and homogenization of soils and excavated sludge, or pumping of groundwater as well as the management of soil, sludge or water after treatment. Permanganate is one of the most commonly used and best-known chemical oxidants. It allows the complete or partial destruction of organic contaminants.
Permanganate is available in liquid or salt form. Potassium permanganate is the most common form of salt. In addition, calcium and magnesium salts are also used. The salts are dissolved in water prior to their addition to the soil, sludge or water to be treated. Permanganate oxidation is effective under pH conditions ranging from 3.5 to 12, but the specific oxidation reaction is pH dependent.
4.16 Chemical Reduction/Oxidation—FRTR Remediation Technologies Screening Matrix and Reference Guide, Version 4.0
For the treatment of groundwater, extraction structures are put in place to collect contaminated groundwater and convey it to the treatment system, where it is treated and discarded.
The implementation of this technology may include:
For the treatment of contaminated soil, conventional excavation equipment is used to remove or mix the contaminated soil for on-site treatment. This can include:
The implementation of the groundwater treatment system could lead to the management of contaminated soils resulting from drilling or excavation activities. In this case, these soils must be removed off-site.
The complete mineralization of organic compounds produces carbon dioxide, water and inorganic ions (such as chloride). In some cases, complete mineralization doesn’t occur and contaminant residues can remain in the soil.
Potassium permanganate produces high levels of sodium or potassium and precipitates of manganese dioxide (because of the state of oxidation, dissolved manganese is not usually a problem, but this can be confirmed by means of environmental monitoring).
Treated groundwater typically meets applicable criteria and doesn’t pose a high risk when discharged. However, water quality monitoring is performed prior to discharge to ensure no unacceptable levels of by-products, reagents, or pH remain in the water.
Treated soils must be analyzed for conformity before reuse.
Notes:
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.).
Applies to the degradation of chlorinated compounds, such as perchloroethylene, trichloroethylene, dichloroethylene and vinyl chloride, as well as polycyclic aromatic hydrocarbons.
Application of this technology in a northern region may be difficult because of the monitoring that such a system requires. For remote sites, this implies greater mobilization and higher on-site monitoring costs. The availability of equipment is limited and requires additional mobilization. Work windows are relatively short considering that this technology involves either excavation of the soil or pumping of groundwater. These two activities, as well as the handling of soil or water up to the treatment unit could require additional effort and cost at low temperatures and there is a risk of freezing.
Following soil treatment, whether used for backfilling excavations or for imported materials, environmental and geotechnical control of materials must be performed to ensure that soils do not exceed the applicable criteria for the site and do not create problems in terms of geotechnical stability or differential settlement.
Chemical oxidation of organic compounds by permanganate produces carbon dioxide. Obtaining toxic by-products may be of concern in the event of incomplete reactions. Laboratory tests and/or pilot tests, as well as strict quality control of the injected reagents may be required. Products resulting from oxidation treatment are generally (but not always) less toxic, more mobile and more biodegradable than their precursors.
If free phase is present, a separation process must be implemented prior to the chemical oxidation treatment of soil or groundwater.
The gaseous emissions must be captured and processed. If the contaminated soils are mixed with a permanganate solution, leaching water may be generated and must be collected and processed.
The following website contains application examples:
Chemical oxidation with permanganate is a widely proven technology that allows relatively fast treatment.
The advantage of ex situ treatment over in situ treatment is the control of oxidation conditions (e.g. contact time) and the certainty of a homogeneous distribution of the oxidant in the contaminated material.
Main Exposure Mechanisms
Applies or Doesn’t Apply
Monitoring and Mitigation
Dust
Applies for soil treatment and permanganate separation
Monitoring conditions favourable to dispersion during the excavation of the soil to be treated.
Atmospheric/Steam Emissions—Point Sources or Chimneys
Applies according to the treatment system
Integrate the collection and treatment of waste gases into the design,
emission monitoring (choice of parameters, types of samples and intervention levels depending on source, risk and local requirements).
Atmospheric/Steam Emissions—Non-point Sources
Applies
Estimation of the potential for vapour emissions, and monitoring of emissions to confirm predictions.
Air/steam — by-products
Runoff
Doesn’t apply
N/A
Groundwater—displacement
Modelling and monitoring using pressure sensors
Groundwater—chemical/ geochemical mobilization
Groundwater—by-product
Water quality monitoring
Accident/Failure—damage to public services
File checks and licensing prior to excavation or drilling, development of excavation procedures and emergency response
Accident/Failure—leak or spill
Risk review, development of accident and emergency response plans, monitoring and inspection of unsafe conditions
Accident/Failure — fire or explosion (inflammable vapours)
Other—Accident/Failure—migration of gases and liquids along preferential pathways
Other — Handling of contaminated soils
Composed by : Mélanie Bathalon, B.Sc, MCEBR
Updated by : Karine Drouin, M.Sc., National Research Council
Updated Date : August 17, 2017
Latest update provided by : Nathalie Arel, P.Eng., M.Sc., Christian Gosselin, P.Eng., M.Eng. and Sylvain Hains, P.Eng., M.Sc., Golder Associés Ltée
Updated Date : March 22, 2019
