Fact sheet: Mycoremediation: White Rot Fungus

From: Public Services and Procurement Canada

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Description

Mycoremediation is an aerobic bioremediation technique that uses white rot fungus (Phanerochaete chrysosporium, Trametes versicolor, etc.) as an inoculum for ex situ or in situ treatment of residual organic compound contamination in soil. White rot fungus produces extracellular enzymes, such as peroxidases and lactases, to degrade lignin. These enzymes are able to catalyze the degradative attack on a variety of organic contaminants such as pesticides, conventional explosives, semi-volatile organic compounds (SVOCs) and other recalcitrant contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and pentachlorophenol (PCP). Metals are not degraded by enzymes but accumulate in the fungi fruiting bodies.

This technique consists of mixing contaminated soils with the white rot fungus and a substrate, such as woodchips, to stimulate the development of the fungus and to promote soil aeration. This technique can be used with biopiles, phytoremediation, co-composting or land farming. Several factors affect the performance of this technique including, nitrogen and oxygen concentrations, pH, humidity and temperature.

As mentioned, mycoremediation is not a stand-alone remediation technique but a variant of bioremediation. White rot fungus can be used as an inoculum, for example, in ex situ biopiles or with other bioremediation technologies such as bioventing. While the use of fungi in biopiles has been documented, the in situ application is not widely used commercially and is studied in many universities and research centers.

Fungi is often indigenous to the soils and they are stimulated through the provision of the appropriate growth conditions. Alternatively, non-indigenous fungal strains can be added to the soil (bioaugmentation). In Canada, the introduction of microbial strains into the environment is regulated under the New Substances Notification Regulations (NSNR) of the Canadian Environment Protection Act (1999). Microorganisms must be on the Domestic Substances List (DSL) compiled by Environment Canada in order to be used in remediation procedures.

Internet link:

Implementation of the technology

The application of fungus as part of bioremediation remains largely in the laboratory and pilot scale phase. Few practitioners can comment on the implementation of mycoremediation on-site. The implementation of mycoremediation will depend on the type of bioremediation technology which it is used. This can include both ex situ (biopiles, composting, phytoremediation, etc.) or in situ (aerobic bioremediation) technologies. Please see the individual fact sheets for more details on implementation of these technologies. Laboratory and/or pilot scale preliminary testing could be required. Indigenous white rot fungus can be extracted from the contaminated soils and multiplied in laboratory conditions to produce an inoculum to be re-injected, ideally using site-specific conditions and in presence of site-specific contamination.

The addition of fertilizer, pH adjustment and/or soil texture additives are often required as part of the treatment. As any bioremediation technology, treatment systems will include some sort of measures to control moisture, aeration, nutrients and sometimes temperature. However, compared to other bioremediation techniques more emphasis is often put on moisture control systems since it is a more sensitive parameter for mycoremediation. If soil contaminants include volatile compounds, vapour/off-gas controls may be required. Depending on soil moisture content and contaminant characteristics, leachate collection and treatment may also be required.

Materials and storage

Modest amounts of fertilizer and soil texture additives can be kept on-site. For example, peat moss could be used to increase permeability and moisture retention of the soil matrix. Inorganic nutrients could be added to irrigation water over time. Storage will depend on the complementary bioremediation technique which it is coupled with.

Waste and Discharges

For ex situ treatment with biopiles, landfarming or composting, treatment cells are aerated by tilling/mixing or with ventilation pipes. They may warm up as a function of exothermic reactions or may be heated via other intensive methods and as a result, off-gassing could be expected. If contaminants pose an unacceptable risk, the treatment system will normally include vapour collection with a treatment before being rejected into the environment. If treatment is successful, the primary residual is fungal biomass (which decays over time). Excess reagent typically cannot be recovered, and is generally consumed.

Recommended analyses for detailed characterization

Biological analysis

  • Total heterotrophic and specific bacterial counts (according to the contaminants of interest)

Chemical analysis

  • pH
  • Metals concentrations
  • Contaminant concentrations present in the following phases:
    • adsorbed
    • dissolved
    • free
  • Nutrient concentrations including:
    • ammonia nitrogen
    • total Kjeldahl nitrogen
    • nitrates
    • nitrites
    • total phosphorus

Physical analysis

  • Vadose zone oxygen, nitrogen dioxide, and methane concentrations
  • Temperature
  • Soil water content
  • Evaluation of biological conditions and ecological factors

Recommended trials for detailed characterization

Biological trials

  • Microcosm mineralization trial
  • Biodegradation trial

Physical trials

  • Evaluation of optimal mixing rates

Other information recommended for detailed characterization

Phase II

  • Contaminant delineation (area and depth)
  • Presence of receptors:
    • presence of potential environmental receptors
    • presence of above and below ground infrastructure
    • the risk of off-site migration

Phase III

  • Soil stratigraphy
  • Identification of preferential pathways for contaminant migration
  • Conceptual site model with hydrogeological and geochemical inputs
  • Characterization of the hydrogeological system including:
    • the direction and speed of the groundwater flow
    • the hydraulic conductivity
    • the seasonal fluctuations
    • the hydraulic gradient

Applications

  • Suitable for the treatment of residual contamination in soils
  • Applicable to ex situ or vadose zone treatment only
  • Applies to organic contaminants that can be degraded or transformed under aerobic conditions such as pesticides, conventional explosives, semi-volatile organic compounds (SVOCs) and other recalcitrant contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and pentachlorophenol (PCP).
  • In general, white rot fungus prefers an environment with low nitrogen content

Applications to sites in northern regions

Remote sites are prone to high mobilization and on-site monitoring costs, limited equipment availability and short work windows. Difficulties in procuring timely analytical results may necessitate reliance on field screening, staged interventions and/or risk management. Biotreatment methods are popular options in remote areas but must be designed to operate without operator intervention for long periods.

Cooler temperatures (below 10 °C) significantly impair biodegradation using fungi. Soils may be heated and/or insulated, for example, using electrical heat-trace and expanded polystyrene (EPS) panels.

Treatment type

Treatment type
Treatment typeApplies or Does not apply
In situ
Applies
Ex situ
Applies
Biological
Applies
Chemical
Does not exist
Control
Does not exist
Dissolved contamination
Does not exist
Free Phase
Does not exist
Physical
Does not exist
Residual contamination
Applies
Resorption
Applies
Thermal
Does not exist

State of technology

State of technology
State of technologyExist or Does not exist
Testing
Exist
Commercialization
Exist

Target contaminants

Target contaminantsApplies, Does not apply or With restrictions
Aliphatic chlorinated hydrocarbons
Applies
Chlorobenzenes
Applies
Explosives
Applies
Metals
With restrictions
Monocyclic aromatic hydrocarbons
Applies
Non metalic inorganic compounds
Does not apply
Pesticides
Applies
Petroleum hydrocarbons
Applies
Phenolic compounds
Applies
Policyclic aromatic hydrocarbons
Applies
Polychlorinated biphenyls
Applies

Notes:

Metals are not degraded by this technology but accumulate in the fruiting bodies and should be collected regularly.

Treatment time

Treatment time
Treatment timeApplies or Does not apply
Less than 1 year
Applies
1 to 3 years
Applies
3 to 5 years
Does not apply
More than 5 years
Does not apply

Notes:

Note: Commercialization is mainly limited to ex situ applications, mostly biopiles with limited information available. in situ application is mainly at the testing stage.

Long-term considerations (following remediation work)

No monitoring is required for ex situ nor in situ treatment, since this technology doesn’t affect soil properties and structure.

Secondary by-products and/or metabolites

By-product and metabolite production during biodegradation or transformation with white rot fungus need to be analyzed to ensure that no production of compounds of greater concern than the parent compound are produced.

Limitations and Undesirable Effects of the Technology

  • High metal or contaminant concentrations can be toxic to the white rot fungus
  • Development and growth of white rot fungus was not observed below 10 °C
  • Competition between native bacterial populations can reduce the efficiency of the treatment
  • Soil mixing can interfere with the production of enzymes by the fungus
  • Fungi are susceptible to water stress
  • Little knowledge is available regarding the ability of white rot fungus to compete with other types of fungi
  • Whether as a consequence of fertilizer addition, changes in pH and / or ORP, the solubility of metals may change during treatment, for example through the formation or destruction of sorbent material, sulphides, phosphates, carbonates and/or hydroxides

Complementary technologies that improve treatment effectiveness

  • Thermal enhancement

Required secondary treatments

Using fungi as part of a biological treatment doesn’t require any additional secondary treatments. However, depending on the type of contaminants and treatment conditions, a vapour collection may be required.

Application examples

Application examples are available at this address:

Performance

Literature provides a lot of different results about the performances of white rot fungus. Efficiency depends widely on the type of soils, contamination and complementary technology.

It is important to verify whether white rot fungus technology meets the remediation objectives before applying this technique to a large volume of soil.

Measures to improve sustainability or promote ecological remediation

Mycroremediation is a variant of bioremediation and is applied as part of other technologies, such as biopiles, composting, phytoremediation, or in situ aerobic bioremediation. Please see the individual fact sheets for more details measures to improve the sustainability of the technology.

Potential impacts of the application of the technology on human health

Unavailable for this fact sheet

References

Author and update

Composed by : Magalie Turgeon, National Research Council

Updated by : Jennifer Holdner, M.Sc., Public Works Government Services Canada

Updated Date : March 1, 2015

Latest update provided by : Marianne Brien, P.Eng., Christian Gosselin, P.Eng., M.Eng., Golder Associés Ltée

Updated Date : March 31, 2018

Version:
1.2.1