Farm drainage water can carry soil, nutrients, organic matter, pathogens, salts, pesticides, metals or other substances away from fields and working areas. Managing that water may require a combination of source control, storage, settling, filtration and treatment. Mycofiltration is one approach that may be considered in suitable situations, particularly where a low-energy biological treatment step is useful.
What is mycofiltration?
Mycofiltration uses fungi, fungal materials or fungal growth systems to interact with water and the substances it carries. The term “myco” refers to fungi, while “filtration” describes the treatment function. In practice, a mycofiltration system may contain fungal mycelium—the thread-like growth of fungi—within a porous material, organic medium, filter bed or constructed treatment unit.
The system is not necessarily a fine physical filter. Depending on its design, fungal material may help intercept suspended solids, support biological breakdown of some organic substances, or retain and transform particular pollutants. Other organisms and the surrounding filter material may also contribute to treatment. For this reason, it is more accurate to view mycofiltration as a biological treatment process than as a universal replacement for conventional filters.
Fungi can be useful because their growth forms extensive networks through a treatment medium. However, the effectiveness of any system depends on the fungal material selected, the pollutants present, the water chemistry, temperature, moisture, oxygen availability, contact time and hydraulic loading. A system that works in one setting cannot automatically be transferred to another.
Where might it be considered on a farm?
Mycofiltration may be considered where drainage water is collected or can be directed through a defined treatment area. Possible situations include:
- runoff from areas where soil, plant residues or organic materials are being moved or stored;
- drainage from livestock-related or other high-organic-matter areas, subject to appropriate assessment;
- water leaving growing areas, nurseries or protected production spaces;
- drainage affected by sediment, nutrients or selected organic contaminants;
- pre-treatment or polishing of water after settling, storage or another primary treatment step; and
- small or moderate drainage flows where a controlled biological treatment unit can be installed and maintained.
These are potential applications rather than guarantees. The approach may be less suitable for highly variable, very large or heavily contaminated flows unless it forms part of a larger engineered system. It may also be unsuitable where the water contains substances that inhibit fungal activity or where the treatment area cannot be protected from uncontrolled flooding and bypass flows.
Start with the water-quality problem
The first step is not choosing a fungus. It is identifying what needs to be managed. A basic site assessment should consider the likely sources of contamination, the timing of drainage and the route water takes across the property.
Where appropriate, water testing can help establish whether the main concerns are suspended solids, nutrients, organic matter, salts, metals, pesticides, pathogens or another pollutant. Testing requirements depend on the site and the intended discharge or reuse. Visual observations alone are not enough to confirm water quality.
Flow is equally important. Estimate typical, peak and low-flow volumes, and note how these change after rainfall, irrigation, cleaning, harvesting or other activities. Seasonal changes can affect both pollutant concentrations and the biological activity of a treatment system. A unit designed for a modest, steady flow may be overwhelmed by stormwater or bypassed during a sudden surge.
What a system may involve
A practical system could include several connected stages rather than a single fungal barrier. Source controls may reduce the amount of contamination entering the drainage. A settling area, screen or other preliminary step may then remove coarse material and protect the biological treatment zone.
The mycofiltration stage might use fungal growth supported by a porous medium, replaceable fungal material, a contained bed or another site-specific configuration. Water needs to contact the treatment material for long enough to allow the intended processes to occur. The system also needs a controlled inlet and outlet, stable support, protection from erosion and a way to manage overflow safely.
Design should allow operators to inspect the unit, remove accumulated solids, replace or renew spent material and reach the system with suitable equipment. Access is often as important as the treatment medium itself. A treatment area that cannot be safely cleaned or serviced may quickly lose practical value.
Maintenance and operational requirements
Mycofiltration should not be treated as a set-and-forget installation. Organic matter and sediment can block flow paths, reduce contact with the fungal material and cause water to pass around the treatment zone. Regular checks can identify ponding, odours, erosion, unusual colour, damaged containment, pest activity or bypassing.
Maintenance planning should address:
- screening or settling solids before they reach the fungal treatment stage;
- removing accumulated sediment and managing it appropriately;
- checking flow distribution so that water does not form preferential channels;
- replacing, refreshing or safely handling spent fungal materials;
- protecting the system from excessive rainfall, flooding and physical damage; and
- recording inspections, maintenance work and any operational changes.
Spent material should not automatically be spread on land or placed in general waste. Its handling depends on what it has collected or transformed, as well as applicable waste, soil and environmental requirements. If contamination is possible, obtain advice before reuse or disposal.
Monitoring performance
Monitoring should be linked to the original water-quality objective. Depending on the risk and scale of the operation, this may include visual checks, flow observations and periodic sampling at the inlet and outlet. Results should be considered alongside rainfall, flow rate, maintenance history and any changes in the drainage source.
A reduction in visible sediment does not prove that dissolved pollutants or pathogens have been removed. Conversely, a system may appear unchanged while its treatment performance is declining because the material is becoming blocked or exhausted. Monitoring should therefore be designed around the pollutants that matter at the site, with support from a suitably qualified water, agricultural or environmental professional where necessary.
Benefits and limitations
Potential advantages of mycofiltration include the use of biological materials, the possibility of integrating treatment into a wider drainage plan and the opportunity to develop systems that are relatively low energy or use locally manageable materials. Fungal systems may also be useful as one stage in treating certain organic pollutants or improving water quality before discharge or further treatment.
These benefits are not guaranteed. Some applications remain promising but require site-specific testing, specialist design or further validation. Fungi will not remove every contaminant, and performance may be inconsistent when flow, temperature, pollutant loading or water chemistry changes. A fungal treatment unit may need conventional settling, constructed wetlands, chemical treatment, storage, source reduction or other controls alongside it.
Planning before installation
Before building or relying on a mycofiltration system, compare it with other treatment options on the basis of capital cost, land requirement, operating effort, maintenance access, replacement frequency, reliability and consequences of failure. Consider whether the system can be isolated or bypassed safely during maintenance and extreme flows.
Check relevant environmental, agricultural, planning, waste and discharge requirements before construction. Extra care is needed where drainage water could reach waterways, livestock, crops, workers or the public. A site assessment and appropriate technical advice can help determine whether mycofiltration is suitable, what level of monitoring is needed and how it should fit within the farm’s wider water-management or remediation strategy.
Used with realistic expectations, mycofiltration may be a useful part of a broader drainage plan. Its value comes from matching the biological treatment approach to the actual water-quality problem, flow conditions and operational capacity of the site—not from treating fungi as a universal solution.