Many of us are aware of the dire situation in our fresh water systems – but both the reasons and the solutions are multiple and complex.

Flete Field Lab works predominantly on tributaries leading into the Erme River in South Devon. We use small scale mycofiltration trials to test whether this extraordinary and under researched kingdom of fungi can support the ‘cleaning’ of water. Mycofiltration can remove harmful pollutants like petrochemicals or bacteria and in some cases even heavy metals.

The Erme is a good place to trial mycofiltration since in 2022 this beautiful river was polluted by sewage outflow 232 times lasting over 2000 hours (EA 2022: Top of the Poops 2023). As a result we have focused on remediating E Coli using Pleurotus Pulmonaria (Summer Oyster) during our first three years.

Fungi is a mostly unknown Kingdom of its own, but we do know that they are made up of a vast number of different species. Many of them are ‘nature’s engineers of transformation’, changing dead matter by decaying it into life-giving soil, creating the conditions for the cycle of life and death in the world whilst also distributing various nutrients across species in the plant Kingdom. We believe there is a role for them to play in what is essentially a big clean up, and that with their help we can begin to restore our natural world to its fully functioning, biodiverse and healthy self.

To limit potentially unseen negative consequences we use a native strain of Summer Oyster from our amazing supplier Adrian at Gourmet Mushrooms. We also gather the fruiting bodies as they near maturity to avoid spawn being released into the wild. (Please also see our manifesto and ecology report for more information about our methodology.)

The first trial of mycofiltration took place in 2022 on Holbeton Brook, a small tributary leading into the Erme estuary. Together with our student Caleb Akpogbero Ndudi, we created an intervention of twelve small sacks filled with Pleurotus Pulmonaria. The results were impressive with a 47% reduction in E-coli.

Then in 2023 we again worked with our student Rhianna Trim on that stream with an intervention at three points but using the same substrate and species of fungi and in this case the overall reduction of E Coli was reduced to 28%. For 2024 we are trialling a larger E Coli intervention on another tributary and will have a longer period of testing which will build on these two previous projects and give us much needed information about the efficacy and potential for this type of mycofiltration.

Another student Ambar Jimenez Hernandez, supported our work with a local dairy farm and collated research on any global projects being done on the potential of mycofiltration to remove lipids from dairy waste water which has a huge negative impact on water quality the world over. It transpires that this was the first test of its kind – and one we are repeating with a more rigorous academic framework in 2024 with a student from University of Plymouth and a supportive local farm. This is exciting because it appears to be the first trial of its kind but also seemed to show some very encouraging early results during testing in 2023.

“England’s rivers… are widely agreed to be a national treasure yet only 14% are in good ecological health and every single one fails to meet chemical standards.”

State of our Rivers, Rivers Trust »