Mycofiltration: using mushrooms to clean the river!

Mycofiltration is the pioneering technique of using fungi to filter out pollutants from water.  First developed in the USA by Paul Stamets, we are trialling it here along the River Wandle for the first time in the UK!  We have put several ‘mycofilters’ around surface water outfalls that drain into the river to capture pollutants such as heavy metals, hydrocarbons, bacteria and excess nutrients and will be monitoring their effectiveness over the coming year.

A mycofilter is basically a hessian sack filled with wet straw and wood chip and mycelium (the non-fruiting part of fungi).  They look a bit like slightly mouldy sandbags, but don’t let that put you off!!  They are doing important work.

Getting to the point of being able to install mycofilters along carefully selected study sites by the Wandle took several stages…here’s what we did in a quick run-through:

Stage 1: preparing materials


40 kg of mushroom spawn was ordered from a specialist UK supplier and carefully weighed out to the correct portions needed per hessian sack.4 m


Several locally sourced straw bales were acquired from Bushells Farm in Carshalton.


Freshly chipped wood sourced from native deciduous trees cut by Sutton Council was collected from Central Nursery Wood Station in Croydon.

 Stage 2: building

Then the first of three workdays was held at Sutton Ecology Centre to make the mycofilters themselves.








All the materials needed: straw, wood chip, hessian sacks, mycelium spawn and a plentiful supply of fresh water were laid out as an attractive buffet (!) for volunteers to build


Volunteers worked in pairs – one to hold the bag open and the other to scoop in the materials.


The ingredients were layered like a special lasagne: first a good layer of wet straw…


Then a scoop or two of wood chip…


Then a generous sprinkling of mycelium was added and the layering process repeated, until the bags were tightly packed and full.


The finished sacks were put into rubble bags to protect them and volunteers took a bag or two each home with them to develop in their gardens over the next few weeks.


After five weeks typically, the mycelium had grown throughout the sacks and was visible on the outside as a white feathery network of filaments – they were ready to install!

Stage 3: installation

Three more workdays were held to invite the volunteers back with their sacks and to install them at the study sites by the river.


The first site tackled was Bennetts Hole Local Nature Reserve in Mitcham, where pollution was entering the site via pipes from a neighbouring Industrial Estate feed to a reedbed.


Despite a hailstorm during proceedings, no one’s ardour was dampened and three sets of installation were completed successfully.


Thanks to everyone who braved the inclement weather!


Despite the weather, there was no let up and installations were then carried out at the Mill Race in Grove Park


at Wandle Bank


Butter Hill


and Beddington Park!

The mycofilters will now be monitored regularly, with water and silt samples sent away for analysis.  Watch this space for further updates!

 If you notice the mycofilters have been disturbed or removed at any site, please let us know. 

 Thanks to everyone who has worked so hard to help Claire with this project; it has been great fun and you can feel proud of the fact that you are all conservation pioneers!

Photos by Claire Bedford, Mark McLellan, Bella Davies and Erica Evans.

6 thoughts on “Mycofiltration: using mushrooms to clean the river!

  1. Eric Slyter

    I read your article: Mycofiltration: using mushrooms to clean the river!, and I am wondering if there are any updates. I have been studying mycofiltration, and stumbled on this article. When was it written? Have you been testing the outflow for pollutants? What types of pollutants do you test for? Thank you, Eric Slyter.

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  3. Polly

    Hi Justin, we tried to use this to address polluted outfalls and prevent road run-off from getting into the river. At our sites, the bags did not work. When the outfalls flowed, the volume of water was too large (with most of the surrounding area being paved, there is a lot of water entering the river following rain) and so the water simply overtopped the bags, missing the treatment. However, in a system where there is time for the bags to work their magic, this could well be successful and has in other places.

  4. vandana sharma

    I just want to ask that after how many days there is need to replace these bags at the site itself

  5. Feidhlim Harty

    Thanks for setting out such a clear description of the work you’ve done. Also for your feedback that the bags over-topped during heavy rainfall. That’s all really useful for other projects that want to try this approach and learn from previous examples. I’ve been using wetland plants and willows for many years to treat sewage, stormwater and to improve natural habitats and have only just started to dig deeper into mycofiltration. Your page was a great help. Thanks!

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