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.
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.
