What can you do with varnish, plywood, a wheelbarrow inner tube and a solar panel not much bigger than a mobile phone?
The answer, if you are a computer genius with a conscience, is to fight back against sewage pollution.
John Clifford has created an early warning system.
He said: “When pollution spikes, if it goes up more than 10%, we know that something’s gone on in the river.
“When several sensors all at once that are telling us the same thing, then we know that there’s a big problem.
“The app on my phone will update regularly and quite often.
“It’s the first thing I check in the morning.”
Mr Clifford lives in west London and the kit will float on the River Brent which, like so many of our rivers, is regularly polluted.
Alongside colleagues he’s making at least 30 of these sensors which measure what’s called TDS or total dissolvable solids – shorthand for faeces, food waste and soap residue.
They send data on the level of these unwanted ingredients in real time to an app, but despite that sophistication they are cheap.
At around £100 per sensor they are a fraction of the cost of professional kit which typically can cost £6,000.
The team behind the tech, CURB (Clean Up River Brent), got together after local resident Ben Morris was outraged by an incident in 2021, which turned the river grey with sewage sludge bordered by soapy white residue and was very smelly.
They began with campaigning and clean ups, but he feels their gadgets will make the biggest difference.
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Mr Morris said: “Once you know what’s in the river, you can then start to have a conversation about what should be done about it.
“At the moment, there are too many unknowns about the sewerage system, too many unknowns about water quality.
“You get something like this in nationwide, we can really raise public awareness and political awareness, and then we have to have that tough conversation about what we’re going to do about it.”
Across England, there were over 300,000 sewage spills in 2022
And he is perfectly happy to get to grips with the dirty end of the stick too.
I join him mid-stream, up to our waists in the River Brent just beside a massive drainage pipe.
The water around us is flecked with fragmented toilet paper and twigs trapped beneath the surface are draped with a flowing beard of dirty tissue.
‘It does whiff’
Thankfully we are in waders, but it does whiff.
We are installing two types of sensor.
One is static, fixed to a stake hammered into the river bed, the other their new floating design.
It is tethered to a paving slab on a length of rope.
It has a solar panel on the top, a box of electronics beneath, sitting on the inflated inner tube while dangling below in the water are the actual sensors.
When the river rises after heavy rain, it remains on the surface and able to communicate 24/7.
This is important as pollution is often worse when the sewerage system is overwhelmed in a downpour.
Across England, there were over 300,000 sewage spills in 2022.
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The Environment Agency faces accusations of failing to protect our waterways but its budget has been cut by half in the past decade and Lewis Elmes, the area catchment coordinator, says they will gladly accept help from talented amateurs.
He said: “It complements what we’re doing, as it really increases the scope of what we’re able to achieve by producing a bit of equipment that’s so much cheaper than our much more expensive bits of kit.
“It really allows us to work to expand the boundaries of what we can look at in our rivers and the amount of outfalls that we can keep an eye on.”
River Brent’s own ‘Q branch’
The Environment Agency is trialling the brilliant shed tech from the River Brent’s own “Q branch” over the next year.
If it works the idea could go nationwide giving a much clearer, immediate picture of water pollution.
When it comes to fighting back, knowledge is power.
