His company, Matter, which is based in Bristol, was on Saturday revealed by the Prince of Wales as one of 15 finalists in the world's most prestigious environmental award, the Earthshot Prize. Root, now 35, said it was "unbelievable" to be selected.
"It's just wild," he said. "You can't apply, you have to be nominated. In 2017 it was just me; now we've grown to 45 people having global impact across a number of regions and we've raised £15 million."
He added: "Microplastic is one of the most pervasive pollution sources on the planet. People don't want microplastic in the water, they don't want it in their food and they don't want it in their bodies."
Yet with every load of laundry we put on, 700,000 microplastic fibres are flushed out of our washing machine into the drainage system. Eventually it makes its way into rivers and into the ocean. "Last year there were 171 trillion particles of plastic in our ocean," Root said.
A keen scuba diver, he decided in his mid-twenties to use his engineering skills to tackle water pollution. Now father to a 16-month-old little girl, and with another baby on the way, he said: "When I spend time with my daughter I realise what we're trying to build the future for. It's a reason to get out of bed. We have to get on and make this happen. We don't have a choice."
Five winners of the Earthshot Prize will be announced next month at a ceremony in Brazil before the Cop30 conference. Each will win £1 million. "I had better buy a tie," said Root, who will be at the ceremony in Rio de Janeiro.
Prince William, who founded the Earthshot Prize in 2020, said in a video broadcast on Saturday that "future generations will judge us" if we fail to act to protect the environment.
Change is needed by the end of the decade, he said. "[That] is the point at which our actions, or lack of them, will have shaped forever the trajectory of our planet."
William said the ambitions of the 15 finalists, selected from 2,500 nominees, embodied the "urgent optimism" required to save the planet. "And it feels unstoppable," he said. "The people behind these projects are heroes of our time, so let us back them."
The actress Cate Blanchett, an Earthshot council member, said: "Optimism isn't abstract -- it's something made real by people bold enough to act now."
Other shortlisted projects include the Quay Quarter Tower in Sydney, the world's first "upcycled" skyscraper; Lagos fashion week in Nigeria, which promotes sustainable practices; and the nation of Barbados, which is on track to become fossil-free by 2030.
In July, the Matter filtration technology went on sale, made by Bosch and its sister company, Siemens. The water outlet tube is connected into the filter unit and a second tube connected to the drainage system.
The unit filters 97 per cent of microplastics out of the water and the resulting plasticky fluff -- similar to the lint removed from tumble dryers -- has to be removed every six washes. At the moment, this is then thrown into the bin, to be taken to landfill or incineration, but in time Root hopes to set up a collection system for this to be recycled into new products.
Root, who studied mechanical engineering at university and then worked for Dyson and General Electric before setting up on his own, is also in talks with companies to integrate the filtration system into washing machines themselves.
At some point, he believes, legislation will be passed to compel manufacturers to reduce the microplastics they pump into the sewage system. "The future of where we're going, this will not be a 'nice to have', it's a case of when it's going to become law."
His company has also developed a much larger system, capable of processing a million litres of water per day, for use in the textile industry. "It can process 10 tons of fabric each day," he said.