(CNN)Many of the world's cities are built around waterways. Paris and the Seine, Allahabad, India and the Ganges, Cairo and the Nile -- these rivers, at one time the life-force of their city, are now so polluted they're unfit for swimming and host very little natural wildlife.
How floating islands can make urban waterways green and clean
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After a year and a half of highly restricted movement, many people have been confined to the gray spaces of the inner city with little opportunity to escape to the countryside. A report published in April found that frequent visits to nature improved psychological well-being and reduced mental distress. Now more than ever the need for relaxing green spaces in cities is clear.
Biomatrix Water, a biological technology company based in Scotland, says it has developed a solution using a system of floating modular plant platforms that green and clean urban waterways.
The 2.3 x 1.15 meter (7.5 x 3.8 feet) interlocking platforms are made from 100% recycled and recyclable materials -- predominantly old water pipes welded together, covered with coconut fiber. These lush green islands rewild city rivers and hard-edged canals, providing a place for native plant species to re-establish themselves.
The plants above the surface offer vital habitats for urban fauna and improve air quality, while below the water flourishes a micro-wilderness of submerged roots where fish can thrive, and communities of microorganisms break down harmful substances -- filtering pollution from the water like an artificial wetland.
Biomatrix Water was founded in 2008 by Lisa Shaw and Galen Fulford. Shaw grew up talking about sewage over dinner, as her father engineered climate-friendly, chemical-free wastewater treatment solutions.
Working on river-cleaning projects in India and the Philippines, Shaw and Fulford were struck by the water pollution and lack of "adequate wastewater treatment," Shaw says.
"In many of the situations ... the sewage can flow directly into those water bodies," she adds. "We decided that there was a real need for systems that could go directly into the water bodies."
In a river in Chennai, India, Biomatrix Water introduced an experimental island system to treat raw sewage in situ. "We put a big liner underneath the floating ecosystem so that the water could be held within the ecosystem," Shaw tells CNN, where it would be stored for a matter of days while undergoing treatment. The project uses solar-powered aeration to accelerate the water treatment process.
The impact of this project proved to be further reaching than sewage treatment alone. With the transformation of the river through the introduction of the plant islands, native species of plants and animals started to return to the waterway, and the lives of the communities on the riverside were transformed, too.
After that success, Shaw and Fulford made it their mission to restore greenery and life to waterways. In 2019 they launched the "Living Water Cities" campaign, which aims to turn urban rivers and canals into ecological corridors.