It is a low-tech solution consisting of a platform about 10 feet by 10 feet that is elevated on one end. Inside, a river of granular material zig-zags back and forth from the elevated end to the low end.
Semi-aquatic plants such as water mint, whose roots have disinfectant qualities, as well as yellow flag iris, marsh marigold and the common reed, are rooted into the granular material.
Waste water from washbasins, baths, and showers is pumped into the platform and allowed to trickle down through the granular material.
As the water seeps through the system, the plant roots take up the dissolved pollutants, leaving behind useable, but non-drinkable water that could be dyed blue with vegetable color to signify its quality and used to flush toilets or to water gardens on the ground.
By using GROW, more than half of the water that enters a building or home could be used twice before being flushed into the communal waste management system.
The lesson here: nature knows what it’s doing. Plus, a homeowner receives the double benefit of green roof technology along with water treatment. While the GROW system, like other grey water treatment systems, can’t produce drinking water or treat waste water from toilets, it looks like a much more affordable method of treating reusable waste water than current high-tech systems. They’re still testing; we’ll keep an eye on it.