In 2012, New Zealand built a floating wetland with 20,000 native plants and nearly 500,000 recycled bottles; it was expected to remove five tonnes of lake nutrients yearly

Lake Rotorua has a nutrient problem. More than 750 tonnes of nitrogen wash into the lake every year, much of it from farm runoff and old septic systems, feeding the kind of algae blooms that turn clear water into green scum, as NIWA's reporting on the Rotorua lakes clean-up describes.

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