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The City of Edmonton, Canada, has recently opened Canada’s first all-natural public pool. Instead of using harsh chemicals like chlorine to remain algae-free, the pool is filtered using entirely natural methods. The Borden natural pool is one of a number of projects we have seen that seek to use more eco-friendly materials. Others have included building bricks made from recycled plastic and a hotel that produces more energy than it uses.

The Borden pool complex consists of a children’s wading pool and a larger swimming pool with a sloped entry. There are also three separate ‘working’ pools. These are the filtration ponds. They contain plants such as blue water iris, marsh marigolds, duckweed, water lilies, bladderwort and cattails to help oxygenate and filter the water. These plants also provide a habitat for zooplankton which eat bacteria. Layers of granite rock filter out large particles, while a biofilm on top of the rock filters smaller microorganisms.

Maintaining the pools is a delicate balancing act. There is a ban on use of sunscreens or shampoos that contain phosphorus, as this can kill off the zooplankton. All users must take a warm-water shower before using the pool. They also cannot wear anything made of cotton to the pool. In addition, no more than 400 people can be in the water at any one time, and a maximum of 980 each day. And any time the water temperature rises to 29 Celsius, the pool has to close. Despite these restrictions, the pool had long lines of people waiting around the block in its first week of opening. Many were even turned away due to the limit on numbers using the pool.