Home Do You Know? How the water of this pool cleaned without using chemicals?

How the water of this pool cleaned without using chemicals?

Crystal clear water in a swimming pool may not necessarily mean that water is pure. You may be actually swimming in a pool of chemicals! This is the Borden Park Natural Swimming Pool (NSP) which is the first chemical–free public outdoor pool to be built in Canada. Do you know how this was made possible?

The NSP replaces an existing pool built in the 1950s with a seasonal pavilion and landscaped pool precinct for the activities of 400 swimmers. At the NSP, the challenge of water quality control, essential to any public bathing facility, is compounded by the scale and the technical demands required to achieve an environmentally healthy and natural filtration process. However, the architectural firm, gh3*, was successful in marrying the technologies that cleanse water through stone, gravel, sand, and botanic filtering processes with a materials-oriented concept to achieve a rigorous technically and aesthetically integrated design.

The fundamental conceptual connection between the technical demands and the design here is realized through relationships between the materiality of built enclosure and the landscape elements. The dark limestone and steel of the gabion wall construction defines the enclosure’s vertical dimension as filter-like or breathable, as granular and porous. The pool precinct is defined by a planar landscape where flush to surface detailing creates seamless interfaces among sandy beach, the concrete pool perimeter and wood decking.

NSP is a balanced ecosystem where plant materials, microorganisms, and nutrients come together within a gravel and sand filtering process to create living water. This is an unsterilized, chemical– and disinfectant–free filtering system in which isolating membranes contain water as it circulates and is cleansed by means of a natural process, which takes place at the north end of the pool precinct. On deck, water passes through a sand and stone submersive pond and a planted hydrobotanic pond. Adjacent to these ponds, a granular filter PO4 adsorption unit is enclosed by the gabion walls continuous with the building. There is no soil involved in this process. Filtration is achieved in two ways: by means of a biological–mechanical system or the constructed wetland and gravel filter, and in–situ, with zooplankton.

The project has won several international awards – 2021 Civic Trust International Award (2021), OAA Design Excellence Award (2020) and RAIC Award of Excellence for Innovation in Architecture (2019) – to name a few.

gh3* is a peer-recognized and award-winning Canadian design practice. The practice has completed projects at every scale, from small park pavilions and private houses to large civic and transit infrastructure. gh3* was named one of the World’s Twenty Most Innovative Companies in 2020 by Fast Company for their projects related to urban water.



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