Date of Award:
Master of Landscape Architecture (MLA)
Landscape Architecture and Environmental Planning
Phillip S. Waite
Vertical gardens such as living walls can filter air and water, in addition to cooling buildings, reducing noise, increasing urban biodiversity, providing food, and enhancing well-being. Natural swimming pools (NSPs) are an ecologically sound alternative to chemically treated pools, but they have not reached their potential in the U.S. We investigated whether a living wall could be integrated into an NSP system for water filtration purposes, given that the vertical filter would have to produce excellent water quality for human swimmers. This could be a novel landscape design, particularly in the cases of steep contours, urbanized sites with limited space, or the retrofitting of old pools. We evaluated two filter media: limestone gravel, based on a lime fen ecosystem, and Sphagnum moss, based on an acidic bog ecosystem. We also tested the effects of vertical vegetation by planting half of the filter media variants and leaving the other half unplanted. We installed 12 systems (3 of each of the 4 variants), each comprised of a living wall frame atop a basin with water pumped and recirculated through the living wall. Beginning in summer 2019 and ending after summer 2020, we analyzed the water quantity, water quality, and vegetation quality over two growing seasons. We found that all of the variants attained good water quality with minor exceptions. Also, most of the trial systems consistently met German NSP water quality standards. As expected, evapotranspiration losses occurred, especially with the Sphagnum moss acidic bog variants. The vegetation did not have a significant impact on water quality, but the benefits of vertical planting (including cooling, noise reduction, and air pollution reduction) could justify their use. Overall, this exploration of living walls as water filters verified their feasibility for further study and practice. As the U.S. faces more water shortages, heat waves, and sprawling development, we could integrate pools into our water systems more ecologically, which NSPs and living walls could facilitate. Our study concludes with a hypothetical design concept proposal for an NSP with a vertical water filter.
Farb, Anna, "A Deep Dive Into Natural Swimming Pool Filtration: Living Walls as Technical Wetland Filters" (2020). All Graduate Theses and Dissertations. 7970.
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