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Elon University, Elon, NC, ESCS filter 11 years in service |
Bioretention is one of the best practices for managing stormwater in urban areas and many of these devices have been in operation for years. Aging bioretention systems that still infiltrate and support vegetation may cease removing enough contaminants to meet local water protection guidelines. What happens when the filter media becomes exhausted and unable to adsorb pathogens or heavy metals?
Expanded shale, clay and slate (ESCS) porous aggregates and particles have been utilized in filtration for more than twenty-five years. Long enough to confirm they do a great job of fixing phosphorous and heavy metals while promoting infiltration and healthy plant growth. ESCS extends a biofilters’ life cycles because of its durable and porous structure. But even ESCS has a set amount of surface area for adsorption.
New research from UCLA and CSU* found that ESCS aggregates aged with heavy metals, which are abundant in urban stormwater, develop antibacterial properties that will remove pathogens long-term.
We know that ESCS biofilters improve infiltration, plant growth and TSS reduction. According to this research, the adage “older is better” seems to apply as well. It’s expensive to replace filter media in stormwater devices. These findings may be able to postpone bioretention repairs and renovations even longer when ESCS is in the mix.
Compared with other advanced filter components lightweight ESCS is economical and available. ESCS is manufactured and distributed across the USA.
*Reprinted from Journal of Hazardous Materials, Volume 429, 5 May 2022, 128309, Annesh Borthakur, Kristida L. Chhour, Hannah L. Gayle, Samantha R. Prehn, Michael K. Stenstrom, Sanjay K. Mohanty, “Natural Aging of ESCS Amendment with Heavy Metals in Stormwater Increases its Antibacterial Properties: Implications on Biofilter Design,” pgs. 1-10, Copyright 2022, with permission from Elsevier.
https://www.sciencedirect.com/journal/journal-of-hazardous-materials
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Richmond Hill Park, Asheville, NC, ESCS filter 15 years in service |
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Graham HS, Graham, NC, ESCS filter 16 years in service |