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Alternative Medias | Oyster Shells

 

Port of Seattle Oyster Barrel Filtration System

After these barrels were installed, the oyster shells and the water output were measured for copper, zinc, and turbidity. The oyster shell barrels:

  • Improved turbidity on average 57%
  • Reduced zinc on average 40%
  • Reduced copper on average 27%

Here is a link to the Port of Seattle downspout treatment drum with Oyster Shells. (pdf)

Here is a significant note from the Port After one year, the pH begins to decrease (become more acidic) and metal concentrations in effluent increase.  

Note that they also describe that the oyster shells were washed before using.

 

 

Oyster Shell Catch Basin Retrofit, Mercer Island

Using oyster shells to clean up stormwater: a new pilot study

King County is partnering with the City of Mercer Island, with funding from the Stormwater Action Monitoring (SAM) program, to determine the effectiveness of treating stormwater with oyster shells from 2019-2020.

Study update

King County researchers collected samples during four storms in 2019 to test if stormwater in Mercer Island Town Center was cleaner after passing through oyster shells. Unfortunately, the results showed that the oyster shells were not reducing suspended solids and heavy metals in the stormwater and the study was halted in March 2020.

Oyster shells have been found to provide successful stormwater treatment in smaller scale applications, like treating runoff from parking lots or roofs (see Port of Seattle link ). The stormwater system at the Mercer Island Town Center is much larger. It’s likely that in this setting the ratio of oyster shells to stormwater was too small or the oyster shells were in contact with the stormwater for too short a time to provide sufficient treatment. The results suggest that this type of oyster shell treatment is not likely to be successful in larger stormwater systems like the Town Center area. For more information, please see the study report (coming soon!).

See Website for More Information about the Mercer Island test.

 

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