The effectiveness of whole oyster shells vs. crushed oyster shells as a filter for 100 ppb Copper (Cu) in stormwater: a laboratory experiment

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2021-11-17

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Jankowski, Julianna. Master of Environmental Assessment. The effectiveness of whole oyster shells vs. crushed oyster shells as a filter for 100 ppb Copper (Cu) in stormwater: a laboratory experiment Copper (Cu) is a trace metal naturally found in the Earth's crust. It is also commonly found in stormwater pollution from different sources such as roofs, industrial facilities, and highways or roads. If left untreated, this harmful metal can impact human health and the environment. Oyster shells, a common food waste, are made mainly from the chemical compound calcium carbonate which acts as a natural filter (Stroumboulis, 2018). A coal-fired power plant in Belmont, North Carolina was exceeding stormwater benchmark values set by the state for certain metals such as Cu and Zinc (Zn). To address this issue, a pilot study was conducted where partially crushed oyster shells in mesh bags were lined in two outfall drains to determine if metal reduction would occur after exposure. Due to its success, a laboratory experiment was conducted to study the difference between whole oyster shells and crushed oyster shells to determine which would be most effective in reducing 100 parts per billion (ppb) Cu over a period of 24 hours. It was determined that removal efficiencies increased as exposure times increased. Removal of Cu was seen after one hour in the whole shells, with a reduction of 7.5%. After 24 hours, the whole shells reduced Cu concentrations by a total 41.9%. For the crushed shells, reduction was seen as early as 15 minutes, with a removal efficiency of 16.8%. At one hour, Cu was reduced by 27.0% and by 24 hours, the crushed shells reduced Cu by 53.6%. Due to their greater surface area, the crushed shells were more efficient overall and should be used in similar industrial settings to filter out Cu in stormwater.

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