Tuesday, June 5, 2007
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Removal Efficiencies of Common Pollutants in South Florida Stormwater Treatment Areas

Guoqing He and Joffre Castro. South Florida Natural Resources Center, Everglades National Park, 950 N. Krome Avenue, 3rd Floor, Homestead, FL 33030-4443

To protect the Everglades oligotrophic ecosystem, agricultural runoff from Everglades Agricultural Area (EAA) is discharged into Stormwater Treatment Areas (STAs) to reduce its nutrient content (mainly phosphorous) before it is discharged in the marsh. While total phosphorus (TP) is closely monitored for compliance purposes, other water-quality constituents have received less attention.  This work examines data from six South Florida STAs and estimates the removal efficiency for nutrients, major ions, pesticides, and other water quality variables. Results indicate that these STAs are sinks for many constituents. The more efficiently retained constituents (> 50%) are nutrients (TP, total ammonia, and oxidized nitrogen); ions (Fe and Al); turbidity; and chlorophyll a. The less efficiently retained constituents (<50%) are As, TKN, SO4, and Ca.  For DO, atrazine, and methyl mercury, some STAs were sources and others were sinks. In most STAs, however, there was no change between inputs and outputs for pH, TDS, SpC, DOC, K, and Mg.  When comparing STAs, the ENR project was the most efficient in removing TP (83%) and TN (45%).  Other average removal rates were: TP 71%, TN 26%, SO4 16%, and Hg 61%. The atrazine removal rate was found less than 68%, but only STA5 was a source.

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