Abstract
Abstract
In this work, performance of an innovative in-situ passive engineered natural system to remove fluoride from stormwater and to reduce the peak stormwater flow rate was investigated for multiple rainfall events (from August 13 to October 20, 2010). Water flow was measured on site and samples were taken for fluoride analysis throughout several rain events. A mathematical model was developed and used to predict stormwater flow and fluoride concentration in the effluent of an in-situ passive treatment system consisting of roof, green courtyard basin, and an activated alumina (AA) treatment cell. This model is a combination of a mass balance and one-dimensional advection-dispersion model, which involves three components: (1) flow of water, (2) fluoride build up and wash-off on a roof, and (3) fluoride transport. For rainfall events investigated, the fluoride that had accumulated on the roof by deposition during dry weather quickly washed off during the beginning of the storm event. The green courtyard system reduced concentrations of fluoride contaminated runoff. Model and field results indicate that under conditions encountered, the AA effectively removed fluoride from stormwater to undetectable levels (<1 mg/L). Data from this study can be used to aid in determining engineering design parameters needed for scale up and economic analysis. This technology may be appropriate for a range of stormwater contaminants if the appropriate reactive media is used within the system to reduce runoff and the environmental impact of runoff associated contaminants.
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