Hydraulic characterization and field evaluation of a new bi-phasic bioretention rain garden system for storm water runoff management
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Date
2009-03-31T17:53:13Z
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Abstract
Rain gardens are small, landscaped storm water bioretention systems that may reduce peak runoff and improve water quality in a natural and aesthetically pleasing manner. In spite of their popularity, there is little information on how to integrate hydrological, soil, plant, and microbial components to optimize water flow, groundwater recharge, and pollutant removal in the rain gardens. Using a novel bi-phasic (i.e., sequence of anaerobic to aerobic) concept for improving retention and removal of storm water runoff pollutants in rain gardens, two replicate field-scale bioretention rain gardens were constructed to handle a 10-year return storm (44.7 mm for 1 hour rainfall duration). Hydraulic tests with bromide tracer and simulated runoff pollutants (nitrate-N, phosphate-P, Cu, Pb, and Zn) were performed under a simulated 180 mm/24 h continuous rainfall to determine hydraulic characteristics of the bi-phasic rain garden system. The breakthrough curves of bromide tracer suggest that the transport pattern of the system is similar to dispersed plug flow showing mean 10% and 90% breakthrough times of 5.7 h and 12.5 h, respectively. The field evaluation experiments under two simulated rainfall events with spiked concentrations of runoff pollutants (nitrate-N, phosphate-P, and atrazine) were conducted to evaluate the removal capacity of the system. The field evaluation experiments suggest the bi-phasic bioretention rain garden systems are very effective to remove phosphate-P and atrazine.
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bromide tracer, dispersed plug flow, runoff pollutants, best management practice, breakthrough curve