"Bioretention cells and constructed wetlands are both established best management practices (BMPs) for stormwater quality improvement. These systems vary in terms of hydraulic loading where processes such as retention, sedimentation, absorption, infiltration, filtration, phytoremediation, nitrification and denitrification remove waterborne pollutants. However, the boundary between bioretention and wetlands can be blurred when it comes to design and operational parameters, and it is therefore important to explore the causes and consequences of performance variability in these systems. In an experiment to observe optimum water content for treatment pathways for ecological pollutants, five bioretention bays (2-22% water content) and fifteen bioretention columns (7-47% water content, as much as complete pore space saturation) were used to run parallel tests. Pollutant concentrations were reduced in field bays for COD, TN, and total solids (TS), although there was no difference between treatment groups in terms of any pollutant concentrations. Asclepias incarnata, Carex vulpinoidea, Scirpus validus, and Juncus effusus grew slightly taller in wetter bays, although survival of Sagittaria latifolia was uniformly poor in all treatment groups. No net pollutant removal occurred in columns, although effluent concentrations and mass export were significantly lower for near-saturation treatment groups for chemical oxygen demand (COD), nitrate, and total nitrogen (TN). There was no soil moisture level in which COD, nitrate, TN, phosphate, and TS were simultaneously improved."--Page ii.
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