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Runoff from manure piles and permanent outdoor confinement areas are common sources of pollution from livestock operations, which must be properly managed in accordance with local environmental regulations. Seven months of performance data from a pond-free water surface constructed wetland system receiving cattle feedlot runoff in Eastern Ontario, Canada, were used to evaluate performance and quantify first-order reaction rate constants (k) for organic matter and nutrients. Kinetic values were shown to be strongly temperature dependent and to adequately represent average treatment over the operating season; however, k values varied significantly on shorter time scales due to the event-based nature of the treatment system. Plant (duckweed) uptake of soluble phosphorus and ammonia in the pond was shown to be a predominant mechanism of nutrient removal. The pond-wetland system was effective at reducing biological oxygen demand (BOD₅) by 67%, total phosphorus (TP) by 45%, and total nitrogen (TN) by 64%, providing a cost-effective and appropriate solution for beef producers.