Evaluation of constructed wetlands for treatment of agricultural runoff and nutrient recovery

Abstract

When the Lake Okeechobee watershed experienced its worst algal bloom in 2018, constructed wetlands emerged as a frontline defence against nutrient-laden agricultural runoff. This research evaluated four wetland configurations—surface flow, subsurface horizontal, subsurface vertical, and hybrid—for removing TN, TP, and BOD from dairy farm runoff in north-central Florida over 24 months (2021-2023). The hybrid system achieved the highest removal: 84.7% TN, 72.4% TP, and 91.2% BOD. Recovered nutrients offset 23-41% of fertiliser costs for adjacent pastures. These findings support hybrid wetlands as both treatment infrastructure and nutrient recycling systems.