Nutrient retention dynamics of the Everglades Nutrient Removal Project

Abstract

The Everglades Nutrient Removal (ENR) Project was constructed to reduce nutrient concentrations in stormwater runoff water from the Everglades Agricultural Area. Although nutrient concentrations of influent water ranged from 66 to 201 μg TP L and 140 to 541 μg TN L−1 and varied substantially over time, the outlet concentrations remained low, 9 to 39 μg TP L−1 and 99 to 286 μg TN L−1, during the first three years of operation (from August 1994 through August 1997). Nutrient removal efficiency was calculated in terms of decrease in both loads and nutrient concentrations. Nutrient loading rates averaged 1.17 g TP m−2 year−1 (±0.12 SE) and 31.56 g TN m−2 year−1 (±2.92 SE) at the inflow and 0.23 g TP m−2 year (±0.02 SE) and 20.71 g TN m−2 year−1 (±1.63 SE), at the outflow. TP load removal ranged from 66% to 91% and averaged 82% for the period of record. while TN load removal ranged from 11% to 76% and averaged 55%. Rainfall contribution to the ENR Project nutrient budgets was small, averaging only 4% and 3% for TP and TN, respectively. The ENR Project performance results during the first three years suggest that additional Stormwater Treatment Areas (STAs) will be effective in removing TP from stormwater runoff.