Tracer Test as a Tool for Optimizing the Flow Patterns and Efficiency of a Full‐Scale Drainage Water Treatment Wetland

ABSTRACT This article presents research on the assessment of tracer testing and monitoring of nitrate removal efficiency in three full‐scale treatment wetlands, which underwent three tracer tests over a 3.5‐year period. The initial tracer test identified rapid flow and a low residence time, which was attributed to short‐circuited flow patterns. Following the implementation of technical modifications, the second tracer test demonstrated a significant increase in the residence time from approximately 1 to 7 days. The third test reaffirmed the operational effectiveness of the wetlands. The nitrate removal efficiency increased from an average of 37.2% before the repairs to an average of 95.7% immediately after the repairs and 77.7% 3 years after the repairs. The study revealed how short‐circuited flow influenced the degree of functionality. The mean residence time, mobile water volume and nitrate removal efficiency were confirmed to be key parameters in the long‐term monitoring of treatment wetlands.