Evaluating the Efficacy of Artificial Wetlands for Tertiary Treatment

An artificial wetland was created to receive effluent containing relatively low concentrations of nitrogen and phosphorus from the Numana Fish Hatchery, located in a semi-arid environment near Pyramid Lake, Nevada. Detailed inflow and outflow observations were obtained throughout the study period. Fluorescent dye tracer pulse tests were conducted to establish travel times which were subsequently used to implement a Lagrangian water quality sampling program. Dye tracer results were also used to define longitudinal dispersion within the system. Water quality monitoring of the constructed wetland system was conducted in April and August 1995, with additionally follow-up sampling in late September and early December of 1997. The collected data were also used to calibrate and verify a water quality mathematical model (WASP5). The complex WASP5 model, including site specific calibration, was then tested against simple wetland design equations. The predictions of both total and ammonia nitrogen removal made by WASP5 were generally superior to the simple design expressions.