Characterization of the Talking Water Gardens Wetland

The objective of this project is to refine the hydraulic characterization of the Talking Water Gardens (TWG) wetland in Albany, Oregon. The engineered wetland is a collaboration between a municipality, Albany-Millersburg Water Reclamation Facility (AMWRF), and a private-firm, ATI-Wah Chang. Water from AMWRF is city wastewater; water from ATI Wah-Chang is the effluent from a metals processing plant. Designed by CH2M Hill, the purpose of TWG is to remove excess nitrogen and to mitigate the thermal load of both effluents through natural processes, such as evapotranspiration. ATI Wah-Chang water contains significant concentrations of nitrate species that are currently below legal limits for the Willamette River, but are at risk of stricter limits in the future. Inputs into the river are regulated to protect salmon and trout migration routes.

Tests were conducted to determine flow parameters. Rhodamine WT was used as a tracer throughout the entire 50-acre park to determine the residence time of the whole wetland, individual ponds, and to discover the locations of stagnant zones. Samples were collected to measure temperature, ammonia, and nitrate levels at 11 locations. These tests occurred in May and September of 2012. Tests were conducted in July 2012 to study salinity, conductivity, pH, and temperature. Gathered data was combined with information about TWG’s design to create a numerical model that simulates nitrogen transformation and transportation. These processes were based on first-order rate kinetics. The model predicts the behavior of nitrogen species dependent on variables, including temperature, pond volume, and flow rate. 

The experiments were successful in capturing key characteristics about TWG that refined the ability of the mathematical model to predict nitrogen behavior. Trends in simulated data are consistent with experimental results. The model’s peak nitrogen concentrations predicted for high volume ponds are lower than expected. This is the result of the model overestimating the amount of natural mixing that occurs in larger ponds. The outcomes of the model will be used to identify where the largest dead zones are located. Information about hydraulic behavior has the potential to help facilitators plan strategies that will increase nitrogen transformation rates.