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A mathematical model representing the hydrologic and biogeochemical processes of a wastewater treatment wetland was converted into a user-friendly computer simulation model, using Microsoft ® Visual Basic. Our objectives in developing this model were to (1) increase scientific understanding of the processes governing successful operation of constructed wetlands treating secondary wastewater (2)demonstrate the effectiveness of treatment wetland technology and (3) provide designers and operators with a user-friendly computer tool for anticipating wetland responses to common and unusual environmental circumstances. The model requires a number of input parameters regarding wetland dimensions, volume of inflow, type and quantity of vegetation, and the inflow concentrations of algae, organic N, ammonia-N, nitrate-N, CBOD, and dissolved oxygen. Using empirically-derived rate constants, plant and algae dynamics and the fate and transformation of various nutrients are modeled to ultimately predict the outflow concentrations of treated water exiting the wetland. This paper discusses the simulation program as well as the theoretical background of the model and includes examples of input data and parameter coefficients. The final section presents the results from a one-year simulation using actual data from a constructed wastewater treatment wetland near Hemet, CA and compares predicted outflow concentrations with those measured on-site. |
