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Title: Screening-level model for estimating pollutant removal by wetlands
Authors: Dortch, Mark S.
Gerald, Jeffrey A.
Keywords: Model
Pollutant removal efficiency
Removal rates
Water quality
Mathematical models
Numerical models
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technical Report (Wetlands Research Program (U.S.)) ; no. Technical Report WRP-CP-9
Abstract: This report describes the theoretical basis for a screening-level mathematical model for estimating the amount of pollutant removal provided by wetlands. The amount of pollution removed from the receiving water is quantitatively expressed in terms of the removal efficiency (RE), where RE is a percentage between 0 and 100 percent, and RE = 100 percent represents total removal of the pollutant. The approach was to develop a screening-level model that can be rapidly applied with minimal input data for estimating the amount of water quality improvement provided by wetlands. The primary assumption made with this model to achieve simplicity is that the wetland is at steady-state. Either of two conditions are assumed for spatial gradients in concentration: (A.) fully mixed (i.e. no gradients); and (B.) gradients along the main flow axis (i.e., longitudinal gradients). Given basic characteristics about the wetland, RE can be computed for total suspended solids, total coliform bacteria, biochemical oxygen demand, total nitrogen, total phosphorus, and contaminants (e.g., organic chemicals and trace metals). TheRE depends on the wetland detention time and the removal rate, K (day⁻¹) for the constituent. The removal rates depend on a number of processes, such as microbial metabolism, adsorption, volatilization, denitrification, settling, etc., and ambient conditions, such as water temperature. The approach here was to focus on the dominant long-term removal mechanisms, making use of literature values of mathematical formulations for those mechanisms when possible. Methods for estimating K values are discussed, and examples of literature estimates are provided. These techniques have been programmed into an interactive, user-friendly, PC-based computer program, which is also described in the report. Comparisons of predicted versus observed REs for the Cache River wetland, Arkansas, are made for total suspended solids, total nitrogen, and total phosphorus.
Description: Technical Report
Gov't Doc #: Technical Report WRP-CP-9
Rights: Approved for public release; distribution is unlimited.
Size: 68 pages
Types of Materials: PDF
Appears in Collections:Technical Report

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