Author(s): Aren Hansen; Rhys Mcdonald

Linked Author(s): Aren Hansen

Keywords: Tracers; Plume; Mixing; Dilution; Outfall; Diffuser; Modeling

Abstract: Hydrodynamic mixing zone models are frequently used to estimate dilution of wastewater effluent discharges in receiving waters and delineate zones of mixing and potential toxicity. Models serve as important tools for evaluating different mixing scenarios, but unless properly verified or calibrated, models may not account for unique site conditions that often affect the overall dilution achieved. To ensure adequate environmental protection, support reasonable discharge limits, and document compliance with discharge permit limitations, it is prudent and often required to verify and/or calibrate mixing models with appropriate field data. In this paper we present techniques important in characterizing effluent plumes, with particular emphasis on collecting rigorous and defensible dye-dilution data for use in assessing mixing zone models. Techniques to accurately measure tracer dilution, three-dimensional instrument position, and other selected parameters of interest (e.g. conductivity, temperature, pH, dissolved oxygen, turbidity) at sub-second intervals will be discussed. Field measurement of common model inputs (ambient stratification, current velocity, discharge characteristics, etc.) will be examined, as will the measurement of other variables such as local bathymetry and eddies. The plume monitoring techniques that will be included have been employed and developed in numerous mixing zone studies throughout the United States over the past 30 years.

DOI:

Year: 2009