Date of Award
Master of Science
Water Resources Engineering
The United States' Environmental Protection Agency (EPA) provides general water quality guidelines for recreational water use that are similar to recreational standards published throughout the world. These guidelines are enforced by State agencies. In the State of Tennessee, the Tennesese Department of Environment and Conservation (TDEC) is the permitting authority who oversees these water quality guidelines. It sets color limits for a recreational water use color narrative under the auspices of EPA review that requires effluent discharge to be free of objectionable color. However, the narrative lacks numeric guidance on how to determine an acceptable discharge color. The City of Memphis, Tennessee had concerns about the subjectivity of the narrative and initiated a color study to provide TDEC with recommendations to establish numeric limits for NPDES permit compliance. This color study links human perception of river color contrasts (subjective) with measured true and apparent color and environmental data (objective) in four experiments. In Experiment 1, participants visited three riverside locations once a month for a year and only one person noticed an objectionable color, while the remaining perceived color contrasts related to cloud/sky reflections. Experiments 2-4 recruited participants online through Amazon's Mechanical Turk (AMT). In Experiment 2 participants were asked to determine whether two colors of the color palette were different, while their choice and response time was recorded. In Experiments 3 and 4, this procedure was repeated, except that actual Mississippi River pictures taken throughout the year were used for the discrimination task. Results showed that environmental factors - cloud cover (sky reflections) and seasonal leaf foliage - overshadow effects the wastewater effluent may have on perceived objectionable river color differences. Since an individual's perception of objectionable color primarily is the result of environmental factors, suggesting a numeric color limit for NPDES permits in Memphis, TN is deemed unnecessary as these facilities have no control over these factors.
dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.
Girdner, Sarah Elisabeth, "Perception Studies to Determine Receiving-Stream Color Objectionability Due to Effluent Discharge" (2014). Electronic Theses and Dissertations. 1054.