Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Civil and Environmental Engineering

Committee Chair(s)

Gary Z. Watters


Gary Z. Watters


Calvin G. Clyde


Roland W. Jeppson


Joe Middlebrooks


Rex L. Hurst


The treatment efficiency of waste stabilization ponds depends on many factors, the most important of which are generally presumed to be the biological factors such as the type of waste and the organic loading. However, the biological activity in a pond is greatly influenced by the environmental conditions of temperature, wind, sunlight, and the hydraulic flow patterns. In the past little attention has been given to the hydraulic characteristics of waste stabilization ponds. Specifically, little consideration has been given to the gross flow patterns within stabilization ponds as affected by the shape of the pond or lagoon, the pre sence of dead spaces, the positioning of inlets and outlets and the degree of density stratification. These hydraulic flow characteristics will obviously have an effect on the dispersion of the waste as well as the average detention time for the waste and, ultimately, on the organic (BOD) and pathogenic organism removal efficiency of the treatment process.

This research considered the effects of these hydraulic flow characteristics on the treatment efficiency. The approach was to use certain information that can be obtained from the age distribution function of the fluid particles within a continuous flow process vessel. The age distribution function represents a history of the time of retention of the various fluid particles in the vessel and is generated by injecting a tracer into the process vessel and monitoring the outlet from the vessel. The concentration vs. time curves at the outlets, which lead to the age distribution functions for a waste or a tracer, were made dimensionless to aid in the evaluation of each experiment.

The prototype experimental data taken to establish existing flow patterns were obtained on the waste stabilization ponds of the city of Logan, Utah. Fluorometric techniques using rhodamine WT dye were used to trace the pollutant. A hydraulic model of the ponds 20 feet by 40 feet by 3 feet deep was constructed at the Utah Water Research Laboratory. This model, after verification, was used to generate data on the effects of inlet and outlet types and location, density stratification, length to width ratio, and baffling on the hydraulic flow characteristics.

The information gained from the tracer concentration vs. time curves was used in conjunction with the first order reaction equation to predict treatment efficiencies for various pond designs for determining optimum conditions.

Finally, a mathematical model of the mixing process is presented and outlet concentration vs. time curves generated by the model are compared with experimental results. This mathematical model can be used in conjunction with the first order reaction equation to predict treatment efficiencies.

The results of the experitnents perfortned on the existing ponds in the Logan pond system are presented in Chapter 3. The results of the model experiments are presented in Chapter 5. The age distribution function diagratns and the significant paratneters determined frotn these diagrams are presented along with the expected treatment efficiency for each lllodel experiment. Also, derived mathematical tnodels for the age distribution functions are illustrated along with experitnentally determined age distribution functions for various pond and model experitnents.