Gary Z. Watters

Document Type


Publication Date

January 1972


The treatment efficiency of waste stabilization ponds depends primarily on the biological factors of type of waste and 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 such as the gross flow patterns within stabilization ponds as affected by the shape of the pond or lagoon, the presence of dead spaces, and positioning of inlets and outlets and the degree of density stratification. These hydraulic flow characteristics will have an effect on the dispersion and the average detention time of the waste and on the organic (BOD) and pathogenic organism removal efficiency of the treatment process. This research evaluated the effects of these hydraulic flow characteristics on the treatment efficiency by using certain information that can be obtained from the age distribution function of the fluid particles within a continuous flow process vessel. The age ddistribution 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 exisiting flow patterns were obtained on the waste stabilization ponds of the city of Logan, Utah. Fluorometric techniques using rhodamind 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, lenth to width ratio, and baffling on the hydraulic flow characteristics. The information gained from the tracer concentration vs. time curves was used in conjuction with the first order reaction equation to predict treatment efficiences 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.