Date of Award

Fall 11-3-1989

Document Type



Civil and Environmental Engineering

First Advisor

Tittlebaum, Marty


The theoretical hydraulic retention time of wastewater treatment plants is often used to predict the efficiency of treatment and to calculate operational parameters. However, these values are related to the actual hydraulic retention time. When there is a large discrepancy between the actual and predicted values, the actual hydraulic retention time can be determined by marking a parcel of wastewater and recording its passage through the system. This investigation utilized rhodamine WT, a fluorescent dye, to track the movement of wastewater through a stabilization lagoon and a rock-reed filter. The loss of rhodamine WT to sorption, biodegradation and photodegradation was determined as a means of predicting the need to increase dye dosage for future studies. The actual hydraulic retention time in the stabilization lagoon was found to be less than 5% of the theoretical. The history of blue-green algal blooms and accompanying odors in the lagoon were related to the extreme case of short circuiting and suspected stratification. The hydraulic retention time in the rock-reed filter was found to be approximately 136% of the theoretical. The extended retention time is possible explained by evapotranspiration and infiltration. The filter was not tested for its actual hydraulic retention time after its construction so no comparison was possible.