Tennessee Wastewater Operator Practice Exam

In what manner does water flow through a plug flow type activated sludge basin?

1. Radially outward from the center

2. In a linear manner similar to water through a pipe

3. Circularly around the basin

4. By means of turbulent mixing

The correct answer is: In a linear manner similar to water through a pipe

In a plug flow type activated sludge basin, water flows in a linear manner similar to water through a pipe. This system is designed to ensure that the flow through the basin is uniform, allowing for a more consistent treatment process. The plug flow model assumes that the wastewater enters at one end of the basin and exits at the other end, with little back-mixing. This means that the particles move through the basin as coherent "plugs," maintaining their relative positions with minimal lateral mixing or disturbance. This characteristic allows for effective removal of pollutants as the wastewater moves successively through the treatment stages in a predictable and controlled way. In contrast, other flow patterns such as radial, circular, or turbulent mixing do not accurately represent the movement in a plug flow system. Radial flow would imply that the water moves outward from a central point, which is not typical for a linear flow basin. Circular flow suggests a looping movement, which is also not conducive to the linear transport requirements. Turbulent mixing describes a chaotic and irregular flow pattern that is characteristic of different types of systems, which again does not align with the plug flow concept where the aim is to have laminar flow conditions for effective treatment.