Tennessee Wastewater Operator Practice Exam

Which mechanism is used to lift solids in a stair screen?

1. Single operating cycle

2. Two sets of lamella

3. Interlocking links

4. Rectangular openings

The correct answer is: Two sets of lamella

The lifting of solids in a stair screen is primarily facilitated by two sets of lamella. These are inclined surfaces that help to gather and elevate the solid particles and debris that are trapped during the wastewater treatment process. The structure of the stair screen allows water to flow through while at the same time directing the solids to move upwards along the inclined plane created by the lamella. The effectiveness of this mechanism lies in its design, which encourages the collection of solids from the wastewater while minimizing the loss of liquid. This is important in wastewater treatment as it ensures efficient solids removal, protecting downstream processes from potential clogging and ensuring optimal operation of the treatment system. The other choices do not accurately represent the mechanism involved in lifting solids in a stair screen. For example, single operating cycles and rectangular openings are more associated with other types of equipment or processes. Interlocking links might refer to mechanical systems but do not specifically pertain to the functionality of a stair screen in lifting solids. Understanding the role of lamella in these systems can help operators optimize their use in the wastewater treatment process.