Tennessee Wastewater Operator Practice Exam

How does a stair screen operate?

1. Efficiently removes hair and stringy material

2. May be located in a bypass channel

3. Two sets of lamella lift solids up stairs

4. Single operating cycle

The correct answer is: Two sets of lamella lift solids up stairs

The operation of a stair screen is effectively described by the mechanism where two sets of lamella lift solids up stairs. This design is crucial for the effective removal of solids from wastewater. The stair screen consists of a series of inclined plates or steps that operate in conjunction with a chain drive system. As wastewater flows over the screen, the solids settle onto the inclined surfaces and, through the action of the lamellas, are lifted up the incline and subsequently discharged from the system. This process ensures that large debris and potentially troublesome materials, such as hair or stringy items, are captured and removed from the flow, preventing them from entering further treatment processes where they could cause blockages or operational issues. The dual set of lamellae enhances the efficiency of this mechanism, ensuring a continuous and effective removal cycle. While other options mention aspects related to the functionality or placement of stair screens, they do not accurately capture the defining operational characteristic of the stair screen itself, which centers around the design and action of the lamella structures that transport solids effectively upward. Thus, the mention of the two sets of lamella working together to move the solids is the key aspect that highlights the operation of a stair screen.