Surface loading terminology: The ratio of design discharge to the plan surface area of a sedimentation tank is called what?

Introduction / Context:
In clarifier design, the parameter Q/A (where A is the plan surface area) is fundamental. It appears under various interchangeable names in the literature, and recognizing this equivalence helps in reading diverse references and codes.

Given Data / Assumptions:

• Q = design flow.
• A = plan surface area (length × width).
• Ideal clarification theory where removal is related to surface overflow.

Concept / Approach:
Q/A is commonly termed surface loading rate (SLR), overflow rate, or overflow velocity. Under ideal conditions, a particle with settling velocity equal to or greater than Q/A will be removed. These terms are synonymous in most water and wastewater design texts.

Step-by-Step Reasoning:
Compute Q/A as a design check.Use it to compare with settling velocities of particle classes.Recognize that different sources may label it as surface loading, overflow rate, or overflow velocity.

Verification / Alternative check:
Multiple handbooks and standards cross-reference these terms, confirming their equivalence for conventional basins.

Why Other Options Are Wrong:
Each of (a), (b), and (c) is correct; selecting only one is incomplete.Detention coefficient is not a standard name for Q/A.

Common Pitfalls:

• Mistaking Q/A for detention time; detention is V/Q and involves depth.
• Using SLR without considering short-circuiting and flocculation behavior.

Final Answer:
All of these