Weir loading is a measure of the "overflow rate" per ___ of weir, and is a parameter of clarifier design.

• A. Linear Foot
• B. Cubic Foot
• C. Meter
• D. Square Foot

Answer: (A)

Weir loading is defined as the flow over the weir per unit length of the weir. In other words, it measures how much water overflows across each foot (or meter) of the weir boundary. This is why it’s described as an overflow rate per linear length of the weir, typically written as Q divided by L, with units like gallons per day per foot or cubic meters per day per meter. This per-length measure is essential in clarifier design because it tells you how much flow a given length of weir can handle, affecting how evenly the flow distributes along the clarifier and helping prevent issues like short-circuiting or overloading sections of the tank.

The other options aren’t appropriate because they describe rates per area or per volume rather than per length. The flow over a weir is distributed along the length of the weir, so the relevant descriptor is linear length—per foot (or per meter) of weir.