Tennessee Wastewater Operator Practice Exam

What formula is used to determine the surface overflow rate per day for a settling tank?

1. Surface area of the tank divided by volume of flow

2. Volume of flow divided by surface area of the tank

3. Surface area of the tank multiplied by flow rate

4. Flow rate divided by total tank volume

The correct answer is: Volume of flow divided by surface area of the tank

The surface overflow rate (SOR) for a settling tank is a crucial parameter in wastewater treatment, as it helps assess how effectively the tank separates solids from liquid. The correct approach to calculating the SOR involves determining the flow rate of incoming wastewater in relation to the surface area of the tank. The formula for surface overflow rate is the volume of flow divided by the surface area of the tank. This relationship provides a metric that indicates the amount of water passing over a given surface area of the tank per unit time, typically expressed in units like gallons per square foot per day. The higher the SOR, the more water is flowing over the surface, which can affect the settling efficiency of solids. Understanding this calculation is integral for operators to manage and optimize settling tanks effectively, ensuring proper removal of suspended solids and maintaining compliance with environmental regulations. Factors like tank design and operational conditions can also be influenced by the surface overflow rate, making it an essential concept in wastewater management.