Florida Wastewater Practice Test

What is the primary role of a primary clarifier in wastewater treatment?

1. To remove heavy metals

2. To separate solids from liquids

3. To add chemicals for disinfection

4. To enhance aerobic treatment

The correct answer is: To separate solids from liquids

The primary role of a primary clarifier in wastewater treatment is to separate solids from liquids. This process is essential in the treatment of sewage and industrial wastewater. The primary clarifier functions by allowing the wastewater to flow slowly, which gives heavy solids time to settle to the bottom of the tank, forming sludge. At the same time, lighter substances and liquids rise to the top, forming scum. By effectively separating these materials, the primary clarifier reduces the organic load entering secondary treatment processes and minimizes the risk of clogging or overloading these subsequent stages. In the context of the other options, while removing heavy metals is important in some stages of treatment, it is typically managed through other processes such as chemical precipitation or advanced filtration rather than the primary clarifier. Adding chemicals for disinfection is related to later stages in the treatment process, where microbial pathogens need to be eliminated before effluent discharge. Enhancing aerobic treatment is a function of aeration tanks where microorganisms break down organic material in the presence of oxygen, occurring after the primary clarifier has done its job of removing bulk solids.