Basic Wastewater Operator Practice Exam

What is the primary purpose of secondary treatment in wastewater treatment?

1. To settle solids

2. To remove nutrients

3. To degrade organic matter

4. To chlorinate the effluent

The correct answer is: To degrade organic matter

The primary purpose of secondary treatment in wastewater treatment is to degrade organic matter. This stage follows primary treatment, which primarily focuses on removing larger solids from the wastewater. During secondary treatment, biological processes are utilized to break down organic pollutants, typically involving microorganisms that consume the organic matter and convert it into biomass and other byproducts. This significantly reduces the biochemical oxygen demand (BOD) of the wastewater, which is a measure of the amount of organic material present. While removing nutrients can also be a part of the secondary treatment process, the main objective is the degradation of organic material. The processes involved, such as activated sludge systems or trickling filters, are specifically designed to enhance the activity of bacteria and other microorganisms that effectively decompose organic pollutants. The other options, such as settling solids and chlorinating the effluent, pertain to different stages or processes in wastewater treatment. Settling solids is primarily associated with primary treatment, where sedimentation occurs. Chlorination is a disinfection process typically applied afterward, not a focus of secondary treatment. Thus, the emphasis on degradation of organic matter in secondary treatment aligns with its role in making wastewater safer for discharge or further processing.