Tennessee Wastewater Operator Practice Exam

Which of the following is a primary objective of secondary wastewater treatment?

1. pH adjustment

2. Metals removal

3. BOD reduction

4. Nutrient recycling

The correct answer is: BOD reduction

The primary objective of secondary wastewater treatment is to reduce biochemical oxygen demand (BOD). This phase of treatment focuses on removing organic matter from the wastewater, which is crucial because high levels of BOD can lead to oxygen depletion in receiving water bodies, negatively impacting aquatic life. Secondary treatment typically involves biological processes where microorganisms break down organic matter; thus, a significant reduction in BOD indicates that the wastewater has been effectively treated and that less organic material is present in the effluent. While pH adjustment, metals removal, and nutrient recycling can be important aspects of wastewater treatment, they do not represent the main focus of secondary treatment. pH adjustment is typically considered in primary treatment or post-treatment processes to ensure effluent meets discharge regulations. Metals removal is usually addressed in earlier stages or specialized treatment processes due to the toxicity potential of heavy metals. Nutrient recycling may be an important consideration in advanced wastewater treatment and resource recovery but is not the core goal of secondary treatment, which primarily aims to enhance water quality by reducing organic pollutants as measured by BOD.