California Wastewater Treatment Operator Practice Exam

Which parameter is primarily assessed by measuring CBOD?

1. Presence of heavy metals

2. Oxygen demand from microbial activity

3. Nutrient levels in the wastewater

4. Temperature variations

The correct answer is: Oxygen demand from microbial activity

When measuring Carbonaceous Biochemical Oxygen Demand (CBOD), the primary focus is on evaluating the amount of oxygen required by microorganisms to metabolize organic matter in water. This measurement helps to gauge the oxygen demand driven by microbial activity associated with the decomposition of organic compounds in the wastewater. A high CBOD value indicates a significant amount of biodegradable organic material present, which can lead to oxygen depletion in receiving waters if not managed properly. This parameter is crucial for wastewater treatment as it directly impacts the efficiency of biological treatment processes; operators strive to optimize these processes to ensure that there is sufficient oxygen for microorganisms to effectively break down organic pollutants. Monitoring CBOD helps in understanding the health of aquatic ecosystems downstream and in the planning and operation of wastewater treatment facilities. The other options, while related to wastewater analysis, do not accurately reflect what CBOD measures or indicates. The presence of heavy metals, nutrient levels, and temperature variations are assessed through different analytical methods and parameters that focus on entirely different facets of water quality.