Texas Wastewater Class B Practice Exam

In wastewater treatment, what is a consequence of high BOD levels?

1. Increased plant growth

2. Decreased oxygen availability

3. Improved water quality

4. Accelerated sedimentation

The correct answer is: Decreased oxygen availability

High Biochemical Oxygen Demand (BOD) levels in wastewater indicate a high concentration of organic material that microorganisms will decompose. When these microorganisms break down the organic matter, they consume oxygen in the process. Thus, elevated BOD can lead to decreased oxygen availability in the water body, which can be detrimental to aquatic life. Fish and other organisms that rely on dissolved oxygen may struggle to survive if oxygen levels drop too low, resulting in stress or even death in these populations. The other options reflect circumstances that are less likely to result from high BOD levels. For instance, increased plant growth might occur due to nutrient enrichment, but this is primarily related to nitrogen and phosphorus levels rather than BOD. Improved water quality is generally the opposite effect, as high BOD often signals pollution rather than improvement. Lastly, accelerated sedimentation usually involves physical processes in the water rather than oxygen consumption, making decreased oxygen availability a more direct consequence of high BOD.