Water Treatment Operator-in-Training (OIT) Practice Test

What does a sample with a high BOD level indicate?

1. a) Low organic material content

2. b) High organic material content

3. c) High level of inorganic suspended solids

4. d) Low level of pathogenic bacteria

The correct answer is: b) High organic material content

When a sample exhibits a high Biological Oxygen Demand (BOD) level, it indicates a high organic material content. BOD is a measure of the amount of oxygen that microorganisms will consume while decomposing organic matter in water. Therefore, a high BOD level signals that there is a significant amount of biodegradable organic material present. This elevated organic load can lead to decreased oxygen levels in the water once decomposition begins, which can ultimately harm aquatic life by creating conditions that are not conducive to supporting various organisms. In contrast, low organic material content would result in a low BOD value, while a high level of inorganic suspended solids does not contribute to BOD measurements, as BOD specifically pertains to organic matter. Similarly, a low level of pathogenic bacteria is not directly related to BOD, as BOD primarily measures the oxygen-demanding presence of organic substances, not bacterial counts.