California Wastewater Treatment Operator Practice Exam

The lab results indicate a chemical oxygen demand (COD) of 100 mg/l and a biochemical oxygen demand (BOD) of 300 mg/l. In typical wastewater scenarios, BOD values should not exceed COD values significantly because BOD is a measure of the oxygen that will be consumed by microorganisms breaking down organic matter, while COD accounts for both biodegradable and non-biodegradable substances.

In this case, the BOD is three times greater than the COD, which is highly unusual. This large discrepancy suggests that the numbers may not be consistent with typical wastewater treatment expectations and could point towards an error in lab results. Therefore, the conclusion drawn from the provided values is that the results appear incorrect.

This reasoning is fundamental in assessing the reliability of lab data and understanding the characteristics of wastewater influent, leading to the conclusion that something is amiss with the reported measurements.