How long does it typically take to run a COD test compared to BOD?

The correct answer highlights the significant difference in time required for the Chemical Oxygen Demand (COD) test versus the Biological Oxygen Demand (BOD) test. COD testing typically takes about 2 hours because it is designed to measure the total oxygen demand of all organic and inorganic substances in the water sample through a chemical process. This allows for rapid results, making it advantageous for situations where timely data on water quality is required.

In contrast, the BOD test is a longer process due to its nature of measuring the amount of oxygen consumed by microorganisms while decomposing organic matter in a water sample over a period of time, typically 5 days. This extended duration is necessary for microorganisms to act on the sample, providing an accurate estimate of the biodegradable organic material present.

By comparing the timeframes for these two tests, it's clear why the COD test is favored for quick assessments, while the BOD test provides more comprehensive data over a longer duration.