Lab test for BOD

Biochemical Oxygen Demand (BOD) is a lab test that shows how much oxygen is used by bacteria to break down organic matter in water.

The lab you use will give you specific instructions on how to collect a sample and the method they use. This is an example of a common BOD lab method your lab may use.

To do the test, two bottles of the same water sample are used. One is tested right away to measure its starting oxygen level. The other is sealed and kept in the dark at room temperature for five days, giving bacteria time to use oxygen as they break down waste.

After five days, the oxygen level in the second bottle is measured. The difference between the two readings shows how much oxygen was used—this is the BOD.

A high BOD means there’s a lot of organic pollution, which can harm fish and other aquatic life by lowering oxygen levels in the water. Testing BOD helps scientists check water quality and monitor pollution from things like sewage, runoff, or industrial waste.