What happens if water contains high levels of pollution according to the BOD test?

The biological oxygen demand (BOD) test measures the amount of oxygen that bacteria will consume while decomposing organic matter in water. If water contains high levels of pollution, particularly organic pollutants, the resulting higher BOD indicates that a significant amount of oxygen will be required for the decomposition process. This increase in oxygen demand can lead to a depletion of dissolved oxygen in the water.

When the oxygen levels in the water drop, it can create an environment that is harmful to aquatic organisms, such as fish and invertebrates, which rely on dissolved oxygen for survival. Consequently, this depletion can lead to conditions that may result in the death of these organisms and negatively affect the overall health of the aquatic ecosystem. Thus, an increase in pollution as indicated by a high BOD level correlates directly with a decrease in available oxygen for aquatic life, making it a critical aspect to monitor in water quality assessments.