For what purpose are grab samples particularly useful?

Grab samples are particularly useful for enforcing discharge standards because they provide a snapshot of water quality at a specific point in time. This is important for regulatory compliance, as these samples can be taken at regular intervals or during specific events, such as after a heavy rainfall or following particular operations within a facility. Such sampling helps to assess whether the discharge from a facility meets the established environmental standards at the time the sample was taken.

This type of sampling is often preferred in regulatory contexts because it can deliver immediate and tangible information about compliance with legal limits for pollutants. It allows enforcement agencies to make quick assessments and take necessary actions if standards are not being met.

In contrast, other sampling methods like composite samples are better suited for assessing averages over time rather than the immediate regulatory compliance that grab sampling addresses. Thus, while grab sampling may not be ideal for long-term monitoring or understanding treatment processes comprehensively, its role in the enforcement of discharge standards is crucial and specific.