Wastewater New York State Practice Exam

What is a digester sampling well that allows sampling of contents without venting gas called?

1. Sampling port

2. Thief hole

3. Access well

4. Gas trap

The correct answer is: Thief hole

The digester sampling well that allows for the sampling of contents without venting gas is known as a thief hole. This design is specifically engineered to enable the extraction of a liquid sample from a digester while minimizing the release of gas, which is crucial in maintaining safety and preventing contamination. Thief holes are typically installed at various depths in digesters, and they allow operators to take samples from different operational levels or stages of the digestion process. The importance of this is particularly evident in wastewater treatment processes, where the composition of the sludge can vary significantly at different depths due to factors like stratification and gas production. By using a thief hole, operators can obtain accurate and representative samples needed for analyses, such as monitoring chemical composition and assessing treatment performance, without exhaling harmful gases into the atmosphere. In contrast, a sampling port usually requires venting and may not be designed to prevent gas release as effectively as a thief hole. An access well generally refers to an entry point for maintenance or inspection rather than sampling. A gas trap is designed to safely collect and manage gases, not specifically for sampling liquids. Thus, the thief hole serves a unique and vital function in safe sampling processes within digester systems.