What type of sample must be taken after the filling of a storage tank following construction or maintenance?

The correct choice is the bacteriological sample, which is essential when a storage tank has just been filled following construction or maintenance. This requirement stems from the need to ensure that the water stored in the tank is safe for consumption and free from harmful microorganisms that could proliferate during the construction or maintenance process. Such activities can introduce contaminants that pose a health risk if ingested.

Bacteriological sampling involves testing for the presence of bacteria, specifically coliforms and E. coli, which serve as indicators of fecal contamination and overall water quality. After filling the tank, it’s crucial to analyze the water to confirm that these indicators are not present, ensuring that the tank is safe for use.

In contrast, while chemical and physical samples are also important for assessing water quality, they typically address different concerns. Chemical samples evaluate elements such as pH, total dissolved solids, and potential contaminants (like heavy metals or nitrates), while physical samples assess turbidity and color. A residual sample, which measures the amount of disinfectant remaining in the water, is vital for determining sufficient disinfection levels but does not directly assess the microbiological safety of the water. Thus, the focus on bacteriological sampling is critical immediately after filling a tank post-con