Which item is used for bacteriological water sampling?

• A. A composite sample.
• B. A Whirl-Pak bag.
• C. A Cubitainer.
• D. A DPD Kit.

Answer: (B)

Bacteriological water sampling hinges on using a sterile, sanitary container that can be sealed to prevent contamination and keep the sample intact during transport. A Whirl-Pak bag fits this need perfectly: it’s pre-sterilized, single-use, easy to fill in the field, and seals securely to minimize handling contamination. This design helps ensure that the bacteria detected in the lab reflect the water’s quality, not the collector’s environment. For bacterial tests such as coliforms or E. coli, this type of sterile bag is the preferred collection tool.

By comparison, a composite sample describes combining multiple samples rather than the container itself, which isn’t a sampling device. A Cubitainer is a general-purpose container that may not be sterile or optimized for preserving bacterial integrity. A DPD Kit is used for measuring chlorine residual, not for collecting or preserving a bacteriological sample.