What is a common method for testing water for coliform bacteria?

• A. Filtration
• B. Membrane filter technique
• C. Grab sample methodology
• D. Composite sampling

Answer: (C)

The grab sample methodology is a straightforward and widely used method for testing water for coliform bacteria. This technique involves taking a single sample of water at a specific point in time, which captures a snapshot of the water quality at that moment. It is particularly useful for detecting the presence of coliform bacteria, which can indicate contamination by fecal matter and the potential for waterborne diseases.

In practical application, grab samples are often collected directly from a water source, such as a tap or well, and transported to a laboratory for analysis. The results can provide immediate insight into the water quality and safety for consumption or recreational use.

While other methods like filtration and the membrane filter technique are also employed for bacterial testing, these approaches may require more complex procedures and equipment. Composite sampling involves collecting multiple samples over time and is suited for analyzing variations in water quality, but it does not provide the immediate assessment that grab sampling does. This makes grab sampling particularly advantageous for routine assessments and urgent water quality testing scenarios.