Which of the following is a common method to test for coliform in water samples?

The method to test for coliform in water samples is quite crucial in ensuring the safety and quality of drinking water. Multiple-tube fermentation is one popular technique where water samples are added to a series of tubes containing a nutrient broth, and the tubes are observed for gas production which indicates coliform presence.

Membrane filtration is another effective method that involves passing a known volume of water through a membrane filter, which captures any coliform bacteria. The filter is then incubated on a culture medium and checked for colony growth, which signpost contamination.

Direct plating is yet another technique, where a sample is spread onto a solid growth medium to allow for the growth of coliform colonies, which can then be counted and analyzed.

All of these methods are commonly used in various situations to test for coliform bacteria in water samples. Each method has its own advantages and is suited to different testing scenarios, making them collectively essential tools for environmental monitoring and public health protection in water quality assessments.