Bacteriologic testing of water is done to insure that enteric pathogens, capable of causing infectious disease in people consuming the water, are not present. Pathogens such as Shigella and Salmonella are difficult to detect because they are fragile and usually present in low numbers. Thus, water is tested for fecal contamination by screening for indicator organisms (e.g., Escherichia coli or other coliforms). A coliform is a facultative anaerobe that ferments lactose to produce acid and gas and is a Gram-negative, non-spore forming rod.
During labs 22-24, we will be testing samples of "drinking water" for the presence of coliforms. Each table will receive a water sample from a different water source, including the Laramie River, Laramie Water Treatment Plant, a mountain spring, a drinking fountain, etc. Record the source of the water sample that your group is analyzing. We will use three methods to screen the water samples:
P-A (Presence Absence) test
Membrane Filtration Technique
Multiple Tube Fermentation Method (MTFM)
If these methods used to screen the water can detect no coliforms, than the water is considered safe to drink (potable).