48 hours, produces indole in tryptophan-containing peptone water and gives positive result in methyl red test. When organisms of coliform group other than E.coli are found in a water sample, Presence of S.faecalis confirms fecal pollution of water. The presence of C. perfringenes in the absence of coliform group in water suggests fecal pollution of water at some remote date since cloostridial spores are capable of surviving in water for a long duration.
Collection of a water sample Technique: . Sample of water must be collected in sterile bottles. . Hold the base of sterile bottle in one hand, remove the stopper and
cover together with the other hand. . Fill the bottle with sample water, replace the stopper and cover
Collecting a sample from tap: . Remove any external fittings from the tap. . Clean carefully the outside nozzle of the tap. . Turn on the tap and allow the water to run for1 min. . Sterilize the tap using the flame by igniting a piece of cotton wool
soaked in alcohol
holding with a pair of tongs.
. Allow the tap to cool by running the water for few seconds.
. Fill the sample bottle from a gentle flow of water, and replace the