Coliform bacteria, on the other hand, can be easily identified in the laboratory and are used as an indicator of the bacteriological quality of water. Some members of the coliform indicator group occur naturally in the intestines of humans as well as other warm- blooded animals and are discharged in great numbers in human and animal waste. Others occur naturally in surface water of varying quality and in topsoil. A positive analysis for coliform bacteria indicates that the well sample may have been contaminated by surface water or fecal material. This may suggest that the water well may not be properly constructed to protect it from sources of bacteriological contamination.
Negative results indicate there was no contamination at the time of sampling.
A new water supply should be tested for nitrates. Nitrates found in ground water are usually produced by agricultural fertilizers, livestock wastes or septic systems. All bacteriological water sample bottles are sterilized prior to distribution. Handle them carefully to avoid introducing contaminants during the sampling process itself and be sure to follow closely the instructions included with the bottle. Select a sampling point as close as possible to the water supply source.