Purpose of Bacteriological Analysis

Purpose of Bacteriological Analysis

Purpose of Bacteriological Analysis
The main purpose of bacteriological analysis of water is to determine the potability of water. There are three groups of bacteria present in abundance in the intestinal tract of man and animals-the coliforms, the anaerobiclactose-fermenting sporeformers and the faecal streptococci. Of these three groups, the coliform organisms are more closely related to the intestinal pathogens (typhoid, dysentery and paratyphoid organisms) and hence are affected by storage, sedimentation, chlorination and other natural or induced processes of purification to approximately the same degree.

Positive tests for E.coli do not prove the presence of enteropathogenic organisms but do establish this possibility. Because E. coli is more numerous and easier to grow than the enteropathogens, the test has a built-in safety factor for detecting potentially dangerous faecal contamination. E.coli meets many of the criteria for an ideal indicator organism but there are limitations to its use as such and various other species have been proposed as additional or replacement indicators of water safety.

Thus the absence of the coliforms would indicate also the absence of the intestinal pathogens. The test for the coliform group thus is an indirect one. The test should be quantitative to measure the density of the organisms in water.

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