The production by nature of a mineral water entirely free from bacterial infection is not to be expected. Happily most of the bacteria with which we come into contact are either harmless or useful. There are only a comparatively few bacteria commonly met which are harmful. For the purpose of protecting water from bacterial infection, the good as well as the bad organisms are to be excluded. To this end the spring or well producing the mineral water should be as carefully guarded from bacterial infection as possible.

Especially is it necessary that no sources of infection exist in the neighborhood of the spring, nor along the areas of its source. If the source of the spring be contaminated, it is almost impossible to expect a purification even during its course deep under ground and filtration through sand, gravel and soil. This mechanical treatment by nature may serve to remove the greater part of the infection, but it can hardly be expected to remove it all. Particularly the immediate neighborhood of the spring should be free from any infection, and the admixture of infection of any kind from surface waters must be guarded against with care.

Many waters which, as they approach the surface of the earth, are in excellent condition for consumption, become infected at their exit or during the process of bottling and shipping. Thus the exit of the well must be carefully cemented or concreted and so covered as to exclude external infection from surface water and from the air. All utensils used in handling the water must be sterilized, and the bottling must be done under standard conditions of sanitary cleanliness. The same character of problem that faces the safeguarding of ordinary potable waters must be observed with the mineral waters.

The occurrence of large numbers of colon bacillus in water is always a suggestion of pollution. While it is recognized that the colon bacillus may sometimes be innocent and be derived from a source which is unobjectionable, its original habitat in the animal organism, and especially in that part of the digestive apparatus which is known as the colon, makes its presence always a cause of suspicion if an inspection of the sanitary conditions of the premises shows that precautions are not observed to exclude the possibility of such an infection.