There is a group of beneficial soil microbes, which are undesirable in water. These are the iron bacteria, which tend to become so numerous that they are called water-pest bacteria. Iron bacteria are a natural part of the environment. These microorganisms, when examined under a compound microscope, mix dissolved iron or manganese with oxygen and use it to develop rust-colored deposits. These bacteria, in the process, manufacture a brown slime that build up on well screens, pipes, and plumbing fixtures. They not only cause pipeline obstructions, but also increase the organic material in the water encouraging the abnormal growth of other microbes, as seen in a compound microscope.

According to Dr. J. Greaves, there may he 500,000 to 12,000,000 microbes in fifteen drops of sewage when examined under a compound microscope. Dr. Puller estimates that every person connected with a drainage sewer contributes an average of about 322,000,000,000 microbes per day. When the population of the average modern city multiplies such numbers, it becomes apparent that the problem of sewage disposal is one of critical importance.

Fortunately, as we know, relatively few of these teeming myriads of microbes are pathogens. They mostly are saprophytic scavengers living off dead or dying material, and, therefore, man’s benefactors. But in saying this one must not forget that into the sewers flow also the solid and fluid excreta of persons ill with such infectious diseases as typhoid fever, the dysenteries, tuberculosis, etc. It is against these that every precaution must be taken. All other considerations apart, the mere idea of imbibing water contaminated by sewage is repulsive; and yet such contamination will occur unless persistently and vigilantly guarded against.

The more progressive among modern communities subject their sewage to a form of treatment, which precludes it from becoming a source of disease. One of the most efficient plants for this purpose is that of Milwaukee, Wisconsin, as described by J. A. Wilson in Chemistry and Medicine. Milwaukee’s sewage treatment is one of filtration and sedimentation, called the “activated sludge process, and involves both biological and chemical action. There is no need here to describe such a process save to note that microbes, through ingestion, fermentation, and putrefaction, destroy the objectionable odors as well as the dangerous materials. An indication of the vast microbial action-taking place in sewers and sewage-disposal plants was furnished in September 1929, by the sewer-gas explosion, which rocked Newburgh, N. Y. And it is a noteworthy fact that some power engines today are operated with sewer-gas fuel.

Some conception of the extraordinary efficiency of modern sewage disposal plants may be gleaned from the fact that when, after treatment, Milwaukee’s sewage is returned to Lake Michigan, it is 99 percent pure as pure, in fact, as the city’s drinking water from the same lake. The treated residue in the sewage tanks is dried, and in this form furnishes excellent fertilizer.

It might be well to conclude with a word of advice to the thirsty: when camping, hiking, touring, always boil the water you propose to drink. Do this no matter how clear and clean the water may appear to be. Appearance is no test, and neither is taste, but boiling places your water beyond question.