BACTERIA IN WATER SUPPLIES.
Specially written for FIRE AND WATER ENGINEERING.
Bacteria belong to the lowest order of plants and follow the algæ very closely. They are superficially divided into three classes, as follows: Micrcoccus; bacillus; spirillum. They are cells composed of a membranous cell-wall and cell-contents, with probably cell-nuclei. In shape they are round or cylindrical, of an average diameter or transverse section of 0.001 mm (— 1 micromillimetre). The cell-wall is of plant cellulose, with a firm membrane; the cell-contents are chiefly protoplasm, generally homogeneous, but sometimes finely granular, or holding pigment, composed chiefly of mycoprotein. The streptococci and staphylo-cocci are the result of the gelatinous membrane becoming water-soaked and forming either a small envelope or capsule round the bacterium, or handling the newlybranched germs from separating—thus, forming chains and bunches and sometimes long filaments. If this gelatinous mass is very thick, there will be formed irregular masses of bacteria in one jellylike lump. Some bacteria possess the power of self-movement; some vibrate and appear to move, but do not change their place – molecular movement. Bacteria are reproduced by simple division or by fructification by means of small round or oval seeds or spores, which, in turn, multiply in the same way. What the real contents of these spores are is not certainly known; but in the mother cell, wherever the site of the spore is, are found minute granular bodies, whose stain differs from the rest of the cell. 1 liese sporogemc bodies are supposed to be the beginnings. For the germination of these spores a certain amount of heat and oxygen is necessary. The envelope of these spores is said to be the most resisting object of the organic world, so much so, indeed, that chemical and physical agents that destroy other life without difficulty have very little effect upon them. Many require a temperature of 140° ( dry heat for several hours to destroy them, and on many, such as typhoid bacillus, for instance, the intensest cold lias no effect. tor the life and growth of bacteria, as a rule, a temperature ranging from to” C. to 4° C. Sunlight is very destructive to bacteria, as is electricity. Some grow in the air and are called aerobic; others (anaerobic) live without air. With age bacteria lose their strength and die; but, while alive, they are busy workers, breathing, eating, digesting, excreting and multiplying the same as the highest organised life. The harmful bacteria are called pathogenic; the harmless (and many of these destroy the pathogenic relatives), nonpathogenic.
Impure water, that is. water contaminated with sewage and kindred pollutions is the medium for importing various pathogenic bacteria into the human system. Hence, no source of water supply should be accepted till it has been not only chemically. but, also, bacteriologieally analysed. And this analysis should be applied even in the case of filtered waters, though, of course, not at such frequent intervals, as when the water is not filtered. And Here it may be observed that, while a water containing thousands of germs to the cubic centimetre may sometimes be quite harmless (though very disgusting to look at, smell, or taste), it, at all events, may be much less dangerous than one containing only two germs, if one of these is—say, that of typhoid fever. In such a case, it is not the quantity that kills, but the quality. As to the number of germs that go to make up an impure water, it is sufficient to say that the source of any natural water that on investigation contains over 500 germs to the cubic centimetre should lie examined. It must also lie remembered that, while bacteriology is of the greatest service in testing the devices which are intended to render water fit for drinking, it is of but little use as a diagnostic aid. For instance. in the case of a typhoid epidemic, the suspected water is examined. Meanwhile, however, the days of incubation and those passed before the water is analysed have allowed whatever typhoid germs may have been present (if any) plenty of time to disappear, as, where other bacteria are in the water, the typhoid germs live but a short time. Or, today the water may IK entirely free from germs and tomorrow the contrary may be the case, so that the epidemic may have died out before the presence of the typhoid germ can be detected in that water. But. wherever the colon bacillus is present in water that is a sign that there is sewage pollution, and measures should be at once taken to fitter the supply. The examination should not be restricted to the water only, but, wherever possible (as in the case of wells, ponds or lakes and creeks from which the supply is taken), the surrounding soil should be analysed, since it is often impregnated with sewage and other polluting matter, the result of percolation from cesspools, privies, cattlesheds, stables, pigstyes and the like. With this impure matter, fecal or other, the source of water supply becomes infected, with disastrous results, directly, through the water, or, indirectly, through impure milk, oysters and other shellfish. The soil, like the water, should be examined immediately or very soon after samples of it have been collected, as the bacteria multiply very rapidly in it, as they do, also, in stagnant water. If, then, even in the case of filtered vvatcr, periodical chemical and bacteriological analyses should be held, much more should this be the case in that of a non-filtered water supply, however pure its source. The purest is, of course, the natural spring water that has slowly filtered through layers of gravel and sand and bubbles up from the ground—that ground, all the same, being liable to surface pollution—or out of the living rock. But only so long as that water is not walled up in cisterns, storage reservoirs, or wells, it may be looked upon as pure; otherwise, it is likely—even sure to be infected with all sorts of impurities. Artesian well water to a certain extent secures pure water, and is the only form of well or cistern water that guarantees purity, since the water does not become stagnant in if. In too many cases, however, a fatal reliance is reposed in such wells, and sickness and death result from their use, because of their proximity to a privy, cesspool or other filthy place. Under such conditions, as the soil is often very loose, the products of germs of refuse water and animal secretions find their way into the well, and poison the water. 1 f, on being examined chemically, there are found in the water increased amounts of chloride of sodium, there is danger. Bacteriological examination is of service in determining if a water, that has been filtered, and is, therefore, clear to the eye, and gives no hurtful chemical reaction, is entirely or nearly entirely free from germs. It will, also, determine whether or not the filter is doing its work properly. Nor let this ever be forgotten, that as the eye cannot detect, nor the nose smell, nor the mouth taste the harmful germ, the sparkling clearness of the water is no criterion of its purity.