Part 9 (1/2)
It is common for small slaughter-houses to be built on the side of a stream, so that the offal, carrion, and refuse of the place may be carried off without effort on the part of the owner, and there are a number of such places where brooks, used as places of deposit for slaughter-house refuse, discharge directly into the reservoirs of water works.
But this sort of animal refuse is not the most serious pollution. The leachings and was.h.i.+ngs from privies and cesspools, carrying, as they do, germs of contagious diseases, are most to be dreaded, and when a privy (with no vault underneath) is built on the side of a steep ravine and is so located that the natural drainage of the sidehill on which it is built cannot help but run around and through the building, then the pollution of the stream in the gulley is not only direct and inevitable, but of a deadly sort (see Fig. 36). Fortunately, the germs thus carried into the stream suffer the vicissitudes of all life exposed to the attacks of hostile forces.
At the time of freshets the streams carry mud in abundance, which mud is continually settling out of the water as opportunity offers, and with this settlement of mud there occurs also the settlement of the germs.
Also the pathogenic or disease-producing germs are usually weaker and more susceptible than the putrefactive and other organisms which are found in the water in great abundance after any rain storm, and which tend to inhibit or destroy the pathogenic germs. But some will survive, and, with favoring conditions, may pa.s.s through the water-pipe to the house, causing sickness, if not death.
[Ill.u.s.tration: FIG. 36.--Stream draining a privy.]
Any inspection of the watershed, therefore, should look to the elimination of the dangers above described, and to the location of barns and barnyards, pig-pens and poultry yards, privies and cesspools, so that no direct drainage into the stream shall be possible.
It is out of the question for any surface water-supply to be pure, since the mere fact of the pa.s.sage of water over the soil inevitably results in the collection of organic matter; and it is no exaggeration to say that the time will inevitably come in this country, as it has already in Germany, when no surface supply will be considered satisfactory unless the water is filtered. The only alternative is water gathered from areas that are owned by the individual and on which, therefore, all dwellings may be prohibited, all cultivated land avoided, and where the primeval forest may be restored, making the watershed equal to that from which forest streams emerge.
But usually, in the case of a single house, it will not be possible entirely to eliminate the dangers of surface pollution, although an inspection will show the dangers, and possibly some of them may be avoided. Certainly any direct drainage into the streams should be cut out, as well as the drainage from barnyards in the immediate vicinity of the point where the water is taken out. Just what percentage of pollution may be eliminated in this way it is impossible to determine, but it is not too much to say that no brook or pond should be used for a water-supply of a house unless _every known pollution_ of an organic nature has been removed. Under the most favorable circ.u.mstances there will be enough accidental contamination to make the water at times dangerous, and no added risks ought to be a.s.sumed.
In looking over a watershed the possibility of sewage entering the stream is, of all pollutions, the most to be avoided. To adequately investigate the quality of a stream, the inspector must satisfy himself as to the point of discharge of the sewer of every house on the watershed, and this must be done personally, without apparently reflecting on the statements of the owner of the house. If any such points of discharge are found, the sewage should be either diverted into some other watershed, or spread out over the ground away from the stream, or purified by some artificial treatment before discharge, or else the creek water cannot be used.
The next point to be noted in the source of the water-supply is the presence and location of privies. These nuisances should be as far back from the banks of the streams as possible to eliminate all danger since the surface of the ground always slopes toward some stream, and pollution may be carried for considerable distances over or through the soil. Water-tight boxes can be provided so that no possible pollution of the surface-wash can occur, and if periodically the contents of these boxes be hauled away and buried, the privy loses its dangerous character. The city of Syracuse has installed on the watershed of Skaneateles Lake a most admirable system of collection of privy wastes, and the lake water is thoroughly protected, although there are several hundred privies on the watershed.
Cesspools, in general, are not dangerous if they are located fifty feet or more from the stream and if no overflow occurs.
Barnyards ought not to drain directly into streams, but when, as in so many cases, the stream flows through the barnyard, the only remedy is to move either the stream or the barnyard, and it is difficult to persuade even a well-disposed neighbor to do either. It is sometimes possible to appeal to his sense of right; but, too often, the neighbor feels that it is his land, his barn, his drain, even his brook, and he will do whatever he pleases with them, whether the water further down stream is to be used for drinking purposes or not. The question resolves itself into an inspection of the watershed and a determination of the existing conditions. If those are tolerable, the water may be used. If evident contamination is present, the water must usually be given up, and some other source of supply sought.
_Well water._
The pollution of wells, if it exists at all, is usually very p.r.o.nounced, and it is probably safe to say that, except where buildings, drains, or cesspools have been crowded too close to wells, or where some manifest and gross cause of pollution exists, a well water is safe to drink.
To protect properly a well from gross pollution, two precautions should be observed. The wall of the well should be built up in water-tight masonry, so that surface wash cannot enter the well except at a depth of at least six feet, and second, this water-tight masonry should be carried above the surface of the ground at least six inches and the well then covered with a water-tight floor so that no foreign matter can drop through the floor into the well or can be washed in by the waste water from the pump (see Figs. 28, 29, 30). If these precautions are taken, it is safe to say that nine tenths of the pollution occurring in isolated wells would be stopped.
Besides the above, a well may be polluted by a stream of underground water was.h.i.+ng the contaminating matter through the soil. Experiments have been made to show this very plainly. A large number of bacteria were placed six feet below the surface just in the top of the underground stream of water. Within a week they were found in considerable numbers in the water of the soil one hundred feet distant, but when the same number of bacteria were placed in the soil four feet below the surface above the level of the ground water, none of them found their way into the water of the soil. This experiment shows the folly of building a cesspool in the vicinity of a well when they both go down to the same water level, since the contents of the cesspool will be carried into the well if the underground stream flows in the proper direction. A shallow cesspool, however, would not be open to the same objection.
It is always difficult to detect the direction or flow of underground water, and various technical and delicate methods have been selected to make this determination. A very simple test, however, is to dig a hole at the point where pollution is suspected, carrying the hole down to where ground water is reached, and then to throw a gallon of kerosene oil into the hole, and if the ground-water flow is toward the well, the presence of kerosene in the well water will make the fact known. This would not, however, prove that the actual contamination would produce disease, since a liquid like kerosene can find its way through the pores of the soil to much greater distances than bacteria can be carried. But, to be on the safe side, water from such a well should not be used.
To make sure of the quality of the water proposed for a water-supply, it is wise to have such water examined by a chemist. The chemist will make certain determinations of ammonia and other chemical combinations, and will report his findings with an interpretation or explanation of the result. What he finds is not the presence or absence of disease or disease germs, but substances that suggest or involve the presence of organic pollution. A test is made for the number of bacteria, and a well of spring water which contains more than about fifty in a cubic centimeter is a suspicious water. Surface water, on the other hand, may contain two or three hundred without being necessarily bad, the types of bacteria being harmless. Generally, a chemist will also determine the presence of the colon bacillus which is found in the intestinal tract of man or warm-blooded animals. Wherever this is found, in even such a small quant.i.ty as one cubic centimeter of water or less, there is strong presumption that the water has been polluted by human wastes and is therefore not fit to drink.
_Dangers of polluted water._
Since no evidence of the danger of drinking polluted water can be so graphically expressed as by a direct reference to epidemics caused by the unwise use of such water, it will not be out of place to refer briefly to some of the instances in which a direct connection has been traced between a specific pollution of a certain water and disease or death resulting from it.
Although, as has already been explained, an infected water causes various kinds of intestinal disorders, particularly among children, the most characteristic evidence of pollution occurs when the noxious material comes directly from a typhoid fever patient, so that this same disease can be recognized as transmitted to another individual or family. This transmission of typhoid fever, while in some cases very plainly due to other agencies than water, as, for example, milk, oysters, and flies, yet, by far the largest proportion of the transmitted cases comes through the agency of polluted drinking water, and there are many examples both of contaminated wells and streams which emphasize this possibility beyond all question.
Two historic investigations of epidemics which have thoroughly convinced sanitarians that typhoid fever is a communicable disease and that water is the vehicle for its transmission may be briefly cited.
In 1879 Dr. Thorne reported an epidemic in the town of Caterham, England, which he had investigated, and disclosed the following facts: The population of the village was 5800. The first case of fever appeared on January 19. Others followed in rapid succession, until the number reached 352, of whom in due time 21 died.
The possibility of infection was carefully looked into. The influence of sewer air was ruled out because there were no sewers. The milk supply was proved un.o.bjectionable. No theory of personal or secondary infection could account for the widespread prevalence, particularly as only one isolated case had occurred during the preceding year, and this had been imported.
Of the first 47 persons attacked, 45 lived in houses supplied with the public water-supply, and the other two were during the day in houses supplied with public water. Further, in the Caterham Asylum, with nearly 2000 patients, not a single case appeared, their water coming from driven wells. Investigation of the water-supply showed the undoubted cause of the epidemic. The public water-supply was derived from three deep wells, connected by tunnels in the chalk. In one of these tunnels, from January 5 to the end of the month, a laborer worked, who, though unattended by a physician, was evidently suffering from mild typhoid fever, the symptoms of the disease being carefully detailed by Dr.
Thorne. The laborer at the time of his going to work had a severe diarrhoea, and while in the tunnel was obliged to make use of the bucket, in which the excavated chalk was hauled to the top. He admitted that at times the bucket, in being hauled up, would oscillate in such a way as to spill part of its contents and thereby pollute the water of the well below. Two weeks from this accidental pollution the epidemic began, and there can be little doubt of the relation of this mild case of typhoid to the epidemic which followed.