EXAMINATION OF SPRING WATERS. There is a large quantity of spring water sold throughout the State, particularly in cities and towns where the regular water supply is thought to be unsatisfactory, or where the water, as is not infrequently the case with surface-water supplies in the summer time, has an unpleasant taste and odor. A considerable number of these spring waters were collected for examination during the summer of 1891, and at the same time a careful inspection of the surroundings of the springs was made, to discover possible sources of pollution. Not only is there a large sale of spring waters as such, but there is also a large amount consumed in bottled form, as soda water and other effervescing drinks. As the result of this investigation, it was found that some of the springs were situated in regions nearly or quite free from population, where the land was not under cultivation, and the chemical examinations of these waters showed them to be of the highest purity. Other springs were situated in populous districts, or had near them direct sources of pollution, and the water gave evidence, on chemical analysis, that it had, in its course, received a large amount of drainage from sinks, cesspools, privies or stables. In most of the springs of this character which were examined the water showed, however, a high degree of purification by filtration through the ground. The results of the chemical and bacteriological examinations are given below. In accordance with the system of classifying waters adopted in the Report on the Water Supplies of the State (see Special Report on the Examination of Water Supplies, 1890, pages 679 to 716), these spring waters have been divided into three groups, based on their chlorine contents. The first group includes the normal waters and those in which the chlorine is not over 0.20 parts per 100,000 in excess of the normal; the second, those in which the excess of the chlorine is from 0.21 to 0.60 parts; the third group, those in which the excess of chlorine is over 0.60 parts. The first group contains the springs deriving their supply from water-sheds with little or no population; the second group, those in a moderately populated area; and the third includes the springs which are located in regions with considerable population.' Normal waters have been defined to be those which have not received any waste products of human life. They are as a rule conAny excess of chlorine fined to the water-sheds without population. above the normal of the region in which the water is found is a measure of the amount of waste products, human and animal, that the water has taken up. But the evidence of contamination based on the chlorine alone does not tell us whether the source of pollution is near by or remote. This information is obtained from the determination of the nitrogen, which in freshly polluted water is present in the form of organic matter (albuminoid ammonia) and free ammonia, while in water which has percolated under favorable conditions through porous ground the nitrogen is all oxidized and appears in the form of nitrates. In interpreting the analyses of the waters in the following classification, it is necessary to take into consideration the degree of purification which has taken place in those waters which are shown by their chlorine contents to have been at some time more or less contaminated. It is easily possible for a spring water which has somewhere in its course received a large amount of polluted drainage to be organically much purer than another in which the amount of contamination has been much less. The purifying power of porous ground, in which organic matter is exposed to bacterial action with access of air, is sufficiently great, under favorable conditions, to convert completely organic into mineral matter, as far as chemical analysis can indicate. It will be seen in the accompanying analyses that some of the waters which have received a large amount of pollution, and which may be said to be to a considerable extent filtered sewage, have less organic matter remaining in them, as shown by the albuminoid ammonia, than others in which the degree of contamination was originally much less. In the process of filtration through porous ground, whereby organic matter in water is oxidized, there may also be effected a purification as regards disease germs. This latter and most important purification may be due to the removal of the germs by the mechanical straining of the water at an extremely slow rate through the ground, or to the death of the germs, owing to unfavorable conditions for their life in the filtering process. While we cannot always know in any particular case which of these processes may have been the principal factor in the purification of the water, we know that the conditions of perfect mechanical filtration (whereby all suspended matters are removed from the water), and the conditions of perfect chemical purification, are those also most favorable for the complete removal of bacteria. Although water badly contaminated with sewage or the wastes of human life may be purified by thorough filtration so as to be free from organic matter and from bacteria, yet in cases of ground waters of this origin and character we seldom feel complete security that the conditions of perfect filtration will always exist. A long-continued rainfall, for instance, may result in more rapid filtration and consequently less perfect purification; or the creation of new sources of contamination, nearer the spring, may result in its dangerous pollution. It is for such reasons that a certain suspicion always attaches to ground waters which have at any time in their history been seriously polluted. The use of ground waters, whether springs or wells, in built-up communities, should therefore be avoided, for we have no control over the conditions of filtration, and have no means of knowing (except by constant vigilance in the examination of the water) when a water hitherto well purified may become injuriously impure. The danger from the use of ground waters in populous regions increases with the increase of population, and with the nearness of the sources of pollution to the spring or well. No attempt was made to determine the species of bacteria in these spring waters, and the numbers of bacteria given in the tables are not, therefore, to be interpreted as expressing in any sense the relative fitness of the waters for drinking. In open wells, for instance, we may often find a large number of harmless bacteria. which have come from the air or from dust, and which would not be found in the water if better protected. A favorable construction is, of course, to be put on the low numbers of bacteria, since they show that few bacteria of any kind are present, and that the conditions under which the water is filtered in the ground are favorable to its purification. |