STANDARDS FOR HYGIENIC PURITY OF MONTANA WATER
The public water supplies of Montana are taken from a variety of sources. The purpose of this paper is to show the differences in the composition of the waters from these sources. With these data it will be possible to draw conclusions concerning chemical standards of purity suitable to Montana conditions. In the mountainous portions of the State, city water supplies are taken from streams above human habitation as a rule. These represent the purest waters found in the State, and the average of the analyses of thirteen of these water supplies is tabulated below. These samples were collected during the fall and winter months, when the organic content was the lowest.
Parts per million.
Shortly after the above results were obtained the writer attempted to use them as a partial guide in passing opinions on the sanitary qualities of water supplies taken from the Yellowstone River at various points where there was some reason to suspect that the water was a menace to health. The results of analyses at these points on the river were much higher than could be accounted for by the amount of sewage known to be entering the ruer. Consequently, samples were then taken from the Yellowstone River above the town of Gardiner and above the mouth of the Gardiner River. This is a point on the Yellowstone River above all sewage contamination, and it was expected that the analyses we uld give results similar to other mountain streams. That this was not the case is shown by a typical analysis tabulated below.
Parts per Million.
This analysis was checked by taking other samples and it was learned thatthe Yellowstone River at points above sewage contamination contains more free ammonia and nitrites and at times more albuminoid ammonia than it does at the intakes of any of the cities using the water, all of which are located at varying distances below sewage outlets. In this connection it should be stated that the mountain streams flowing into the river below Gardiner contain no nitrates and only a small amount of free ammonia. The results so far point to the conclusion that the river water contains more free ammonia and nitrates during the winter months when most of the water in the river comes from Yellowstone Lake than it does in the spring and summer, when the flow is increased by melting snow. The varying character of the water above sewage contamination and the fact that the water normally carries substances usually contributed by sewage makes it very difficult to give chemical data obtained at city intakes and diagnostic value. While it is evident in this case that the free ammonia and nitrates do not have their origin in sewage, still the exact source has not been traced, so far as the writer knows. It is possible they are developed by chemical action in the geysers and springs of the Yellowstone National Park. Water of still a different character is found in Northwestern Montana. The chief sources for city use are the Milk and Missouri rivers. The water of these rivers are high in organic matmater, which is not derived from city sewage. The organic content increases as the rivers flow to the eastern part of the State, where outcrops of lignite coal frequently occur. The effect of the coal is shown in the following analysis of a spring in a sandstone strata which is underlaid with lignite coal. The spring is far from any source of contamination.
Water of this character flows into both the Missouri and Milk rivers at numerous places. It is evident that the chemical data on waters of this kind cannot be compared with the data reported on the pure mountain streams. Another source of water for city use in Montana is the deep well. The following is a typical analysis. The well was drilled, cased and is 610 feet deep. It is located far from any source of contamination.
Parts per Million.
It is evident that there is a great variation in the organic content of the surface waters in Montana, known to be free from sewage contamination. This variation is so great that it is impossible to use a universal chemical standard of purity for all waters of the State. However, it has been possible by carefully studying the qualities of the waters fron various sources to adopt local standards of purity, which are very necessary in connection with bacteriological data.
* Paper read before Illinois Water Association, March, 1014.
Parts per Million.