THE SANITARY EXAMINATION OF WATER.

A Paper Written For Non-professional Health Officers.

BY PROF. W. W. DANIELLS, OF THE STATE UNIVERSITY.

The rapid development of "preventive medicine" during the last twenty-five years, and its especially rapid advance within the last decade has greatly stimulated investigation as to the part which water plays in producing disease. These investigations while not always resulting in absolute knowledge, have shown with positive certainty that water is frequently the means of conveying disease from one person to another, and from one community to another, even when considerable distance intervenes. It is also generally regarded as proven that water which has been long in contact with decomposing organic matter, may as a result of this contact become the bearer of germs, ferments or septic poisons which produce in those habitually drinking such waters diarrhoeal or malarial diseases.

Hence the examination of water used for domestic purposes has become an important feature of sanitary work. There are two methods of water examination for sanitary purposes. By one of these methods, the biological, a search is made for the minute organisms (bacteria) which are the specific cause of disease. The other method, the chemical, seeks to detect substances either organic or of organic origin, held in solution by the water, and which indicate the presence of polluting material.

Both methods recognize that it is from organic matter that the unwholesome qualities of water are obtained, rather than from the inorganic salts which are present to a greater or less extent in all earth waters.

Neither method is complete in itself. Theoretically the biological method is the more perfect, as if germs that are

The Sanitary Examination of Water.

known to produce disease are found, there can be no question of the dangerous character of the water containing them. But the uncertainty of always finding the minute organisms when present, together with the great skill required in distinguishing between those which are harmless and those which are harmful, render this method difficult of execution and frequently unreliable.

The chemical method of water examination seeks to determine the amount and the nature of the organic matter present, and also the amount of those inorganic substances which usually accompany organic contamination, or are produced by the decomposition of organic matter. The results obtained from such an examination afford a basis of judgment as to the wholesomeness or un wholsomeness of the water in question.

This method is imperfect in that it does not directly distinguish between harmful and harmless substances, that the methods are crude and inexact, and also that the results obtained are not specific. As a basis of judgment of the wholesomeness of a water, these results need to be accompanied by a knowledge of the character of uncontaminated water from of the same locality, and the history of the sample examined. Hence the value of an opinion of the wholesomeness of a water based upon its chemical examination, depends to a large extent upon the experience the person giving it has had with waters from the same region together with his knowledge of the conditions surrounding the source of the sample in question.

Both methods of water examination then, have their limitations and their imperfections. It is quite possible for a water to contain disease germs, or dilute sewage, to be reported as having no unwholesome qualities after careful and skilful examination by both methods.

Notwithstanding these facts both methods are not only useful to the sanitarian, but are in the main reliable when carried out by those accustomed to their eexcution. The

The Sanitary Examination of Water.

writer claims no knowledge of the biological method, and what follows has reference to the chemical method only.

In the sanitary examination of water by this method as has been said above, an attempt is made to prove the presence or absence of polluting substances, rather than of the specific cause of disease. The polluting substances are in the main organic, and may come from sewage, or they may result from the decomposition of animal or vegetable matter. The inorganic substances sought for are those which frequently accompany organic pollution, as chlorine, or result from its decomposition, as ammonia, nitric and nitrous acids. The detection and the determination of the amount of this inorganic matter are operations easily performed by the chemist. To be able to state its source is a matter of much greater difficulty. Its probable source can only be stated by comparing the results of the examination of the water in question with those obtained by the examination of other waters from the same locality which are known not to be polluted.

The detection and determination of organic matter in water is a much more dificult problem. There is no known method of obtaining it in a definite form in which it may be estimated. Hence indirect methods must be used. Organic matter is composed in the main of the elements carbon, hydrogen, oxygen and nitrogen. Generally speaking the richer it is in nitrogen, the more readily it undergoes decomposition, and hence the more dangerous to health. Frankland and Armstrong have based their method of water analysis upon these facts. They determine the amount of each of these gases contained in the residue left by the evaporation of a known quantity of the water, and from the results thus obtained judge of the character of the organic matter in the water. This method is capable of being carried out with great precision, but unfortunately the composition of organic matter is not sufficient to indicate its character. Harmless and dangerous substances may have the same

The Sanitary Examination of Water.

chemical composition, so that the combustion method of water analysis fails in important particulars.

Another method intended to determine the nature of the organic matter in water is called after its originator, "the Wanklyn method." This method seeks to convert the nitrogen of the organic matter of a measured quantity of water into ammonia, and to determine the amount of this substance obtained. This ammonia can be determined with great accuracy, but the conversion of all the nitrogen into ammonia is frequently difficult and in many cases quite impossible. So that we have here again an imperfect meth. od. Its advantages are that it is comparatively easy of execution, and one can usually determine by it if there is a large amount of nitrogenous matter present, and it also, by the relatively slow or rapid development of ammonia during the early stages of the process, enables one to judge with tolerable certainty the character of the organic matter present.

Still a third method of the treatment of water in order to judge of the nature of the organic matter present, is to ascertain the quantity of oxygen a measured volume of the water will consume in a given time and under known conditions. The oxygen consumed is obtained from a solution of potassium permanganate which is added to the water. This process is naturally known as the Forchammer process, of which Wanklyn's "wet combustion method" is only a modification. No one claims for this process more than that it is an aid in forming a judgment as to the character of the organic matter present.

I have given this resume of the methods of water examination now in use, not only to indicate their imperfections, but also to point out that even could a layman execute them with accuracy, the results obtained could hardly be interpreted by him until he had gained much experience by practice, observation, and comparison. Executed and interpreted by one experienced in the work, the results ob

The Sanitary Examination of Water.

tained from the sanitary examination of water may be relied upon with much certainty, and are of the greatest value to the Health Officer. But with our imperfect methods of examination, the value of the results obtained must greatly depend upon the ability of the analyst to correctly interpret his work. Notwithstanding the emphasis I would put upon the above statement, I believe every Health Officer may, without great difficulty, educate himself to judge of the wholesomeness of drinking water with a fair degree of certainty that his judgment will be correct. It is with a desire to aid those who wish to make themselves intelligent in this important branch of sanitary work that this paper is written.

The great rule of universal application in all sanitation is, "avoid filth." Filth contaminates and renders unwholesome everything with which it comes in contact. Filthy air, filthy bodies, filthy houses, and filthy surroundings of the house are the conditions under which disease incubates and is brought forth in its most malignant form. Filthy water is unwholesome water, and filthy water must result from filthy surroundings of its source of supply.

The greater portion of the people of our state obtain their water from wells, and except in the larger cities and towns must continue to do so for an indefinite future. These wells are usually from twenty to forty feet in depth, and are for convenience placed near the house. A well is only a hole in the ground extending down to a water-bearing stratum. In its relations to the water in the surrounding soil, it acts as any other hole in the ground, affording an outlet toward which this soil-water gravitates. Unless some more available outlet exists, the soil-water will gradually find its way through the soil to the well for a distance in each direction of at least three times the depth of the well to the surface of the water.

Soils have a considerable power of extracting from water percolating through them the organic matter held in solution. This power varies with the character of the soil,