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The Evolution of the Conservation Movement, 1850-1920
Conservation by sanitation; disposal of waste (including a laboratory guide for sanitary engineers) by Ellen H. RichardsStandards of Purity
For the information and convenience of those who read this report, the following limits have been provisionally adopted as a reasonable basis for reaching conclusions regarding the wholesomeness
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of waters in the State of Illinois. No absolute standards of purity whereby to judge the condition of any and all potable waters can be justly established, because of differences due to the nature of the strata from which waters are drawn or with which they have been in contact, the topography of the district, and the general environment of the sources.
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SUGGESTED LIMITS OF IMPURITIES[Note 1: 1 Analyses of water ten miles from shore of Lake Michigan. Streams Examination Sanitary District of Chicago, p. 18.]
[Note 2: 2 This standard of purity is seldom found in the unfiltered water, as all streams are more or less polluted.]
[Note 333333: 3 None when drawn from wells. They may become turbid and develop color on standing.]
[Note 44: 4 Varies, as the waters contain ferrous salts.]
"The formation of a reasonable and just opinion regarding the wholesomeness of a water requires that there be taken into consideration all the data of the analysis together with the history of the water; the nature of the source; character of the soil and earth or rock strata, and the surroundings. The interpretation of results is a task for the expert. The purpose of this explanation is, therefore, merely to present to the layman such information
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as shall aid him to an understanding and appreciation of the analytical data."
A marked contribution was made by Dr. Drown in the clear statement of interpretation of results or, as the author expresses it, the diagnosis. A judgment founded on the sum total of the evidence given by the twenty or more chemical tests, the physical characters, the local conditions, and the bacterial count as well as at times other special tests is the only safe one.
This involved path of evidence requires the skilled detective rather than the mere analyst. Numerical results may mean much or little as the circumstances exist.
This fact is now generally recognized, and no reputable water analyst will now allow himself to be induced to give results in terms of standards.
In the first place, the sample must be taken so as to have some meaning. Any gallon of water taken anywhere along the stream will not do. There is to be a decided relationship between place of collection and the inferences to be drawn from the analysis.
In the second place, care must be used in collection so that no contaminating influence shall affect the sample--dirty hands, dirty sticks or stones, etc.
In the third place, it is usually a comparison that is needed rather than an absolute statement, because the identical circumstances occur but once.
In the fourth place, since permanence is the best assurance, the test of a condition favorable to change is important, that is, test on incubated samples or of the original sample after a week's standing.
Fifth, in studying the published results of other laboratories, methods of procedure should be known, since it has been true in the past that great differences were found. In 1897 a portion of the same sample of spring water was sent by the town authorities, to five chemists in three different states. The returns were as follows:
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Parts in 1,000,000As recently as 1900 a printed bulletin was sent out purporting to come from aa State Board of Health with, among others, the following remarkable statements:
"The following simple tests are issued in order that people who are not practical chemists may have a reliable method of detecting impurities in drinking water.
"(a) Good drinking water should not give any reaction with acid (red) or alkaline(blue) litmus paper.
"(b) Transparency, and (c) Color.
"Test: Fill a 6-inch test cylinder with the suspected water, and place it upon a white sheet of paper. Fill a similar glass with distilled water for comparison. Look through the water from the top. Any turbidity or want of transparency in the suspected water should be sufficient cause to have it condemned for drinking purposes, unless it filtered and boiled.
"Odor.--Drinking water should be absolutely odorless.
"Test: Fill a 500 c.c. (about a pint) Florence flask with water under examination. Heat it gently up to 43.3°C. (110°F.) or 48.6°C. (120°F.). If any odor develops, the water should be condemned, as it will generally be found to contain organic impurities.
"Test: Heat the residue in a platinum dish. If it is dissipated by heat or becomes charred, the water is unfit for use. (See also 2, below.)
"Test:(a) Chlorine may be detected: (1) By its odor; (2) By
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turning paper dipped in a solution of potassium iodide brown; (3) By bleaching a solution of indigo or litmus.
"Tests.--Nitrates: 1. When heated with sulphuric acid, they evolve pungent fumes of nitric acid.
"2. When heated with a solution of ferrous sulphate and a few drops of sulphuric acid, a black coloration is produced.
"3. Evaporate 4 cc. (60 drops) of the suspected water to dryness and add a few drops of phenyl-sulphuric acid (1 part of water); if nitrates are present a reddish color of nitro-phenol is produced.
"Should water become contaminated by the extra from cholera or typhoid fever patients, it will respond to the tests for organic matter and to those for nitrites and nitrates and the albuminoid compounds. The microscope will be able to differentiate between the micro-organisms of cholera, typhoid fever, etc."
As late as 1909, these were held official in some quarters.
Legal enactments are in not infrequently effective spurs to investigation. A notable example occurred when in 1886 the Legislature of Massachusetts passed an Act "to protect the purity of inland waters" and gave into the charge of the State Board of Health the experimental and supervisory measures required for this efficient protection. Stimulated by this responsibility, it instituted, for the time, a remarkable combination of scientific organization, engineering skill, chemical and bacteriological knowledge, which resulted in ten years of most fruitful investigation, although at the time so much seemed unproductive work.
The expenditure has been amply justified not only in the efficient work for the State continued along the similar lines but also in the development of certain principles and methods which have served as points of departure for further investigation all over the world.
The value of these investigation lies not only in their comprehensiveness but in the long time given to each series to prove
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or disprove their lessons. Consecutive records of twenty-three years available. Snap judgments are thus precluded.
The student is to take the "Outlines" in Part II as "subject to change without notice." The whole procedure as well as the theories on which it is founded is in a mobile state and will be for many years to come. There will be yearly need for revision, but that is no reason for delaying the trial of any scheme which promises in a given case to give information, for that is the end to be sought. Such information, however, must enable the worker to find his way--not merely give a mass of figures to print.
On the other hand, let not the worker despise pages of printed figures; they often reveal facts to another set of workers, twenty years later, facts which have been safely buried until needed. Also it has happened that a sudden illumination has come from studying columns of figures. Such was the origin of the idea of isochlors, or lines of normal chlorine.
Let the young engineer, impatient of routine work, therefore, not wholly despise the long columns of figures the laboratory files away for him.
REPORT OF WATER ASSAY
Parts per 1,000,000
Address for report
Locality
Date
Description of Water
Remarks
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The purpose of the water assay is to permit an estimate on certain points, as for instance:
To the engineer's laboratory may be brought for assay--
Safe water (supposedly) but which may be proved suspicious.
Natural water from uncontaminated sold or from mountain streams.
Tests may also be asked for treated samples to determine the success (or otherwise) of the process.
The laboratory outfit should include the means for all this work on a small scale.
A special laboratory connected with a purification plant need not necessarily comprise all the appliances if it has a single problem to deal with.
The general laboratory should be supplied with materials for simple bacteria counts. Media can now be obtained of known quality, and the mere plating and comparison of counts is not beyond the average chemist or engineer.
The economic trend so often referred to is not wholly bad--not all bad if it enables a greater benefit to be conferred.
In the case of water analysis, the old-time laborious concentration of gallons of liquid in the open laboratory regardless of
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the collection and absorption of dust and vapors, and of the solution of the earthen dish, in order to obtain sufficient material to weigh, was superseded in the latter half of the nineteenth century by colorimetric determinations which reduced quantities and times and avoided much contamination. There were, however, few laboratories where the degree of cleanliness and exactness now recognized prevailed. Room 36, Walker, M. I. T., was said to be the only really clean laboratory as late as 1887. Certain it is that the value of the ten years of classical water investigation, 1887-1897, carried on in that laboratory owed much to the refinement of method there maintained.
It is the engineer and not the chemist or bacteriologist who has the front rank to-day, and he must be, above all else, an economist. Why make twenty tests when five will tell him what he wishes to know? Why have an expensive laboratory when a simpler one will do five times the work of the kind he wishes to do? There has been great danger in this attitude lest the untrained engineer should think the simpler work always all-sufficient, the twenty tests never required. The fullest analyses must be made sufficiently often to establish a base line.
With education, the confidence of the worker has lessened, and a modest willingness to take the scientific attitude of "knowledge in suspension" has made possible the trusting of an engineer with the tools of a chemist and a bacteriologist with less fear that he will jump to conclusions or be rash in his judgments.
But a preliminary essential is that he shall have had experience in a well-ordered laboratory, not merely have read books, however clearly written. Some important points can never be put on a black-and-white page. A student will not catch himself doing a ridiculous thing as will the skilled worker watching him. Experience will, in the end, teach, but it is costly and sometimes fatal.
A man sent out to collect samples was found using an old stick picked up anywhere to push the bottle down to the prescribed
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twelve inches below the surface. One collector, having broken the glass stopper, glued it together. The laboratory, naturally, detected the dissolved glue by the abnormal excess of albuminoid ammonia, but that one of the all-important series of samples was irrevocably lost.
The collection and safe transportation of samples are of the utmost importance, as is a noting of all the surroundings of the spot where they were taken.
In the mining and metallurgical professions the assay or test for the one or two essential values in the ore sample has been developed to a high degree. When gold is the question the assay for gold proves its presence or absence; if absent, the character of the rock itself has no further interest.
In the case of the water assay, it is foreign substances that we look for to warn us of possible danger. The test for free ammonia or nitrites, for instance, if positive, gives the same decisive knowledge as absence of gold in the ore assay. The material is useless for its purpose. In neither case is further search precluded in another spot.
What is the decisive test which may be included under the head of preliminary but decisive enough to be classed as assay?
Water rightly read is the interpreter of its own history, and the untrained worker, not having this background, did not appreciate his own limitations. Several biologists have exceeded the bounds because of lack of training on the chemical side--of experience with great varieties of water. It is in this wider scope that the Mass. State laboratory had the advantage over the city laboratories of London, Berlin, and Paris.
Given the trained worker, he may safely use the five instead of twenty tests, with the permanent standards and the field kit, to aid his mature judgment.
Whatever tests are decided upon, the investigator is to bear in mind that the end sought is a correct diagnosis of the condition and of the causes of that condition. All sanitary work aims at prevention in future, not merely cure of present trouble.
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In doubtful case a long series of experiments, week after week, month after month, will, if studied carefully, finally reveal the source of trouble. Therefore, the laboratory must be prepared to carry out some of the exactly comparable examinations without deviation of methods and solutions.
These reports will be more elaborate in character than the simple water assay and more minutely follow directions.
Whatever value is attached to the results of the lesser or the greater examination is dependent on the conscientious exactness in measuring and recording, the sensitiveness of the eye to color, absolute cleanliness, and unswerving honesty in reports.
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