GENERAL CONSIDERATIONS

Necessity for Proper Supply

One of the most important requisites in maintaining the organization of the material in the living body is a proper supply of water. It is absolutely indispensable to the expression of animal and vegetable life. Although not classed as a food it enters into the composition of food and hence becomes an essential article of diet.

The greatest value has always been placed upon a sufficient supply of pure water. The history of the race shows that the earliest settlements were made with a view to obtaining a supply of water; they were either on waterways or in places where water was easily obtainable from springs or shallow wells.

Water is needed not only as an article of diet, but it is also required for sanitary purposes: for cleansing the body externally, for washing clothes, and also for sprinkling streets and for other purposes such as sewage disposal in the thickly populated centers. Even in ancient times great sums of money were expended for the public supply of water.

History of Public Water Supply

A bit of history on this subject might be of interest to some. It is asserted by historians that there are aqueducts in China dating back to prehistoric times. Channels cut in solid rock have been revealed in Jerusalem in recent excavation which indicate that they were used for conveying the water supply from the country near Bethlehem and Hebron. There have been found in these excavations channels of earthen pipes cemented together and covered with rough rocks. The fact is also quite well established that water was brought to Athens from Mount Hymettos and Mount Pentelikon.

As early as 312 B. C. water was carried to Rome through an aqueduct ten miles long. It is estimated that the cost of construction of this aqueduct was about $12,700,000. Another was begun in 272 B. C., the length of which was forty-five miles. The water carried by this aqueduct was not used for drinking but for irrigating purposes and for flushing drains.

Altogether there were at least nine aqueducts that supplied the ancient city of Rome. Of these nine, three are still used to supply modern Rome. One of these was finished by Agrippa in 27 B. C.

We see by the foregoing that from time immemorial there has been a great expenditure of energy and money in producing a proper water supply for the human family. It also reveals the fact that the ancients knew something about engineering projects which some of us are likely to consider as modern accomplishments.

Composition of Water

Water is not, as was previously supposed, an elementary substance. In 1781 it was shown by Cavendish that it consisted of two parts of hydrogen and one part of oxygen (H₂O), and that it could be made synthetically by combining hydrogen and oxygen in this proportion, and that it could be separated analytically by various methods into its component parts.

By volume, water is composed of two parts of hydrogen to one part of oxygen; by weight, one part of hydrogen to eight parts of oxygen. However, pure water does not exist in Nature since water is a universal solvent and in Nature it comes in contact with so many substances; therefore, it contains many substances in solution. Chemically pure water is found only in the chemist’s flask.

Water is a liquid which is clear, colorless and odorless. To be palatable it should be cool, soft, well aerated and free from sediment and suspended impurities. One cannot judge the purity of water by any one of these qualities, for water that is palatable and gives no offense upon drinking might be polluted with that which would be detrimental to health. The palatability of water may be due to the carbonic acid present, which results from the decomposition of products contained in it.

The carbon dioxide, which is present in rain water, is obtained from the air through which the rain passes. Carbon dioxide is also taken up by the water as it percolates through ground covered with vegetation. The presence of this gas increases the solvent powers of the water. Water may also contain metal in solution such as iron, arsenic and copper.

The important foreign ingredients in water are those of organic origin, such as microscopic plants, vegetable fungi, detritus of vegetable life, minute insects, infusoria, ova of insects, minute parasites, and animal debris. Water usually contains millions of various micro-organisms, mostly harmless, although at times it may also contain so-called pathogenic germs.

States of Aggregation

Water is formed into the solid state, ice, at zero degrees centigrade. At 100° C. water boils and is converted into gas or vapor, although water is contained in the air in the gaseous form at ordinary temperatures. Between these two limits, 0° C. and 100° C. water obtains in the liquid form which is its most common state. Water is the most widely distributed of all the substances. It is practically incompressible. When heated it contracts until it reaches 4° C, or 39.2° F., and is at this point taken as the basis for specific gravity of liquids and solids.

Universal Solvent

Water is the most universal solvent known in Nature. Practically all substances yield to it. Most of the water taken into the body passes through unchanged, although it is only reasonable to suppose that some of it is broken up into its elements and united with other compounds of the body.

Necessity for Water in Body

Water composes about 70% of the entire weight of the body (about 58.5% per volume). A very great amount of water is required by the tissue for the performance of the bodily functions. As the gears of machinery must be bathed in oil to prevent undue wear, so must the tissue cells be bathed in water (secretions) that there be no undue wear. The tissue cells are spoken of as being aquatic in their habits.

Rosenau in summarizing the use of water in the body says: “It enters into the chemical composition of the tissues; it forms the chief ingredient of all the fluids of the body and maintains their proper degree of dilution, and thus favors metabolism; by moistening various surfaces of the body, such as mucous and serous membranes, it prevents friction; it furnishes in the blood and lymph a fluid medium by which food may be taken to remote parts of the body and the waste material removed, thus promoting rapid tissue changes; it serves as a distributor of bodily heat; it regulates the body temperature by the physical process of absorption and evaporation.”

Chemically Pure Water

Chemically pure water can be obtained only by distillation; it is undesirable, however, for drinking purposes because of its insipidity. Before such water is agreeable for drinking it must be aerated; this may be accomplished by agitation or by passing it through a porous substance containing air. One of Nature’s methods of aerating water is found in mountain streams where the water flows down over rocks. The same thing is accomplished by fountains and waterfalls. It is the mineral matter and the gases held in solution that give water its taste, and it is the difference in these minerals and gases that causes the individual to dislike the taste of water which he is not accustomed to drinking. But this is purely a matter of taste and has no value from a hygienic standpoint, for the most impure water, water that contains so-called pathogenic germs, may taste very good.

Turbid or muddy water is not necessarily impure from a hygienic standpoint when found in rivers, but when subsoil water becomes turbid it should be regarded with suspicion.

Hard and Soft Water

The question of hard and soft water is one that must of necessity receive some consideration, but it is of more importance from an economic standpoint than from a sanitary standpoint. Soft water is generally considered to be more desirable for drinking purposes, and it is certainly more desirable for cooking. From an economical standpoint, soft water is more preferable as the hard water requires more soap to produce a lather.

Hardness of water is spoken of as being temporary or permanent. If the water remains hard after having been boiled it is known as permanently hard water. Hardness of water is due to the presence of the soluble salts of the alkaline earth metals, especially calcium and magnesium. Temporary hardness is due to calcium or magnesium carbonate held in solution as a bicarbonate by the dissolved carbon dioxide. The hardness is temporary because the carbon dioxide is driven off by boiling, and the soluble bicarbonates are precipitated as insoluble carbonates.

Permanent hardness, on the other hand, is due mainly to sulphates and chlorides of calcium or magnesium. These salts are stable and therefore are not precipitated by boiling.

Elimination of Water from Body

Water is excreted from the body through the various channels. The kidneys excrete about 50%, the lungs about 20%, the skin about 28%, while the other 2% is excreted through the feces and other minor channels.

Amount of Water Needed for All Purposes

The amount of water needed for all purposes varies just the same as the amount of water needed by the body varies with conditioning factors. The locality and the climate will enter into the consideration of the amount of water needed to meet the requirements of hygiene and sanitation.

The amount of water required by the human body in twenty-four hours varies with many factors. The age of the individual and his occupation and health, and climate would be conditioning factors. However, authorities are pretty well agreed as to the amount necessary. It is estimated that the body requires a little less than one gallon of water per day, about two quarts taken as drinking water and the balance in food.

There is a wide range of difference in the amounts estimated, for under some conditions, a minimum of seventeen gallons, or even twelve gallons, would be sufficient, while under other circumstances and in other localities as much as 300 gallons per day per individual would not be an excessive or wasteful amount. The average amount estimated per individual per day for domestic purposes is placed at seventeen gallons for all purposes. In 1918 the statistics showed that Buffalo used an average of 260 gallons per capita per day, but many cities used much less. In Berlin in 1913 the water consumption amounted to an average of twenty-four gallons per capita per day.

The hygienic importance of these figures is insignificant since they are only approximate. There are a number of factors that are not taken into consideration. The figures are estimated on the number of gallons of water pumped and no account whatsoever is taken of the water waste through precipitation and loss through leaky pipes. Some engineers maintain that fully half the water pumped is lost in these various ways. Another thing that must be considered when comparing the amount of water used by different cities is the industries. Some industries require much more water than others, therefore, if a just comparison is to be made between cities only the water that is actually passed through the private meters must be considered.

Water Waste

Consideration of the subject of water would not be complete without some reference to the amount of water that is wasted. It seems a small matter to waste water. We sometimes say there is plenty in the river. But the proposition of preparing the water for use and getting it to the individual for consumption may involve many phases of hygiene from several different angles and one of these angles may be industrial hygiene. To get water into the home and factory requires a great many processes such as laying and maintaining water mains, purifying the water and pumping. This involves several industries and trades, so the problem of a water supply is far reaching and is of vital importance to the community.

There should never be a sacrifice on the part of hygiene and cleanliness for the purpose of saving water. A sufficient amount of water should at all times be insisted upon, but certainly there should be a strenuous effort to eliminate undue waste.

The main causes of water waste will be found to be leakage in mains and service pipes and waste from defective fixtures in the house. All of this leakage and waste should be properly attended to because of the direct relation which it bears to hygiene and particularly to industrial hygiene.

The introduction of meters has been an important factor in reducing water waste. It is not the thought to limit the amount of water used or to deprive one of a sufficient amount, but there is nothing to be gained by an unnecessary waste. The introduction of meters in Milwaukee reduced the amount of water used per tap from 1,781 gallons per day to 644 gallons per day without putting any restrictions upon the consumers. It is an enormous task to provide a sufficient amount of pure clean water for a large city and certainly an effort should be made to avoid waste.