Popular Science Monthly/Volume 25/June 1884/Clean Drinking-Water
AMONG the subjects that claim the study of the sanitarian, there is none that has a closer relation to public health, and hence none more worthy of careful investigation, than the water we drink. Receiving it, as we do, from varied sources—from spring, well, brook, or river—its character varies greatly; and, while in its purity bringing with it refreshment and health, in a polluted condition it too often carries in its wake disease and death.
The study of sanitary science during the last few years has demonstrated beyond a doubt that many severe epidemics have arisen from the use of impure water, as the reading of Witthaus, Parkes, Buck, Flint, Pavy, or other writers on the subject, will clearly prove.
When we remember that water has greater solvent properties than any other liquid known, we can readily understand how it often becomes such a disease-spreading medium. Besides carrying with it vegetable and organic impurities in suspension, it dissolves many of those that are the most subtile and dangerous to the human organism. The dangers of drinking impure water may best be presented in a few quotations from well-known authorities.
Pavy, in "Food and Dietetics," says: "Water has much to answer for in the causation of disease. ... It" (polluted water) "is acknowledged to be one of the common causes of dysentery, and has been alleged, when derived from a marshy district, to be capable of inducing malarial fever and its concomitant, enlargement of the spleen. ... Typhoid has been frequently communicated through the medium of water. Milk, adulterated with polluted water, has been the cause of serious outbreaks of fever." Parkes, in his "Manual of Practical Hygiene," shows that the baneful effects of polluted water were known to the ancient Greeks. Hippocrates, who was born 460 b. c, asserts, "The spleens of those who drink the water of marshes become enlarged and hard." Parkes considers typhoid, cholera, scarlet fever, and diphtheria, and some forms of skin-disease, "likely to be propagated by means of water."
Polluted water that has been frozen, though improved by the freezing, does not become innocuous. "Ice and snow may be the means of conveying malarial poisons to places at a distance," by distributing organic matter held in suspension. Dr. Edwards, of Montreal, found two grains of organic matter to the gallon of melted shore-ice, and one grain to the gallon of river-ice. One writer, Pavy, says, "River water and the water of shallow wells should always be regarded with suspicion," and he adds, "There is evidence to show that the most serious consequences have arisen from the consumption of impure water." Buck, in "Hygiene and Public Health," says, "The weight of evidence and authority favors the idea that the drinking-water may become the cause of disease, and in drinking a polluted water one always runs more or less risk." The River Pollution Commission of London, after analyzing water from different sources, reported dangerous "river-water to which sewage gains access."
The conclusion from the above quotations is, not that one should abstain from drinking water on account of the difficulty in obtaining it pure, but that proper precautions should be observed to obtain it pure. Water is Nature's means of slaking thirst, and with its refreshing properties combines valuable therapeutic qualities.
An excellent article, published in the "Boston Journal of Chemistry," in treating of the curative value of water says: "We notice the salutary influence of water-drinking upon many of those who resort to the so-called mineral springs which abound in the country. It is not necessary that these springs should hold abnormal quantities of salts of any kind to effect cures; it is only necessary that the water should be pure. Ordinary springs, such as are found in every farmer's pasture, are curative springs if the waters are used freely by those who suffer from certain gastric or renal difficulties." This writer asserts that the best known of our Eastern mineral waters shows, on analysis, that its curative value consists solely in its purity.
It may be truthfully asserted that it is impossible to procure perfectly pure water. "Even distilled water and fresh rain-water contain some ammonia, carbonic acid, and other matters which detract from their purity; while the best water from rivers, wells, ponds, and tanks, contains a large number of chemical compounds, chiefly salts." The skillful use of the microscope would condemn the water from many sources for drinking purposes which now is considered pure. But while we can not obtain strictly pure water, even by distillation, we can obtain it so pure that it will meet our demands, and that without danger to the consumer's health. The means by which this may be accomplished is filtration.
A filter is an apparatus for separating from fluids the foreign substances mechanically intermixed with them and held in suspension. While this is all that most filters aim to accomplish, yet experiments show that a filtering material may be used which very markedly diminishes the foreign bodies usually held in solution in water, and also removes those held in suspension.
The devices that have been used and are now employed for filtering purposes are very numerous. Tracing their history from the old Hippocratic sleeve, which was a cone-shaped bag of cotton or wool, we find, among others, the following materials: Thick unsized paper; cloth of various texture; sand; asbestus; animal charcoal; vegetable charcoal; felt; porous stones of various kinds; spongy iron; porous earthenware; perforated metallic disks; sponge; carferal, a composition consisting of a mixture of charcoal, iron, and clay; silicated carbon; ground slag, or compounds of two or more of these substances mentioned.
The essentials of a good filter for domestic purposes are—1. Efficiency in removing foreign bodies held in suspension. 2. Chemical power to destroy animal and vegetable impurities in solution or to convert them into innocuous substances. 3. Freedom from all possibility of tainting the water. 4. Simplicity of construction, so as to admit of the filtering material being readily renewed. 5. Cheapness. A good filter for domestic purposes must possess all five of these qualities. Those that have two or three of them and lack the remainder do not practically solve the problem of giving us clean water to drink.
The Japanese use a porous sandstone hollowed in the shape of an egg, through which the water percolates into a receptacle underneath; the Egyptians resort to a similar device; the Spaniards use a porous earthen pot. But these and other similar contrivances can not be thoroughly cleansed; after the most thorough rinsing, some impurities will remain in the pores of the stone. Spongy iron and carferal are open to the same objection; they will answer well for a short time, but soon become contaminated by pollution retained in their pores. Sponge, cloth, and felt, unless cleaned every day or two with hot water, will do more harm than good, and the average servant-girl will not clean them or any other filter unless under the eye of her mistress.
The various forms of filters that are screwed to the faucet have only to be hastily examined to be discarded, as there is not sufficient filtering material in them to be of much utility, and they very soon become foul and offensive. Buck says, "There is no material known which can be introduced into the small space of a tap-filter and accomplish any real purification of the water which passes through at the ordinary rate of flow."
The various complicated closed filters, filled with any material which can not be removed for cleansing, condemn themselves. No amount of pumping water through them at different angles, which is at all likely to be used, can cleanse them of the impurities that adhere to the mass and in the pores of the filtering material used. Parkes, in his "Manual of Practical Hygiene," says, "Filters, where the material is cemented up and can not be removed, ought to be abandoned altogether."
The various metal filters in which the water comes in contact with metallic surfaces, either iron, lead, tinned iron, or zinc, are objectionable from their appreciable influence upon the water retained in them for any considerable time. Pure block-tin is the least objectionable of any of the metals.
The aim of most filters is to remove impurities from the water speedily—as rapidly as it escapes from the faucet. Experiment shows that effective filtration can not be accomplished in this way, as the water does not remain long enough in contact with the filtering material used to become purified of much that might be removed by slow filtration or percolation through the same appliance. Of all the filtering materials mentioned, it seems to me that sand and charcoal are the two that accomplish the best results, and of these vegetable charcoal is the best.
Clean quartz sand will retard the passage of some impurities held in suspension, but no very careful investigation is necessary to demonstrate the presence of many impurities in water that has passed through it. The naked eye can detect them in most samples. Buck states, "The spores of algæ are not removed by the passage of water through sand," and he adds that "clean quartz sand can produce little effect" on polluted water. But he and many if not all other sanitarians assert that charcoal does purify the water and remove the odor of putrefaction. While there is no lack of authority to prove the value of animal charcoal as a filtering material, the claims of vegetable charcoal seem to me to make it more serviceable. Vegetable charcoal is "the solid residuum of the destructive distillation of wood." It is insipid and inodorous, it is insoluble in water, it is but little affected by either acids or alkalies. The ash consists chiefly of carbonate of potash, silica, lime, and the oxide of iron. Vegetable charcoal has a strong deodorizing power. Water containing sulphureted hydrogen speedily loses its odor when filtered through it. The taste of liquids, when dependent on the presence of certain organic substances, is almost or entirely removed by filtering through it. "The purifying, antiseptic power of charcoal is due to the action of its absorbed oxygen upon organic matter." A careful authority says: "Charcoal, by possessing the properties of absorption, decomposition, and combination, is eminently fitted as a filter for the purification of water, removing from it the color, odor and taste of its impurities by oxidizing and recombining them into other and inoffensive substances." A reference to chemistry shows us that the following gases are absorbed by charcoal: Hydrogen, nitrogen, carbonic oxide, marsh-gas, nitrous oxide, carbonic acid, olefiant gas, sulphurous acid, air, sulphureted hydrogen, muriatic acid, hydrochloric acid, and ammonia.
Witthaus, in his "General Medical Chemistry," says on this subject: "Its" [vegetable charcoal's] "power of absorbing odorous bodies renders it valuable as a disinfecting and filtering agent, and in the prevention of putrefaction and fermentation of certain liquids. It is with this view that the interiors of barrels intended to hold wine, beer, or water, are carbonized. Certain odorous culinary operations are rendered inodorous by the introduction of a fragment of charcoal into the pot. The efficacy of charcoal as a filtering material is due in a great measure to the oxidizing action of the oxygen contained in its pores."
In the article on vegetable charcoal in the "National Dispensatory," the writer says: "The most fetid gases disengaged by putrefaction are among those which are the most abundantly absorbed by charcoal, viz., ammonia, sulphureted hydrogen, and sulphurous acid, and the oxygen contained in the charcoal combines with the other deleterious substances and generates new and inodorous compounds." Buck says, "All varieties of carbon formed by the destructive distillation of vegetable or animal matter possess the property of removing organic matter from solution." Fowne's "Chemistry" says of charcoal, "It is said to absorb ninety times its volume of ammonical gas." But sufficient authorities have been quoted to prove the high estimate in which vegetable charcoal is held as a filtering material by chemists and sanitarians. Careful experimenting with it has satisfied me of its efficacy and practicability. It is efficient, clean, easily obtained by any one, and so cheap that after a few weeks' use it can be thrown away, and a clean supply substituted, and the cost need not be taken into consideration. Animal charcoal possesses valuable filtering properties, but it is very expensive, difficult to be obtained, and is so associated in the minds of the people with dead horses and the bone-yard that a strong prejudice exists against it. I have thus tried to show in this paper—1. That clean drinking-water is essential to health. 2. Some of the well-established results of drinking polluted water. 3. The various filtering materials that have been used, with their merits and objections. 4. The superiority and availability of vegetable charcoal as a filtering material.
In conclusion, in answering the question, "How, then, may we obtain clean drinking-water?" I would answer, by filtering the water slowly through properly adjusted vegetable charcoal placed in an earthen receptacle of some kind so that the water will not come in contact at any stage of its passage through the filter with metal of any kind. Cool the filtered water by placing ice under or around the vessel in which the water is contained, but do not put the ice into the water, or its impurities will be liberated by melting and contaminate it. Acting on these suggestions, I believe clean drinking-water may be obtained in any family, and, with clean water, less sickness.